[Updated] Tropical Storm Sally Rapidly Strengthens Into A Hurricane

12:00 PM Update – Data from a NOAA Hurricane Hunter aircraft investigating Sally indicate the system has rapidly strengthened to a hurricane, with maximum sustained winds of around 85 mph (140 km/h) with higher gusts. The estimated minimum central pressure is 985 millibars.

Tropical Storm Sally continues to strengthen in the Gulf of Mexico, creating a life-threatening storm surge and flooding situation across parts of the U.S. Gulf Coast.

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 Wilfred. We still have approximately half the 2020 Atlantic Hurricane Season to go, and with one name left on the list of names for the year, it is highly likely we will begin to use names from the Greek Alphabet for the second time in history.
List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Wilfred. We still have approximately half the 2020 Atlantic Hurricane Season to go, and with one name left on the list of names for the year, it is highly likely we will begin to use names from the Greek Alphabet for the second time in history.

Data from an Air Force Reserve Hurricane Hunter aircraft indicate that the center of Sally has reformed to the east of the previously estimated location. At 11:00 AM AST, the center of Tropical Storm Sally was located near latitude 28.4 North, longitude 86.9 West. Sally is moving toward the west-northwest near six mph (9 km/h). This general motion is expected to continue today, followed by a decrease in forward speed and a turn toward the northwest tonight and a northward turn sometime on Tuesday. On the forecast track, the center of Sally will move over the north-central Gulf of Mexico today, approach southeastern Louisiana tonight, and make landfall in the hurricane warning area on Tuesday or Tuesday night. Afterward, Sally is expected to move slowly north-northeastward near the northern Gulf Coast through Wednesday.

Maximum sustained winds are near 65 mph (100 km/h) with higher gusts. Strengthening is expected over the next day or so, and Sally is forecast to become a hurricane by tonight, with additional strengthening possible before the center crosses the northern Gulf Coast.

Tropical-storm-force winds extend outward up to 125 miles (205 km) from the center. The latest minimum central pressure estimated from reconnaissance aircraft data is 991 millibars.

Tropical Storm Sally Forecast Track as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)
Tropical Storm Sally Forecast Track as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)

Watches & Warnings

Tropical Storm Sally Watches and Warnings as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)
Tropical Storm Sally Watches and Warnings as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)

A Storm Surge Warning is in effect for:

  • Port Fourchon Louisiana to the Alabama/Florida Border
  • Lake Pontchartrain, Lake Maurepas, and Lake Borgne Mobile Bay

A Hurricane Warning is in effect for:

  • Morgan City Louisiana to the Alabama/Florida Border
  • Lake Pontchartrain and Lake Maurepas including metropolitan New
    Orleans

A Tropical Storm Warning is in effect for:

  • Alabama/Florida Border to Indian Pass Florida
  • Intracoastal City Louisiana to west of Morgan City

A Tropical Storm Watch is in effect for:

  • Indian Pass to Ochlockonee River Florida

A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. Preparations to protect life and property should be rushed to completion.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours.

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

Hazards Affecting Land

Tropical Storm Sally Storm Surge forecast as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)
Tropical Storm Sally Storm Surge forecast as of 11:00 AM Monday 14th 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: 7-11 ft
  • Ocean Springs, MS to MS/AL Border: 5-8 ft
  • MS/AL Border to AL/FL Border including Mobile Bay: 4-7 ft
  • Lake Pontchartrain and Lake Maurepas: 4-6 ft
  • Port Fourchon, LA to Mouth of the Mississippi River: 3-5 ft
  • AL/FL Border to Chassahowitzka, FL including Pensacola Bay, Choctawhatchee Bay, and Saint Andrew Bay: 1-3 ft
  • Burns Point, LA to Port Fourchon, LA: 1-3 ft

Overtopping of local levees outside of the Hurricane and Storm Damage Risk Reduction System is possible where local inundation values may be higher than those shown above.

