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Tropical Storm Iselle Forecast Discussion Number 6
2020-08-27 22:32:49| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Thu Aug 27 2020 000 WTPZ44 KNHC 272032 TCDEP4 Tropical Storm Iselle Discussion Number 6 NWS National Hurricane Center Miami FL EP142020 200 PM PDT Thu Aug 27 2020 Since the previous advisory, a new burst of deep convection developed near the center of Iselle the persisted for much of the morning. It was not until recently that the easterly shear has begun to push the convection to the west of the center. The latest Dvorak estimates from TAFB and SAB as well as data from a recent ASCAT overpass all agree that the initial intensity has increased to 45 kt. Moderate-to-strong easterly to northeasterly vertical wind shear should prevent Iselle from further strengthening over the next couple of days. After that time, the shear is forecast to relax somewhat. However, by that time 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 late this weekend into early next week before degenerating into a remnant low. The latest NHC intensity forecast is close to the LGEM guidance. Iselle continues moving northeastward at 4 kt, embedded in a large monsoon gyre. The steering flow is forecast to become more southeasterly this weekend inside the gyre, resulting in a gradual turn to the northwest. As the cyclone breaks north of the gyre and becomes shallow, a turn to the west is anticipated while the system becomes steered by a low- to mid- level ridge to its north. The latest NHC track forecast was nudged just a little to the right of the previous one due to a shift in the guidance, and lies in between the previous forecast and the various track consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 17.2N 115.8W 45 KT 50 MPH 12H 28/0600Z 17.8N 115.3W 45 KT 50 MPH 24H 28/1800Z 18.6N 114.7W 45 KT 50 MPH 36H 29/0600Z 19.6N 114.4W 40 KT 45 MPH 48H 29/1800Z 20.8N 114.3W 35 KT 40 MPH 60H 30/0600Z 21.9N 114.6W 30 KT 35 MPH 72H 30/1800Z 22.8N 115.4W 25 KT 30 MPH 96H 31/1800Z 23.2N 116.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/1800Z 23.1N 117.8W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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