Fall officially arrived this month – at least the fall most important to meteorologists (astronomical fall begins later this month) – and although South Floridians still have to wait another month before feeling some relief, the hottest months of the year are at least behind us.
But for areas to our north, cold fronts are beginning to once again make an appearance, this week bringing the first taste of fall into the southeastern U.S.
With the return of fall fronts into the southeast, we begin to look closer to home for tropical formation. September is a transition month where we still track tropical waves moving across the deep tropical Atlantic, but also keep an eye on stalled cold fronts draped over still-warm Gulf of Mexico and western Atlantic waters. These cold fronts can be triggers for storm formation, especially when they loiter long enough.
Today, 2 of the 5 systems being marked by NHC for development are along a stalled cold front and, although development odds remain low with both, they remind us to look under our noses in the coming weeks for tropical mischief.
What’s cooking in the deep tropics
Beyond the two non-tropical disturbances attached to the stalled front, we’re monitoring 3 tropical waves in the deep tropics. The only one with immediate land implications is the disturbance moving into the western Caribbean today.
This system has been on our radar since last Tuesday but remains disorganized. Although it’s not expected to develop before moving inland over Central America and southern Mexico tomorrow, there’s a low chance it tries to organize as it reemerges over the southern Gulf. Forecast models generally keep it weak and tucked away in the lower reaches of the Gulf or over Mexico early next week. Regardless of development, it’s primarily a rainmaker for areas well south of the U.S.
Meanwhile, two other areas are being tagged by NHC over the open Atlantic: one closer to Africa and the other closer to the Caribbean islands. Neither is expected to make much headway in the coming days and while the one closest to the islands could graze parts of the Lesser and Greater Antilles this weekend, no significant threats to land are expected.
Rain and flood threat for coastal Texas and Louisiana
Although development of the non-tropical low-pressure area along the stalled front near the Texas coast is unlikely due to hostile upper-level winds, it will enhance a heavy rain and flood threat for parts of coastal Texas and Louisiana to round out the week.
Though the exact timing and location of heaviest rainfall are to be determined, widespread totals of 4 to 6 inches can be expected, with localized double-digit totals, especially south of the I-10/I-12 corridor in southern Louisiana, through Saturday morning. Scattered to even numerous flash floods, some significant, are possible across parts of southeast Texas, southern Louisiana, and coastal Mississippi.
First Invest in weeks in the Atlantic
The other non-tropical area of low pressure along the section of the stalled front draped across western Atlantic waters has been designated Invest 99L. Although it’s decidedly non-tropical, it could make an attempt at gaining some tropical characteristics over the next 24 to 48 hours.
Regardless, forecast models keep it well offshore of the United States and by Saturday it will be moving into the cooler waters of the Canadian Maritimes.
