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Hurricane JOAQUIN Forecast Discussion Number 11

2015-09-30 16:58:19| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT WED SEP 30 2015 000 WTNT41 KNHC 301458 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 AM EDT WED SEP 30 2015 Joaquin has continued to strengthen overnight. Satellite imagery shows that the convection has become more symmetric, and recent visible images show what might be an eye trying to form. An Air Force Reserve Hurricane Hunter aircraft reported 700-mb flight- level winds of 83 kt and estimated 70 kt surface winds from the Stepped Frequency Microwave Radiometer, with a central pressure of 971 mb estimated from the aircraft data. Based on these, the initial intensity is increased to 70 kt. Joaquin has moved a little south of the previous track with an initial motion of 230/5. The shortwave ridge causing this motion is expected to weaken during the next 24-48 hours as a strong deep-layer trough develops over the southeastern United States. This is expected to cause the hurricane to turn northward by 72 hours. There is disagreement in the track guidance between the ECMWF and the other dynamical models. The majority of the guidance forecasts Joaquin to turn west of north after 48-72 hours, with the storm moving inland over the mid-Atlantic states and merging with the trough. On the other hand, the ECMWF forecast the hurricane to move out to sea between North America and Bermuda. The ECMWF forecasts Joaquin to move more to the south during the first 24-48 hours than the other models. In addition, it shows the hurricane interacting with an upper-level low to its northeast that results in a more eastward motion after 48 hours. The new forecast track, which is similar to the previous track, leans more toward the non-ECMWF guidance. However, out of deference to the ECMWF, it lies to the east of the center of the guidance envelope and the consensus models. The NOAA G-IV jet is scheduled to fly a synoptic surveillance mission this afternoon, which, along with special rawinsonde launches over the eastern U. S., hopefully will reduce the spread of the guidance. Joaquin is expected to remain in an environment of moderate northeasterly vertical shear for the next 24-36 hours. However, since it has been steadily strengthening in such an environment, there is no obvious reason to think it will stop doing so. After 36 hours, the hurricane is likely to move into an area of divergent southerly upper-level winds associated with the eastern U. S. trough. While there is uncertainty as to how much shear should occur, it is expected that additional intensification could occur through 72 hours. Based on this, the intensity forecast calls for Joaquin to peak as a major hurricane in about 72 hours, and it is possible it could be stronger than currently forecast. After 72 hours, increasing shear and cold air intrusion should cause weakening and the start of extratropical transition. KEY MESSAGES: 1. Confidence in the details of the track forecast late in the period remains low, since the environmental steering currents are complex and the model guidance is inconsistent. A wide range of outcomes is possible, from a direct impact of a major hurricane along the U.S. east coast to a track of Joaquin out to sea away from the coast. It is therefore way too soon to talk about specific wind, rain, or surge impacts from Joaquin in the U.S. 2. Should the threat to the U.S. increase, any further adjustments of the forecast to the west would likely be accompanied by an increase in the forecast forward speed, with impacts along the coast occurring sooner than currently forecast. A hurricane watch could be required for portions of the U.S. coast as early as Thursday evening. 3. Many areas of the eastern U.S. are currently experiencing heavy rains and gusty winds associated with a frontal system. This inclement weather is expected to continue over the next few days, which could complicate preparations for Joaquin should it head toward the coast. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 24.7N 72.6W 70 KT 80 MPH 12H 01/0000Z 24.3N 73.2W 80 KT 90 MPH 24H 01/1200Z 24.1N 74.0W 85 KT 100 MPH 36H 02/0000Z 24.4N 74.4W 90 KT 105 MPH 48H 02/1200Z 25.3N 74.5W 95 KT 110 MPH 72H 03/1200Z 28.5N 73.5W 100 KT 115 MPH 96H 04/1200Z 34.0N 73.0W 90 KT 105 MPH 120H 05/1200Z 38.5N 74.0W 75 KT 85 MPH $$ Forecaster Beven

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Tropical Depression MARTY Forecast Discussion Number 16

2015-09-30 16:36:03| Tropical Depression LIDIA

Issued at 1000 AM CDT WED SEP 30 2015

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Tropical Depression MARTY Forecast Discussion Number 15

2015-09-30 10:42:16| Tropical Depression LIDIA

Issued at 400 AM CDT WED SEP 30 2015

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Tropical Storm JOAQUIN Forecast Discussion Number 9

