Upper-air flow steers Elsa east, still supplies downpours around here

The Weather Authority

Two main factors control Tropical Storm Elsa’s future and our chance of hit-or-miss, unevenly-scattered showers and storms through the end of this week: an upper-air low over the western Gulf of Mexico and a ridge over the Bahamas.

Elsa, which will be a strong tropical storm or Category 1 hurricane at landfall Wednesday, finds the gap between the low to the west and the high to the east. There’s an old saying among forecasters that says “forecast the high, forecast the storm.” In other words, if you can accurately identify and forecast that ridge, the storm’s forecast track becomes much more accurate, too.

So, with the high to the east and the low to the west, Elsa’s track across Florida then through Georgia, the Carolinas and to the Atlantic again is a lock.

What does it mean for us?

A rule of thumb around Alabama is that a storm tracking to the east usually means drier weather. That only works if there’s some dry air available.

This week, we’re actually getting a wide-open flow of moisture from the Gulf in spite of Elsa’s path to the east, and that means a healthy dose of scattered thunderstorms on Wednesday and Thursday (and some still in the area Friday, too).

Total rainfall is highly variable! The slam dunk guarantee rain is in Florida, Georgia and the Carolinas. It’s much more uneven around here.

A 60% chance of rain Wednesday literally means you have a 60% probability of getting at least a tenth of an inch of rain.

Take Tuesday’s downpours for an example:

6-hour rainfall through 6 PM Thursday

Isolated downpours dropped tremendous rain in a few areas. Other more widespread areas got a little rain, and there’s an even larger part of the map untouched by rain.

Fewer of us miss the rain on Wednesday and Thursday, but it is still very uneven, spotty, hit-some, miss-some rain.

By the way, Elsa will not ‘hit’ the Alabama coast or any of the usual vacation hot spots in the Panhandle like Pensacola, Destin, Fort Walton Beach or Panama City. Elsa will generate some rough surf and keep the rip current risk ‘high’ through the end of the week on the northern Gulf Coast, though!

Looking for the rest of the forecast? It’s always online at WHNT.com/Weather and in the “Daily Forecast” section on Live Alert 19!

-Jason
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