U.S. Reeling From Violent Tornadoes, Epic Flooding, Winter Weather, and Weird Heat
By: Bob Henson and Jeff Masters , 10:54 PM GMT on December 28, 2015
Wild weather continued to plaster the nation’s midsection on Monday as a multi-barreled storm system shifted eastward. Thankfully, the severe weather threat has ramped down somewhat, with the highest risks now shifting to river and flash floods--from eastern Oklahoma to the Appalachians--and snow and ice, from Nebraska to New England. More than 40 weather-related deaths have been reported since Wednesday. The storminess is related to a gradual realignment of the large-scale pattern over North America, as described in detail by wunderblogger Steve Gregory in his Monday afternoon post. A stunningly warm, moist air mass across the eastern and southern U.S.--by some measures the most tropical on record for early winter--is in the process of being displaced by a strong upper-level storm moving into the central states, bringing much more seasonable cold.
North Texas cleans up from Saturday’s deadly tornadoes
Ahead of a strong cold front in west Texas, supercell thunderstorms that ripped across the sprawling eastern part of the Dallas area spawned several tornadoes that killed at least 11 people. One violent tornado that killed eight people in Garland was rated EF4, while “at least EF3” damage was found in Rowlett, just east of Garland, due to the same tornado or one that closely followed. Two people died in Copeland, about 15 miles to the northeast, where EF2 damage was documented. Several other weaker tornadoes struck North Texas. According to the Dallas Morning News, as many as 1000 structures were damaged across north Texas, many of them severely. The storms were fed by a very strong upper-level jet as well as unusually high instability for December (around 3000 joules per kilogram, which would be concerning in springtime, much less wintertime). Temperatures reached 80°F in Dallas just hours before the tornadic supercell arrived, with a summerlike dew point of 67°F.
The widespread persistence of warm, humid conditions over the last few days has led to an unusual U.S. stretch of severe weather for December, including tornadoes from Mississippi to Michigan on Wednesday. The EF1 tornado that touched down in Canton, Michigan on December 23 was Michigan's first December tornado on record. If tornadoes are confirmed on Monday, it will be the sixth calendar day in a row with at least one U.S. tornado reported, tying a monthly record set on December 22-27, 1982, during the “super El Niño” of 1982-83. (The streak would be even longer if we counted early-morning tornadoes on December 23 as part of the December 22 “tornado day”, per NOAA recordkeeping.) Another tragic milestone: 2015 is the first year in records going back to 1875 that has seen more confirmed tornado-related deaths in December than in the rest of the year combined. The only other year with December having more deaths than any other single month was 1931, according to statistics analyzed by Harold Brooks (NOAA National Severe Storms Laboratory).
A historic flood is building on the Mississippi River
The updated flood forecasts for the Mississippi River issued Monday afternoon by NWS River Forecast Center are about two feet higher than the forecasts issued on Sunday. Nearly all of the Lower Mississippi is expected to enter major flood stage over the next few weeks, as are the lower portions of two main tributaries, the Ohio and Arkansas Rivers. The Mississippi River near St. Louis was already near flood stage late last week due to excessive rains of 2 - 4" (400 - 600% of average) that fell during the past two weeks farther upstream in Iowa, Wisconsin, and Minnesota. A massive pulse of flood waters from the epic December 26 - 28 rains will pile into the Mississippi River over the next few days, bringing the river to flood levels that will be the highest on record outside of the usual spring to early summer flood season. The Mississippi River at St. Louis was at moderate flood stage on Monday afternoon, and is forecast to crest on Wednesday at the second highest level ever observed, just five feet below the all-time record set during the disastrous flood of 1993. Flood records at this location extend back to 1785. Downstream from St. Louis, the Mississippi River is forecast to crest late this week in Chester, Cape Girardeau, and Thebes at the highest levels ever recorded. NOAA warns that at the flood levels expected, the Degognia, Fountain Bluff, Stringtown, and Prairie DuRocher levees will be overtopped near Chester. NOAA projects that the massive flood crest will propagate downstream to the Gulf of Mexico during the first three weeks of January, bringing flood heights that are expected to be between the 2nd highest and 4th highest on record all the way to Louisiana.
more
http://www.wunderground.com/blog/JeffMasters/us-reeling-from-violent-tornadoes-epic-flooding-winter-weather-an
