Use these links to access detailed analyses of Global and U.S. data. 
|
|
Sea-surface temperatures (SSTs) remained above average during December 2006, as the moderate El Niño event persisted across the equatorial Pacific. Since May 2006, the SST anomalies in the Niño 3.4 region have been warmer than average each month, and remained above normal with a monthly anomaly of +1.37°C (+2.47°F) in December, an increase of +0.29°C (+0.52°F) over the November anomaly.
In the classical Niño region of the eastern equatorial Pacific and along the South American coast, the warming of the ocean surface and mixed-layer temperatures abated over the past month as the SST anomalies declined in the Niño 1+2 region to +0.50°C (+0.9°F) above average. This was a fairly dramatic decrease of -0.54°C (-0.97°F) since November. In the western tropical Pacific, warmer-than-average SSTs persisted during December with an anomaly of +1.06°C (+1.91°F) above average in the Niño 4 region, a slight cooling of +0.03°C (+0.05°F) compared with the previous month. The atmospheric conditions during December continued to show significant variability. Equatorial zonal wind anomalies were near average in the western and central Pacific over the past month. However, the Outgoing Longwave Radiation (OLR) index was once again close to neutral, with a value of -0.3 for the month. The Southern Oscillation Index (SOI) shifted signs back to a negative value in December, with a standardized monthly value of -0.5. Therefore, the primary atmospheric indicators continued to lag the warming in the upper ocean, and have varied considerably on a month-to-month basis in comparison with the consistently warm anomalies in the ocean. KEYWORDS: ENSO; Niño Regions; Southern Oscillation Index (SOI); Kelvin Waves; Thermocline; Sea-Surface Temperatures (SSTs); Madden-Julian Oscillation (MJO); Walker Circulation |
December
SSTs COOL SLIGHTLY IN THE EASTERN EQUATORIAL PACIFIC
Larger image of December SSTs 
Larger image of December Sub-Surface Temperatures 
Larger image of December SST Anomalies 
Larger image of 3-month (Oct-Dec) averaged SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
A large area of Sea-Surface Temperature (SST) anomalies greater than +1.0°C (+1.8°F) stretched from the Date Line in the west-central Pacific to the South American coast in December, with anomalies greater than +1.5°C (+2.7°F) near the Dateline between 170°E and 150°W. Water temperatures in the mixed-layer also remained warm over the past month, with a large area of +3.0°C (+5.4°F) and greater temperature anomalies as deep as 150 meters in the eastern equatorial Pacific. In addition, a layer of cooler water below 100 m depth developed in mid-November in the western Pacific and moved eastward in December. For the month of December, the SST anomaly in the Niño 3.4 Index region was +1.37°C (+2.47°F), which was an increase of +0.29°C (+0.52°F) compared to the November anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific also remained warm during December, although they decreased slightly from the previous month to an anomaly of +1.06°C (+1.91°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for December 2006. With warmer SSTs in the Niño 3.4 index region in December, the 3-month running mean remained above the +0.5°C (+0.9°F) threshold that indicates the presence of an El Niño episode (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition). The Climate Prediction Center's most recent ENSO Diagnostic Discussion indicated that the warm event (El Niño) had reached maturity and has now shown signs of weakening slightly over the past month. The ENSO forecast from the Australian Bureau of Meteorology (BoM) also continues to reflect the persistence of warm event conditions in the tropical Pacific basin into the first part of 2007 (see the Australian BoM ENSO Wrap-Up). |
Larger image of December Zonal Winds 
Larger image of 17 December 2006 Pacific Sea Level Anomalsies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
Anomalous westerly winds were observed across a portion of the far western equatorial Pacific during December, while the easterly Trade winds were slightly above normal across the central and eastern equatorial Pacific. Significant week-to-week variability in the near-surface winds has been observed along the equatorial region of the Pacific over the past month, as shown in the loop of December zonal winds. A period of anomalous westerly flow occurred in the equatorial Pacific region during early December, followed by a return to easterly Trade winds across the Pacific basin later in the month. Pacific sea levels measured by the NASA/JPL Jason-1 satellite were above average across the eastern equatorial Pacific in early and mid-December, reflecting the warmer-than-average ocean temperatures and the maturing El Niño event (see the most recent image of 17 December 2006 sea level anomalies). |
 Larger image of December OLR Anomalies Larger image of October-December OLR Anomalies Larger image of December OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) measured by satellite during December. A region of negative OLR anomalies was observed in the western equatorial Pacific near the Date Line, which suggests that enhanced tropical convection has developed in this region. The monthly OLR index for December was -0.3 W m-2 averaged across an area in the western Pacific between 160° E and 160° W. This was the fifth consecutive month that the OLR index was below the long-term mean, although an OLR Index value of -0.3 is considered near-neutral. Persistently negative OLR indices are typical of the mature phase of a warm event. At present, NOAA's Climate Prediction Center (CPC) has forecasted the current El Niño episode to persist into 2007. Therefore, it is expected that the OLR Index will decrease further as the Walker Circulation shifts to the east and tropical convection in the central equatorial Pacific intensifies. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of December SOI |
Southern Oscillation Index (SOI): The standardized SOI was -0.5 in December, switching signs from a positive value in November. The near-neutral SOI in November followed six consecutive months with negative index values. Note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions. However, negative SOI values are expected to redevelop by the end of the year, as NOAA's Climate Prediction Center (CPC) continues to forecast the persistence of the current El Niño episode into the first few months of 2007. |
