Tropical Storm Sally is now the 18th named storm of the 2020 Atlantic hurricane season.
Hurricane warnings have now been issued from Morgan City, Louisiana, east to Ocean Springs, Mississippi, including New Orleans, Lake Pontchartrain and Lake Maurepas. Sally continues to strengthen across the Gulf of Mexico with sustained winds of 60 mph.
Storm surges of up to 7 to 11 feet are possible near the center of the storm and just east of where landfall is expected. Along with storm surge, extreme rainfall amounts of over a foot are expected in some locations between southeast Louisiana and the western Florida panhandle.
Tropical Storm Sally is the 18th named storm of the 2020 Atlantic hurricane season, the earliest 18th-named storm on record. On Saturday, the storm brought heavy rain and gusty winds to south Florida as it moved into the Gulf of Mexico.
Louisiana Gov. John Bel Edwards declared a state of emergency Saturday evening ahead of Sally’s arrival, and on Sunday, he said he had spoken with President Donald Trump and will submit a pre-landfall federal declaration request.
“While we ultimately don’t know where Sally will make landfall, much of Southeast Louisiana is in the storm’s cone and the risk of tropical storm force or hurricane strength winds continues to increase. This storm has the potential to be very serious,” Edwards said in a news release.
We “have every reason to believe that this storm represents a very significant threat to the people of Southeast Louisiana,” Edwards said at a press conference Sunday.
Mississippi Gov. Tate Reeves signed a preliminary state of emergency for the state, he said Sunday, and has also sent a request to the President “to provide the necessary guidance” for pre-landfall activity, saying he expected to the storm to “persist over most portions of the state for basically 48 hours.”
In New Orleans, Mayor LaToya Cantrell issued a mandatory evacuation order for residents outside of the city’s levee protection system. The evacuation will begin Sunday at 6 p.m. for the areas of Venetian Isles, Irish Bayou and Lake Catherine.
Cantrell said Sunday that sandbags were available throughout the city and that water pumps are in place and operational.
In coastal Louisiana, Grand Isle and St. Charles Parish are under mandatory evacuation declarations, and a recommended evacuation notice went out to the community of Port Fourchon.
“We want residents to heed our warnings and make preparations to leave now,” St. Charles Parish President Matthew Jewell said on the official Facebook page of St. Charles Parish.
Three jails with 1,200 inmates in total have been evacuated, Edwards said Sunday, and at least one nursing home is evacuating.
Gulf Coast expecting 6 to 12 inches of rain
Flash flood watches are in effect along the Gulf Coast across much of southern Louisiana, east to the Florida Panhandle, and along the western Florida peninsula. These watches include the city of New Orleans, Biloxi, Mississippi, Mobile, Alabama, and Panama City and Tampa, Florida.
Sally is expected to slow in speed as it approaches the Gulf Coast which will result in significant flash flooding across the region. Widespread rainfall totals of 6 to 12 inches is expected along the Gulf Coast through Wednesday, but isolated rainfall of up to 20 inches is not out of the question.
The combination of extreme rainfall and the high storm surge will bring widespread flooding to much of the Gulf Coast beginning on Monday and lasting at least through Wednesday.
Most forecast models have Sally moving toward the northern Gulf Coast and likely making landfall somewhere between New Orleans and Panama City by late Monday or Tuesday, however if the track shifts farther west or slows down, landfall may hold off until Wednesday.
“The cyclone will likely become a hurricane in 2 to 3 days, although an increase in vertical shear could slow the rate of intensification over the northern Gulf of Mexico,” according to the National Hurricane Center.
Once it reaches that area of the Gulf Coast the steering patterns break down and the system meanders near the coast.
Whether the meandering is offshore prior to a landfall or onshore will not make much of a difference in terms of rainfall. In either case, because of the slow forward movement along the Gulf Coast significant flooding is possible.
Active hurricane season stays busy
Another system, Tropical Storm Twenty, has formed in the central tropical Atlantic, according to the NHC. Twenty has sustained winds of 35 mph.
Twenty is expected to strengthen to a tropical storm by tomorrow and a hurricane by next week, and if so, will be named Teddy. The previous record for the earliest 19th named storm is October 4, 2005.
Many storms broke records for being the earliest named to date, including Cristobal was the earliest named “C” letter storm in recorded history and Hanna was the earliest “H” letter storm. All but three named storms (Arthur, Bertha and Dolly) set records for being the earliest named storm for their respective letter.
Sally is just one of several systems in the Atlantic. The NHC is currently watching six areas: two tropical storms, two tropical depressions, and two tropical disturbances. Thursday marked the peak of the Atlantic hurricane season.
“Tropical Storm Paulette is forecast to strengthen into a hurricane today,” says Haley Brink, CNN Meteorologist. “Paulette is forecast to track toward Bermuda and potentially make landfall early Monday morning as a category 2 storm. A hurricane watch is in effect for Bermuda with hurricane conditions possible within 48 hours. Tropical storm conditions will begin to impact Bermuda by Sunday afternoon and hurricane conditions will begin Sunday night.”
On Thursday the National Oceanic and Atmospheric Administration announced they are issuing a La Niña Advisory, meaning La Niña conditions are present in the central and eastern Pacific Ocean.
In a typical El Niño phase, much of the Pacific Ocean is characterized by warmer waters, whereas La Niña features a cooling of those same Pacific waters. In the case of hurricanes, La Niña weakens high atmospheric winds, which allows warm air pockets to grow vertically and develop into hurricanes.