Hurricane Zeta and Inland Effects

Visible satellite 151 pm CDT
NEXRAD Doppler Radar 215 pm CDT

Latest reports from USAF Hurricane Hunter Aircraft, and Doppler radar imagery (right, above) indicate that Hurricane Zeta continues to intensify, even over the cooler continental shelf waters of the northern Gulf, this afternoon. Central pressure has dropped to 973 mb, and max sustained surface winds are up to 105 mph. Radar is picking up winds up to 131 mph, but that fat out the radar beam is around 11,000 feet altitude. The center is only 80 miles SW of Grand Isle, LA, and given its fast movement of 20 mph, the center will be onshore by 430 pm, and eyewall hurricane winds before that. Hurricane-force wind gusts will affect New Orleans between 5 pm and 10 pm CDT, and the Mississippi Gulf Coast between 6 pm and midnight.

Given the rapid movement of the storm and its rapid intensification over the past 24 hours, it hasn’t had time to build up as much storm surge as other storms earlier this season. However, as shown below, many areas along the Gulf Coast, including the LA delta, Gulfport, Biloxi, Pascagoula, and Dauphin Island, may see water 3 feet or more above ground level.

NOAA storm surge inundation forecast

As the storm makes landfall early this evening, hurricane-force wind gusts will affect areas from Southeast Louisiana across SE Mississippi and SW Alabama. The storm will continue to accelerate rapidly northeast, as an intense upper-level storm system, associated with the cold air and ice storm over Oklahoma the past 2 days, pushes the storm.

500 mb flow, pivotalweather.com
NHC official forecast track

Given the very dynamic storm system to the west, Hurricane Zeta will accelerate through the night, reaching forward speeds of 35 to 40 mph as it moves inland across southeast Mississippi and then Alabama. The center of the storm will be near Meridian, MS by 10 pm CDT, near Birmingham, AL by 3 am CDT, and near Chattanooga, TN by 7 am CDT. Given the extremely rapid movement, the storm will not have time to weaken below tropical storm strength until it gets to Tennessee. So, large parts of southern Alabama could see wind gusts of 50 to 65 mph, and even areas in northern Alabama, including Birmingham, Tuscaloosa, and Gadsden, could see wind gusts of 50 mph late tonight and early Thursday morning. This wind will likely cause power outages and lots of downed trees from southeast Mississippi into Alabama. The National Weather Service has issued a Tropical Storm Warning for most of Alabama for tonight, and they have issued a map showing the likely maximum winds and arrival times of the highest winds. Both shown below.

NWS Tropical Storm Warning (left, red) and max expected wind gusts (right)

Fortunately, the rapid movement means there is a low probability for widespread flooding due to rainfall, as it simply won’t rain that long. Some areas in SE Mississippi could get 3-5″ of rain, and most areas in Alabama will get 1-2″ of additional rain from the storm.

NOAA WPC 72-hour rainfall

It is quite unusual to see a Categrory 2 hurricane make landfall this late in the season, but it has been an active year for hurricanes in the western Gulf. Given that the days are shorter, the sun angle lower, and the northern latitudes are already cooling down rapidly, this allows this storm to interact with the vigorous winter-like storm system over the Plains and move so rapidly. Behind the hurricane, temperatures will drop into the 30s and 40s over Mississippi, Alabama, and Georgia by Friday night, and even colder air is on the way for early next week.

Dr. Timothy A. Coleman

Consulting Meteorologist

Coleman and Knupp, LLC

http://www.colemanandknupp.com

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