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Tropical Storm IRWIN Forecast Discussion Number 34
2017-07-30 22:32:06| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Sun Jul 30 2017 000 WTPZ45 KNHC 302031 TCDEP5 Tropical Storm Irwin Discussion Number 34 NWS National Hurricane Center Miami FL EP102017 200 PM PDT Sun Jul 30 2017 Although the mid-level eye feature is no longer evident in satellite images, the compact circulation of Irwin is still fairly well organized. The convective pattern consists of a central dense overcast with fragmented curved bands mostly to the south of the center. The Dvorak CI-numbers from TAFB and SAB remain 3.5/55 kt, so the initial intensity is held at that value. Irwin has now crossed the 26 deg C isotherm, and it will be headed for even cooler waters during the next few days. In addition, a large area of stratocumulus clouds are wrapping into the western and southern portions of the circulation, indicative of stable air beginning to affect the system. These unfavorable environmental conditions should lead to steady weakening and ultimately cause Irwin to degenerate into a remnant low in about 36 hours, or possibly sooner. The remnant low is now expected to dissipate by day 4, following the global model guidance. The NHC intensity forecast is largely an update of the previous one and in line with the bulk of the guidance. Irwin is moving north-northwestward, or 335 degrees, at 8 kt embedded in the flow in the wake of Hilary. This motion with an increase in forward speed is expected during the next day or two. Once Irwin becomes a remnant low, the shallow system is expected to turn a little to the left and slow down when it becomes steered by the low-level flow. The NHC track forecast is similar to the previous one, and it lies close to the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 18.5N 125.6W 55 KT 65 MPH 12H 31/0600Z 20.3N 126.5W 50 KT 60 MPH 24H 31/1800Z 22.6N 127.7W 40 KT 45 MPH 36H 01/0600Z 24.7N 129.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 01/1800Z 26.4N 130.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 02/1800Z 28.1N 132.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 03/1800Z...DISSIPATED $$ Forecaster Cangialosi
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