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Tropical Storm Irwin Forecast Discussion Number 33
2017-07-30 16:36:34| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Sun Jul 30 2017 000 WTPZ45 KNHC 301436 TCDEP5 Tropical Storm Irwin Discussion Number 33 NWS National Hurricane Center Miami FL EP102017 800 AM PDT Sun Jul 30 2017 Even though Irwin is crossing the 26 deg C isotherm, it does not appear to be weakening yet. In fact, recent microwave data indicate the tropical storm has a mid-level eye, which has occasionally appeared in geostationary satellite images. The system is still producing a fair amount of deep convection, especially to the south of the center. The latest Dvorak CI-numbers from TAFB and SAB are 3.5/55 kt and accordingly, the initial intensity is set a bit higher to 55 kt. This wind speed estimate is also in agreement with ASCAT data from several hours ago that showed maximum winds near 50 kt. Despite the recent increase in intensity, Irwin is expected to begin weakening soon as it moves over even cooler waters and into a drier and more stable air mass. The storm is likely to become a remnant low in 36 to 48 hours when it will be over SSTs near 22 deg C. Most of the global models show the remnant low dissipating in 4 to 5 days. The NHC intensity forecast follows the trend of the guidance, and it is largely unchanged from the previous prediction. Irwin is moving north-northwestward, or 345 degrees, at 8 kt. The system is embedded in south-southeasterly flow in the wake of Hilary, and it is expected to remain in this steering flow for another day or two. Once Irwin becomes a remnant low, the shallow system is expected to turn a little to the left and slow down as it becomes steered by the low-level flow. The NHC track forecast is adjusted a little to the north and east of the previous one, to come into better agreement with the latest consensus models. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 17.9N 125.4W 55 KT 65 MPH 12H 31/0000Z 19.4N 126.1W 50 KT 60 MPH 24H 31/1200Z 21.7N 127.3W 40 KT 45 MPH 36H 01/0000Z 23.9N 128.6W 35 KT 40 MPH 48H 01/1200Z 25.7N 130.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 02/1200Z 27.9N 132.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 03/1200Z 29.0N 133.2W 15 KT 15 MPH...POST-TROP/REMNT LOW 120H 04/1200Z...DISSIPATED $$ Forecaster Cangialosi
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