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Tropical Storm RACHEL Forecast Discussion Number 7
2014-09-26 04:36:40| National Hurricane Center (East Pacific)
Issued at 800 PM PDT THU SEP 25 2014 000 WTPZ43 KNHC 260236 TCDEP3 TROPICAL STORM RACHEL DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182014 800 PM PDT THU SEP 25 2014 While there is strong, deep convection associated with Rachel, microwave and last light visible imagery indicate that the tropical storm is still being sheared with the center at the edge of the convective overcast. Subjective Dvorak assessments from TAFB and SAB as well as the CIMSS AMSU method suggest peak sustained winds of about 45 kt, which is the initial intensity. While an upper-level anticyclone is contributing toward about 15 kt of northeasterly shear over Rachel currently, this should subside to quite low values from 24 through 72 hr. However, at the same time, Rachel's track should take it over gradually cooler waters and into much drier, stable air. The NHC intensity forecast calls for slow intensification through two days, followed by gradual weakening. This prediction is based upon a blend of the LGEM and SHIPS statistical and GFDL dynamical models and is about the same as in the previous advisory. No in situ observations were available for the tropical-storm-force wind radii, so no changes were made to the initial small size of Rachel. The global and regional hurricane models suggest that Rachel will remain relatively small for the next few days, which is the basis for the NHC wind radii forecast. Rachel is moving toward the west-northwest at 13 kt, primarily being steered by a mid-level subtropical ridge to its northeast. The tropical storm should round the western periphery of the ridge in about two to three days. After that time, Rachel will meander as a decaying vortex in the weak lower tropospheric flow. The NHC track forecast is based upon the tightly clustered TVCE multi-model ensemble and is about the same as that issued in the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 17.7N 111.9W 45 KT 50 MPH 12H 26/1200Z 18.4N 113.4W 50 KT 60 MPH 24H 27/0000Z 19.2N 114.7W 55 KT 65 MPH 36H 27/1200Z 20.2N 115.6W 60 KT 70 MPH 48H 28/0000Z 20.9N 116.2W 60 KT 70 MPH 72H 29/0000Z 22.2N 116.3W 50 KT 60 MPH 96H 30/0000Z 23.0N 116.0W 40 KT 45 MPH 120H 01/0000Z 23.0N 116.0W 25 KT 30 MPH $$ Forecaster Landsea
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