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Tropical Storm Gonzalo Forecast Discussion Number 7
2020-07-23 10:42:54| National Hurricane Center (Atlantic)
Issued at 500 AM AST Thu Jul 23 2020 000 WTNT42 KNHC 230842 TCDAT2 Tropical Storm Gonzalo Discussion Number 7 NWS National Hurricane Center Miami FL AL072020 500 AM AST Thu Jul 23 2020 A 0441 UTC ATMS/Soumi NPP microwave overpass revealed a well-developed banding feature wrapping into the center from the east semi-circle. Cloud tops have once again cooled near the surface center and subsequently, the Dvorak satellite intensity estimates from both TAFB and SAB have increased to T3.5 (55 kt). Accordingly, the initial intensity is raised to 55 kt for this advisory. No major changes were made to the intensity forecast and there still remains a relatively high degree of uncertainty beyond day 3 while the cyclone moves through the Caribbean Sea. Strengthening is forecast through 48 hours as Gonzalo approaches the Islands and the forecast is close to a blend of the HCCA intensity consensus, the IVCN multi-model guidance and the Decay SHIPS. Beyond mid-period, the forecast reflects a weakening trend in respect to the European models solution, but at much more gradual rate. It should also be noted that the small size of this system makes it susceptible to significant fluctuations in intensity, both upward and downward. The initial motion is estimated to be due west, or 270/10 kt. The forecast track philosophy remains unchanged. Gonzalo is moving within low to mid-level easterly steering flow produced by a subtropical ridge anchored to the north of the cyclone, and this high pressure should steer the storm generally westward at a faster forward speed for the next few days. After that time, a motion toward the west-northwest is expected. Two distinct model clusters with differing forecast track solutions persist. The European models along with the Canadian indicate a weak cyclone moving generally westward through the southern Windward Islands and dissipating in 5 days or less. The NCEP models, on the other hand, show a much stronger tropical cyclone with a west-northwestward to northwestward motion toward Hispaniola. The NHC forecast basically down the middle of these to model clusters and is very close to the TVCA consensus aid. Interests in the Windward Islands should continue to monitor the progress of this system. A Hurricane Watch is in effect for Barbados. Key Messages 1. There is an increasing risk of wind and rain impacts from Gonzalo in portions of the southern Windward Islands this weekend. Hurricane conditions are possible on Barbados where a hurricane watch has been issued. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 10.0N 47.0W 55 KT 65 MPH 12H 23/1800Z 10.1N 48.7W 65 KT 75 MPH 24H 24/0600Z 10.4N 51.1W 70 KT 80 MPH 36H 24/1800Z 10.9N 53.9W 75 KT 85 MPH 48H 25/0600Z 11.5N 57.0W 75 KT 85 MPH 60H 25/1800Z 12.2N 60.1W 70 KT 80 MPH 72H 26/0600Z 13.0N 63.1W 65 KT 75 MPH 96H 27/0600Z 14.8N 68.8W 50 KT 60 MPH 120H 28/0600Z 16.5N 74.5W 40 KT 45 MPH $$ Forecaster Roberts
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