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Tropical Storm IVETTE Forecast Discussion Number 18
2016-08-07 04:34:03| National Hurricane Center (East Pacific)
Issued at 800 PM PDT SAT AUG 06 2016 000 WTPZ45 KNHC 070233 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 800 PM PDT SAT AUG 06 2016 Visible and infrared satellite imagery indicate that all of Ivette's deep convection has been sheared away by moderate-to-strong southwesterly vertical wind shear, leaving the low-level circulation center fully exposed more than 80 n mi southwest of any convection. Satellite intensity estimate from TAFB and SAB have decreased as a result, and the latest UW-CIMSS intensity estimate is T2.7/39 kt. Allowing for some vortex spin down since the previous advisory intensity of 45 kt, the initial intensity has been lowered to 40 kt for this advisory. Ivette has continued to move west-northwestward, or 290/10 kt. This general motion should continue for the next 36 hours or so while the cyclone moves toward a weakness in the subtropical ridge around 139W-140W longitude. After that time, however, Ivette is expected to be a vertically shallow remnant low pressure system that will be steered westward and then west-southwestward by the low-level tradewind flow. The new NHC track forecast is essentially just an extension of the previous advisory track and lies a little south of the multi-model consensus TVCN due to more rapid weakening than previously expected. Ivette still has a very robust low-level circulation and is moving over near-28C SSTs, so redevelopment of deep convection seems likely tonight after 0600Z during the convective maximum period, which should allow the cyclone to retain tropical storm status. However, by 24 hours and beyond, strong southwesterly shear of 25 kt or more, along with considerably drier mid-level air and SSTs of around 26C, should cause any remaining convection to dissipate. As a result, Ivette is forecast to become a remnant low pressure system by 36 hours, with dissipation expected by 96 hours, if not sooner. The official intensity forecast closely follows a blend of the SHIPS and LGEM intensity model solutions. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 16.7N 136.4W 40 KT 45 MPH 12H 07/1200Z 17.2N 137.7W 35 KT 40 MPH 24H 08/0000Z 17.9N 139.3W 30 KT 35 MPH 36H 08/1200Z 18.4N 140.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 09/0000Z 18.5N 142.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 10/0000Z 17.9N 146.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 11/0000Z...DISSIPATED $$ Forecaster Stewart
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