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Tropical Depression Fourteen Forecast Discussion Number 2
2020-08-20 22:57:44| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Thu Aug 20 2020 000 WTNT44 KNHC 202057 TCDAT4 Tropical Depression Fourteen Discussion Number 2 NWS National Hurricane Center Miami FL AL142020 500 PM EDT Thu Aug 20 2020 An Air Force Reserve Hurricane Hunter aircraft investigating the system found an area of lighter winds--likely where the center would be--farther south than previous estimates. The highest flight-level wind measured by the aircraft was 30 kt at an altitude of 2500 feet, and although there were some SFMR measurements over 40 kt, these looked coincident with some heavy rain rates and thus are probably not reliable. Therefore, the initial intensity remains 30 kt. Structurally, the depression has a large cloud envelope with sporadic convective cells located in loose bands. The updated initial position derived from the aircraft data indicates that the current motion is still westward, or 270/16 kt. This southward adjustment really only affected the first 36 hours or so of the forecast, with NHC's official track forecast being shifted southward during that period. This ends up taking the cyclone's center over extreme northern Nicaragua and northeastern Honduras in 12-24 hours. After 36 hours, model guidance remains in good agreement that the system should turn northwestward due to a deep-layer trough over the Gulf of Mexico. The new set of model guidance has not shifted much from the previous cycle, and the NHC track forecast is very close to the morning forecast despite the initial position adjustment, with perhaps a slight eastward shift on days 4 and 5. In general, the NHC forecast is closest to the GFS and HCCA model solutions. The depression's farther-south position makes the intensity forecast more complicated with potentially more land interaction with parts of Central America. Slight strengthening to tropical storm strength is expected before the center reaches Honduras and Nicaragua, with little change thereafter until the center re-emerges over the Gulf of Honduras. Low shear and warm sea surface temperatures should then support further intensification up until it reaches the Yucatan Peninsula. Since there is significant uncertainty in how land interaction will affect the cyclone's intensity, the forecast intensity has been flat-lined between day 2 and day 4, with the understanding that the the winds could increase or decrease from the value shown. Vertical shear is expected to increase by day 5, and some weakening is shown at that time. Key Messages: 1. Tropical Depression Fourteen is expected to strengthen over the northwestern Caribbean Sea through Saturday, and is likely to produce tropical-storm-force winds and heavy rainfall over portions of the coasts of Nicaragua and Honduras, including the Bay Islands, beginning tonight through Friday. The system could be near or at hurricane strength when it reaches the Yucatan Peninsula of Mexico late Saturday, and watches could be required for a portion of that area tonight. 2. The system is expected to move into the south-central Gulf of Mexico as a tropical storm on Sunday. Some strengthening is anticipated while it moves northwestward over the western Gulf of Mexico early next week, but it is too soon to know exactly how strong it will get or the location and magnitude of impacts it will produce along the central or northwestern Gulf Coast. Interests in that area should continue monitoring the progress of this system over the next few days. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 14.3N 81.0W 30 KT 35 MPH 12H 21/0600Z 14.7N 83.0W 35 KT 40 MPH 24H 21/1800Z 15.6N 84.7W 35 KT 40 MPH...INLAND 36H 22/0600Z 17.0N 85.6W 45 KT 50 MPH...OVER WATER 48H 22/1800Z 18.7N 86.6W 55 KT 65 MPH 60H 23/0600Z 20.3N 87.9W 55 KT 65 MPH...INLAND 72H 23/1800Z 22.1N 89.2W 55 KT 65 MPH...OVER WATER 96H 24/1800Z 26.0N 91.5W 55 KT 65 MPH 120H 25/1800Z 28.5N 93.5W 50 KT 60 MPH $$ Forecaster Berg
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