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Tropical Storm Iselle Forecast Discussion Number 5
2020-08-27 16:50:42| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Thu Aug 27 2020 000 WTPZ44 KNHC 271450 TCDEP4 Tropical Storm Iselle Discussion Number 5 NWS National Hurricane Center Miami FL EP142020 800 AM PDT Thu Aug 27 2020 Iselle consists of a rather ragged looking area of deep convection being sheared to the southwest of a partially exposed low-level center. A blend of the latest satellite intensity estimates from TAFB and UW-CIMSS support keeping the initial intensity at 40 kt. Moderate-to-strong easterly to northeasterly vertical wind shear will likely prevent Iselle from strengthening over the next couple of days. After that time, the shear is forecast to relax somewhat. However, the cyclone will then be moving over SSTs of only 26 C and into a more stable atmospheric environment. This should cause the deep convection to gradually dissipate, and the cyclone is expected to weaken this weekend before degenerating into a remnant low early next week. The latest NHC intensity forecast is a blend of the IVCN consensus and SHIPS guidance. Iselle is moving northeastward at 4 kt, embedded in a large monsoon gyre. The steering flow is forecast to become more southerly this weekend inside the gyre, resulting in a more northward motion. As the cyclone breaks north of the gyre, a turn to the northwest then west is anticipated while the system becomes steered by a low- to mid- level ridge to its north. The latest NHC track forecast is little changed from the previous one, and lies in between the HFIP corrected consensus HCCA and the TVCX track consensus. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 17.0N 115.8W 40 KT 45 MPH 12H 28/0000Z 17.5N 115.4W 40 KT 45 MPH 24H 28/1200Z 18.2N 115.0W 40 KT 45 MPH 36H 29/0000Z 18.9N 114.6W 40 KT 45 MPH 48H 29/1200Z 19.9N 114.2W 40 KT 45 MPH 60H 30/0000Z 21.2N 114.4W 35 KT 40 MPH 72H 30/1200Z 22.2N 115.3W 30 KT 35 MPH 96H 31/1200Z 22.5N 116.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/1200Z 22.3N 117.3W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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