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TD 18, Rafael course means rain, no wave

Vaseline November 4, 2024

Ryan Truchelut
| WeatherTiger

Tropical Depression 18, the future Tropical Storm Rafael, has sprung to life as expected in the central Caribbean south of Jamaica. The system is likely to enter the southern Gulf of Mexico as a hurricane by mid-week.

While that is an alarming statement, the risks of damaging winds or wave action on the US Gulf Coast remain quite low due to hostile conditions near the coast, and the increased rain chances should be the only meaningful impact of TD 18 on Florida and the surrounding area.

Tropical Storm Rafael could peak as a Category 2 hurricane before weakening

As of the 10 a.m. NHC advisory, the storm has maximum sustained winds of 55 mph and is moving north at about 10 mph. There should be a left turn once the storm feels the impact of a high-pressure steering ridge over Florida, which will keep the storm moving northwest through Thursday.

With Rafael’s future low circulation developing in the middle of the range of possibilities, the near-term trajectory comes into clearer focus.

Look for downtown Rafael to cross western Cuba or the Yucatan Canal and enter the southeastern Gulf late Wednesday. The system is on the eastern side of an upper level low that will increase its outflow and keep wind shear at a favorably manageable level over the next few days. So strengthening will likely occur midweek as it crosses Caribbean waters still in the mid 80s. So the storm will likely peak Thursday as a Category 1 or 2 storm if land interaction can be avoided.

That’s the scary part.

The good news is that while Rafael could enter the Gulf as a hurricane by mid-week, the storm’s chances are very slim. reaches land like a hurricane. As I discussed last week, a November hurricane landfall in the Gulf would require a strengthened steering trough or cutoff low over the Mississippi Valley so that a storm could move quickly north or northeast across a hostile Gulf without weakening much.

In this case, a front that pushes into the Deep South later this week will be weak and mainly oriented east-west. That front will push the steering ridge eastward into the Atlantic Ocean, but the western flank of the high front will continue to extend over Florida and the northern Gulf Coast.

That means that instead of accelerating north toward Florida, Rafael will likely slow Friday and Saturday and track west-northwest or northwest into the central or north-central Gulf.

That slowdown will also be accompanied by weakening. While Gulf water temperatures off the immediate coast are around 80 degrees and still capable of sustaining a hurricane, Rafael will draw a very dry continental air mass into its circulation late this week, while also being sandblasted by wind shear of 30 knots or more. . The further north and closer to land the storm gets, the worse conditions will be, so the weakening could be dramatic on Friday and Saturday.

Ultimately, it’s too early to say whether or not the storm will technically make landfall on the central or east-central Gulf Coast as a tropical storm, but I don’t think it will make much difference in terms of weather impacts whether it whether it is a tropical storm or not. it either works or it doesn’t.

What Florida can expect from Rafael: Mostly useful rain with little risk of coastal flooding

Off the Florida peninsula, Rafael will reach the border late Wednesday and Thursday. As the storm strengthens through Wednesday, it will likely pass a little closer to Florida, but under all scenarios it should remain well southwest of the Keys.

The storm’s main impact on Florida will be an increase in rain chances between Wednesday and the weekend. Although the tropical cyclone remains well offshore of Florida’s Gulf Coast, it will drag tropical moisture north from the Caribbean and over most of the state, bringing isolated showers and thunderstorms through Saturday thunderstorms averaging 1-3 inches.

With the Peninsula receiving little rain since Milton and the Panhandle receiving almost no rain since Helene, this rainfall will provide a net benefit outside of Central Florida watersheds that are still in flood stage. Similar rain totals should extend across eastern Alabama and most of Georgia and South Carolina.

As the storm moves west-northwest or northwest across the southeastern and central Gulf, offshore winds along Florida’s Gulf Coast mean there is little to no risk of wave action or coastal flooding.

Conditions across Florida will be windy inland and on the coast late this week, but the storm will initially be too far from Florida to pose a wind threat, and then be too weak to cause much concern. wind if it does move towards the coast. or by the weekend on the central Gulf Coast. (The Keys could see more frequent low-end tropical storm surges midweek.)

Rafael would also have to be too far offshore to produce any kind of widespread tornado outbreak, although isolated spin-ups are always possible in bands well east of even modest tropical systems.

Overall, my concerns about the major impact of this late-season tropical threat remain low, with things generally going according to plan: the depression did not develop any faster than expected, nor has it (at least not yet) quickly became more intense and the control characteristics did not budge in the modeling. That means the eastern half of the U.S. Gulf Coast and the Deep South will likely see some rain, but little other impact.

Another low-threat system could also keep an eye on Florida after Rafael

A final note: Another tropical system may develop near Hispaniola this weekend and also approach South Florida from the east early next week. The conditions aren’t favorable for that to be a major problem either, but it could increase rain chances in Florida in the longer term.

We hope that the wave of late-season tropical activity stays within the beneficial or at least irritating range for impacts, which they appear to be doing so far. Keep looking at the sky.

Dr. Ryan Truchelut is chief meteorologist at WeatherTiger, a Tallahassee-based company that provides forensic meteorology witness services and agricultural and hurricane forecasting subscriptions. Visit weretiger.com for more information. Email Ryan Truchelut at [email protected].