Tropical Storm Sally Forms, Forecast To Become A Hurricane On Monday

Tropical Storm Sally has formed off the south Florida coast and its forecast to make landfall on the U.S. Central Gulf Coast as a powerful hurricane. This depression could become a tropical storm tonight or later this weekend as it moves across the state of Florida.

This is the nineteenth tropical cyclone of the 2020 Atlantic Hurricane Season and the earliest 18th named storm in Atlantic history. The previous record was Stan, which formed on October 2nd, 2005.

This tropical cyclone is not forecast to impact Trinidad, Tobago, or the Lesser Antilles.

List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Teddy.
List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Teddy.

At 5:00 PM AST, the center of Tropical Storm Sally

Tropical Storm Sally Forecast Track as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)
Tropical Storm Sally Forecast Track as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)

Watches & Warnings

Tropical Storm Sally Watches and Warnings as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)
Tropical Storm Sally Watches and Warnings as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)

A Storm Surge Watch is in effect for:

  • Mouth of the Mississippi River to the Alabama/Florida Border
  • Lake Pontchartrain, Lake Maurepas, and Lake Borgne
  • Mobile Bay

A Hurricane Watch is in effect for:

  • Grand Isle Louisiana to the Alabama/Florida border
  • Lake Pontchartrain and Lake Maurepas including metropolitan New
    Orleans

A Tropical Storm Watch is in effect for:

  • Alabama/Florida Border to Ochlockonee River Florida

A Storm Surge Watch means there is a possibility of life-threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area within the next 48 hours.

Hazards Affecting Land

Tropical Storm Sally Storm Surge forecast as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)
Tropical Storm Sally Storm Surge forecast as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide:

  • Mouth of the Mississippi River to Ocean Springs, MS including Lake Borgne: 6-9 ft
  • Ocean Springs, MS to MS/AL Border: 4-6 ft
  • MS/AL Border to AL/FL Border, including Mobile Bay: 2-4 ft
  • Lake Pontchartrain and Lake Maurepas: 2-4 ft
  • AL/FL Border to Chassahowitzka, FL, including Pensacola Bay, Choctawhatchee Bay, and Saint Andrew Bay…1-3 ft

The deepest water will occur along the immediate coast near and to the right of the landfall location, where large and damaging waves will accompany the surge. Surge-related flooding depends on the relative timing of the surge and the tidal cycle and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

Tropical Storm Sally probabilities for tropical-storm-force winds as of 5:00 PM AST Saturday 12th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)
Tropical Storm Sally probabilities for tropical-storm-force winds as of 5:00 PM AST Saturday 12th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

WIND: Hurricane conditions are possible within the hurricane watch area by early Tuesday, with tropical storm conditions possible within the watch area by Monday.

Wind gusts to tropical-storm-force are possible across the southern portion of the Florida peninsula through this evening, especially over the Florida Keys.

Tropical Storm Sally rainfall forecast as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)
Tropical Storm Sally rainfall forecast as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)

RAINFALL: Sally is expected to produce additional rainfall amounts of 2 to 4 inches over southern Florida and the Florida Keys through tonight. Rainfall amounts of 2 to 4 inches with isolated amounts of 6 inches are expected along the west coast of Florida through Sunday. This rainfall will produce flash and urban flooding across southern Florida and prolong high flows and ongoing minor flooding on rivers across central Florida.

Sally is expected to produce rainfall amounts of 5 to 10 inches across the Florida Panhandle, and 6 to 12 inches with isolated amounts of 18 inches over the Central Gulf Coast from Sunday into the middle of next week. Sally is expected to be a slow-moving system that will continue to produce heavy rainfall and considerable flooding near the central Gulf Coast through the middle of next week. Flash, urban, and rapid onset flooding along small streams and minor to moderate flooding on rivers is likely.

SURF: Swells are expected to spread northward along the west-central coast of Florida and reach the Florida Panhandle and the northern Gulf Coast during the next couple of days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

TORNADOES: A tornado or two is possible through tonight over south Florida.

This system is of no direct threat to the Windward Islands, including Trinidad and Tobago.

Tropical Storm Sally Forecast Discussion

Tropical Storm Sally south of Florida (Weathernerds)
Tropical Storm Sally south of Florida (Weathernerds)

Sally continues to gradually become better organized, with developing convective banding features primarily over the southern portion of the circulation at this time. Upper-level outflow is still rather limited over the northern semicircle, possibly due to a weak upper low near the Georgia/Florida border. The latter feature is likely to move away from the area soon, however. Based on earlier scatterometer passes that showed tropical-storm-force winds over the Straits of Florida, the advisory intensity remains 35 kt. With very warm waters and a moist tropospheric environment ahead of Sally, strengthening seems likely. Some increase in westerly shear over the northern Gulf in 48-72 hours could at least slow down the intensification process around that time. The official intensity forecast is not far from the latest model consensus and a little above the previous forecast.

Fixes from an Air Force Hurricane Hurricane aircraft, radar, satellite, and surface observations indicate a slow, generally westward motion of about 280/6 kt. A weakening mid-level high-pressure system to the northeast of Sally should cause a generally west-northwestward to northwestward motion for the next few days. Because of the weakening steering currents, the cyclone should move rather slowly while it approaches the northern Gulf Coast. However, there is expected to be enough of a narrow north-south oriented ridge to the east of Sally in 3-4 days to steer the cyclone northward across the coast. The official track forecast has been nudged just slightly west of the previous one and lies between the simple and corrected dynamical track model consensus predictions.

Users are reminded to not focus on the exact details of the track or intensity forecast as the average NHC track error at 96 h is around 150 miles, and the average intensity error is around 15 mph. In addition, winds, storm surge, and rainfall hazards will extend far from the center.

Key messages for Tropical Storm Sally (National Hurricane Center)
Key messages for Tropical Storm Sally (National Hurricane Center)

Key Messages:

  1. Life threatening storm surge is possible along the Gulf Coast beginning on Monday, and a Storm Surge Watch is in effect for areas outside the southeast Louisiana Hurricane and Storm Damage Risk Reduction System from the Mouth of the Mississippi River to the Alabama/Florida border. Residents in these areas should follow any advice given by local officials.
  2. Hurricane conditions are possible by early Tuesday from Grand Isle, Louisiana to the Alabama/Florida border, including Metropolitan New Orleans, with tropical storm conditions possible by Monday.
  3. Sally is expected to produce flash flooding across portions of southern Florida and prolong existing minor river flooding across central Florida through Sunday. Flash, urban, and minor to moderate river flooding is likely across portions of the central Gulf Coast from Sunday through the middle of next week.
  4. Tropical storm conditions are possible early next week in portions of the Florida Panhandle, where a Tropical Storm Watch is in effect. Wind gusts to tropical-storm-force could occur over portions of the southern Florida Peninsula and the Florida Keys this evening.

Forecast Discussion by Forecaster Pasch from the NHC.

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