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Hurricane JIMENA Forecast Discussion Number 22
2015-09-01 04:45:32| National Hurricane Center (East Pacific)
Issued at 800 PM PDT MON AUG 31 2015 000 WTPZ43 KNHC 010245 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 PM PDT MON AUG 31 2015 Jimena is experiencing another eyewall replacement. Satellite data show a double eyewall structure within the hurricane's inner core, with the eye having become cloud-filled and less defined throughout the day. There has also been a dramatic warming of cloud top temperatures during the past 12 hours or so. Dvorak intensity estimates have decreased substantially since the last advisory, and a blend of latest Final T- and CI-numbers from TAFB and SAB is used to lower the intensity to 115 kt. Although the vertical wind shear should be extremely low and Jimena should still be moving over SSTs greater than 28 deg C during the next 48 hours, the intensity guidance shows slow weakening. Neutral thermodynamic conditions and a notable drop-off in oceanic heat content along the cyclone's track likely contributes to a decrease in intensity, at least in the statistical guidance. Regardless, internal dynamics in the hurricane's inner core are likely to be key to the short-term intensity forecast, and given Jimena's current structure of multiple wind maxima at large radii, it is reasonable to expect a slow decay during the next few days. Only at days 4 and 5 does westerly shear increase and the waters become marginally warm. That being said, the large-scale factors do not support anything more than a slow filling. The one caveat is that the cyclone's slow movement could induce oceanic upwelling and result in faster weakening. The new intensity forecast is lowered some from the previous one and is a bit lower than the multi-model consensus after 24 hours, in best agreement with the FSU Superensemble output. The initial motion estimate is 285/14. The tail of a mid-latitude trough, extending south-southwestward from the Pacific Northwest, is forecast to temporarily weaken the subtropical ridge between 140- 155W during the next day or two. As a result, Jimena's forward speed should decrease very soon, and the cyclone should continue to gradually decelerate over the next couple of days. A northwestward to north-northwestward drift in response to the weakness in the ridge is shown by the global models from days 3 to 5. The new track forecast is close to the multi-model consensus, albeit not as far east as the consensus in the latter part of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 16.3N 138.1W 115 KT 130 MPH 12H 01/1200Z 16.6N 139.5W 105 KT 120 MPH 24H 02/0000Z 17.2N 140.9W 100 KT 115 MPH 36H 02/1200Z 17.8N 142.0W 90 KT 105 MPH 48H 03/0000Z 18.3N 142.8W 85 KT 100 MPH 72H 04/0000Z 19.2N 143.7W 75 KT 85 MPH 96H 05/0000Z 20.5N 144.3W 65 KT 75 MPH 120H 06/0000Z 22.0N 144.9W 55 KT 65 MPH $$ Forecaster Kimberlain
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