Rafael course means rain, no wave

On By Littum

Ryan Truchelut
| Weather Tiger

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Tropical Storm Rafael has swirled to life in the central Caribbean south of Jamaica as expected. The system is likely to enter the southern Gulf of Mexico by midweek as a hurricane.

While that’s an alarmist phrase, the risk of damaging winds or waves on the US Gulf Coast is still fairly low due to hostile conditions near the coast, and increased rain chances should be Rafael’s only meaningful impact on Florida and the surrounding area.

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

As of the 10 a.m. NHC advisory, the storm has maximum sustained winds of 45 mph and is moving north at about 9 mph. A bend to the left should begin as soon as the storm feels the influence of a ridge of high pressure centered over Florida, which will keep the storm moving northwest through Thursday.

With future Rafael’s low-level circulation developing amid the array of possibilities, the short-term track comes into better focus.

Look for Rafael’s center to cross western Cuba or the Yucatan Channel and enter the southeast gulf by Wednesday. The system is located on the eastern side of an upper level low that will increase its outflow and keep wind shear at favorable to manageable levels for the next few days, so strengthening is likely through midweek as it still crosses Caribbean waters in the mid-80s. Thus, the storm will probably peak as a Category 1 or 2 storm on Thursday if it can avoid land interaction.

That’s the scary part.

The good news is that while Rafael may well enter the Gulf as a hurricane by midweek, there is very little chance of the storm reach land like a hurricane. As I discussed last week, a hurricane landfall in the Gulf in November would require a strengthened trough or cutoff low over the Mississippi Valley, such that a storm could quickly run north or northeast across a hostile Gulf without weakening much.

In this case, a front that descends into the deep south later this week will be weak and oriented mostly east-west. That front will push the ridge eastward into the Atlantic, but the western flank of the ridge will continue to extend across Florida and the northern Gulf Coast.

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

That slowdown will also be accompanied by a weakening. While gulf water temperatures away from the immediate coast are in the lower 80s and still capable of sustaining a hurricane, Rafael will pull a very dry continental air mass into its circulation late this week while also becoming sandblasted with 30 knots or more wind shear. The further north and closer to land the storm comes, the worse the conditions will be for it, so the weakening could be dramatic on Friday and Saturday.

Ultimately, it’s too early to say whether 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 of a difference in terms of weather impacts whether it do or not.

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

For the Florida peninsula, Rafael will come closest late Wednesday and Thursday. If the storm strengthens more by Wednesday, it will likely pass a bit closer to Florida, but in 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. While the tropical cyclone remains well off Florida’s Gulf Coast, it will pull tropical moisture north out of the Caribbean and across most of the state, leading to intermittent showers and thunderstorms equivalent to a general 1-3″ by Saturday.

With the Peninsula seeing little rain since Milton and the Panhandle barely a notch since Helene, this rainfall will be a net benefit outside of the Central Florida river basins still in flood stage. Similar rainfall amounts should extend across eastern Alabama and most of Georgia and South Carolina.

With the storm moving west-northwest or northwest across the southeastern and central Gulf, offshore winds along Florida’s Gulf Coast mean there is little or no risk of flooding or coastal inundation.

Conditions across Florida will be breezy inland and gusty on the coast late this week, but the storm will initially be too far away from Florida to be a wind threat, and then too weak for much in the way of wind problems , if it moves toward or over the central Gulf Coast over the weekend. (The Keys could see more frequent tropical storm surges on the low end by midweek.)

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

Overall, where things generally go according to plan, my concerns about major impacts from this late-season tropical threat remain low: the storm didn’t develop faster than expected, hasn’t rapidly intensified (yet, anyway), and the refuge controls haven’t budged in modeling. That means the eastern halves of the US Gulf Coast and the Deep South will likely see needed rain, but have different impacts.

Another low-threat system could also see Florida after Rafael

One final note: another tropical system may develop near Hispaniola this weekend and also approach southern Florida from the east early next week. Conditions aren’t favorable for it to be a big deal either, but it could keep Florida’s rain chances up for the long term.

Here’s hoping that late season tropical activity stays in the beneficial or at least pesky area for impacts, which so far they appear to be doing. Keep an eye on the sky.

Dr. Ryan Truchelut is chief meteorologist at WeatherTiger, a Tallahassee firm that provides forensic meteorological expert witness services and agricultural and hurricane forecasting subscriptions. Visit weathertiger.com for more information. Email Ryan Truchelut at [email protected].