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Subtropical or Tropical Development Possible in Gulf of Mexico, But Heavy Rain Threat to Florida Regardless


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Tropical Development Possible in the Gulf of Mexico

There is a possible tropical system developing in the Gulf of Mexico. The biggest potential threats will be heavy rains and rip currents. 

Story Highlights

An area of low pressure is being monitored for subtropical or tropical development in the Gulf of Mexico.

The National Hurricane Center currently gives it a medium chance of development over the next 5 days.

Heavy rainfall will be the primary concern regardless, especially in Florida.

The 2018 Atlantic hurricane season is trying to get off to another early start.

An area of low pressure will be closely monitored for subtropical or tropical development in the Gulf of Mexico this week as it spreads heavy rainfall across Florida and other parts of the Southeast.

When low-pressure systems like this one form over the warm waters of the Gulf this time of year, we must always watch them closely for potential development.

(MORE: Hurricane Central)

Right now, the National Hurricane Center gives the system a medium chance of development into a subtropical or tropical depression or storm over the next five days. Heavy rainfall will be the primary concern regardless, especially in the Sunshine State.

Current Satellite

Current Satellite

The hatched area over the Gulf of Mexico is where the National Hurricane Center is monitoring for subtropical or tropical development over the next 5 days.

If it were to develop, this would be the first subtropical or tropical depression or storm of the 2018 Atlantic hurricane season, which doesn’t officially begin until June 1. If it reached tropical storm strength, it would earn the name Alberto.

Four of the past six years have featured named storms before June 1 in the Atlantic, including 2012, 2015, 2016 and 2017. Two of those years – 2012 and 2016 – featured the genesis of two named storms before June 1.

(MORE: When Hurricane Season Starts Early)

This system’s rainfall is much-needed in central and southern Florida, where drought conditions have recently developed, and coincides with the start of Florida’s wet season.

Current Radar, Watches and Warnings

Current Radar, Watches and Warnings

Watches and warnings are issued by the National Weather Service.

Much of central and southern Florida can expect at least 1 to 3 inches of rainfall through midweek. Locally higher amounts are expected in heavier thunderstorms, and totals of 3 to 7 inches are likely in southeastern and eastern Florida through midweek.

The moisture will also fuel downpours that result in rainfall totals of 1 to 3 inches across other parts of the Southeast this week.

(MORE: We’re Entering the Prime Time for Flash Flooding)

Rainfall Forecast

Rainfall Forecast

Locally higher rainfall amounts are possible.

Although this rain is beneficial overall, there could be pockets of localized flooding in the week ahead.

The good news: higher rainfall amounts look likeliest in areas where it is most needed in the Sunshine State.

As of May 8, more than 26 percent of the state was in moderate drought, with a portion of South Florida in severe drought, according to the U.S. Drought Monitor.

Drought conditions as of May 8, 2018.
(U.S. Drought Monitor)

Additionally, just over half of the state was at least abnormally dry. Drought conditions did not begin to develop there until late February.

Miami only measured 0.37 inches of rainfall in February, 1.88 inches below average for the month. This dry trend was exacerbated in March, when Miami only picked up 0.19 inches, compared to the average rainfall for March – 3 inches. Similar experiences were observed all across South Florida.

(MORE: What to Watch Out For and Look Forward to in May)

This dry pattern began to shift in late April in the area, but locations such as Fort Lauderdale and Naples remained more than 6 inches below average year-to-date as of Friday. But there appears to be hope for a wetter pattern as the wet season commences.

Wet Season Begins This Month in Parts of Florida

The May-to-October time period when most of the annual precipitation occurs in Florida is known as the wet season.

For example, Miami receives about 45 inches of rain – almost 75 percent of its average annual rainfall – from May to October. By late May, the rainy season is usually ramping up across South Florida. 

Farther north, Tampa records about 70 percent of its average annual rainfall of 46.3 inches during the wet season. The beginning of the rainy season is a bit later, usually in mid-June, across central and northern Florida.

Florida’s Wet Season Setup

The purple dashed lines depict typical sea-breeze boundaries that help to trigger storm formation from late spring into early fall.

The reason for the increase in rainfall is that cold fronts do not track into Florida during this time, which allows for warmer temperatures and humid conditions to dominate.

(MORE: Rip Currents Have Been More Deadly Than Tornadoes and Lightning This Year)

As humidity increases, thunderstorm activity increases. Thunderstorms develop along sea-breeze fronts as cooler air slides inland from the Gulf of Mexico and the Atlantic Ocean, as shown above.

In addition, hurricane season officially runs from June 1 through Nov. 30 and brings an increased chance for rainfall. It’s important to remember that a strong hurricane is not needed to bring excessive rainfall; slow-moving tropical storms or even tropical depressions can result in heavy rainfall and flooding in the region.

Although the beginning of the wet season is good news regarding the needed rainfall, one problem this brings is the possibility of dry lightning. This occurs when lightning strikes hit the ground outside of rainfall, and these strikes can create grass fires, especially where the ground is dry following the dry season. 

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