weather, weather safety/preparedness

Enhanced severe weather threat for southeast U.S. (H. Michael Mogil, CCM, CBM, NWA-DS*)

Batten down the hatches (and be prepared to take shelter today and tonight) if you live or are traveling across the southeast U.S. The Storm Prediction has issued a highly unusual severe weather outlook for the region – calling for a moderate to high severe weather risk for South Carolina, Georgia, a small part of southeast Alabama and much of northern and

central Florida (Fig. 1). According to news reports, the storm system behind today’s severe weather threat has already claimed the lives of at least six people across Mississippi and Georgia.

Fig. 2 and Fig. 3 show the radar and satellite images, respectively, late this Sunday morning. What is most telling is that the current strong thunderstorm activity is occurring in a region of dry air aloft (the oranges and blacks on the water vapor satellite image – Fig. 3). This means that rising air

inside the thunderstorms must be moving at very high velocity to counter this dryness. Hence, many of the stronger thunderstorms are already likely acting as “supercells (isolated storms ahead of a line of storms).” Two apparent supercells can be seen in the northern Gulf of Mexico (Fig. 2).

As a new low-pressure system develops across the southeast today, and moves to northern Georgia and eastern Tennessee by tonight,

(Fig. 4), a very strong jet stream aloft (winds greater than 130 miles per hour) and a very warm and unstable air mass (dew points above 70 degrees F) will all be factoring into the storm evolution as the day and night progress.

The local storm potential graphic (Fig. 5) indicates just how strong the storms may be, even removed from the main threat region.

As the newly forming low develops, it will move to the northeast and spread a large shield of rain along the entire east coast during the next several days. Except for parts of New England, the atmosphere is just too warm for snow.

Although winds will be strong across the southeast today, coastal wave action, higher than average tides,

rip current danger and other coastal and boating dangers (including offshore gale warnings in the Gulf of Mexico) will be the watchwords across the west coast of the Florida peninsula into the Gulf beginning tonight and continuing until Tuesday (Fig. 6). That is because strong west and northwest winds will arrive once the cold front clears the area (Fig. 4).

Although skies may be sunny to partly cloudy across much of the Florida peninsula now, conditions will rapidly deteriorate during the latter part of the calendar day and early Monday morning.

Stay tuned to the National Weather Service, local broadcast media outlets and any tailored private weather subscriptions you may have for watches, warnings and advisories.

If you have loose objects outdoors, consider bringing these inside before the storms arrive.

© 2017 H. Michael Mogil

Originally posted 1/22/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.