State of the Climate
National Overview
May 2002
National Oceanic and Atmospheric Administration
National Climatic Data Center
Use the form below to access monthly reports.
June 2001-May 2002
Temperatures
larger
image
|
The graph to the left
shows the twelve-month mean temperature averaged across the
contiguous United States based on long-term data from the U.S.
Historical Climatology Network (USHCN). The 2002 value
is estimated from preliminary Climate Division data using the
first difference approach.
June 2001-May 2002 ranked as the 4th warmest such
period in the 1895 to present record. The preliminary nationally
averaged temperature was 54.4° F (12.4° C) which was
1.6° F (0.9° C) above the long-term mean. |
| Every state in the
contiguous US, except Georgia, Alabama, Mississippi, Louisiana and
Washington, had above average temperatures for the 12-month period.
Much above normal (top ten percentile) temperatures were observed
in many states in the northeast and southwest, with 6 states in the
northeast ranking as the warmest June-May on record. |
larger
image
|
larger image
|
As can be seen in the graph to the left, two-thirds of the
contiguous U.S. was unusually warm in November 2001, which
contributed significantly to the 12-month mean. However, at least
15% of the contiguous US has averaged very warm in all but 4 of the
past 12 months. |
June-May
Precipitation
| The graph to the left
shows the twelve-month precipitation averaged across the contiguous
United States. June 2001-May 2002 ranked as the 33rd driest such
period in the 1895 to present record. |
| As can be seen in the
map to the right, the last 12-months were characterized by dryness
in the west and along the eastern seaboard with above average
precipitation from Michigan and Wisconsin to Louisiana. Both
Colorado and Arizona had their driest June-May on record, and this
has resulted in extreme drought especially for Colorado. In
contrast Indiana
had its wettest June-May on record. |
larger
image
|
March-May
Temperatures
larger
image
|
The graph to the left
shows seasonal mean temperature averaged across the contiguous
United States based on long-term data from the U.S. Historical
Climatology Network (USHCN). The 2002 value
is estimated from preliminary Climate Division data using the
first difference approach.
March-May 2002 ranked as the 45th warmest such period in the 1895
to present record. The preliminary nationally averaged temperature
was 51.9° F (11.1° C) which was 0.1° F (0.06° C)
above the long-term mean. The near-average national mean
temperature for this period belies significant regional variability
which is discussed below. The March-May temperature values
from 1895 through 2002 are available. |
| Warmer than
average temperatures covered much of the south while below
average temperatures occurred from Wisconsin to Washington state.
As is evident in the map to the right, much below average spring
temperature rankings occurred in North and South Dakota and
Montana. As can be seen by the spring 500mb
height and anomalies map, there were significant negative
anomalies over the northern tier of the country, corresponding to
the unusually cool surface temperatures. However, Alaska's
temperatures were above normal for the 3rd consecutive spring
and averaged 0.8°C (1.4°C) above the 1961-1990 mean for
March-May. Only 4 of the last 20 springs have averaged below the
mean. |
larger
image
|
March-May
Precipitation
larger
image
|
The March-May
precipitation was near average for the contiguous US, ranking as
47th
driest in the 1895-2002 record. However, as can be seen in the
map to left, there was considerable
regional variability. While many states in the central and
northeastern regions received above normal precipitation, much of
the west and southeast experienced continued
dryness during the spring. |
National
Temperatures - May
larger
image
|
The graph to the left
shows monthly mean temperature averaged across the contiguous
United States based on long-term data from the U.S. Historical
Climatology Network (USHCN). The value is
estimated from preliminary Climate Division data using the first difference approach. May 2002
ranked as the 42nd coldest May in the 1895 to present record, which
is slightly below average. The preliminary nationally averaged
temperature was 60.6° F (15.9° C) which was 0.5° F
(0.3° C) below the long-term mean. The May temperature values
from 1895 through 2002 are available. |
| This is the first May
since 1997 which has averaged below the long-term mean temperature.
The May Mean
500mb Height and Anomalies chart shows large negative anomalies
over Canada, spreading into the far northern states of the
contiguous United States. These height anomalies are associated
with below average temperatures in this region for the month. For
the spring
season, the pattern is similar with the addition of higher
positive anomalies over the southeastern quadrant of the country,
associated with greater warmth for the 3-month mean.
A more detailed analysis
including how statewide and regionwide temperatures compare to
other years is available.
|
larger
image
|
Temperature Departures
| The map to the right,
based on more than 500 airport stations, shows departures from the
1971-2000 normal temperatures for May 2002. The largest negative
temperature anomalies occurred around the Great Lakes and upper
Midwest, but significant cold anomalies (< -1.8° F[-1°
C]) occurred throughout the northern half of the country. The
southeast and southwest experienced warmer than average
temperatures, with the largest positive anomalies of 3.6° F
(5° C) or greater from south Texas to northeastern New
Mexico. |
larger
image
|
larger
image
|
Greater than normal
day-to-day temperature variability is particularly noticeable in a
band from the panhandle of Oklahoma to North Carolina, but above
normal variability can be seen across most of the eastern half of
the country. This is associated with the frequent passage of cold
fronts in this region as seen both by the cold temperature
departures in the map above and in an animated map of daily temperature
anomalies. |
National Precipitation
larger
image
|
The graph to the left
is a time series depicting precipitation averaged across the
nation. Based upon preliminary precipitation data, May 2002 was the
30th driest May on record. However, the month was characterized by
considerable regional variability as is evident in the map
below. |
Precipitation Anomalies
| The map to the right,
based on more than 500 airport stations, shows May 2002 total
precipitation as a percent of the 1971-2000 station normals. Above
normal precipitation generally occurred from Missouri to New York,
while the rest of the country was mostly dry. Especially dry were
the southwestern states, as well as the Gulf coast and eastern
Colorado to South Dakota. |
larger
image
|
