Like a nation pulled out of the fridge and briefly popped into a toaster oven, the contiguous United States was relatively cool on the inside and quite warm on the margins last month, according to the monthly U.S. climate roundup
released on Wednesday by NOAA’s National Centers for Environmental Information (NCEI). For the 48 states as a whole, it was a fairly moderate May, ranking as the 62nd coolest and 45th wettest in the past 122 years of recordkeeping. Temperatures reflected the influence of the fast-receding 2015-16 El Niño event, with relative coolness from the south central states into the mid-South and unusual warmth across the northern tier of states as well as California and Florida. None of the contiguous states had a top-ten coolest or warmest May, although Washington had its 11th warmest. Figure 1.
Statewide rankings for average temperature during May 2016, as compared to each May since 1895. Darker shades of orange indicate higher rankings for warmth, with 1 denoting the coldest month on record and 122 the warmest. Image credit: NOAA/NCEI
.A stunted temperature range for the Upper South and Mid-Atlantic
The month gets more interesting temperature-wise when you dig into the statewide average high and lows, where the general moistness of the atmosphere really plays out. Virginia is a striking example: the state’s average low temperature was the 38th mildest on record, but the average high temperature placed 7th coolest! The outcome was similar, if less dramatic, in neighboring states from South Carolina to Pennsylvania and New Jersey, all of which had cooler-than-average highs and warmer-than-average lows (see Figure 2 below).
It’s not surprising that Virginia led the pack in this tamped-down temperature range when you consider that the state had its 5th wettest May on record, as did Delaware (see Figure 3 below). Thick, low clouds are a surefire way to keep nights milder and days cooler, as they block sunlight by day and trap outgoing radiation from Earth at night that would otherwise cool the surface
. The sogginess was reflected in Washington, D.C., with a stretch from April 27 to May 23 in which rain fell on 23 out of 27 days, the capstone to what Capital Weather Gang's Jason Samenow called "a truly lackluster spring."
Many other U.S. states were wetter than average in May. The most noteworthy dry pocket was in Alabama and Mississippi, with relative dryness also prevailing from the Upper Midwest to New England.Figure 2.
Statewide rankings for average maximum temperature (left) and minimum temperature (right) during May 2016, with rankings depicted as in Figure 1 above. Image credit: NOAA/NCEI
Statewide rankings for average precipitation during May 2016, as compared to each May since 1895. Darker shades of green indicate higher rankings for moisture, with 1 denoting the driest month on record and 122 the wettest. Image credit: NOAA/NCEI
Average temperatures and long-term rankings for May 2016 in various communities across Alaska. Image credit: NWS/Alaska
.Alaska continues baking
After its warmest April on record, Alaska ended up with its second-warmest May, behind only the exceptional warmth of May 2015. At least five Alaskan communities had record monthly warmth in both April and May: Bethel, King Salmon, Kotzebue, St. Paul, and Talkeetna. Still on track for a very warm U.S. year
Boosted by the influence of El Niño atop sharply rising global temperatures, the contiguous U.S. remains on track for what could be one of the warmest years in U.S. weather history. The January-to-May period came in fourth behind 2012, 2000, and 2006, with a departure from the long-term Jan-to-May average of an impressive 3.21°F. Some noteworthy June heat has already played out in the far West: Phoenix hit 115°F on Saturday, its earliest such reading on record. The heat will be building across much of the central and eastern U.S. as we head toward the first day of summer (which will be June 20 this year, but June 21 during the rest of the 2010s
On the global scale, there’s an extremely good chance
that 2016 will beat out 2015 as the warmest year on record. We’ll see where that distressing competition stands next week when NOAA releases its monthly global climate report on Friday, June 17, after similar reports from NASA and other temperature-tracking agencies.
I'll be back with a new post by midday Thursday.