A new tropical disturbance could bring days of heavy rain to Florida

The Atlantic hurricane season is far from over.

The National Hurricane Center is monitoring two areas for possible storm development in the days ahead – one near Florida and another in the open waters of the eastern Atlantic. While the first probably won’t intensify into a tropical storm, it will enhance downpours in the Sunshine State into next week, bringing a risk for flooding. Localized rain totals could exceed a foot, and there’s even the chance for a tornado or two.

The second disturbance doesn’t pose an immediate threat to land, but it could approach the Caribbean islands later next week. The risk to the Leeward Islands and Puerto Rico is increasing, and the National Hurricane Center estimates a 40 % chance of the system becoming a named storm by the middle of next week.

The next name up on the list is Jerry.

There could also be some tropical mischief in the gulf or Caribbean toward mid-October, though there’s nothing that’s specifically being tracked yet. Instead, exceptionally warm sea surface temperatures have left a reservoir replete with heat content that could fuel anything that develops – and the atmosphere could become increasingly favorable for storm formation in the next week or two.

Florida rainstorm

Whether a system gets named depends solely on wind – maximum winds must reach at least 39 mph for a system to be classified as a tropical storm. But in this case, winds do not really matter. The east coast of Florida is dealing with torrential heavy rains, and some localized potentially significant flooding is possible. Thursday is the first of four expected days of heavy rain.

The thunderstorm-driven nature of the rainfall has so far made for highly variable totals; Homestead is up to 3 inches so far, but the nearby Homestead Air Reserve Base, just 3 miles away, has seen only an inch.

Elsewhere, rainfall totals in Plantation, just west of Fort Lauderdale, is up to 7.54 inches. Nearby Sunrise reported 5.09 inches at Fire Station 39. Fort Lauderdale itself, about 10 miles to the east, has seen about an inch .

Downpours will continue as tropical moisture pools along a stalled frontal boundary draped across the peninsula. There are signs that a wave of low pressure will form on the front near the Bahamas and trek west-northwest, enhancing heavy rain as it crosses the Sunshine State on Saturday. High-resolution weather models suggest another 5 to 10 inches is possible along the Florida East Coast; hardly anything will fall along the Gulf of Mexico, and some places near Tampa may not see a drop of rain through the weekend.

There’s also a low-end risk of an isolated tornado or waterspout somewhere in the Miami to Fort Lauderdale or Port St. Lucie corridor. There will be just enough vorticity, or spin, associated with the passage of low pressure that a rogue thunderstorm or two may acquire some rotation.

Second system approaching Lesser Antilles

The National Hurricane Center has also increased its predicted odds of a named storm developing before approaching the Lesser Antilles next week. It is estimating a 40 percent chance of tropical development, and it’s probable those odds will be increased even more.

On Friday morning, there were two features to discuss over the Atlantic: a broad zone of isolated showers/thunderstorms over the central tropical Atlantic, and then a clump of convection, or shower and thunderstorms, near Burkina Faso and Ivory Coast. That second cluster has a bit more spin with it.

It’s possible both batches of storminess will combine into a more focused tropical wave over the weekend, then work westward.

Numerous weather models simulate a tropical storm closing in on the Leeward Islands toward Tuesday or Wednesday.

Confidence diminishes markedly after Wednesday.

Will the system continue westward toward the northeast Caribbean? Or will it curve out to sea over the open North Atlantic? That depends on the strength of the “Bermuda high” and the strength of the system. A stronger, taller system will be affected by the winds – just like a sailboat hoisting its sails – and be blown northwards. That could bring it closer to Puerto Rico first before it slips out to sea.

But a weaker system could theoretically continue farther west, eventually becoming a problem for Puerto Rico, Hispaniola or even locations farther west. That forecast will be ironed out in the days ahead.

Busy tropics during October

There’s elevated potential for tropical storms and hurricanes in mid-to-late October because of a regularly rotating pulse of rain and clouds around the global tropics called the Madden-Julian Oscillation.

This feature is like an energy drink for the tropical atmosphere. When it passes over a particular area, it changes the wind, causing the air to turn moister and spin – ingredients necessary for forming hurricanes.

One area to watch is the Caribbean Sea, where ocean heat content is currently extremely high and well above-average, possibly fueling a very strong storm before the season officially ends on Dec. 1.

In the Pacific Ocean, La Niña is forming, marked by a tongue of cool ocean water extending westward from South America. La Niña typically leads to winds that are more favorable for storm formation in the Atlantic.

These factors suggest that hurricane season could end with a flurry of storms.