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Hurricane Irwin Forecast Discussion Number 16
2017-07-26 10:47:05| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Wed Jul 26 2017 000 WTPZ45 KNHC 260846 TCDEP5 Hurricane Irwin Discussion Number 16 NWS National Hurricane Center Miami FL EP102017 200 AM PDT Wed Jul 26 2017 An earlier 0500 UTC METOP-A AMSU image and fortuitous ASCAT A/B overpasses indicate that Irwin's circulation center is located near the southern edge of the cloud canopy. Apparently, the moderate southeasterly outflow produced by Hurricane Hilary is affecting Irwin's core structure. Cloud tops have warmed during the past several hours and a compromise of the Dvorak subjective T-numbers from SAB and TAFB support an initial intensity of 70 kt for this advisory. The global models as well as the statistical-dynamical intensity guidance show continued slow weakening during the next 36 hours while the hurricane remains within the impinging upper-level outflow of Hilary. Afterward, further gradual weakening is forecast as the cyclone traverses cooler oceanic temperatures and enters a less than favorable thermodynamic environment. The official forecast is similar to the previous package and is based on the IVCN consensus. The much anticipated turn toward the west-southwest has finally commenced, and the cyclone motion is estimated to be 255/6 kt. Some binary interaction with Hilary during the next 48 hours or so should cause Irwin to stall, and then accelerate cyclonically around the southeast through northeast periphery of Hilary on days 4 and 5. Global and ensemble models, however, show a much slower forward motion beyond 72 hours than what was indicated in the previous advisory, and adjustments to the 96 and 120 hour forecast periods have been made accordingly. The NHC forecast reflects this significant change in the guidance and is based a blend of the TVCX and HFIP Corrected Consensus (HCCA) models. The ASCAT 0502 UTC scatterometer data and the RVCN multi-model consensus were used for the initial and forecast wind radii. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 15.7N 121.5W 70 KT 80 MPH 12H 26/1800Z 15.5N 122.5W 65 KT 75 MPH 24H 27/0600Z 15.1N 123.7W 60 KT 70 MPH 36H 27/1800Z 14.8N 124.4W 55 KT 65 MPH 48H 28/0600Z 14.7N 124.7W 55 KT 65 MPH 72H 29/0600Z 14.9N 124.5W 55 KT 65 MPH 96H 30/0600Z 18.0N 124.5W 50 KT 60 MPH 120H 31/0600Z 20.5N 126.0W 45 KT 50 MPH $$ Forecaster Roberts
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