November
ABOVE NORMAL SSTs PERSIST ACROSS THE EQUATORIAL PACIFIC
Larger image of November SSTs 
Larger image of November Sub-Surface Temperatures 
Larger image of November SST Anomalies 
Larger image of 3-month (Sep-Nov) averaged SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
A large area of Sea-Surface Temperature (SST) anomalies greater than +1.0°C (+1.8°F) stretched from the western Pacific to the South American coast in November, with anomalies greater than +1.5°C (+2.7°F) near the Dateline between 170°E and 150°W. Water temperatures in the mixed-layer also continued to warm over the past month, with a large area of +3.0°C (+5.4°F) and greater temperature anomalies as deep as 150 meters in the central and eastern equatorial Pacific. For the month of November, the SST anomaly in the Niño 3.4 Index region was +1.21°C (+2.18°F), which was an increase of +0.25°C (+0.45°F) compared to the October anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific also continued to warm during November, resulting in a monthly anomaly of +1.26°C (+2.27°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for November 2006. With warmer SSTs in the Niño 3.4 index region in November, the 3-month running mean has surpassed the +0.5°C (+0.9°F) threshold that would indicate the onset of an El Niño episode (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition). The Climate Prediction Center's most recent ENSO Diagnostic Discussion indicated that a warm event (El Niño) had developed by mid-September, and has continued to strengthen since that time. The ENSO forecast from the Australian Bureau of Meteorology (BoM) also continues to reflect the development of warm event conditions in the tropical Pacific basin (see the Australian BoM ENSO Wrap-Up). |
Larger image of November Zonal Winds 
Larger image of 20 November 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
Anomalous westerly winds were observed across much of the western and central equatorial Pacific during November, while the easterly Trade winds were near-normal across the far eastern equatorial Pacific. Significant week-to-week variability in the near-surface winds has been observed along the equatorial region of the Pacific over the past month, as shown in the loop of November zonal winds. A period of westerly flow occurred in the equatorial Pacific region during early November, followed by a return to near-normal easterly Trade winds across the eastern Pacific later in the month. Pacific sea levels measured by the NASA/JPL Jason-1 satellite were above average across most of the equatorial Pacific in mid-November, reflecting the warmer-than-average ocean temperatures and the maturing El Niño event (see the most recent image of 20 November 2006 sea level anomalies). |
 Larger image of November OLR Anomalies Larger image of August-November OLR Anomalies Larger image of November OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) measured by satellite during November. A region of negative OLR anomalies was observed in the western equatorial Pacific near the Dateline, which suggests that enhanced tropical convection has begun to develop in this region. The monthly OLR index for November was -0.2 W m-2 averaged across an area in the western Pacific between 160° E and 160° W. This was the fourth consecutive month that the OLR index was below the long-term mean, although an OLR Index value of -0.2 is considered near-neutral. Note that significantly negative OLR indices are typical of the mature phase of a warm event. At present, NOAA's Climate Prediction Center (CPC) has forecasted the current El Niño episode to persist into 2007. Therefore, it is expected that the OLR Index will decrease further as the Walker Circulation shifts to the east and tropical convection in the central equatorial Pacific intensifies. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of November SOI |
Southern Oscillation Index (SOI): The standardized SOI was near-neutral in November, with an averaged value of +0.1 for the month. The near-neutral SOI in November followed six consecutive months with negative index values. Note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions. However, negative SOI values are expected to redevelop by the end of the year, as NOAA's Climate Prediction Center (CPC) continues to forecast the persistence of the current El Niño episode into the first few months of 2007. |
October
SSTs INCREASE ACROSS THE EQUATORIAL PACIFIC
Larger image of October SSTs 
Larger image of October Sub-Surface Temperatures 
Larger image of October SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
A large area of Sea-Surface Temperature (SST) anomalies greater than +0.5°C (+0.9°F) stretched from the central Pacific to the South American coast in October, with anomalies greater than +1.0°C (+1.8°F) between 120°W and the South American coast. Water temperatures in the mixed-layer also continued to warm over the past month, with a large area of +1.0°C (+1.8°F) and greater temperature anomalies as deep as 150 meters in the central and eastern Pacific. For the month of October, the SST anomaly in the Niño 3.4 Index region was +0.96°C (+1.73°F), which was an increase of +0.35°C (+0.63°F) compared to the September anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific also continued to warm during October, resulting in a monthly anomaly of 0.86°C (1.55°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for October 2006. With warmer SSTs in the Niño 3.4 index region in October, the 3-month running mean in this region was above average for the third month in a row, and has surpassed the +0.5°C (+0.9°F) threshold that would indicate the onset of an El Niño episode (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition). The Climate Prediction Center's most recent ENSO Diagnostic Discussion indicated that a warm event (El Niño) had developed by early September, but the future strength of the event remains uncertain at this time. The ENSO forecast from the Australian Bureau of Meteorology (BoM) also continues to reflect the development of warm event conditions in the Pacific basin (see the Australian BoM ENSO Wrap-Up). |
Larger image of October Zonal Winds 
Larger image of 15 October 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
