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NHC: Historic Flooding Possible in Florida Panhandle from Sally

September 15, 2020

Days of heavy rain may lead to historic flooding over parts of the central Gulf coast, including the western Florida Panhandle.

The National Hurricane Center said extreme life-threatening flash flooding is likely through Wednesday in their early morning advisory. As of the its midday update Tuesday, maximum sustained winds were near 85 mph. It is moving slowly toward the northwest at 2 mph.

30 MPH
1000 MB

1. Widespread flooding is expected from central Georgia through southeastern Virginia. Along the central Gulf Coast, most widespread moderate to major river flooding from the historic rainfall event will crest by the weekend, but rivers will remain elevated well into next week.

There are no coastal watches or warnings in effect.

Key messages for Sally can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml

RAINFALL: Rainfall totals expected as Sally moves across the Southeast U.S. through Friday: Central Georgia: Sally will produce additional rainfall totals of 3 to 6 inches, with localized higher amounts, on top of 3 to 6 inches which has already fallen. Widespread flash flooding and minor to moderate river flooding is likely. Central to upstate South Carolina: 3 to 6 inches, with isolated amounts of 10 inches. Widespread flash flooding and minor to moderate river flooding is likely. Western to central North Carolina into southcentral and southeast Virginia: 4 to 6 inches, isolated amounts up to 8 inches. Flash flooding and widespread minor river flooding is likely.

STORM SURGE: Water levels will continue to recede through the day today.

TORNADOES: A couple of tornadoes may occur early this morning across southern Georgia and northern Florida. The threat of tornadoes will shift northeastward into eastern Georgia and much of the Carolinas today and tonight.

SURF: Swells from Sally will continue to affect the Gulf Coast from the Florida Big Bend westward to southeastern Louisiana through today. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 400 AM CDT (0900 UTC), the center of Tropical Depression Sally was located near latitude 31.8 North, longitude 85.7 West. The depression is moving toward the northeast near 12 mph (19 km/h), and a northeastward to eastnortheastward motion is expected into Friday. On the forecast track, the center of Sally will move across southeastern Alabama this morning, over central Georgia this afternoon and evening, and move over South Carolina late tonight into Friday.

Maximum sustained winds have decreased to near 30 mph (45 km/h) with higher gusts. Additional weakening is forecast during the next couple of days, and Sally is expected to become a remnant low by tonight or Friday morning.

The estimated minimum central pressure based on nearby surface observations is 1000 mb (29.53 inches).

Although the overall convective cloud and rain shield in satellite and radar imagery continues to erode, Tropical Depression Sally is still producing significant rainfall across east-central Alabama and west-central and central Georgia. Surface observations and Doppler radar data indicate that Sally has weakened to a 25-kt depression over southeastern Alabama. Sally will continue to weaken, and fairly rapidly at that, due to increasing friction and loss of convection owing to very hostile westerly to southwesterly vertical wind shear in excess of 40 kt. Sally will likely degenerate into a remnant low pressure system by tonight or early Friday, and merge with a frontal system over North Carolina by Friday evening.

Sally is moving northeastward or 055/10 kt. A northeastward to east-northeastward motion will continue for the next 36 hours or so as the cyclone moves ahead of a broad deep-layer trough over the northeastern United States. The official track forecast is downthe middle of the tightly packed NHC model guidance suite, and lies close to the previous advisory track and the consensus model HCCA.This is the last NHC advisory on Sally. Future information on this system, including the rainfall threat, can be found in Public Advisories issued by the Weather Prediction Center beginning at 10 AM CDT, under AWIPS header TCPAT3, WMO header WTNT34 KWNH, and on the web at http://www.wpc.ncep.noaa.gov

Rain bands from the storm are already onshore. The strongest bands were a few miles offshore and are expected to move inland Tuesday afternoon through Wednesday. Coastal Hurricane Warnings are in effect from Navarre westward. Coastal Tropical Storm Warnings were in effect east of Navarre to just west of St George Island. Hurricane Warnings were also in effect inland for Escambia and Santa Rosa counties, and a Tropical Storm Warning was in effect for inland Okaloosa county.

Sally is forecast to make landfall on Wednesday as a category 1 hurricane between Biloxi and Pensacola, but Sally’s slow movement means water, not wind, will be the primary hazard from the storm.

Storm Surge Warnings are in effect from the Okaloosa/Walton county line and westward. The official forecast from the National Hurricane Center is projecting surge of 2 to 4 feet of water above normally dry ground, particularly in northern Escambia Bay near the Escambia and White Rivers; in Blackwater Bay near the Yellow and Weaver Rivers; and near the Blackwater River in Santa Rosa county. Other areas of surge are likely along the barrier islands in places from Perdido Key to Pensacola Beach to Santa Rosa and Okaloosa islands. Peak surges of 1 to 3 feet are possible eastward toward Panama City, Apalachee Bay, and the Big Bend coastline. High surf and dangerous rip currents are expected to pose a danger to swimmers, as well.

Three-day rainfall forecast from Sally (beginning Monday)

Rainfall amounts of 10 to 20 inches are anticipated in Escambia, Oklaoosa, and Santa Rosa counties, with isolated amounts up to 30 inches possible. These amounts were expected to lead to widespread and potentially historic flash flooding in some areas, forecasters said. Amounts of 5 to 10 inches are possible for the Panama City to Marianna areas. The Tallahassee to Apalachicola area was expecting 2 to 5 inches of rain through Thursday. Flash Flood Watches are in effect for much of the panhandle.

NOAA’s Storm Prediction Center said a couple of tornadoes may occur Tuesday and Wednesday over the Florida Panhandle associated with Sally’s rainbands. The center issued a Tornado Watch, mainly for the Apalachicola River and westward until 6 PM Tuesday. Oftentimes, tornado watches are extended in slow-moving storms like Sally when the tornado threat is likely to continue past the expiration time.

Sally is expected to merge with a cold front and move off the Carolina coast on Friday. Slightly drier air is likely over the Panhandle this weekend, but the cold front may produce areas of rain over the Florida peninsula this weekend even after Sally’s departure.

Expires at 10:00pm on Tuesday September 15th, 2020

Sources include nearest National Weather Service office, National Hurricane Center, and the Florida Public Radio Emergency Network (@FloridaStorms).
Sources include nearby emergency management agencies, FEMA, and your local NPR affiliate. 
Sources include the Florida Department of Transportation, Florida Highway Patrol and other nearby traffic information.

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