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Tropical Storm Iselle Forecast Discussion Number 11
2020-08-29 04:32:14| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Fri Aug 28 2020 000 WTPZ44 KNHC 290232 TCDEP4 Tropical Storm Iselle Discussion Number 11 NWS National Hurricane Center Miami FL EP142020 800 PM PDT Fri Aug 28 2020 Persistent bursts of deep convection continue to develop just to the west of Iselle's center, which occasionally becomes hidden beneath the cirrus outflow (as it is now). Dvorak final-T numbers from TAFB and SAB are 3.0/45 kt based on a shear pattern, and along with what was shown by an afternoon ASCAT pass, Iselle's intensity remains 45 kt. Strong shear from the east-northeast is forecast to continue for the next 24 hours or so. After that time, the shear should relax, but then the thermodynamic environment becomes more limiting with Iselle moving over sub-26C waters and into a much more stable environment. All told, Iselle is expected to steadily weaken during the next several days, and it is likely to degenerate into a remnant low on Sunday. The NHC forecast is very similar to the previous prediction and is close to HCCA and the IVCN intensity consensus aid. The remnant low is expected to dissipate in about 4 days. Iselle is moving slowly north-northeastward (015/5 kt) on the western periphery of a low- to mid-level area of high pressure centered over Mexico. This high, along with a trough extending off the coast of California, should cause Iselle to gradually turn toward the north and then north-northwest with some increase in forward speed during the next couple of days. There is a typical amount of spread among the track models, and they generally agree on this northward motion with a slight bend to the left through the forecast period. The regional hurricane models appear almost in a cluster all to themselves on the eastern side of the guidance envelope, and the NHC forecast therefore closely follows the TVDG model consensus aid, which gives double weight to the global models. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 19.3N 115.2W 45 KT 50 MPH 12H 29/1200Z 20.2N 115.0W 40 KT 45 MPH 24H 30/0000Z 21.7N 115.0W 35 KT 40 MPH 36H 30/1200Z 23.1N 115.4W 30 KT 35 MPH 48H 31/0000Z 24.2N 115.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 31/1200Z 24.9N 116.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 01/0000Z 25.6N 116.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 02/0000Z...DISSIPATED $$ Forecaster Berg
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