Elevated Tornado Risk Sunday Night, Storms Continue Monday
Sunday started on an active note, with hail reports and a deluge of rain across the South and Southeast. Through the rest of the evening, strong storms are likely to continue and could even put down a tornado or two near the Gulf Coast.
Active Sunday Evening. The Storm Prediction Center has highlighted a threat zone for severe weather tonight that encompasses eastern Texas, all of Louisiana, and portions of Mississippi, Alabama, and Florida. Expect showers and thunderstorms to continue to fire throughout this area with a handful of cells becoming severe.
Recipe For Severe Weather. Conditions are ripe for strong thunderstorms to develop Sunday night. A few factors that play into storm intensification are instability, wind shear, and synoptic forcing — all of those happen to be present this evening. The map above shows an elevated amount of “storm energy” available in the atmosphere along the Gulf Coast later tonight. This is called “CAPE” or Convective Available Potential Energy. “CAPE” is effectively the positive buoyancy of an air parcel and is an indicator of atmospheric instability, which makes it very valuable in predicting severe weather. Read more about it here: http://en.wikipedia.org/wiki/Convective_available_potential_energy
In addition to CAPE, we also have wind shear to aid in vertical storm growth. Wind shear is simply differing wind direction and/or speed between different layers of the atmosphere. The map below shows the surface wind arrows along with the upper level wind arrows — turning clockwise (or “veering”) as the height increases. This aids in vertical development within the storms which also increases their strength.
Now that we have favorable conditions for storm development, we need a spark to set it all off and start the storm growth. This forcing mechanism is our cold front, which will be dragging across the Gulf Coast through tonight and into Monday evening. Dewpoints are high to the east of the front, which adds to the instability in the atmosphere. See map below:
West of the front, the air is cooler and drier, and will sink low down to the surface. The cold front itself will wedge its way into the warm, moist air, forcing it to go up and over. This vertical motion will help force thunderstorms to form and strengthen through the evening. See image below (via the National Weather Service):
Elevated Tornado Risk. With all these components coming together, the Storm Prediction Center has highlighted an area of elevated tornadic risk here in yellow. This means that atmospheric conditions are favorable for tornadoes, and there’s potential for some strong ones to form. Please heed all watches and warnings and take these storms seriously!
Continued Thunder. The cold frontal boundary takes its time moving east, so we also extend the severe weather threat into northern Florida and the Atlantic coast for Monday. Central Florida bears the brunt of the showers on Tuesday, but by then the storms should be running out of steam and general rain & thunder are the only worry.
Weather At Your Fingertips. We have a great interactive severe weather map here on our website that you can follow for all of the latest watches and warnings. Keep your NOAA Weather Radio handy for overnight storms and tune in to WeatherNation for your full forecast. Stay safe out there! -Meteorologist Miranda Hilgers (@mhilgersWNTV)