| The NHC says "the cyclone appears to have a relatively intact and well-defined inner core". That's unfortunate since it's about to move over very deep warm water. Tropical Storm Nate Discussion Number 7 NWS National Hurricane Center Miami FL AL162017 1100 PM EDT Thu Oct 05 2017 Nate's center has been moving northwestward across eastern Honduras, but it is just about to reach the waters of the northwestern Caribbean Sea. Despite moving over land for the past 12-15 hours, the cyclone appears to have a relatively intact and well-defined inner core. Deep convection has actually been increasing over the center, and recent 85-GHz microwave data showed at least some form of a convective ring. Given these signs, the maximum winds are being held at 35 kt. An Air Force Reserve Hurricane Hunter aircraft will be investigating Nate during the next several hours to get a better handle on the storm's intensity and structure. Nate has been moving northwestward while crossing Nicaragua and Honduras, and the initial motion estimate is 325/10 kt. The storm is currently embedded within a broad Central American gyre, and it should swing north-northwestward on the east side of this gyre during the next 36 hours. After 36 hours, Nate should turn northward and then northeastward along the western periphery of a mid-tropospheric high centered off the southeastern U.S. coastline. Compared to yesterday at this time, the track models have come into much better agreement, and all the reliable models take Nate's center across the northeastern portion of the Yucatan peninsula in 24 hours and then across the U.S. central Gulf coast between 48 and 60 hours. Because of this tight clustering, there are no notable cross-track changes in the NHC forecast. Speed-wise, however, the updated official forecast is a bit faster than the previous one and has caught up to the various consensus aids. Due to low shear and very high oceanic heat content in the northwestern Caribbean Sea, Nate should at least steadily strengthen once it moves offshore, especially since it appears to have a well-defined inner core. Rapid intensification is still not out of the question, and Nate could be near hurricane intensity by the time it reaches the Yucatan coast in about 24 hours. Land interaction with the Yucatan peninsula could cause a brief hiatus in the strengthening trend, but conditions should be conducive for additional intensification while Nate is over the Gulf of Mexico. Overall, the intensity models have not changed much on this cycle, and the NHC forecast still calls for a 48-hour intensity of 70 kt, which is at the upper end of the guidance between HWRF and HCCA. As mentioned before, Nate could strengthen further in the time between the 48-hour position and when it crosses the U.S. Gulf coast. KEY MESSAGES: 1. Heavy rainfall is the main threat from Nate in portions of Central America, with life-threatening flash flooding and mud slides possible in portions of Nicaragua, Honduras, Costa Rica, Panama, and Belize through Friday night. 2. Nate could be near hurricane intensity when it approaches the Yucatan Peninsula late Friday, bringing direct impacts from wind, storm surge, and heavy rainfall. A tropical storm warning and a hurricane watch are in effect for a portion of this area, and life-threatening flash flooding is also possible. 3. Nate is forecast to reach the northern Gulf Coast this weekend as a hurricane, and the threat of direct impacts from wind, storm surge, and heavy rainfall is increasing from Louisiana through the western Florida Panhandle. Hurricane and tropical storm watches, as well as a storm surge watch, have been issued for a portion of the northern Gulf Coast, and residents in these areas should monitor the progress of Nate, heeding any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 15.8N 84.7W 35 KT 40 MPH...INLAND 12H 06/1200Z 17.8N 85.6W 40 KT 45 MPH...OVER WATER 24H 07/0000Z 20.8N 87.1W 50 KT 60 MPH...INLAND 36H 07/1200Z 24.3N 89.1W 60 KT 70 MPH...OVER WATER 48H 08/0000Z 27.5N 90.2W 70 KT 80 MPH 72H 09/0000Z 33.7N 87.9W 45 KT 50 MPH...INLAND 96H 10/0000Z 40.0N 79.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 11/0000Z 43.0N 68.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg |