Heavy rain, localized flooding threatens Gulf Coast this week
AccuWeather meteorologists will be closely monitoring the Gulf of Mexico in the coming days for the potential of heavy rain and unsettled conditions along the Gulf Coast. While the disturbance responsible for this was once a potential early season tropical threat, forecasters say that despite the poor weather conditions, a subtropical or tropical system is now looking less likely.
It is generally a rare occurrence for tropical depressions or storms to form in April, but it has happened over the years. The most recent named storm to form in April was Tropical Storm Arlene, which formed over the central Atlantic in 2017. However, no tropical systems have ever been documented in the Gulf of Mexico during April. Interestingly enough, the first name on the list that will be used to identify 2023 Atlantic storms is Arlene.
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Despite this threat, there is a list of factors that would have to line up correctly for a tropical system to develop. AccuWeather forecasters say that meeting all of this criteria will be a tall order for this week's system.
The initial spark for tropical system formation may occur as a dip in the jet stream, high in the atmosphere, plunges toward the Gulf of Mexico this week. The jet stream may then break off and form what meteorologists call a closed low. Provided this closed low can linger over the Gulf of Mexico long enough, it is possible that a low-pressure area may spin down to the lower part of the atmosphere and acquire some tropical characteristics.
"The closed low must sit over the Gulf of Mexico for 48-72 hours in order to gain tropical characteristics, and it appears that it may only get into the northern Gulf of Mexico for about 24 hours before moving inland," AccuWeather Chief On-Air Meteorologist Bernie Rayno explained.
"If this is correct, the storm will not have enough time to develop tropically."
Since Gulf of Mexico water temperatures are barely high enough this early in the spring, any system that forms would take more time to strengthen. Gulf of Mexico water temperatures range from near 70 F along the Louisiana coast to the low 80s in the waters between Cuba and Mexico. Temperature departures are 5-8 degrees above the historical average in the northern parts of the Gulf to close to the historical average near the Caribbean.
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In order for a true tropical system to develop, water temperatures generally need to be in the mid- to upper 70s F. Because of the above normal water temperatures, a subtropical storm or hybrid storm may develop - or perhaps not form at all.
As of Monday morning, forecasters expect the disturbance to form somewhere in the vicinity of the central Gulf Coast, though could meander a bit toward the west or east before moving inland. Because of this, a swath of heavy rain may extend from central Louisiana through the Florida Peninsula, with cities such as Pensacola, Florida, and New Orleans, Louisiana, in the region likely to be impacted. More localized heavy rain can spread as far west as the Houston metro area, and as far east as South Florida, during the middle of this week.
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A stiff breeze from the east is likely to develop along the Florida Peninsula, the northern Gulf of Mexico and perhaps farther north along the Atlantic coast this week. These breezes could create rough surf and strong rip currents.
"At the very least, it appears that portions of Florida and southern Louisiana will receive some much-needed rain from the ordeal," AccuWeather Meteorologist Alex DaSilva said.
Soil conditions range from normal moisture in the Florida Panhandle to extreme drought in the southwest part of the peninsula.
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AccuWeather meteorologists also have another concern that relates to heavy rainfall.
"Areas from northeastern Texas to the Carolinas that got doused with heavy rain in recent days could be more prone for flooding issues this week, provided a storm throws more rain over some of the same locations for a several-day period," AccuWeather Senior Meteorologist Joe Lundberg said.
A powerful storm with high winds is unlikely. However, one aspect of a weak subtropical system, or merely a closed low nearby, is the potential for severe thunderstorms. Any thunderstorms that develop could generate torrential downpours, strong wind gusts and perhaps a few tornadoes or waterspouts.
In any event, a period of unsettled weather is likely along much of the Gulf Coast. The greatest threats to swimmers, beachgoers and boaters will be lightning strikes and rough seas/surf.
During March, AccuWeather issued its first look at the upcoming 2023 Atlantic hurricane season. The team of meteorologists, led by Hurricane Expert Dan Kottlowski, expects a near-historical average number of named systems (11-15). The numbers are based on the latest developments with the routine fluctuation of sea surface temperatures in the tropical equatorial Pacific known as the El Niño Southern Oscillation (ENSO).
Studies have shown over many decades that water temperatures in the tropical Pacific can have a profound effect on weather patterns throughout the globe. When waters are cool in that part of the Pacific, or during a La Niña, conditions can be conducive for tropical cyclone development, and an above-average number of tropical systems can form in the Atlantic. However, when waters in the Pacific are warm, conditions may be more hostile for tropical development in the Atlantic.
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Kottlowski's team of tropical weather experts indicated in the 2023 Atlantic hurricane forecast that there would be a good chance for a preseason storm to form. Last year was the first since 2014 in which a named storm didn't develop prior to June 1.
AccuWeather's tropical weather team expects conditions to transition slowly from ENSO-neutral to El Niño later in the hurricane season. Should the transition occur quickly, then the number of tropical systems may be lower than average. If the transition occurs slowly or Pacific water temperatures hover near average or revert back to La Niña, then the number of tropical systems may be higher than anticipated.
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