Anomalous westerly winds were observed across much of the western and central equatorial Pacific during October, while the easterly Trade winds were weaker-than-normal across the eastern equatorial Pacific. Significant week-to-week variability in the near-surface winds has been observed along the equatorial region of the Pacific over the past month, as shown in the loop of October zonal winds. A period of westerly flow in the equatorial region during early October gave way to stronger than normal easterly Trade winds later in the month. Pacific sea levels measured by the NASA/JPL Jason-1 satellite were above average in the central and eastern tropical Pacific in October, reflecting the warmer-than-average ocean temperatures and the development of an El Niño event (see the 15 October 2006 sea level anomalies image to the left). |
 Larger image of October OLR Anomalies Larger image of August-November OLR Anomalies Larger image of October OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during October. The lack of any large-scale tropical convection in the central and eastern equatorial Pacific suggests that the atmosphere has lagged the ocean during the formative phase of the current El Niño event. The monthly OLR index for October was -0.8 W m-2 averaged across an area in the western Pacific between 160° E and 160° W. This was the third consecutive month that the OLR index was below the long-term mean. At present, NOAA's Climate Prediction Center (CPC) : has forecasted the current El Niño episode to persist into early 2007. Therefore, it is expected that the OLR Index will decrease further as the Walker Circulation shifts to the east and tropical convection in the central and eastern equatorial Pacific intensifies. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of October SOI |
Southern Oscillation Index (SOI): The standardized SOI was negative in October, with an averaged value of -1.7 for the month. Therefore, October was the sixth consecutive month with a below average SOI. Note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions, and persistence of negative SOI values will likely occur over the next few months as the current El Niño episode continues through the end of the year and into early 2007. |
September
SSTs WARM ACROSS THE EQUATORIAL PACIFIC
Larger image of September SSTs 
Larger image of September Sub-Surface Temperatures 
Larger image of September SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
A large area of Sea-Surface Temperature (SST) anomalies greater than +0.5°C (+0.9°F) stretched from the central Pacific to the South American coast in September, with anomalies greater than +1.0°C (+1.8°F) between 120°W and the South American coast. Water temperatures in the mixed-layer also continued to warm over the past month, with a large area of +1.0°C (+1.8°F) and greater temperature anomalies as deep as 150 meters in the central and eastern Pacific. For the month of September, the SST anomaly in the Niño 3.4 Index region was +0.61°C (+1.1°F), which was an increase of +0.23°C (+0.41°F) compared to the August anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific also continued to warm during September, resulting in a monthly anomaly of 0.73°C (1.31°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for September 2006. With warmer SSTs in the Niño 3.4 index region in September, the 3-month running mean in this region was above average for the third month in a row, but remained below the +0.5°C (+0.9°F) threshold that would indicate the onset of an El Niño episode (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition). The Climate Prediction Center's most recent ENSO Diagnostic Discussion indicated that a warm event (El Niño) had developed by early September, but the future strength of the event remains uncertain at this time. The ENSO forecast from the Australian Bureau of Meteorology (BoM) remains somewhat more conservative for the evolution of the current conditions (see the Australian BoM ENSO Wrap-Up). |
Larger image of September Zonal Winds 
Larger image of 15 September 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The easterly Trade winds were stronger-than-normal across much of the eastern and central equatorial Pacific during September, while anomalous westerly winds were observed in the western Pacific. Significant week-to-week variability in the near-surface winds has been observed along the equatorial region of the Pacific over the past month, as shown in the loop of September zonal winds. A period of westerly flow in the equatorial region during early September gave way to stronger than normal easterly Trade winds later in the month. Pacific sea levels measured by the NASA/JPL Jason-1 satellite were above average in the central and eastern tropical Pacific in September, reflecting the warmer-than-average ocean temperatures and the developing El Niño event (see the 15 September 2006 sea level anomalies image to the left). |
 Larger image of September OLR Larger image of September OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during September. The absence of strong positive or negative OLR anomalies (typically associated with La Niña and El Niño, respectively) is indicative of neutral ENSO conditions. At present, the lack of any large-scale atmospheric signal suggests that the atmosphere has lagged the ocean during the formative phase of the current El Niño event. The monthly OLR index for September was -0.2 W m-2 averaged across an area in the western Pacific between 160° E and 160° W. This was the second consecutive month that the index was below the long-term mean. At present, NOAA's Climate Prediction Center has forecasted the current El Niño episode to persist through the end of 2006. Therefore, it is expected that the OLR Index will decrease further as the Walker Circulation shifts to the east and tropical convection in the central and eastern equatorial Pacific intensifies. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of September SOI |
Southern Oscillation Index (SOI): The standardized SOI was negative in September, with an averaged value of -0.7 for the month. Therefore, September was the fifth consecutive month with a below average SOI. Note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions, and persistence of negative SOI values will likely occur as the current El Niño episode develops over the next few months. |
August
SSTs WARM ACROSS THE EQUATORIAL PACIFIC
Larger image of August SSTs 
Larger image of August Sub-Surface Temperatures 
Larger image of August SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
