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Hurricane KARINA Forecast Discussion Number 9
2014-08-15 04:34:33| National Hurricane Center (East Pacific)
Issued at 800 PM PDT THU AUG 14 2014 000 WTPZ41 KNHC 150234 TCDEP1 HURRICANE KARINA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 800 PM PDT THU AUG 14 2014 Karina's structure has degraded significantly since the last advisory. A 2326 UTC AMSU pass showed that the low-level center has become displaced from the deep convection due to 20-25 kt of easterly shear, as diagnosed by CIMSS at the University of Wisconsin. In addition, cloud top temperatures have warmed during the past few hours. The initial intensity remains 65 kt based on the latest TAFB Dvorak estimate, but this could be a little generous. The recent evolution of Karina's structure makes the intensity forecast quite tricky. The SHIPS and LGEM models appear to be responding to less of a positive contribution from persistence and GOES satellite predictors, and show much less strengthening than before. The GFDL and HWRF, on the other hand, continue their pattern of showing more immediate weakening. Since vertical shear is expected to remain rather strong for another 36-48 hours, Karina may have a difficult time recovering. Therefore, the new NHC intensity forecast has been lowered for the entire forecast period but still lies above all of the guidance, especially beyond 24 hours. If Karina cannot recover soon, however, subsequent forecasts will likely require additional decreases to fall in line with the preponderance of the intensity model solutions. The mid-tropospheric pattern consists of a mid-level high centered over the southwestern U.S. with a ridge extending west-southwestward over the Pacific. The ridge is steering Karina westward, or 270/11 kt, and the subtropical ridge is expected to keep the cyclone on a westward or west-northwestward track through the forecast period. Karina could begin to interact with one or two adjacent disturbances toward the end of the forecast period, possibly forcing it to move west-southwestward and at a slower speed by day 5. The track guidance envelope shifted to the north on this cycle, but it was not enough to require a significant change from the previous official forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 17.1N 118.3W 65 KT 75 MPH 12H 15/1200Z 17.4N 119.9W 70 KT 80 MPH 24H 16/0000Z 17.9N 122.0W 70 KT 80 MPH 36H 16/1200Z 18.3N 124.2W 70 KT 80 MPH 48H 17/0000Z 18.4N 126.4W 70 KT 80 MPH 72H 18/0000Z 18.0N 130.5W 65 KT 75 MPH 96H 19/0000Z 17.5N 133.5W 65 KT 75 MPH 120H 20/0000Z 17.0N 136.0W 60 KT 70 MPH $$ Forecaster Berg
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