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Tropical Storm JOAQUIN Forecast Discussion Number 5
2015-09-29 04:37:08| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT MON SEP 28 2015 000 WTNT41 KNHC 290237 TCDAT1 TROPICAL STORM JOAQUIN DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM EDT MON SEP 28 2015 Satellite images indicate that the shower and thunderstorm activity associated with the depression has increased and become better organized during the past several hours. In addition, the low-level center now appears to have moved closer to the convection than it was earlier. The latest Dvorak classifications from TAFB and SAB were 2.5/35 kt, and the initial intensity is set at that value, making the cyclone Tropical Storm Joaquin. This intensity analysis also agrees with the reconnaissance aircraft data from earlier today that showed winds just under tropical-storm force. The center of Joaquin has been moving southwestward during the last several hours, but it is expected to begin moving slowly westward overnight. This westward track is forecast to continue for a couple of days while a mid-level ridge remains to the north of the storm. After that time, a trough is anticipated to amplify over the eastern United States, which should cause Joaquin to turn northward and accelerate. There is considerable spread in the models, mainly due to the timing of when and how fast the storm makes the northward turn, due to differences in the evolution of the trough. In general, the guidance envelope has shifted southward for the first couple of days and then westward after that time. The official track forecast has been adjusted accordingly, but additional southward and westward adjustment may be needed in subsequent advisories. Northwesterly shear of about 20 kt is currently affecting Joaquin, causing most of the thunderstorm activity to be located to the southeast of the center. The shear is expected to lessen some during the next couple of days, which in combination with warm water and high relative humidity values should allow Joaquin to strengthen. The official intensity forecast is raised from the previous one, but is lower than the intensity model consensus at days 3-5. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 26.7N 70.4W 35 KT 40 MPH 12H 29/1200Z 26.9N 71.0W 40 KT 45 MPH 24H 30/0000Z 27.1N 72.0W 40 KT 45 MPH 36H 30/1200Z 27.2N 72.8W 45 KT 50 MPH 48H 01/0000Z 27.4N 73.4W 50 KT 60 MPH 72H 02/0000Z 28.6N 74.0W 55 KT 65 MPH 96H 03/0000Z 32.4N 74.0W 55 KT 65 MPH 120H 04/0000Z 38.0N 74.0W 55 KT 65 MPH $$ Forecaster Cangialosi
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