A large area of Sea-Surface Temperature (SST) anomalies greater than +0.5°C (+0.9°F) stretched from the central Pacific to the South American coast, with anomalies greater than +1.0°C (+1.8°F) near 180°W. Water temperatures in the mixed-layer also continued to warm in August, with a large area of +1.0°C (+1.8°F) temperature anomalies as deep as 150 meters in the central Pacific. For August, the SST anomaly in the Niño 3.4 Index region was +0.38°C (+0.68°F), which was an increase of +0.27°C (+0.49°F) compared to the July anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific also continued to warm during August, resulting in a monthly anomaly of 0.58°C (1.04°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for August 2006. With warmer SSTs in the Niño 3.4 index region in August, the 3-month running mean in this region was above average for the third month in a row, but remained short of the +0.5°C (+0.9°F) threshold that would indicate the onset of an El Niño episode. (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition). The Climate Prediction Center's ENSO Diagnostic Discussion indicated that a warm event (El Niño) had developed by early September, but the future strength of the event is uncertain at this time. The Australian Bureau of Meteorology (BoM) has a slightly more conservative forecast for the evolution of the current conditions (see the Australian BoM ENSO Wrap-Up). |
Larger image of August Zonal Winds 
Larger image of 22 August 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The monthly averaged easterly trade winds remained near-normal across much of the eastern and central equatorial Pacific during August, with only a small area of negative U-component anomalies in the eastern Pacific (reflective of slightly stronger than average easterlies). Weaker than normal easterly winds persisted near the Date Line again in August as evidenced by positive U-component anomalies. There was considerable week-to-week variability as shown in the loop of August zonal winds. Pacific sea levels measured by the NASA/JPL Jason-1 satellite were slightly above-average along the equatorial zone in August, reflecting the warmer than average ocean temperatures (see the 22 August 2006 sea level anomalies image to the left). |
 Larger image of August OLR Larger image of August OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during August. The absence of strong positive or negative OLR anomalies (typically associated with La Niña and El Niño, respectively) is indicative of the presence of neutral ENSO conditions. The monthly OLR index for August was -0.3 W m-2 averaged across an area in the western Pacific between 160° E and 160° W. This was only the second time this year that the index was below the long-term mean. If conditions continue to evolve toward an El Niño episode, the OLR Index will continue to decrease as convection in the central and eastern equatorial Pacific increases. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of August SOI |
Southern Oscillation Index (SOI): The standardized SOI was negative in August, with a monthly averaged value of -1.6 for the month, a further decrease from the value of -0.8 in July. August was the fourth consecutive month with a below average SOI. Note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions, and a further decrease of this index will likely occur as the current El Niño episode develops over the next few months. |
July
SSTs WARM IN THE EQUATORIAL PACIFIC
Larger image of July SSTs 
Larger image of July Sub-Surface Temperatures 
Larger image of July SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
Sea-Surface Temperatures (SSTs) increased across most of the equatorial Pacific Ocean during July. Water temperatures in the mixed-layer also increased this past month, with the warmest anomalies in the eastern equatorial Pacific between 90°W and 120°W. For July, the SST anomaly in the Niño 3.4 Index region was +0.11°C (+0.2°F), which was a slight decrease compared to the June anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific continued to warm during July, resulting in a monthly anomaly of +0.41°C (+0.74°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for July 2006. Below average SST anomalies persisted throughout the latter half of 2005 and into the first few months of 2006 in the central equatorial Pacific basin (as seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature [ERSST version 2] dataset). Due to the warming of SSTs and mixed-layer temperatures in the central tropical Pacific, the 3-month running mean of the Niño 3.4 index region increased above -0.5°C in April, and has continued to remain above the long-term mean in July. (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and also see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of July Zonal Winds 
Larger image of 23 July 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The monthly averaged easterly trade winds were near-normal across the eastern and central equatorial Pacific during July. Weaker than normal easterly winds were observed near the Date Line, with westerly zonal winds developing in the far western Pacific (see the loop of July zonal winds). Pacific sea levels measured by the NASA/JPL Jason-1 satellite were near-average along the equatorial zone in July, as the sea level heights reflected the near-normal conditions during the month (see the 23 July 2006 sea level anomalies for the most recent overpass). |
 Larger image of July OLR Larger image of May-July OLR Larger image of July OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during July. Positive OLR anomalies (typically associated with La Niña) that persisted over the past several months in the equatorial western Pacific region dissipated in July, with only a small area of above average OLR remaining south of the equator near the Date Line. Convection associated with the monsoon trough and tropical cyclone activity increased north of Indonesia in the western Pacific in July. Despite the changes this past month, the 3-month averaged OLR anomalies remained positive along the equator over sections of the eastern and central Pacific, reflecting the reduced cloudiness that was observed during the latter stages of 2005/2006 La Niña. The monthly-averaged OLR Index became positive during July, although it remained near-neutral. For the month, the OLR index was +0.4 W m-2 averaged across an area centered over the Date Line in the western Pacific between 160° E and 160° W (positive OLR Index values are typically associated with La Niña conditions in this region). Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of July SOI |
