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Tropical Storm GUILLERMO Forecast Discussion Number 5
2015-07-31 04:47:11| National Hurricane Center (East Pacific)
Issued at 800 PM PDT THU JUL 30 2015 000 WTPZ44 KNHC 310247 TCDEP4 TROPICAL STORM GUILLERMO DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015 800 PM PDT THU JUL 30 2015 Microwave and conventional satellite imagery indicate that Guillermo is continuing to become better organized. The microwave imagery shows a developing eye, which has occasionally appeared in visible and infrared imagery. Satellite intensity estimates are 55 kt from TAFB and SAB, and the latest intensity estimate from the CIMSS Advanced Dvorak Technique is 65 kt. Based on these, the initial intensity is increased to 60 kt. Guillermo has turned to the right during the past several hours with the initial motion now 305/12. Other than that, there is little change in the forecast philosophy. The subtropical ridge north of the storm is forecast to strengthen slightly, causing Guillermo to accelerate west-northwestward during the next 36 hours. After that time, a mid- to upper-level low well west of California is expected to produce a break in the ridge, which should cause the cyclone to slow down and turn more northward by day 5. The forecast track from 0 to 72 hours has been adjusted northward based on the initial position and motion. After 72 hours, the forecast guidance has again shifted to the left or west, and the forecast track has also been moved in that direction. However, this part of the forecast lies to the north of the various consensus models. The developing eye seen in microwave imagery shows that the structure of Guillermo is conducive for additional rapid intensification. Also, the Rapid Intensification Index of the SHIPS model shows a 50 percent chance of a 30 kt increase in intensity during the next 24 hours. Based on this, the intensities during the first 48 hours of the forecast have been increased over those of the previous advisory, and this part of the forecast lies near the upper edge of the intensity guidance. After 48 hours, the cyclone will move over decreasing sea surface temperatures and possibly encounter westerly vertical wind shear. This combination is expected to cause the cyclone to weaken below hurricane strength by 120 hours. It should be noted that the early part of the intensity forecast is of low confidence due to the uncertainties associated with rapid intensification, and the later part is of low confidence due to uncertainties in how much shear Guillermo will encounter. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 10.8N 129.3W 60 KT 70 MPH 12H 31/1200Z 11.4N 131.4W 70 KT 80 MPH 24H 01/0000Z 12.3N 134.5W 80 KT 90 MPH 36H 01/1200Z 13.1N 137.5W 90 KT 105 MPH 48H 02/0000Z 13.9N 139.8W 95 KT 110 MPH 72H 03/0000Z 15.5N 143.5W 85 KT 100 MPH 96H 04/0000Z 16.5N 146.5W 70 KT 80 MPH 120H 05/0000Z 18.0N 149.5W 55 KT 65 MPH $$ Forecaster Beven
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