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Tropical Storm Gonzalo Forecast Discussion Number 6
2020-07-23 04:35:15| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Wed Jul 22 2020 000 WTNT42 KNHC 230235 TCDAT2 Tropical Storm Gonzalo Discussion Number 6 NWS National Hurricane Center Miami FL AL072020 1100 PM AST Wed Jul 22 2020 A series of earlier microwave passes over Gonzalo reveal a small eye feature beneath a relatively ragged, Central Dense Overcast with associated -75.5C cloud tops. Based on the evidence of the small eye and a blend of the subjective and objective satellite intensity estimates, the initial intensity is raised to 50 kt for advisory. The intensity forecast philosophy remains the same as the previous advisory with a higher than normal degree of uncertainty in the latter half of the period as the cyclone moves through the Caribbean. Gonzalo should remain in an environment of relatively low shear, although the impacts of dry, stable air and large-scale subsidence could hamper further intensification in a few days. It's worth noting that the ECMWF Ensemble model is showing a pretty significant low- to mid-level easterly surge that spreads just to the north of the cyclone's forecast track and over the northeastern Caribbean in a couple of days. This predicted event could possibly curtail strengthening at that time. On the other hand, with the exception of the ECMWF, the global models now show the cyclone maintaining tropical storm strength while moving into the eastern Caribbean. The official intensity forecast is adjusted slightly above the previous forecast, hedging toward the HFIP HCCA consensus and the IVCN multi-model intensity aid solutions. 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. There is no change to the track forecast philosophy. Gonzalo is on the south side of a low- to mid-level tropospheric ridge, and this feature 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. The NHC track forecast is nudged a bit to the north of the previous one and is close to the various consensus aids. Interests in the Windward Islands should continue to monitor the progress of this system. A Hurricane Watch is now issued for Barbados. Key Messages 1. Gonzalo is expected to move near or over the southern Windward Islands this weekend, and could bring direct impacts from winds and heavy rainfall. While it is too soon to determine the magnitude and timing of those impacts, interests in the southern Windward Islands should monitor the progress of Gonzalo. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 9.9N 45.9W 50 KT 60 MPH 12H 23/1200Z 10.0N 47.6W 60 KT 70 MPH 24H 24/0000Z 10.2N 50.0W 65 KT 75 MPH 36H 24/1200Z 10.6N 52.7W 70 KT 80 MPH 48H 25/0000Z 11.2N 55.5W 75 KT 85 MPH 60H 25/1200Z 11.8N 58.6W 70 KT 80 MPH 72H 26/0000Z 12.6N 61.8W 60 KT 70 MPH 96H 27/0000Z 14.3N 67.6W 50 KT 60 MPH 120H 28/0000Z 15.6N 73.1W 40 KT 45 MPH $$ Forecaster Roberts
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