HIGH RAIN CHANCES TODAY; WATCHING PTC#9/ISAIAS… If you’re tired of the seemingly endless rain we have had over the last few days, there is good news in that today is the last day of elevated rain chances for awhile. Rain chances won’t ever get to zero later this week and into the weekend, but the odds of any given spot having rain on Thursday, Friday, or Saturday will be significantly lower than today.
HEAVY RAIN & STORMS POSSIBLE AT TIMES TODAY… Heavy rain and thunderstorms will again be likely across south Alabama and northwest Florida on this Wednesday. The “fire hose” of Gulf moisture is set to continue with storms training from southwest to northeast today. Storms could produce very heavy rain at times, cloud-to-ground lightning, and loud thunder. Widespread severe weather is not expected today, however. High temperatures will be in the mid-80s across the region.
POTENTIAL TROPICAL CYCLONE #9 APPROACHING THE LESSER ANTILLES… The system formerly branded as INVEST 92L is now Potential Tropical Cyclone #9. This branding is used by the National Hurricane Center to designate a system that will almost certainly become a tropical storm. NHC issues this designation in order to be able to issue Tropical Storm Warnings. Regardless of that technicality, PTC#9 continues to organize this morning. There is a very high (90+%) chance that this system will form a low-level circulation center today or tonight and ultimately move northwest. There is high confidence in that idea. There is also high confidence in the idea of the system moving in a general northwesterly fashion regardless of how strong the system becomes or how weak it remains. See the paragraph below for a more technical discussion about how this system may evolve. Interests in south Florida, The Bahamas, Cuba, Haiti, and the Turks and Caicos (in addition to the places already involved in a Tropical Storm Warning – outlined extensively below) should closely monitor the progress of this system.
LOW CONFIDENCE FORECAST FOR PTC#9/ISAIAS… There is high confidence in the broad ideas concerning Potential Tropical Cyclone #9, aka Isaias-to-be, but there is VERY LOW confidence in the specifics on how this happens. We know with near certain confidence that the system will be moving to the northwest. The problem beyond that arises because we don’t yet have a low-level circulation center, thus models don’t have a firm grip of exactly where the center develops. If a given model doesn’t know the “starting point” of a tropical cyclone, all “future points” are subject to large error. Once we get a low-level center of circulation on the board, this will be the first problem in the forecast that is resolved. Second point that we just do not know yet – Will the system move directly over the Dominican Republic and Haiti (Hispaniola)? If yes, there is a high chance this system is ripped apart completely by the extremely tall, rugged terrain of the large island. There is a chance the whole system falls apart and only a weak tropical wave axis with some rain moves toward south Florida. IF, however, the system moves just north of Hispaniola (as many models are currently suggesting), that could allow the system to maintain its center and slowly acquire strength. Explosive strengthening does not seem likely because of increasing southwesterly shear as the system approaches the south part of Florida by the weekend. While most models show the system taking a turn to the north when it reaches the western Bahamas, it is still unfortunately a bit too early to completely rule out Gulf of Mexico impacts. We’re getting closer to that point but we’re certainly not there yet.
TROPICAL STORM WARNINGS FOR PUERTO RICO & SURROUNDING ISLANDS… Due to the approach of Potential Tropical Cyclone #9, aka what will likely be Tropical Storm Isaias, a Tropical Storm Warning is now in effect for the following areas: Puerto Rico, the U.S. and British Virgin Islands, Antigua, Barbuda, Montserrat, St. Kitts, Nevis, Anguilla, Guadeloupe, Martinique, St. Martin, St. Barthelemy, St. Marteen, Dominica, and the Dominican Republic coastline from Cabo Caucedo to the Dominican Republic/Haiti border. A Tropical Storm Warning means that tropical storm conditions are expected within the warning area within 36 hours. We also note that a Tropical Storm Watch is in effect for the Turks & Caicos and the southern coastline of the Dominican Republic.
LOWER RAIN CHANCES LOCALLY LATER THIS WEEK INTO WEEKEND… We finally will get a break from the higher rain chances starting on Friday when drier air will be in place across our region. Friday and Saturday will see near or below average rain chances (10-20%) with high temperatures in the low-90s. Temperatures will go back up this weekend (compared to the lower overall temperatures we’ve had this week due to all the rain around) but I don’t see any signs of excessive heat (95°+) in the forecast over the next 7-10 days.
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See all the details in your Wednesday #rzw forecast video… Have a great day!