James Spann: Tropical rain returns to Alabama late this week

BEAUTIFUL AFTERNOON: With sunshine in full supply, temperatures are mostly between 76 and 80 degrees across Alabama this afternoon, right at seasonal averages for early October. Tonight the sky will stay clear, with a low in the 50s early Tuesday.

Tuesday and Wednesday will be dry with a warming trend; the high will be in the low 80s Tuesday, followed by mid 80s Wednesday. The sky will be partly to mostly sunny both days. On Thursday, clouds will increase and rain returns to the southern counties during the morning. Showers will slowly move northward, reaching the northern half of the state by afternoon or Thursday evening.

Hurricane Delta will bring tropical rain to Alabama Friday, Friday night and into part of the day Saturday. At this point, we are projecting rain amounts of 3-6 inches for the southern two-thirds of the state (generally from I-20 south), with 2-4 inches for north Alabama. For now no major flash flooding is expected since the rain will be mostly light to moderate during the event, and the ground is not saturated due to the recent dry spell. For now we are not expecting a big tornado threat for most of inland Alabama, since the air should be stable.

Rain will end from southwest to northeast during the day Saturday. It’s just about impossible now to forecast the time the rain ends at any specific point since we are dealing with a tropical system that it is just getting organized in the Caribbean. Rain could linger through the evening over the Tennessee Valley region of north Alabama. On Sunday, the sky becomes partly sunny with only a small risk of a stray shower. The high will be in the 70s Saturday, followed by low 80s Sunday.

NEXT WEEK: For now the weather looks mostly dry during the first half of the week, but showers are possible by Thursday or Friday (Oct. 15-16) with an approaching cold front.

TROPICS: Tropical Storm Gamma is just a swirl of low clouds with no deep convection. It will likely dissipate within the next 36 hours, and the remnant circulation will be absorbed by the dominant system in the region, Delta.

Delta is a rapidly strengthening tropical storm in the Caribbean with sustained winds of 60 mph; it most likely becomes a hurricane tonight. It sure seems like Delta will become a major hurricane (Category 3 or higher) by Tuesday night in the southern Gulf of Mexico. Landfall is expected Friday morning on the Louisiana coast between Grand Isle and Morgan City.

Increasing southwesterly shear and the cooler shelf waters over the northern Gulf are likely to induce some weakening before landfall.

COASTAL IMPACT: A hurricane watch will be required for parts of the central Gulf Coast by Tuesday afternoon or evening. At this point it looks like the greatest wind and storm surge impact will come across southeast Louisiana and Mississippi, but some storm surge flooding is possible along the Alabama coast as well. It all depends on the position, size and strength of the hurricane.

Dangerous rip currents are likely along the Alabama and northwest Florida coasts Tuesday through Friday night; expect double red flags.

Most of the rain on the coast will come Thursday, Friday and Friday night. The weather will improve over the weekend as the system lifts northeast, away from the region. Rain amounts on the coast of 3-6 inches are likely, with isolated amounts to 8 inches. A few isolated waterspouts or brief tornadoes are possible Thursday night and Friday.

We will be much more specific about the impact on the coast within a day or two as the system evolves.

It is important to watch for updates; when it comes to tropical systems, if you are working with old information, you are working with bad information. Always expect changes.

ON THIS DATE IN 1972: Tropical Storm Joanne, earlier a hurricane, moved across the Baja California peninsula and came ashore in western Mexico south of Ajo. The storm brought heavy rain and flooding to much of Arizona. This storm is the first documented tropical storm to reach Arizona with its cyclonic circulation intact. More than 5 inches of rain was reported on the Mogollon rim southeast of Flagstaff. Additional rainfall amounts included 4.44 at Flagstaff, 3.8 at Prescott, 2.21 at Yuma, 1.95 at Phoenix, 1.63 at Nogales and 1.63 at Tucson.

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