Southern Oscillation Index (SOI): The standardized SOI was negative in July, with a monthly averaged value of -0.8 for the month. Note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions. However, the monthly values of the SOI were inconsistent during the relatively weak 2005/2006 La Niña event, fluctuating several times between near-neutral values and positive indices that were more indicative of the weak cold event. The shift to a negative SOI during the Boreal spring coincided with the development of warmer than average SSTs across the equatorial Pacific. It also coincided with a transition in the Walker Circulation to a near-neutral mean sea level pressure (MSLP) pattern. |
June
ACROSS THE EQUATORIAL PACIFIC
Larger image of June SSTs 
Larger image of June Sub-Surface Temperatures 
Larger image of June SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
SSTs increased across most of the equatorial Pacific Ocean during June. The observed SST anomalies this past month were slightly above average in the western and central parts of the tropical Pacific basin. Water temperatures in the mixed-layer warmed during June and were slightly above normal at the end of the month, with the warmest anomalies in the eastern Pacific near 120°W. For the month, the SST anomaly in the Niño 3.4 Index region was +0.25°C (+0.45°F). The SSTs in the Niño 4 Index region of the western equatorial Pacific were also warmer-than-normal, with a monthly index of +0.39°C (+0.7°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for June 2006. Below average SST anomalies persisted throughout the latter half of 2005 and into the first few months of 2006 in the central equatorial Pacific basin, and this can be seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature dataset (ERSST version 2). Due to the warming of SSTs and mixed-layer temperatures in the central tropical Pacific, the 3-month running mean of the Niño 3.4 index region increased above -0.5°C in April, and has continued to warm during June. (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and also see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of June Zonal Winds 
Larger image of 11 June 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The monthly averaged easterly trade winds were slightly above-normal across the eastern and central equatorial Pacific during June. Weaker than normal easterly winds were observed in the western equatorial Pacific, where the trade winds were below average during this past month. However, there were several periods during June when the trade winds weakened substantially, especially in the western Pacific region at the beginning of the month (see the loop of June zonal winds). The most recent Pacific overpass of the NASA/JPL Jason-1 satellite measured an area with large positive sea level anomalies in the southwest equatorial Pacific, which was associated with enhanced tropical convection along the South Pacific Convergence Zone (SPCZ). Sea levels were mostly near-average throughout the equatorial Pacific region during June, as the sea level heights reflected the near-normal SST conditions at the end of the month (see the 11 June 2006 overpass). |
 Larger image of June OLR Larger image of April-June OLR Larger image of June OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during June. Positive OLR anomalies (typically associated with La Niña) that persisted over the past several months primarily in the equatorial western Pacific region dissipated in June. Tropical convection increased over Indonesia and along the equatorial region west of the Date Line in the western Pacific this past month. Despite the changes observed in June, the 3-month averaged OLR anomalies remained positive over sections of both the eastern and western Pacific along the equator, reflecting the reduced cloudiness that was observed during the latter stages of 2005/2006 La Niña. The monthly-averaged OLR Index switched to a negative index during June, although it remained near-neutral. For the month, the OLR index was -0.3 W m-2 averaged across an area centered over the Date Line in the western Pacific between 160° E and 160° W (note that negative OLR Index values are typically associated with El Niño conditions in this region). Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of June SOI |
Southern Oscillation Index (SOI): The standardized SOI was negative in June, with a monthly averaged value of -0.7 for the month. The SOI was inconsistent during the relatively weak 2005/2006 La Niña event, fluctuating several times between near-neutral values and positive indices that were more indicative of the weak cold event. The shift to a negative value during May and June coincided with the development of warmer than average SSTs across a majority of the equatorial Pacific. |
May
ACROSS THE EQUATORIAL PACIFIC
Larger image of May SSTs 
Larger image of May Sub-Surface Temperatures 
Larger image of May SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
SSTs increased across most of the equatorial Pacific Ocean this past month. The observed SST anomalies during May were close to average in the western and central parts of the tropical Pacific basin. In the mixed-layer, water temperatures were near-normal to slightly above normal in the western and central Pacific, while warm anomalies developed near the South American coast. For the month, the SST anomaly in the Niño 3.4 Index region was +0.13°C (+0.23°F). The SSTs in the Niño 4 Index region of the western equatorial Pacific were +0.16°C (+0.29°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for May 2006. Below average SST anomalies persisted throughout the latter half of 2005 and into the first few months of 2006 in the central equatorial Pacific basin, and this can be seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature dataset (ERSST version 2). Due to the recent warming of SSTs in the central tropical Pacific, the 3-month running mean of the Niño 3.4 index region increased above -0.5°C in April, and continued to warm to near-average in May. (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and also see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of May Zonal Winds 
