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Tropical Storm IRWIN Forecast Discussion Number 24
2017-07-28 10:39:47| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Fri Jul 28 2017 000 WTPZ45 KNHC 280839 TCDEP5 Tropical Storm Irwin Discussion Number 24 NWS National Hurricane Center Miami FL EP102017 200 AM PDT Fri Jul 28 2017 Although conventional satellite imagery shows recent improvement in the banding feature wrapping around the eastern half of the cyclone, an ambiguity solution of a 0514 UTC ASCAT-B overpass indicates that Irwin has weakened. Based on the scatterometer data and a blend of the subjective Dvorak satellite estimates from TAFB and SAB, the initial intensity is lowered to 45 kt for this advisory. The CIMSS wind shear analysis and the SHIPS model both indicate that moderate northeasterly shear, produced by an anticyclone to the north, will be the primary inhibitor for any significant strengthening prior to Irwin's demise in 4 days. Little change in the cyclone's intensity is forecast before the merging of Irwin with Tropical Storm Hilary occurs around the 96 hour period. The initial motion estimate continues as a drift toward the west, or 270/02 kt. The large-scale models indicate this slow motion, or meander, continuing through the 36 hour period. Afterward, Irwin is expected to accelerate northward around the eastern peripheral flow of Hilary. The global and regional models also generally agree with the merging of the two tropical cyclones to occur in 4 days, or less. The official forecast has been adjusted to the right of the previous track forecast beyond 36 hours to align more closely to the TVCX and HCCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 14.9N 124.8W 45 KT 50 MPH 12H 28/1800Z 14.9N 124.9W 50 KT 60 MPH 24H 29/0600Z 15.0N 124.8W 50 KT 60 MPH 36H 29/1800Z 15.7N 124.5W 50 KT 60 MPH 48H 30/0600Z 17.4N 124.5W 45 KT 50 MPH 72H 31/0600Z 22.0N 126.3W 45 KT 50 MPH 96H 01/0600Z...DISSIPATED $$ Forecaster Roberts
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