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Hurricane NORBERT Forecast Discussion Number 9
2014-09-04 16:53:26| National Hurricane Center (East Pacific)
Issued at 800 AM PDT THU SEP 04 2014 000 WTPZ44 KNHC 041453 TCDEP4 HURRICANE NORBERT DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP142014 800 AM PDT THU SEP 04 2014 Norbert has become a little better organized overnight, with the TRMM and AMSR2 microwave sensors indicating that the low- and mid-level centers have become more vertically aligned. The cyclone is still experiencing northeasterly shear though, given the asymmetric shape on the latest satellite images. Dvorak intensity estimates are all near 75 kt, so that will used as the initial wind speed. An Air Force Hurricane Hunter aircraft is en route to investigate Norbert, and should provide a more precise estimate of its intensity. While moderate shear has been affecting the cyclone, it has not been strong enough to prevent slow strengthening. Although the shear is not forecast to change much over the next few days, Norbert is expected to move into an environment characterized by cooler SSTs and drier, more stable air. These negative factors should cause some weakening on Friday, with a more significant downward trend anticipated by late this weekend. The latest NHC forecast is close to a blend of the previous interpolated forecast and the intensity consensus. Norbert should become a remnant low in about 4 days due to it moving over very cool waters west of Baja California. The track of Norbert has been quite erratic over the past 24 hours, but a 12-hour motion still appears to be northwestward at about 6 kt. A mid-level ridge is expected to remain over northwestern Mexico, keeping Norbert on the same general course during the next few days, offshore of Baja California. At long range, model guidance remains divergent on how much of a northward turn that Norbert will take due to a mid-latitude trough weakening the ridge. The 3-5 day track also partially depends on the intensity at that time range, with a deeper system probably moving farther west, more like the ECMWF solution. Since there has not been much change to the overall guidance, the new NHC forecast is about the same as the previous one, and remains relatively close to the dynamical model consensus. Moisture from the remnants of Dolly and the Pacific ITCZ is being advected northward by the outer circulation of Norbert across northern Mexico and into the southwestern United States. This could result in heavy rains and life-threatening flash flooding in these areas during the next few days. Please see information from your local weather office for more details. FORECAST POSITIONS AND MAX WINDS INIT 04/1500Z 20.7N 110.4W 75 KT 85 MPH 12H 05/0000Z 21.5N 111.1W 80 KT 90 MPH 24H 05/1200Z 22.5N 112.2W 80 KT 90 MPH 36H 06/0000Z 23.5N 113.3W 75 KT 85 MPH 48H 06/1200Z 24.3N 114.5W 65 KT 75 MPH 72H 07/1200Z 25.9N 117.0W 50 KT 60 MPH 96H 08/1200Z 27.6N 118.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 09/1200Z 29.0N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Blake
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