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Tropical Storm IGNACIO Forecast Discussion Number 8

2015-08-26 22:41:30| Tropical Depression LIDIA

Issued at 200 PM PDT WED AUG 26 2015

Tags: number discussion storm tropical

 

Tropical Storm ERIKA Forecast Discussion Number 7

2015-08-26 16:46:57| National Hurricane Center (Atlantic)

Issued at 1100 AM AST WED AUG 26 2015 000 WTNT45 KNHC 261446 TCDAT5 TROPICAL STORM ERIKA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 1100 AM AST WED AUG 26 2015 Deep convection associated with Erika has increased during the past 24 hours, but the overall organization of the tropical cyclone has not changed very much. Reconnaissance aircraft data indicate that the center is located near the northwestern edge of the thunderstorm activity due to moderate northwesterly shear. The aircraft has measured believable SFMR winds of around 40 kt this morning, and the initial intensity is set at that value. Erika is forecast to pass through an environment of moderate to strong westerly vertical wind shear during the next two to three days. The shear will be caused by an upper-level low that is expected to remain near eastern Cuba through Friday. The upper low is forecast to weaken on Saturday, which should produce a more conducive upper-level wind pattern over the Bahamas. The NHC intensity forecast calls for little change in strength through 72 hours, which is in line with the latest statistical guidance. After that time, strengthening is indicated due to the expected more favorable upper-level environment. The official forecast lies between the more robust HWRF/GFDL and lower statistical guidance. An alternative forecast scenario, supported by the GFS model, is that Erika weakens to a tropical wave due to the shear and interaction with the Greater Antilles. The amount of strengthening on days 4-5 will be dependent in part on how Erika responds to the the preceding unfavorable shear. The initial motion estimate is 280/15 kt. Erika is expected to move westward to west-northwestward during the next several days to the south of a subtropical ridge over the western Atlantic. The track guidance is in good agreement through much of the forecast period, with the exception of the GFDL model that takes a stronger storm northwestward much sooner. The new NHC track is essentially an update of the previous advisory and is close to a consensus of the ECMWF, GFS, HWRF, and UKMET. This is also in good agreement with the Florida State Superensemble. One should remember to not focus on the exact forecast track, especially at the long range where the average NHC track errors during the past 5 years are about 180 miles at day 4 and 240 miles at day 5. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 16.1N 57.6W 40 KT 45 MPH 12H 27/0000Z 16.7N 59.9W 45 KT 50 MPH 24H 27/1200Z 17.6N 63.0W 45 KT 50 MPH 36H 28/0000Z 18.7N 65.9W 45 KT 50 MPH 48H 28/1200Z 19.8N 68.7W 45 KT 50 MPH 72H 29/1200Z 22.0N 73.7W 45 KT 50 MPH 96H 30/1200Z 24.4N 77.7W 55 KT 65 MPH 120H 31/1200Z 26.5N 80.5W 65 KT 75 MPH...INLAND $$ Forecaster Brown

Tags: number discussion storm tropical

 
 

Tropical Storm IGNACIO Forecast Discussion Number 7

2015-08-26 16:33:29| Tropical Depression LIDIA

Issued at 800 AM PDT WED AUG 26 2015

Tags: number discussion storm tropical

 

Tropical Storm IGNACIO Forecast Discussion Number 6

2015-08-26 10:38:56| Tropical Depression LIDIA

Issued at 200 AM PDT WED AUG 26 2015

Tags: number discussion storm tropical

 

Tropical Storm ERIKA Forecast Discussion Number 5

2015-08-26 04:54:23| National Hurricane Center (Atlantic)

Issued at 1100 PM AST TUE AUG 25 2015 000 WTNT45 KNHC 260254 TCDAT5 TROPICAL STORM ERIKA DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 1100 PM AST TUE AUG 25 2015 Both NOAA and Air Force hurricane hunter planes investigated Erika and found a disorganized storm. The central pressure rose to 1006 mb, and the strongest winds were confined to the eastern semicircle. The low-level center remains exposed to the north of the limited thunderstorm activity. Based on the current appearance on satellite imagery, and data from the plane, the initial intensity is generously kept at 35 kt. The intensity forecast continues to be highly uncertain. Erika has a large cyclonic envelope, and this is a favorable factor for the cyclone to strengthen. However, SHIPS model forecasts a hostile west-northwesterly shear over the cyclone and, in fact, it only strengthens Erika a little bit at the end of the forecast period. This coincides with the solution of the GFS and the ECMWF global models which either weaken the cyclone or show little change in strength. The NHC forecast follows the intensity consensus, and shows a modest strengthening beyond 3 days. By then, the cyclone is expected to be near the Bahamas where the environment could be a little more favorable for intensification. However, I will not be a surprised if Erika dissipates like Danny in the the northeastern Caribbean Sea where the environment is hostile. Erika is embedded within the easterly flow south of a moderate subtropical ridge which is covering the western Atlantic. This pattern will likely continue to steer Erika between the west and west-northwest at about 15 kt for the next 2 to 3 days. As the cyclone reaches the western edge of the ridge in the area of the Bahamas, the cyclone is then expected to decrease in forward speed. The NHC forecast is very similar to the previous one and follows very closely the multi-model consensus. Tropical storm watches and warnings have been adjusted and added for some of the islands of the northeastern Caribbean by the respective Meteorological Services. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 16.0N 54.4W 35 KT 40 MPH 12H 26/1200Z 16.4N 56.9W 35 KT 40 MPH 24H 27/0000Z 17.0N 60.1W 35 KT 40 MPH 36H 27/1200Z 17.8N 63.2W 40 KT 45 MPH 48H 28/0000Z 18.8N 66.0W 40 KT 45 MPH 72H 29/0000Z 21.0N 70.9W 45 KT 50 MPH 96H 30/0000Z 23.0N 75.0W 55 KT 65 MPH 120H 31/0000Z 26.0N 78.5W 65 KT 75 MPH $$ Forecaster Avila

Tags: number discussion storm tropical

 

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