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Hurricane JIMENA Forecast Discussion Number 14
2015-08-30 04:51:23| National Hurricane Center (East Pacific)
Issued at 800 PM PDT SAT AUG 29 2015 000 WTPZ43 KNHC 300251 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 PM PDT SAT AUG 29 2015 Jimena continues to undergo an eyewall replacement, with significant inner-core structural changes seen in satellite data throughout the day. Microwave images show a small inner eyewall rotating around an irregularly-shaped outer eyewall at about 60 n mi radius, the latter which could be slowly contracting. Although Jimena's cloud pattern has fluctuated some during this period of inner-core change, its overall organization has remained about the same since the last advisory. Satellite classifications seem to bear this out, with intensity estimates of T6.0/115 kt and T6.5/127 kt from SAB and TAFB, respectively, at 0000 UTC. These are blended with the latest UW-CIMSS ADT value of 6.1/117 kt to keep the initial intensity estimate at 120 kt. The intensity forecast is challenging. The large-scale environment is forecast to remain relatively favorable during the next day or two, apart from some north-northwesterly shear associated with a cold low to the northeast of Jimena. This could allow an opportunity for reintensification if the current eyewall replacement fully plays out, but predicting intensity fluctuations due to inner-core dynamics is nearly impossible and beyond the scope of this forecast. Thus, a slow decrease in intensity is indicated in the new forecast as large-scale conditions only gradually become less conducive. This is a blend of the statistical-dynamical guidance. As Jimena gradually gains latitude later in the forecast period, global models show a minor increase in westerly shear while other thermodynamic factor remain generally neutral, except for slowly decreasing SSTs. These factors suggests a slow decay of the cyclone, and the new intensity forecast is in agreement with the latest multi-model consensus that shows a monotonic decrease in intensity from days 3 to 5. The eye of Jimena has been wobbling quite a bit, but smoothing through these yields a faster initial motion estimate of 295/11. Jimena should continue moving west-northwestward during the next few days as it approaches the western end of a subtropical ridge around 140W. A weakness in the ridge around this longitude should induce a significant deceleration by days 4 and 5. The track guidance is in excellent agreement through the first 2 days, with less-than-typical spread beyond that time. The new track forecast is faster and adjusted slightly southward and then westward after day 3, but not as far south or west as the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 13.3N 127.5W 120 KT 140 MPH 12H 30/1200Z 13.9N 129.3W 115 KT 130 MPH 24H 31/0000Z 14.7N 131.8W 110 KT 125 MPH 36H 31/1200Z 15.4N 134.4W 110 KT 125 MPH 48H 01/0000Z 16.0N 136.7W 105 KT 120 MPH 72H 02/0000Z 16.9N 139.9W 95 KT 110 MPH 96H 03/0000Z 17.6N 141.9W 85 KT 100 MPH 120H 04/0000Z 18.1N 143.4W 75 KT 85 MPH $$ Forecaster Kimberlain
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