April in January: spring-like severe weather and record warmth in the Midwest
Posted by: Dr. Jeff Masters, 03:19 PM GMT em 29 de Janeiro de 2013
The calendar says its January, but the atmosphere looks more like April over the Midwest U.S., where a spring-like surge of warm air is interacting with a strong low pressure system to create a dangerous severe weather situation. The warm air surging northwards has already broken high temperature records for the date in Chicago, where the mercury hit 61°F at 7 am CST; a tornado watch is posted for portions of Texas, Oklahoma, Kansas, and Arkansas. Golf-ball sized hail fell at three locations in Oklahoma already this morning, and a wind gust of 75 mph was reported in a thunderstorm near Omega, Oklahoma. NOAA's Storm Prediction Center has placed portions of Arkansas, Louisiana, Mississippi, Tennessee, Missouri, and Texas in their "Moderate Risk" region for severe weather on Tuesday. This is the first "Moderate Risk" forecast issued during 2013. The primary threat will be damaging thunderstorm winds, but we will also see tornadoes, with the potential for a few strong EF-2 and EF-3 twisters. The surge of warm moving northwards ahead of the cold front spawning today's severe weather is bringing in warmth unprecedented for January in some locations. Monday was the hottest January day on record in Topeka, Kansas, which hit 77°F. That's 36°F above average. and 3° warmer than their previous highest January temperature. Columbia, Missouri tied its all-time warmest January temperature, 77°. Kansas City (74°F) and Wichita (74°F) both fell 1° short of tying their all-time January hottest temperature records. Balloon soundings of the atmosphere taken last night showed moisture levels in the top 5% for a January day over much of the Midwest, and several stations may set all-time rainiest January day records today. One candidate is Flint Michigan, where a heavy thunderstorm moved in at 7:30 am, dumping 0.75" of rain. With another round of thunderstorms expected tonight, Flint is poised to break its record for rainiest January day in its history--the 1.34" that fell on January 18, 1949.
Figure 1. A crazy weather day for the U.S.: our severe weather map from 10 am EST Tuesday, January 29. Severe thunderstorms were occurring in Kansas and Oklahoma, flood watches were posted for Illinois, Michigan, Indiana, Ohio, and Wisconsin, and winter weather advisories, high wind advisories, and fire weather advisories were posted in other locations.
Figure 2. NOAA's Storm Prediction Center has placed portions of Arkansas, Louisiana, and Mississippi in their "Moderate Risk" region for severe weather on Tuesday. This is the first "Moderate Risk" forecast issued during 2013.
Chicago's wild January weather ride continues
Chicago's craziest January in memory got even stranger today, when a surge of warm air pushed the temperature to 61°F at 7 am, breaking the previous high temperature record of 59°F for the date. Spring-like thunderstorms, accompanied by temperatures in the mid-60s are expected this afternoon--just a week after the city recorded a high temperature of 11°F and a low of -1°F (on January 22nd.) Chicago has been above 65°F in January just once in its history--on January 25, 1950, when the mercury hit 67°F. The average January high in the Windy City is 30°F, and today will be the 4th day the city has been 20 or more degrees warmer than that during January 2013. The roller coaster goes back downhill after the cold front moves through early on Wednesday, though--Chicago's high on Friday is expected to be near 15°F, with a morning low around 5°F. Chicago has also experienced record low snowfall this winter; the city got it's first 1-inch snowstorm of the season on Friday, when 1.1" fell at O'Hare Airport. This was the latest first 1-inch snow in city history, and ended a 335-day streak without a 1-inch snowstorm, the longest such streak since records began in 1872. Chicago has managed just 2.9" of snow during the winter of 2012 - 2013, which is 16" below average.
Chicago's roller coaster of temperatures doesn't compare, though, to what happened in Nowata, Oklahoma during the period February 10 - 17, 2011. A cold air mass combined with a fresh snow pack and calm winds allowed Nowata to hit a low of -31°F on February 10, 2011--the all-time coldest temperature ever recorded in Oklahoma. Gradual warming accelerated over the next week, and temperatures peaked at a record high of 79 degrees on February 17. According to the National Weather Service in Tulsa, Okla., this 110-degree temperature rise was the greatest change within seven days in Oklahoma history.
[link to www.wunderground.com