Larger image of 30 May 2006 Pacific Sea Level Anomalies |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The easterly trade winds were slightly below-normal across the central and western equatorial Pacific basin during May. Stronger than average easterly winds were observed in the eastern equatorial Pacific, where the trade winds were above average during the month. The most recent Pacific overpass of the NASA/JPL Jason-1 satellite observed several areas with large positive sea level anomalies in the southwest and northwest equatorial Pacific, most likely associated with enhanced tropical convection in these areas. Sea levels were mostly near-average throughout the equatorial Pacific during May, as the sea level heights reflected the near-normal SST conditions at the end of the month (see the 30 May 2006 overpass). |
 Larger image of May OLR Larger image of March-May OLR Larger image of May OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during May. Positive OLR anomalies (typically associated with La Niña) have persisted over the past several months primarily in the equatorial western Pacific region, centered near the Date Line, and tropical convection was again suppressed along the equator in the central and eastern Pacific this past month. The 3-month averaged OLR anomalies were also positive in the western Pacific basin and along the equator, reflecting the reduced cloudiness during the 2005/2006 cold event. The monthly-averaged OLR Index was positive during May, but remained only slightly above neutral with a value of +0.9 W m-2 for the month, averaged across an area centered over the Date Line in the western Pacific between 160° E and 160° W (note that positive OLR Index values are typically associated with La Niña conditions in this region). May was the tenth consecutive month with a positive OLR Index. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of May SOI |
Southern Oscillation Index (SOI): The standardized SOI switched signs to a negative value in May, with an average value of -0.8 for the month. The SOI was inconsistent during the relatively weak 2005/2006 La Niña, fluctuating several times between a near-neutral value and both positive and negative indices. The recent shift to a negative value in May coincided with the development of warmer than average SSTs in the equatorial Pacific. |
April
Larger image of April SSTs 
Larger image of April Sub-Surface Temperatures 
Larger image of April SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
SSTs increased across most of the equatorial Pacific Ocean this past month. The observed SST anomalies during April increased close to average in the western and central parts of the tropical Pacific basin. In contrast, across the eastern Pacific the observed SST anomalies decreased further below-normal during April in the Niño 1+2 region. In the mixed-layer, water temperatures increased in the western and central Pacific, while cold anomalies remained near the South American coast with the largest monthly anomalies of -1°C located between 95°W and 110°W and at ~50-100 m depth. For the month, the SST anomaly in the Niño 3.4 Index region decreased to -0.11°C (-0.198°F). The SSTs in the western Pacific also warmed during April, with a monthly averaged Niño 4 Index of +0.06°C (+0.108°F) (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for April 2006. Below average SST anomalies persisted throughout the latter half of 2005 and into the first few months of 2006 in the central equatorial Pacific basin, and this can be seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature dataset (ERSST version 2). Due to the recent warming of SSTs in the central tropical Pacific, the 3-month running mean of the Niño 3.4 index region increased above -0.5°C in April. (NOTE: A running 3-month mean SST anomaly below -0.5°C in the Niño 3.4 region is one indicator that a La Niña is occurring. For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and also see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of April Zonal Winds 
Larger image of 6 May 2006 Pacific Sea Level Height Deviation |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The easterly trade winds were near-normal across the central and western equatorial Pacific basin during April, except for the far western equatorial Pacific where the easterly Trade winds were above average during the month. The most recent Pacific overpass of the NASA/JPL Jason-1 satellite observed a number of large positive sea level anomalies in the southwest and northwest equatorial Pacific, most likely associated with enhanced tropical convection in these areas. Negative anomalies that were measured in the central equatorial Pacific during early May were directly related to slightly colder-than-normal SST conditions (see the 6 May 2006 steric height anomaly and the 6 May 2006 surface height deviation maps). |
 Larger image of April OLR Larger image of Feb-Apr OLR Larger image of April OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during April. Positive OLR anomalies (typically associated with La Niña) have persisted over the past several months in the equatorial western Pacific region, centered near the Date Line, and tropical convection was again suppressed just north of the equator in the central and eastern Pacific this past month. The 3-month averaged OLR anomalies were also positive in the western Pacific basin near the Date Line. In contrast, enhanced tropical convection was observed farther west in Indonesia and the maritime continent region. The negative OLR anomalies over parts of Australia were associated with several tropical cyclones that impacted this region during the past month (for more information please go to the Tropical Cyclones section of the April Global Hazards page). The monthly-averaged OLR Index remained positive during April, but declined to near-neutral with a value of +0.5 W m-2 averaged across an area centered over the Date Line in the western Pacific between 160° E and 160° W (note that positive OLR Index values are typically associated with La Niña conditions in this region). April was the ninth consecutive month with a positive OLR Index, a period which coincided with the weak 2005-2006 La Niña event and the persistence of below average SSTs in the mixed-layer in the equatorial Pacific. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of April SOI |
