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Hurricane ISELLE Forecast Discussion Number 10
2014-08-03 04:38:41| National Hurricane Center (East Pacific)
Issued at 800 PM PDT SAT AUG 02 2014 000 WTPZ44 KNHC 030238 TCDEP4 HURRICANE ISELLE DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092014 800 PM PDT SAT AUG 02 2014 Iselle is still strengthening. The central dense overcast has become more symmetric since the last advisory, with cloud top temperatures cooling slightly. The eye was also becoming better defined but has recently become obscured by overshooting convective tops. Satellite intensity estimates from TAFB and SAB at 0000 UTC were T5.0/90 kt and UW-CIMSS ADT values are at 5.4/99 kt. These data support increasing the initial intensity estimate to 95 kt. The initial motion estimate is just north of due west or 275/09. A subtropical ridge north of Iselle should allow the current motion to persist in the short term. However, a mid-latitude trough digging roughly along 130W should temporarily weaken the ridge during the next day or two, causing the forward speed of Iselle to nominally decrease. When the subtropical ridge rebuilds over the central Pacific after day 3, Iselle should move on a westward and then west-northwestward heading a faster forward speed. The track guidance is in relatively good agreement throughout the forecast period, and the forecast track is adjusted only slightly to the south in the direction of the multi-model consensus TVCE. It is difficult to see Iselle strengthening much further. Although northeasterly shear over the cyclone is forecast to decrease during the next couple of days, the thermodynamic contribution from the environment should gradually become less favorable. This would suggest that some additional intensification is possible in the very short term, followed by slow weakening after 24 hours. The one caveat would be that with little shear and marginally favorable thermodynamic conditions Iselle could evolve into an annular hurricane and maintain a somewhat higher intensity during the next few days. By days 4 and 5, even less favorable thermodynamic factors and an uptick in south-southwesterly shear should result in quicker weakening as Iselle approaches the Hawaiian Islands. The intensity forecast is somewhat higher than the previous one in the short term and represents a blend of the multi-model consensus and FSU Superensemble output. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 15.2N 131.0W 95 KT 110 MPH 12H 03/1200Z 15.4N 132.6W 100 KT 115 MPH 24H 04/0000Z 15.6N 134.6W 95 KT 110 MPH 36H 04/1200Z 15.7N 136.4W 90 KT 105 MPH 48H 05/0000Z 15.8N 137.9W 85 KT 100 MPH 72H 06/0000Z 15.9N 141.2W 75 KT 85 MPH 96H 07/0000Z 16.6N 146.2W 60 KT 70 MPH 120H 08/0000Z 17.8N 152.4W 45 KT 50 MPH $$ Forecaster Kimberlain
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