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Hurricane Elsa Forecast Discussion Number 9

2021-07-02 17:24:56| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Fri Jul 02 2021 000 WTNT45 KNHC 021505 TCDAT5 Hurricane Elsa Discussion Number 9 NWS National Hurricane Center Miami FL AL052021 1100 AM AST Fri Jul 02 2021 Satellite imagery indicates that Elsa has become better organized, and radar data from Barbados and Martinique have shown attempts at eye formation. The formative northern eyewall passed over Barbados near 11-12Z, and hurricane-force winds were reported there at that time. The initial intensity is set at 65 kt based on those data. It should be noted that reports from an Air Force Reserve Hurricane Hunter aircraft suggest that the circulation is not well-developed at 700 mb, possible due to the rapid forward speed. The initial motion is 290/25. There is little change to the forecast track or the forecast guidance since the last advisory. The guidance is in good agreement on a rapid west-northwestward notion to near the south coast of the Dominican Republic by 36 hr. After that, the general consensus is that Elsa should turn northward by 96 h through a weakness in the subtropical ridge created by a mid-latitude trough. However, the guidance is quite divergent around this consensus, with possible tracks ranging from a west-northwestward motion through the Yucatan Channel or western Cuba to a northward motion through the Bahamas. Thus, the latter portion of the track forecast remains low confidence. The intensity forecast calls for a little more strengthening during the next 36 h as Elsa moves through an environment of light westerly shear. After that, land interaction, along with less favorable upper-level winds over the Gulf of Mexico, is likely to cause weakening. The new NHC intensity forecast shows major adjustments from the previous forecasts based primarily on the initial intensity. It should be noted that the average NHC track errors are 175 miles and 200 miles at days 4 and 5, respectively. Given the larger-than-normal uncertainty and because hazards will extend well away from the center of the storm, users are urged to not focus on the exact forecast points. Key Messages: 1. Hurricane conditions are expected in the Hurricane Warning area in the Windward Islands for the next few hours. Tropical storm conditions are expected in other portions of the Windward and Leeward Islands. Hurricane conditions are expected in the Hurricane Warning area in Haiti on Saturday. Tropical storm conditions are expected with hurricane conditions possible along the southern coast of the Dominican Republic and in Jamaica. 2. Heavy rainfall from Elsa will move quickly across the Windward and southern Leeward Islands today, including Barbados. Outer rain bands will impact Puerto Rico late today into Saturday, and southern Hispaniola and Jamaica Saturday into Sunday. Flooding and mudslides are possible. 3. There is an increasing risk of strong winds, storm surge and rainfall impacts in portions of Cuba this weekend and early next week, with impacts also possible in the Turks and Caicos and the Bahamas. Interests in these areas should monitor Elsa's progress and updates to the forecast. 4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa's potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa's progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 13.4N 61.2W 65 KT 75 MPH 12H 03/0000Z 14.6N 64.9W 70 KT 80 MPH 24H 03/1200Z 16.3N 69.8W 70 KT 80 MPH 36H 04/0000Z 17.8N 73.6W 70 KT 80 MPH 48H 04/1200Z 19.3N 76.4W 65 KT 75 MPH 60H 05/0000Z 20.7N 78.4W 55 KT 65 MPH 72H 05/1200Z 22.1N 80.5W 55 KT 65 MPH...INLAND 96H 06/1200Z 26.0N 82.5W 55 KT 65 MPH...OVER WATER 120H 07/1200Z 30.6N 81.5W 40 KT 45 MPH...INLAND $$ Forecaster Beven

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Hurricane Elsa Forecast Discussion Number 8

2021-07-02 14:23:57| National Hurricane Center (Atlantic)