Southern Oscillation Index (SOI): The standardized SOI remained positive in April, with an average value of +0.9 for the month. The SOI was inconsistent during the weak 2005-2006 La Niña, due to a number of fluctuations between a near-neutral value and both positive and negative indices. The observed positive values in March and April lagged the cold SSTs in the equatorial Pacific, although the slight decline in the index in April brought it closer to a neutral value. |
March
Larger image of March SSTs 
Larger image of March Sub-Surface Temperatures 
Larger image of March SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
SSTs remained below average across most of the equatorial Pacific Ocean this past month. The observed SST anomalies during March were below the long-term means in the central parts of the tropical Pacific basin. In contrast, across the eastern Pacific the observed SST anomalies have been above normal but decreased to near-normal by the end of the month in the Niño 1+2 region. In the mixed-layer, below average water temperatures remained in the eastern and central Pacific, with the largest monthly anomalies of -2°C centered near 120°W and at ~50-200 m depth. For the month, the SST anomaly in the Niño 3.4 Index region was -0.59°C (-1.06°F). The western Pacific SSTs increased slightly during March, with a monthly averaged Niño 4 Index of -0.31°C (-0.56°F) (map of Niño regions). For the most recent ocean surface temperature conditions, please see the loop of satellite-derived weekly SST anomalies for March 2006. Below average SST anomalies persisted throughout the latter half of 2005 and into the first three months of 2006 in the central equatorial Pacific basin, and this can be seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature dataset (ERSST version 2). Due to the persistence of the below average SSTs, the 3-month running mean of the Niño 3.4 region remained below -0.5°C in March. (NOTE: A running 3-month mean SST anomaly below -0.5°C in the Niño 3.4 region is one indicator that a La Niña is occurring. For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and also see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of March Zonal Winds 
Larger image of 17 February 2006 Pacific Sea Levels |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The easterly trade winds were above normal across the central and western equatorial Pacific basin during March, with the largest anomalies of 1 m/s near the Date Line. These stronger-than-average trade winds increased equatorial upwelling in the mixed-layer, which maintained the observed colder-than-average SSTs in both the Niño 3.4 and 4 regions. Satellite altimetry of ocean surface topography from the NASA/JPL Jason-1 satellite over the Pacific basin and global oceans is shown to the left. As of April 10th the satellite data from March are currently unavailable. However, the most recent Pacific overpass of the Jason-1 satellite showed a number of large positive sea level anomalies in the southwest and northwest Pacific, most likely associated with enhanced tropical convection. Negative anomalies that were measured in the central equatorial Pacific during February were directly related to the cold SSTs associated with La Niña conditions (see the 17 February 2006 overpass). |
 Larger image of March OLR Larger image of Jan-Mar OLR Larger image of March OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during March. Positive OLR anomalies (typically associated with La Niña) have persisted over the past several months in the equatorial western Pacific region, centered near the Date Line, and tropical convection was again suppressed just north of the equator in the central and eastern Pacific this past month. The 3-month averaged OLR anomalies were also positive in the western Pacific basin near the Date Line. In contrast, enhanced tropical convection was observed farther west in Indonesia and the maritime continent region. The negative OLR anomalies over parts of Australia were associated with several tropical cyclones that impacted this region during the past month (for more information please go to the Tropical Cyclones section of the March Global Hazards page). The monthly-averaged OLR Index remained positive during March, with a value of +0.6 W m-2 averaged across an area centered over the Date Line in the western Pacific between 160° E and 160° W (note that positive OLR Index values are typically associated with La Niña conditions in this region). March was the eighth consecutive month with a positive OLR Index, a period which coincided with the development of weak La Niña conditions and the persistence of below average SSTs in the mixed-layer in the equatorial Pacific. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of March SOI |
Southern Oscillation Index (SOI): The standardized SOI switched signs from a negative to a positive index in March, with an average value of +1.4 for the month. The SOI has shown no persistent signal during the current weak La Niña event, and it has fluctuated several times between a near-neutral value and both positive and negative indices. Therefore, the SOI value in March suggests that moderate air-sea coupling has developed over parts of the Pacific basin in response to the weak La Niña and the associated cool ocean temperatures. |
February
BELOW AVERAGE SST ANOMALIES REMAIN ACROSS THE CENTRAL EQUATORIAL PACIFIC
Larger image of February SSTs 
Larger image of February Sub-Surface Temperatures 
Larger image of February SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
SSTs remained below average across most of the equatorial Pacific Ocean in February. The observed SST anomalies during February were below the long-term means in the central and western parts of the tropical Pacific basin. In contrast, across the eastern Pacific the observed SST anomalies increased to above-normal by the end of the month in the Niño 1+2 region. In the mixed-layer, below average water temperatures persisted in the eastern and central Pacific, with the largest monthly anomalies between -2 to -3°C centered near 120°W and at ~100 m depth. In the central equatorial Pacific, the SST anomaly in the Niño 3.4 Index region was -0.64°C (-1.15°F). The western Pacific SST anomaly decreased during February, with a monthly averaged Niño 4 Index of -0.65°C (-1.17°F) (map of Niño regions). For the most recent ocean surface temperature conditions, please see the loop of satellite-derived weekly SST anomalies for February 2006. Below average SST anomalies persisted throughout the latter half of 2005 and into the first two months of 2006 in the central equatorial Pacific basin, and this can be seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature dataset (ERSST version 2). Due to the persistence of the below average SSTs, the 3-month running mean of the Niño 3.4 Index remained below -0.5°C in February. (NOTE: A running 3-month mean SST anomaly below -0.5°C in the Niño 3.4 region is a significant indicator that a La Niña is occurring. For the NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of February Zonal Winds 
