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Tropical Storm NORBERT Forecast Discussion Number 5
2014-09-03 16:44:18| National Hurricane Center (East Pacific)
Issued at 800 AM PDT WED SEP 03 2014 000 WTPZ44 KNHC 031444 TCDEP4 TROPICAL STORM NORBERT DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP142014 800 AM PDT WED SEP 03 2014 Norbert has become significantly better organized this morning. The central dense overcast has become more symmetric with more prominent banding around the center. Microwave images also show that the inner core is becoming better defined, with the likely first stages of a primitive eye. The initial wind speed is set to 55 kt, at the top end of the subjective Dvorak estimates, although the latest objective numbers are higher. With the improvement in the inner core, light-to-moderate shear, and very warm waters, future strengthening seems quite likely. In fact, rapid intensification is a distinct possibility, with the SHIPS-RI showing about a 1-in-3 chance of Norbert becoming 30 kt stronger in the next 24 hours. Considering the environmental factors and the low bias of the deterministic guidance so far, the new NHC intensity forecast is raised considerably from the previous one, about 5 kt above the highest guidance through 48 hours. After that time, cooler waters and a more stable atmosphere are expected to weaken the cyclone. The NHC forecast is blended with the previous forecast and the intensity consensus at long range. With recent microwave and visible imagery, it appears that Norbert has been moving westward over the past few hours. However, a more representative long-term motion is 295/8. Mid-level ridging is expected to weaken later today over northwestern Mexico, which should cause Norbert to turn more to the northwest. While all of the reliable guidance keeps the center of the storm offshore of Baja California Sur, Norbert should come close enough to bring tropical- storm-force winds to the state. The models have shifted somewhat southward since the last cycle, and with the recent westward motion, it makes sense to adjust the NHC forecast a little farther south for the first day or so. There hasn't been much change to the guidance beyond day 3, so the new forecast is basically an update to the previous one. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 19.6N 108.8W 55 KT 65 MPH 12H 04/0000Z 20.1N 109.6W 65 KT 75 MPH 24H 04/1200Z 20.9N 110.3W 80 KT 90 MPH 36H 05/0000Z 21.8N 111.0W 90 KT 105 MPH 48H 05/1200Z 22.6N 111.9W 90 KT 105 MPH 72H 06/1200Z 24.4N 113.9W 70 KT 80 MPH 96H 07/1200Z 25.6N 116.2W 55 KT 65 MPH 120H 08/1200Z 27.0N 117.5W 40 KT 45 MPH $$ Forecaster Blake
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