U.S. has its 23rd coolest April; 16 tornadoes confirmed from Texas outbreak

It was an unusually cool April over much of the U.S. during April 2013, said NOAA's National Climatic Data Center (NCDC) in their latest State of the Climate report. It was the coolest April since 1997, and ranked as the 23rd coolest April in the 119-year record for the contiguous U.S., putting the month in the coldest 20% of all Aprils on record. North Dakota had its coldest April on record, and six additional states--South Dakota, Nebraska, Kansas, Oklahoma, Minnesota, and Wisconsin--had top-ten coldest Aprils on record. No state recorded a top-ten warmest April. Over three times as many record cold highs and lows occurred than record warm highs and lows during April. For the year-to-date period January - April, both temperatures and precipitation over the contiguous U.S. have been near average.

According to NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought, April extremes were near average, and the year 2013 has been slightly below average for extremes. The CEI during January - April 2013 was 18.5%, and on average, about 19.5% of the contiguous U.S. experiences top-10% extreme weather as defined by the CEI.


Figure 1. Historical temperature ranking for the U.S. for April 2013. North Dakota had its coldest April on record, and six additional states--South Dakota, Nebraska, Kansas, Oklahoma, Minnesota, and Wisconsin--had top-ten coldest Aprils on record. No state recorded a top-ten warmest April. Image credit: National Climatic Data Center (NCDC).


Figure 2. Historical precipitation ranking for the U.S. for April 2013. Iowa and Michigan both had their wettest April on record, and Tennessee, Illinois, Indiana, and Wisconsin each had one of the ten wettest Aprils on record. Connecticut had a top-ten driest April. Image credit: National Climatic Data Center (NCDC).

Iowa and Michigan record their wettest Aprils
It was a very April for the continuous U.S., ranking as the 19th wettest April since 1895. Iowa and Michigan both had their wettest April on record, and Tennessee, Illinois, Indiana, and Wisconsin each had one of the ten wettest Aprils on record. The heavy precipitation in the watershed of Lake Huron and Lake Michigan caused those lakes to rise 9.8", one of the largest monthly rises on record. These lakes were at their all-time lowest water levels on record in January 2013. Drought conditions improved across the Southeast, Midwest, and along the northern and eastern periphery of the core drought areas of the Great Plains during April, but worsened for parts of the Southwest. According to the May 16 Drought Monitor report, about 48% of the U.S. is still in moderate or greater drought, down from 52% at the beginning of April. Improvement in drought conditions is expected from Northern Texas to South Dakota during May and June, but drought is expected to spread into Oregon and Idaho.

According to data from the Rutgers Global Snow Lab, the March snow cover extent for the contiguous U.S. was the 6th largest April snow cover extent in the 47-year period of record. However, snowpack, an important water resource in the West, was dismal in part of the West, with only 18 percent of normal snowpack reported in the Sierra Nevada Mountains.


Figure 3. This image of Texas taken by the GOES East satellite at 0045Z on May 16, 2013 shows the vicinity around Granbury, TX approximately 21 minutes before an EF-4 tornado hit Granbury, Texas. Image credit: NOAA Viz Lab.

Sixteen tornadoes confirmed from Texas tornado outbreak
Sixteen tornadoes have now been confirmed from Wednesday night's tornado event in Texas (fifteen on the 15th, and one just after midnight on the 16th.) The most powerful tornado was an EF-4 with 166 - 200 mph winds that tore through Granbury, killing six and leaving seven missing. The outbreak also had a huge EF-3 tornado, 3/5 of a mile wide, that hit Cleburne, causing extensive damage and a state of emergency. The fifteen tornadoes from May 15 make it the biggest day for tornadoes in the U.S. this spring, and the highest number reported in one day since January 30, when 44 tornadoes touched down from Georgia to Indiana. The data we have on the May 15 - 16 tornadoes so far:

Wednesday, May 15, 2013:
1739 CDT  1 W Belcherville, Montague Co TX - EF?, spotter
???? CDT  Nocona Lake, Montague Co - EF?, photos
1835? CDT Millsap, Parker Co TX - EF-1, 100 mph; 5 homes significantly damaged
1841 CDT  3.5 SSE Mineral Wells, Palo Pinto Co TX - EF-0; brief; 4 NW Millsap
???? CDT  West of Annetta South, Parker Co TX - EF?, brief, from Millsap storm
???? CDT  NW Cresson, Hood Co TX - EF? - determined to be in southern Parker Co
1859 CDT  Sunset, Montague Co TX - EF-1, 100 mph, 1 injured, near Hwy 287; 5 homes damaged south of Lake Amon G. Carter, one of them destroyed
1900? CDT Mills Co TX - EF?, spotters
1922 CDT  3 E Millsap, Parker Co TX - EF-0; brief; photograph
???? CDT  Alvord, Wise Co TX - EF?, public and spotter reports
2006 CDT  Granbury, Hood Co TX - EF-4, 6 killed, dozens injured; only foundations left in places; 200 homes damaged/destroyed; 5 dozen of them Habitat for Humanity. First EF-4 in DFW area since the Lancaster tornado in 1994
2006 CDT  6 SE Granbury, Hood Co TX - EF-1, 90-100 mph; near Pecan Plantation; separate path from Granbury tornado
2130 CDT  Cleburne, Johnson Co TX - EF-3, 140 mph, 8.5 mi path, 1060 yds wide
2142 CDT  6 ESE Cleburne, Johnson Co TX - EF-0, 85 mph; separate from Cleburne tornado
2257? CDT North of Evant, Hamilton Co TX - EF?, brief; #1 of two that occurred simultaneously
2257? CDT North of Evant, Hamilton Co TX - EF?, brief; #2 of two that occurred simultaneously

Thursday, May 16, 2013:
0010 CDT  Ennis, Ellis Co TX - EF1, 90 mph, 6 mi path; significant damage in Ennis; began west of I-45 and crossed I-45 south of Ennis Ave

The latest forecasts from NOAA's Storm Prediction Center call for an active severe weather pattern Saturday - Tuesday. The threat will be highest on Sunday and Monday, when conditions may align to bring about a classic spring severe weather outbreak, as a powerful spring weather system gathers strength over the center of the country.

Saturday's main threat areas: northwest KS, southwest NE
Sunday : east SD, east NE, east half KS, central OK, northwest MO, west and central IA, south half MN.
Monday : central OK, east IA, northwest IL

Jeff Masters