Fourth warmest May on record
The globe recorded its fourth warmest May on record, according to the National Climatic Data Center. The period January - May tied with 2003 as the sixth warmest such period on record. Global temperature records go back to 1880.
A warm and wet May for the U.S.
For the contiguous U.S., May temperatures were the 24th warmest in the 115-year record, according to the National Climatic Data Center. The Southeast region experienced its second wettest May in 115-years of record-keeping. In contrast, the West North Central region had their sixth driest May. Both Florida (9.86 inches) and Arkansas (10.91 inches) experienced their all-time wettest May. The last time Florida saw a record wet May was in 1976 when 9.15 inches of precipitation fell. Arkansas experienced its last record wet May in 1930 when 10.07 inches of precipitation fell. U.S. tornado activity was below average in May, according to NOAA's Storm Prediction Center.
On June 9, 2009, 14% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 19% figure observed at the beginning of the year. The amount of the U.S. in the highest levels of drought, extreme to exceptional, decreased from 2.6% on May 12 to 1.5% on June 9. These extreme drought regions were in South Texas.
El Niño watch issued
NOAA's Climate Prediction Center issued an El Niño Watch last week, saying "that conditions are favorable for a transition from neutral to El Niño conditions during June - August 2009". The pattern of changes in surface winds, upper-level winds, sea surface temperatures, and deeper water heat content are all consistent with what has been observed during previous developing El Niños. We are currently experiencing neutral conditions, with ocean temperatures in the Equatorial Eastern Pacific just 0.2°C below the threshold for El Niño. In the week since the El Niño watch was issued, ocean temperatures have remained nearly steady in the Eastern Pacific, so we are not rushing into an El Niño just yet. As discussed in detail in an earlier blog post, most of our more advanced El Niño computer models are predicting a weak El Niño event for the coming Atlantic hurricane season. If this indeed occurs, it is likely that Atlantic hurricane activity will be suppressed due to the strong upper-level winds an El Niño usually brings to the tropical Atlantic, creating high wind shear that tears hurricanes apart.
Sea ice extent in the Arctic near average during May
May 2009 Northern Hemisphere sea ice extent was near average in May, coming in at 15th lowest (16th highest) since 1979, according to the National Snow and Ice Data Center. The record May low was set in 2004. The rate of ice decline in May accelerated, and by the end of the month the decline rate was equal to last year's rate. Warmer than usual temperatures over the Arctic during May contributed to this acceleration. The Arctic remains vulnerable to near-record melting this summer if much warmer than average temperatures occur over the region, since the ice is at record thinness this summer. Thin ice requires less energy to melt, and it also tends to be more fractured, with increased open water amid the ice. Since water absorbs more sunlight than ice, heat from the sun can more rapidly melt this fractured ice.