2015-09-30 04:54:47| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT TUE SEP 29 2015 000 WTNT41 KNHC 300254 TCDAT1 TROPICAL STORM JOAQUIN DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM EDT TUE SEP 29 2015 The cloud pattern of Joaquin has continued to become better organized this evening. The low-level center is located within the northwestern portion of the deep convection and the outflow has continued to expand over the northern semicircle, which suggests that the shear continues to decrease. The latest satellite intensity estimates from TAFB and SAB are T3.5 or 55 kt on the Dvorak scale. Based on the earlier reconnaissance aircraft data and the continued increase in organization this evening, the initial wind speed has been raised to 60 kt. Joaquin is forecast to be over warm water and in an increasingly favorable upper-level wind pattern during the next day or so. These conditions favor intensification and the NHC forecast calls for Joaquin to become a hurricane within the next 12 hours. The upper-level winds are shown by the global models to become quite conducive for strengthening by 36 hours as an upper-level anticyclone builds over the system, and additional strengthening is anticipated. The new NHC forecast is a bit higher than the previous advisory, and is close to the IVCN intensity consensus aid. It should be noted, that the UKMET, GFS, and ECMWF models all significantly deepen Joaquin during the next few days, and the NHC forecast could be somewhat conservative. Joaquin is moving west-southwestward at about 5 kt. This general motion is forecast to continue during the next 24-36 hours while the cyclone remains to the southwest of a weak mid-level ridge. During this time, the center of Joaquin is forecast to move near or over portions of the Central Bahamas. After 48 hours, a deepening mid- to upper-level trough over the southeastern United States is expected to cause a turn toward the north or north-northeast with an increase in forward speed. There remains large spread in the guidance at days 4 and 5, with the ECMWF showing a northeastward motion toward Bermuda. Meanwhile, the 18Z GFS shifted significantly westward and is close to the UKMET and HWRF, which are along the western edge of the guidance envelope. The NHC track has been shifted westward, but it is not as far west as the multi-model consensus. The new track is fairly close to the ECMWF-Ensemble Mean. The government of the Bahamas has issued a Hurricane Watch for the Central Bahamas. Additional watches or warnings may be required early Wednesday. At this time it is very hard to gauge the long-range potential impacts of Joaquin in the United States. The environmental steering currents are complex and are not being handled in a consistent manner by the forecast models. A wide range of outcomes are possible and it is simply too soon to say what impacts, if any, Joaquin will have on the United States. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 25.8N 71.7W 60 KT 70 MPH 12H 30/1200Z 25.5N 72.4W 70 KT 80 MPH 24H 01/0000Z 25.2N 73.3W 75 KT 85 MPH 36H 01/1200Z 24.8N 74.1W 80 KT 90 MPH 48H 02/0000Z 24.9N 74.5W 85 KT 100 MPH 72H 03/0000Z 26.7N 74.0W 90 KT 105 MPH 96H 04/0000Z 31.3N 72.5W 85 KT 100 MPH 120H 05/0000Z 35.5N 72.0W 80 KT 90 MPH $$ Forecaster Brown

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Tropical Storm MARTY Forecast Discussion Number 14

2015-09-30 04:37:16| National Hurricane Center (East Pacific)

Issued at 1000 PM CDT TUE SEP 29 2015 000 WTPZ42 KNHC 300237 TCDEP2 TROPICAL STORM MARTY DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP172015 1000 PM CDT TUE SEP 29 2015 After an unusually long convective burst that began around 1800 UTC, the convective pattern of Marty has deteriorated significantly over the past couple of hours. However, a 2306 UTC GPM microwave overpass indicated that Marty still had a 60-70 percent closed low-level eye with a diameter of 15 n mi. Based on the partial eye feature and a Dvorak classification of T3.0/45 kt from TAFB, the initial intensity is being maintained at 45 kt for this advisory. Microwave satellite images indicate that Marty has essentially been stationary since the previous advisory. However, as Marty's low-level and mid-/upper-level circulations begin to decouple during the next 12 hours or so due to increasing vertical wind shear, the cyclone is forecast to begin moving slowly westward tonight and on Wednesday under the influence of a weak low- to mid-level ridge located over central Mexico. Although the spread in the track guidance is fairly large, the models are in generally good agreement on a slow westward to west-northwestward motion throughout the forecast period. As a result, the official forecast track is similar to the previous advisory track, and lies close to the consensus models TVCE and GFEX. Despite strong shear conditions, the recent convective burst has been sustained by strong upper-level difluence created by southwesterly flow over the northwestern portion of the Marty's circulation and westerly flow over the southeastern portion of the circulation. However, this favorable upper-level pattern is expected to abate during the next 12 hours and be replaced by strong southwesterly unidirectional flow, which should create very unfavorable shear conditions across the cyclone. The result is that Marty should steadily or even rapidly weaken, becoming a tropical depression in about 24 hours, followed by degeneration into a remnant low by 36-48 hours. The NHC intensity forecast follows the weakening trend of the previous intensity forecast, and remains in agreement with the LGEM statistical-dynamical intensity model. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 16.3N 101.2W 45 KT 50 MPH 12H 30/1200Z 16.4N 101.8W 35 KT 40 MPH 24H 01/0000Z 16.6N 102.8W 30 KT 35 MPH 36H 01/1200Z 16.7N 104.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 02/0000Z 16.8N 105.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 03/0000Z 17.0N 107.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 04/0000Z 18.5N 109.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 05/0000Z...DISSIPATED $$ Forecaster Stewart

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