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Hurricane RACHEL Forecast Discussion Number 16
2014-09-28 10:40:21| National Hurricane Center (East Pacific)
Issued at 200 AM PDT SUN SEP 28 2014 000 WTPZ43 KNHC 280840 TCDEP3 HURRICANE RACHEL DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182014 200 AM PDT SUN SEP 28 2014 Rachel's eye disappeared for a few hours, but it is now becoming distinct again. Final-T numbers from TAFB and SAB decreased at 0600 UTC, but the initial intensity is held at 75 kt based on CI numbers of 4.5/77 kt and an ADT estimate of T4.4/75 kt. If Rachel is going to strengthen further, it probably has another 6-12 hours to do so before vertical shear begins to increase out of the south and southwest. In addition, Rachel will be moving into a drier environment over the next couple of days, and upwelling of colder ocean water could have a greater-than-normal influence on the intensity since the cyclone will become nearly stationary in a day or two. The SHIPS and LGEM models show Rachel increasing in strength just a bit later today and then only gradually weaken the system through 48 hours. In contrast, the GFDL, HWRF, and FSU Superensemble show weakening beginning soon and predict a faster weakening rate during the next two days. Given the hurricane's improving appearance in satellite imagery, the official forecast still allows some strengthening in the short term. After 24 hours, the NHC forecast shows steady weakening and essentially splits the difference between the two model scenarios. Rachel is moving slowly north-northwestward--335 degrees at 5 kt-- through a break in the subtropical ridge caused by a deep-layer low over the western United States. The steering currents near Rachel are forecast to collapse during the next few days after the deep-layer low moves eastward, and the cyclone is expected to become nearly stationary in 36-48 hours. Once the vertical shear increases, the low-level circulation is expected to begin moving southwestward and west-southwestward in the trade wind flow. The track guidance, in particular the ECMWF, is not as far south on this cycle, and the new NHC track forecast is therefore shifted north and west during the remnant low phase. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 21.1N 117.0W 75 KT 85 MPH 12H 28/1800Z 21.6N 117.2W 80 KT 90 MPH 24H 29/0600Z 22.2N 117.4W 70 KT 80 MPH 36H 29/1800Z 22.4N 117.5W 60 KT 70 MPH 48H 30/0600Z 22.2N 117.6W 45 KT 50 MPH 72H 01/0600Z 21.6N 118.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 02/0600Z 21.3N 119.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 03/0600Z 21.0N 121.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg
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Category:Transportation and Logistics
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