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Tropical Storm BERTHA Forecast Discussion Number 3
2014-08-01 16:54:26| National Hurricane Center (Atlantic)
Issued at 1100 AM AST FRI AUG 01 2014 000 WTNT43 KNHC 011454 TCDAT3 TROPICAL STORM BERTHA DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 1100 AM AST FRI AUG 01 2014 Bertha is disorganized this morning. While satellite imagery shows a well-defined low-cloud swirl exposed just west of the main convective mass, reports from an Air Force Reserve Hurricane Hunter Aircraft show that the wind field more resembles that of an open wave. The aircraft did report 56 kt winds at 1500 feet to the east-northeast of the center, along with an area of SFMR surface winds in excess of 40 kt. Based on this, the initial intensity is increased to 45 kt. The initial motion is now 295/18, and over the past few hours Bertha may be moving even faster. The cyclone is currently being steered by the flow around the Atlantic subtropical ridge and this should continue for the next 48 hours or so. After that time, the cyclone is expected to turn northward into a break in the ridge caused by a deep-layer trough over the eastern United States. This should be followed by recurvature into the westerlies over the Atlantic north of Bermuda. The track guidance remains in good agreement with this scenario, and it has changed little since the previous advisory. The new forecast track is therefore an update of the previous forecast. Bertha is currently experiencing about 15-20 kt of southwesterly vertical wind shear. and water vapor imagery shows dry mid-/upper-level air near the storm. The forecast track calls for Bertha to interact with one or two upper-level troughs during the next 48-72 hours, which should cause some shear and dry air entrainment to continue. This, combined with the current lack of organization, suggests little change in strength should occur during the next 48 hours or so. After that time, Bertha is expected to move into an environment of less shear and greater moisture. The intensity forecast calls for modest strengthening during that time, but it is weaker than all of the guidance except the Florida State Superensemble. An alternative scenario is that a combination of shear, dry air entrainment, and land interaction causes Bertha to degenerate to a tropical wave during the next 48 hours, followed by possible regeneration in the 72-120 hours when the system reaches the more favorable environment. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 14.0N 58.9W 45 KT 50 MPH 12H 02/0000Z 15.0N 61.5W 45 KT 50 MPH 24H 02/1200Z 16.6N 64.9W 45 KT 50 MPH 36H 03/0000Z 18.6N 67.6W 45 KT 50 MPH 48H 03/1200Z 20.9N 70.4W 45 KT 50 MPH 72H 04/1200Z 26.0N 74.0W 45 KT 50 MPH 96H 05/1200Z 31.5N 72.5W 50 KT 60 MPH 120H 06/1200Z 36.5N 65.0W 50 KT 60 MPH $$ Forecaster Beven
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