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Tropical Storm RACHEL Forecast Discussion Number 23
2014-09-30 04:37:35| National Hurricane Center (East Pacific)
Issued at 800 PM PDT MON SEP 29 2014 000 WTPZ43 KNHC 300237 TCDEP3 TROPICAL STORM RACHEL DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182014 800 PM PDT MON SEP 29 2014 A burst of deep convection with cloud tops of -70C to -75C developed during the late afternoon in the same region where earlier ASCAT overpasses indicated several surface wind vectors of 40-43 kt. As a result, the intensity at 0000 UTC synoptic time was maintained at 45 kt. However, over the past couple of hours, cloud tops have warmed and decreased in areal coverage significantly, so the advisory intensity has been lowered to 40 kt. The initial motion estimate is 360/02 kt. Steering currents are collapsing as Rachel moves into a large break in the subtropical ridge created by a mid-latitude trough to the north of the cyclone. As a result, Rachel is expected to become nearly stationary fairly soon and meander in the same general area for the next 24 hours or so. After that, the ridge to the north of what should be a significantly weakened tropical cyclone is expected to build back in as the mid-latitude trough lifts out, driving Rachel or its remnants slowly toward the west or west-southwest until dissipation occurs in 72-96 hours. The new NHC forecast track is similar to the previous advisory track and the consensus model TVCE. Rachel is not long for this world due to the combination of strong southwesterly vertical wind shear, sea-surface temperatures less than 26C, and a cooler and drier airmass working its way into the inner core region of the cyclone. As a result, the storm is expected to weaken to a remnant low pressure system within 24 hours and dissipate by 96 hours. The official intensity forecast closely follows a blend of the Decay-SHIPS model and the consensus intensity model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 23.3N 117.5W 40 KT 45 MPH 12H 30/1200Z 23.3N 117.8W 35 KT 40 MPH 24H 01/0000Z 23.3N 118.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 01/1200Z 23.2N 118.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 02/0000Z 23.1N 118.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 03/0000Z 23.0N 120.3W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 04/0000Z...DISSIPATED $$ Forecaster Stewart
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