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Tropical Storm Gonzalo Forecast Discussion Number 5
2020-07-22 22:32:11| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Jul 22 2020 000 WTNT42 KNHC 222032 TCDAT2 Tropical Storm Gonzalo Discussion Number 5 NWS National Hurricane Center Miami FL AL072020 500 PM AST Wed Jul 22 2020 Satellite imagery suggests that Gonzalo's intensification has paused since the last advisory. The cyclone continues to show a central dense overcast, and microwave imagery indicates a small convective ring present under the overcast. However, the CDO has become a bit ragged, and the other banding seen earlier has dissipated. Subjective and objective satellite intensity estimates are in the 45-55 kt range, the the initial intensity remains a possibly conservative 45 kt. The initial motion is now 270/12. There is no change to the track forecast philosophy. Gonzalo is on the south side of a low- to mid-level subtropical ridge, and this feature should steer the storm generally westward at a faster forward speed for the next 60 h or so. After that time, a motion toward the west-northwest is expected. The new NHC forecast track is again little changed from the previous track, and it lies very close to the consensus models. The intensity forecast remains very problematic and of low confidence. On one side, the cyclone structure, light shear environment,and warm sea surface temperatures suggest strengthening, possibly even rapidly, should occur. In addition, the SHIPS-based guidance and the HWRF still make the system a hurricane. On the other side, the GFS, UKMET, and ECMWF models continue to forecast the system to weaken to an open wave by 120 h, possibly due to dry air entrainment and large-scale subsidence, and microwave imagery suggests that a tongue of drier air is present west and southwest of the cyclone. The NHC intensity forecast again compromises between these extremes, showing Gonzalo peaking as a hurricane in 36-48 h, followed by weakening in deference to the GFS/UKMET/ECMWF. The new intensity forecast is unchanged from the previous forecast. As noted before, the small size of this system makes it susceptible to significant fluctuations in intensity, both upward and downward. Interests in the Windward Islands should monitor the progress of this system, as watches could be issued sometime on Thursday. 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 22/2100Z 9.9N 45.0W 45 KT 50 MPH 12H 23/0600Z 10.0N 46.8W 55 KT 65 MPH 24H 23/1800Z 10.1N 49.2W 65 KT 75 MPH 36H 24/0600Z 10.3N 51.8W 70 KT 80 MPH 48H 24/1800Z 10.8N 54.6W 70 KT 80 MPH 60H 25/0600Z 11.3N 57.6W 65 KT 75 MPH 72H 25/1800Z 12.1N 60.8W 60 KT 70 MPH 96H 26/1800Z 14.0N 67.5W 50 KT 60 MPH 120H 27/1800Z 15.0N 72.5W 40 KT 45 MPH $$ Forecaster Beven
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