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Tropical Depression Sixteen Forecast Discussion Number 2
2017-10-04 22:51:11| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Wed Oct 04 2017 000 WTNT41 KNHC 042051 TCDAT1 Tropical Depression Sixteen Discussion Number 2 NWS National Hurricane Center Miami FL AL162017 500 PM EDT Wed Oct 04 2017 Visible satellite images show that the depression has lots of curved bands, although it is somewhat lacking any inner core features. An Air Force Reserve Hurricane Hunter flew into the depression this afternoon and found a well-defined circulation, with maximum flight-level winds of 37 kt and SFMR values around 30 kt. These data support keeping the intensity at 30 kt for this advisory. Environmental conditions look quite favorable for strengthening over the next few days, with low shear and very warm and deep water in the path of the cyclone. The various rapid intensification indices are all higher than the last cycle, suggesting an increasing chance of rapid intensification occurring. The fly in the ointment, however, is all of the potential land interaction, first over Central America and then possibly over the Yucatan Peninsula. As a compromise, the intensity forecast is raised considerably from the previous one during the first 3 days, but is still below some guidance, such as the HWRF. The depression continues to move slowly northwestward, steered by a distant ridge over the southwestern Atlantic. However the steering pattern is forecast to change quickly tomorrow as a mid-tropospheric trough over the Florida Straits moves across the northwestern Caribbean into the southwestern Gulf of Mexico. Southerly flow on the eastern side of that trough should cause the cyclone to move much faster to the north-northwest by Friday and northward into the Gulf of Mexico on Saturday. While there is some agreement on the synoptic pattern, the model track agreement is rather poor, even in the short term, with the GFS and ECMWF being 90 miles apart on the forecast track as soon as 24 hours out. This has profound differences down the road, with the GFS-based guidance moving considerably faster and to the left of the ECMWF and UKMET across the Gulf of Mexico. Overall, the guidance has generally shifted a bit westward since the last cycle, so the latest points in the long range have been adjusted in that direction. At this point, I wouldn't focus too much attention on the details of the long-range forecast until the guidance comes into better agreement. A G-IV mission and Florida special soundings have been set up for tomorrow to better determine the synoptic steering flow around the cyclone. KEY MESSAGES: 1. The depression is forecast to strengthen and bring tropical storm conditions to portions of Nicaragua and Honduras tonight through 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 is expected to be near hurricane intensity when it approaches the Yucatan Peninsula late Friday or Saturday, bringing direct impacts from wind, storm surge, and heavy rainfall. A hurricane watch could be issued for this area later this evening. 3. The system is forecast to continue strengthening 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 to Florida should monitor the progress of this system for the next several days and heed any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 12.5N 82.5W 30 KT 35 MPH 12H 05/0600Z 13.2N 83.1W 40 KT 45 MPH 24H 05/1800Z 14.6N 83.8W 40 KT 45 MPH...INLAND 36H 06/0600Z 16.7N 84.6W 50 KT 60 MPH 48H 06/1800Z 19.5N 85.8W 60 KT 70 MPH 72H 07/1800Z 25.0N 88.0W 75 KT 85 MPH 96H 08/1800Z 30.5N 86.0W 65 KT 75 MPH...INLAND 120H 09/1800Z 35.5N 82.0W 30 KT 35 MPH...POST-TROP/INLAND $$ Forecaster Blake
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