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| #905773 (Received by flhurricane at: 5:01 AM 05.Oct.2017) TCDAT1 Tropical Depression Sixteen Discussion Number 4 NWS National Hurricane Center Miami FL AL162017 500 AM EDT Thu Oct 05 2017 Deep convection associated with the depression has increased over the eastern portion of the circulation overnight, however there has only been a slight increase in overall banding. Subjective Dvorak intensity estimates suggest that the depression is near tropical-storm strength, but with the center located near the western edge of the deep convection the cyclone is kept as a 30-kt tropical depression for this advisory. The intensity forecast remains quite uncertain due to expected land interaction today, and possibly again in about 48 hours when the system passes near the Yucatan peninsula. The depression could still become a tropical storm before the center moves over northeastern Nicaragua and eastern Honduras later today. After the cyclone moves north of Honduras, it will traverse the warm waters of the northwestern Caribbean Sea, where the upper-level environment is also forecast to be conducive for strengthening. However, the amount of strengthening is likely to depend on the structure of the inner core after it crosses land. The intensity models have continued their downward trend, but the NHC forecast remains near the higher side of the guidance due to these favorable conditions and persistence from the previous advisory. Some additional strengthening is possible while the system moves over the southern and central Gulf of Mexico, and the NHC intensity forecast brings the system to hurricane strength within 72 hours. This is in best agreement with the SHIPS intensity model. The depression is moving northwestward or 315/6 kt. The cyclone is forecast to move northwestward to north-northwestward during the next day or two around the western side of a ridge the extends from near the southeastern Bahamas southwestward into the central Caribbean Sea. By the weekend, a large mid- to upper-level ridge is forecast to build off the coast of the southeastern United States, and this should steer the cyclone north-northwestward at a faster forward speed. After 72 hours, the system is expected to recurve around the northwestward side of the ridge. The track guidance is in better agreement this cycle with the latest runs of the ECMWF and UKMET models shifting westward, closer to the previous GFS and HWRF iterations. This has required a fairly substantial westward shift in the NHC forecast track at 72 h and beyond. KEY MESSAGES: 1. The depression is forecast to strengthen and bring tropical storm conditions to portions of Nicaragua and Honduras through early Friday. Heavy rainfall could produce life-threatening flash flooding and mud slides in portions of Nicaragua, Honduras, Costa Rica, and Panama through Friday night. 2. The system could be near hurricane intensity when it approaches the Yucatan Peninsula late Friday, bringing direct impacts from wind, storm surge, and heavy rainfall, and a hurricane watch is in effect for a portion of this area. 3. The system is forecast to strengthen over the Gulf of Mexico and could affect portions of the northern Gulf Coast as a hurricane this weekend, with direct impacts from wind, storm surge, and heavy rainfall. However, it is too early to specify the timing, location, or magnitude of these impacts. Residents along the Gulf Coast from Louisiana through the Florida Panhandle should monitor the progress of this system and heed any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 13.3N 83.3W 30 KT 35 MPH 12H 05/1800Z 14.3N 83.9W 30 KT 35 MPH...INLAND 24H 06/0600Z 16.3N 84.8W 35 KT 40 MPH 36H 06/1800Z 19.0N 86.0W 45 KT 50 MPH 48H 07/0600Z 21.8N 87.4W 55 KT 65 MPH 72H 08/0600Z 27.8N 89.5W 65 KT 75 MPH 96H 09/0600Z 34.0N 86.5W 35 KT 40 MPH...INLAND 120H 10/0600Z 39.5N 79.0W 25 KT 30 MPH...POST-TROP/INLAND $$ Forecaster Brown |
