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Tropical Storm Gonzalo Forecast Discussion Number 12
2020-07-24 16:58:13| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Fri Jul 24 2020 000 WTNT42 KNHC 241458 TCDAT2 Tropical Storm Gonzalo Discussion Number 12 NWS National Hurricane Center Miami FL AL072020 1100 AM AST Fri Jul 24 2020 Gonzalo continues to produce bursts of deep convection, especially in the southeast quadrant, but has not become any better organized overall since the last advisory. Microwave imagery overnight indicated the low-level structure of Gonzalo is still largely intact, but this has not translated into better convective organization. ASCAT data valid shortly after 12Z revealed that Gonzalo has accelerated west faster than anticipated and has not strengthened. In fact the strongest winds in the ASCAT data were only 30-35 kt. The resolution of ASCAT likely limits its ability to sample the actual max winds of small storms like Gonzalo, but it is another indication that the cyclone has not strengthened and could be weakening. The initial intensity for this advisory is set at 45 kt, based primarily on the latest TAFB Dvorak fix and the UW-CIMSS SATCON. An Air Force Reserve reconnaissance aircraft scheduled to investigate the storm this afternoon will provide a more information about Gonzalo's intensity and structure. Due primarily to the adjusted initial position, the NHC track forecast has been adjusted a fair amount west and south of the previous advisory. Overall Gonzalo is still forecast to move generally westward or west-northwestward through the period, steered by the subtropical ridge to the north. The new NHC forecast lies between the old forecast, adjusted for the new initial position, and the HFIP Corrected Consensus. The intensity guidance is generally lower than it has been for the last day or so, and none of the operational models forecast Gonzalo to reach hurricane strength. Unfortunately, small storms like Gonzalo are often subject to large swings in intensity, up or down, and that aspect of the forecast remains highly uncertain, even though the spread in the guidance is not particularly high. The NHC forecast has been adjusted only slightly lower for this cycle and is now above all of the guidance at the time the system is forecast to pass through the Windward Islands. A larger adjustment could be made later today if the most recent model trends continue, or if the recon mission finds that Gonzalo is even weaker than the current estimates. Key Messages 1. Gonzalo is forecast to bring tropical storm conditions across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Warning and Watches are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials. 2. Gonzalo is expected to produce heavy rain over portions of the southern Windward Islands. This could lead to life-threatening flash flooding. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 10.0N 54.2W 45 KT 50 MPH 12H 25/0000Z 10.5N 56.0W 50 KT 60 MPH 24H 25/1200Z 11.4N 59.1W 55 KT 65 MPH 36H 26/0000Z 12.4N 62.3W 60 KT 70 MPH 48H 26/1200Z 13.0N 65.7W 50 KT 60 MPH 60H 27/0000Z 13.7N 69.0W 40 KT 45 MPH 72H 27/1200Z 14.0N 72.0W 30 KT 35 MPH 96H 28/1200Z...DISSIPATED $$ Forecaster Zelinsky
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