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Hurricane JIMENA Forecast Discussion Number 18
2015-08-31 04:49:59| National Hurricane Center (East Pacific)
Issued at 800 PM PDT SUN AUG 30 2015 000 WTPZ43 KNHC 310249 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 PM PDT SUN AUG 30 2015 Jimena's cloud pattern has been in a remarkably steady state since the last advisory. The hurricane continues to maintain a large circular eye that has warmed slightly, surrounded by a nearly uniform ring of deep convection. There is a faint asymmetry in the convective distribution, suggestive of northerly or north- northwesterly shear as diagnosed by the SHIPS model output. Satellite classifications were T6.5/127 kt from TAFB and SAB, and UW-CIMSS ADT values have held steady at 6.7/132 kt. A blend of these data is used to set the initial intensity at 130 kt. Even though large-scale atmospheric conditions are forecast to remain relatively favorable around Jimena during the couple of days, the intensity guidance indicates that Jimena should begin to weaken soon. The weakening appears to largely be a function of slowly decreasing SSTs along the cyclone's path. Some westerly shear and a larger drop-off in oceanic heat content later in the forecast period suggest continued gradual weakening should occur, but neither the atmosphere nor ocean should produce conditions hostile enough to result in the cyclone's rapid decline. The one caveat to the intensity forecast is that Jimena, already exhibiting some characteristics of an annular hurricane, could weaken more slowly than forecast. The latest NHC intensity forecast is somewhat above the multi-model consensus and is in best agreement with the HWRF model that shows slower overall weakening. Jimena's heading has been a bit more westerly since the previous advisory, but a longer-term average motion estimate is 290/14. A longwave trough, extending southwestward from the U.S. west coast, has eroded the subtropical ridge ridge between 140-150W. As Jimena nears this weakness during the next few days, its forward speed should gradually decrease on a slightly more poleward heading. In the absence of much steering from days 3 to 5, Jimena should drift northwestward. The latest NHC track forecast has hardly changed from the previous one. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 15.0N 132.5W 130 KT 150 MPH 12H 31/1200Z 15.4N 134.4W 125 KT 145 MPH 24H 01/0000Z 16.2N 136.8W 120 KT 140 MPH 36H 01/1200Z 16.8N 138.6W 115 KT 130 MPH 48H 02/0000Z 17.3N 140.0W 105 KT 120 MPH 72H 03/0000Z 18.3N 141.9W 90 KT 105 MPH 96H 04/0000Z 19.1N 143.0W 80 KT 90 MPH 120H 05/0000Z 20.2N 143.9W 70 KT 80 MPH $$ Forecaster Kimberlain
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