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Hurricane JOAQUIN Forecast Discussion Number 18
2015-10-02 10:42:29| National Hurricane Center (Atlantic)
Issued at 500 AM EDT FRI OCT 02 2015 000 WTNT41 KNHC 020842 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 500 AM EDT FRI OCT 02 2015 The eye of Joaquin has not been apparent in recent infrared imagery. The last pass of the Hurricane Hunter aircraft through the center around 04Z showed indications of a double wind maximum at flight level, which could indicate that an eyewall replacement cycle is underway. The last report from the aircraft indicated that the central pressure still around 935 mb. The initial intensity remains 115 kt pending the arrival of the next aircraft before 12Z. Some fluctuations in intensity are possible during the next 12 to 24 hours due to eyewall replacement. After that time, gradual weakening is forecast as the cyclone encounters increasing southwesterly shear, but Joaquin is expected to remain a powerful hurricane for the next several days. Faster weakening in shown late in the period as the cyclone is forecast move over cooler waters and the shear increases further. The initial motion estimate is a slow drift toward the northwest, or 315/03, with the hurricane now gaining a bit of latitude based on recent center fixes. The ridge north of Joaquin will weaken in the next 12 to 24 hours as a mid/upper-level low moves in from the east, and the hurricane should begin to move more quickly northward today and then accelerate northeastward tonight and Saturday. The track model guidance is in reasonable agreement on this scenario, and the NHC forecast during the first 2 days is a little to the right of the previous one, trending toward the latest multi-model consensus. After that time, there have been some changes in the latest models, with the GFS trending west from its previous forecast with a track still offshore but closer to Cape Cod in about 5 days. The ECMWF has also trended westward this cycle away from Bermuda and now lies closer to the middle of the guidance suite. The UKMET is now the eastern-most model, but still shows a track west of Bermuda. The spread in the guidance at these time ranges appears to be due to differences in the strength and speed of the westward movement of the upper-level low passing north of Joaquin in the next 2 to 3 days. The new NHC forecast at days 3 and 4 has been shifted a little to the east of the previous one and now lies near the latest consensus aids. At day 5, all of the guidance shows the cyclone accelerating east-northeastward, and the NHC track reflects this trend. Given the continued variability in the guidance from cycle to cycle, further adjustments will likely be needed to the NHC track at days 3 through 5. KEY MESSAGES: 1. Joaquin's slow motion means that extremely dangerous conditions will continue over portions of the warning areas in the Bahamas today. 2. The forecast models continue to indicate a track offshore of the United States east coast from the Carolinas to the mid-Atlantic states, and the threat of direct impacts from Joaquin in those areas is decreasing. However, there is still uncertainty in how close Joaquin could come to Bermuda, extreme southeastern New England/Cape Cod, and Nova Scotia during the next several days, and interests in those areas should continue to monitor the progress of the hurricane. A Tropical Storm or Hurricane Watch could be required for Bermuda later today. 3. Efforts to provide the forecast models with as much data as possible continue, with twice daily NOAA G-IV jet missions in the storm environment, and extra NWS balloon launches. 4. Even if Joaquin remains offshore, strong onshore winds associated with a frontal system will create minor to moderate coastal flooding along the coasts of the mid-Atlantic and northeastern states through the weekend. In addition, very heavy rains, not associated with Joaquin, are expected to produce flooding over portions of the Atlantic coastal states. Please see products issued by local NWS Forecast Offices. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 23.3N 74.7W 115 KT 130 MPH 12H 02/1800Z 23.9N 74.8W 115 KT 130 MPH 24H 03/0600Z 25.4N 74.0W 115 KT 130 MPH 36H 03/1800Z 27.4N 72.5W 110 KT 125 MPH 48H 04/0600Z 30.0N 70.9W 100 KT 115 MPH 72H 05/0600Z 34.8N 69.1W 85 KT 100 MPH 96H 06/0600Z 39.0N 66.0W 65 KT 75 MPH 120H 07/0600Z 43.5N 54.5W 55 KT 65 MPH $$ Forecaster Brennan
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