The deepest water will occur along the immediate coast in areas of onshore winds, 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 11:00 AM Monday 14th 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 11:00 AM Monday 14th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

WIND: Hurricane conditions are expected to begin within the hurricane warning area tonight. Tropical storm conditions are possible within the watch area today and are expected to begin within the warning area later today.

Tropical Storm Sally rainfall forecast as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)
Tropical Storm Sally rainfall forecast as of 11:00 AM Monday 14th September 2020. (National Hurricane Center)

RAINFALL: Sally is expected to be a slow-moving system as it approaches land, producing 8 to 16 inches of rainfall with isolated amounts of 24 inches over portions of the central Gulf Coast from the western Florida Panhandle to far southeast Louisiana through the middle of the week. Life-threatening flash flooding is likely. In addition, this rainfall will likely lead to widespread minor to isolated major flooding on area rivers.

Sally is forecast move farther inland early Wednesday and track into the Southeast with rainfall of 6 to 12 inches possible across portions of inland southeast Mississippi and Alabama. Significant flash and urban flooding is likely, as well as widespread minor to moderate flooding on some rivers.

Further heavy rain is then anticipated across portions of eastern Tennessee, northern Georgia and western Carolinas Thursday into Friday. Flash, urban, and minor river flooding is possible across this region.

Outer bands of Sally are expected to produce additional rainfall of 1 to 3 inches across the Florida peninsula today. This rainfall may produce flash and urban flooding and prolong high flows and ongoing minor flooding on rivers across central Florida.

TORNADOES: A tornado or two may occur this afternoon through Tuesday over coastal areas of the Florida Panhandle, Mississippi, Alabama, and extreme southeastern Louisiana.

SURF: Swells from Sally will continue to affect areas from the west coast of the Florida peninsula westward through the coast of southeastern Louisiana 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.

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

Tropical Storm Sally Forecast Discussion

Tropical Storm Sally in the Gulf of Mexico (Weathernerds)
Tropical Storm Sally in the Gulf of Mexico (Weathernerds)

An intense burst of deep convection with cloud tops colder than -80 degrees Celsius has developed over and the to the east of the center this morning. A recent fix from an Air Force Reserve Hurricane Hunter aircraft indicates that the center has reformed to the east of the previously estimated location, beneath the burst of deep convection. NWS WSR-88D radar imagery shows an increase in banding around the eastern and southeastern portion of the new center found by the aircraft, and it appears that an eye is in its formative stage. The aircraft has reported believable SFMR winds of 55 kt, and that is the basis for the initial intensity. The most recent minimum pressure estimated from the aircraft data is 991 mb, down several millibars from the first fix on this flight.

Sally is located within a conducive environment of low wind shear, warm waters, and a moist atmosphere. These conditions are likely to lead to steady strengthening over the next 24 hours or so. With the recent increase in the organization of the inner core, there is more confidence that Sally will strengthen to a hurricane later today or tonight. Additional strengthening is possible on Tuesday while the storm moves slowly northwestward near the coast of southeast Louisiana. Increasing westerly wind shear and land interaction will probably slow the intensification rate by late tomorrow. The new NHC intensity forecast is similar to the previous advisory and is near the upper end of the guidance envelope. Since Sally is forecast to be moving very slowly around the time of landfall, a slower rate of weakening is indicated since a large portion of the circulation will remain over water for some time.

Given the recent reformation of the center, the initial motion is a somewhat uncertain west-northwestward at 5 kt. Weak ridging over the southeastern United States should steer Sally slowly west-northwestward through tonight. After that time, a northwestward to northward turn is anticipated, but the exact timing and location of the turn remain uncertain. The general trend in the guidance has been eastward for the past few cycles, and the NHC forecast has been nudged in that direction and lies between the GFS and ECMWF models but a little west of the various consensus aids.

Regardless of the exact forecast track and intensity of Sally, the slow-moving storm is expected to cause a life-threatening storm surge and freshwater flooding event.

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

Forecast Discussion by Forecaster Brown from the NHC.

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