Larger image of 17 February 2006 Pacific Sea Levels |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The easterly trade winds were above normal across most of the equatorial Pacific basin during February, with the largest anomalies of 1-2 m/s in the western Pacific. The stronger-than-average trade winds increased equatorial upwelling in the mixed-layer, which maintained the observed colder-than-average SSTs in both the Niño 3.4 and 4 regions. Satellite altimetry of ocean surface topography from the NASA/JPL Jason-1 satellite over the Pacific basin and global oceans is shown to the left. The most recent Pacific overpass of the Jason-1 satellite showed a number of large positive sea level anomalies in the southwest and northwest Pacific, most likely associated with enhanced tropical convection. Negative anomalies that were measured in the central equatorial Pacific during February are directly related to the cold SSTs associated with La Niña conditions (see the 17 February 2006 overpass). |
 Larger image of February OLR Larger image of Dec-Feb OLR Larger image of February OLR Index |
Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) observed by satellite during February. Positive OLR anomalies (typically associated with La Niña) have persisted over the past several months in the equatorial western Pacific region, centered near the dateline, and tropical convection was again suppressed along the equator this past month. The 3-month averaged OLR anomalies were also positive in the same region of the western Pacific basin near the dateline. In contrast, enhanced convection was observed further west in Indonesia and the maritime continent region, where large-scale convection and several tropical cyclones developed and impacted Western Australia during the past month. The monthly-averaged OLR Index value remained positive in February, with a value of +0.6 W m-2 averaged across an area centered over the dateline in the western Pacific between 160° E and 160° W (positive OLR Index values are typically associated with La Niña conditions). February was the seventh consecutive month with a positive OLR index value, a period which coincided with the development of La Niña conditions and the persistence of below average SSTs in the ocean. Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices. |
 Larger image of February SOI |
Southern Oscillation Index (SOI): The standardized SOI switched signs from a positive to a negative index in February, with an average index value of -0.2 for the month. The SOI has shown no persistent signal during the current weak La Niña event, and it has fluctuated several times between a near-neutral value and both positive and negative index values. Therefore, the SOI value in February suggests that the atmosphere has yet to completely respond to the below average SSTs over the past several months, and air-sea coupling remains limited during this weak La Niña event. |
January
SST ANOMALIES COOL ACROSS THE EQUATORIAL PACIFIC
Larger image of January SSTs 
Larger image of January Sub-Surface Temperatures 
Larger image of January SST Anomalies |
Sea-Surface Temperatures (SSTs) and
Mixed-Layer Conditions:
SSTs decreased across the equatorial Pacific Ocean in January. The trends in the observed SST anomalies during January were declining relative to the long-term means in the central and western parts of the tropical Pacific basin, while in the eastern Pacific the SST anomalies had actually increased to near-normal by the end of the month in the Niño 1+2 region. In the mixed-layer, below average water temperatures persisted in the eastern and central Pacific, with the largest monthly anomalies between -2 to -3°C centered near 140°W and at ~100 m depth. In the central equatorial Pacific, the SST anomaly in the Niño 3.4 Index region decreased to -1.09°C (-1.96°F) below the mean. The western Pacific SST anomaly decreased as well, with a monthly averaged Niño 4 Index of -0.42°C (-0.76°F) (map of Niño regions). For the most recent ocean surface temperature conditions, please see the loop of satellite-derived weekly SST anomalies for January 2006. Below average SST anomalies have persisted throughout the latter half of 2005 and into January 2006 in the eastern and central equatorial Pacific basin, and this can be seen in the data from NCDC's Extended Reconstructed Sea Surface Temperature dataset (ERSST version 2). Due to the decreases in the monthly averaged SSTs, the 3-month running mean of the Niño 3.4 Index declined below -0.5°C in January. (NOTE: A running 3-month mean SST anomaly below -0.5°C in the Niño 3.4 region is a significant indicator that a La Niña is occurring. For the NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition and see the CPC ENSO Diagnostic Discussion for NOAA's latest official assessment of ENSO conditions.) |
Larger image of January Zonal Winds 
Larger image of 27 January 2006 Pacific Sea Levels |
Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
The easterly trade winds were above normal across much of the central and western equatorial Pacific basin during January, with the largest easterly wind anomalies developing in the western Pacific during the month. The stronger-than-average trade winds increased equatorial upwelling in the mixed-layer, which led to the observed decreases in the monthly averaged SSTs in both the Niño 3.4 and 4 regions. Satellite altimetry of ocean surface topography from the NASA/JPL Jason-1 satellite over the Pacific basin and global oceans is shown to the left. The most recent Pacific overpass of the Jason-1 satellite showed a number of large positive sea level anomalies in the southwest and northwest Pacific, most likely associated with enhanced tropical convection, while the negative anomalies that developed in the central equatorial Pacific during January are directly related to the cold SSTs associated with La Niña conditions (see the 27 January 2006 overpass). |
 Larger image of January OLR |