Issued at 830 AM AST Fri Jul 02 2021 000 WTNT45 KNHC 021223 TCDAT5 Hurricane Elsa Special Discussion Number 8 NWS National Hurricane Center Miami FL AL052021 830 AM AST Fri Jul 02 2021 Surface observations from Barbados indicate that Elsa has become a hurricane, and this special advisory is being issued to update the first 36 h of the intensity and wind radii forecasts. More revisions of the intensity forecast are likely on the next regular advisory. An Air Force Reserve Hurricane Hunter aircraft is currently entering the hurricane, and a NOAA aircraft is scheduled to investigate the system this afternoon. There are no changes to the forecast track at this time. It should be noted that the average NHC track errors are 175 miles and 200 miles at days 4 and 5, respectively. Given the larger-than-normal uncertainty and because hazards will extend well away from the center of the storm, users are urged to not focus on the exact forecast points. Key Messages: 1. Hurricane conditions are occurring on Barbados and are expected elsewhere in the Hurricane Warning area in the next few hours. Tropical storm conditions are expected to begin later this morning in other portions of the Windward and Leeward Islands. Tropical storm conditions are expected and hurricane conditions are possible over southern portions of Hispaniola on Saturday. Tropical storm conditions are possible over Jamaica beginning Saturday night. 2. Heavy rainfall from Elsa will move quickly across the Windward and southern Leeward Islands today, including Barbados. Outer rain bands will impact Puerto Rico late today into Saturday, and southern Hispaniola and Jamaica Saturday into Sunday. Flooding and mudslides are possible. 3. There is a risk of wind and rainfall impacts in portions of Cuba, the Turks and Caicos, and the Bahamas through early next week. Interests in these areas should monitor Elsa's progress and updates to the forecast. 4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa's potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa's progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 02/1230Z 13.1N 60.1W 65 KT 75 MPH 12H 02/1800Z 13.8N 62.4W 65 KT 75 MPH 24H 03/0600Z 15.4N 67.4W 65 KT 75 MPH 36H 03/1800Z 17.1N 71.7W 65 KT 75 MPH 48H 04/0600Z 18.7N 75.2W 60 KT 70 MPH 60H 04/1800Z 20.2N 77.8W 55 KT 65 MPH 72H 05/0600Z 21.7N 79.7W 55 KT 65 MPH 96H 06/0600Z 25.2N 82.2W 55 KT 65 MPH 120H 07/0600Z 29.2N 82.6W 55 KT 65 MPH $$ Forecaster Beven

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Tropical Storm Elsa Forecast Discussion Number 6

2021-07-02 04:57:19| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Thu Jul 01 2021 000 WTNT45 KNHC 020257 TCDAT5 Tropical Storm Elsa Discussion Number 6 NWS National Hurricane Center Miami FL AL052021 1100 PM AST Thu Jul 01 2021 The convective structure with Elsa tonight appears to be somewhat better organized than earlier, with a bursting type pattern of cold -75 to -80 C cloud top temperatures just to the northeast of the estimated center. However, a SSMIS microwave pass at 2130 UTC revealed that, underneath the cirrus, the deeper convection is still struggling to rotate up-shear as the system moves quickly to the west-northwest. Despite that fact, an ASCAT-A pass clipped the northeastern edge of Elsa and showed several wind retrievals of 44-46 kt. In addition, the most recent subjective Dvorak satellite classification from TAFB was T3.0/45 kt. In support of these data, the current estimated intensity was raised to 45 kt for this advisory. Elsa continues to move quickly to the west-northwest at 290/23 kt. A continued rapid motion to the west-northwest is expected for the next 36 hours as the storm remains steered by a strong subtropical ridge to its north, and the guidance has trended a bit faster once again tonight. Thereafter, Elsa will reach the western extent of this ridge which will be eroded by a strong mid-latitude trough centered off the eastern US. Once again, the guidance spread increases greatly by this time, with the GFS/UKMET on the slow and left side of the guidance envelope, the ECMWF and its ensembles on the fast and right side, and the Canadian roughly in the middle. Interestingly, the latest GFS ensembles show some bifurcation within the larger guidance envelope, with the strongest members further south and west. The latest NHC track forecast is close to the previous track early on but somewhat faster, and in the latter period was nudged just slightly eastward towards the TVCN consensus. However, the track forecast in the latter time period remains low confidence. The intensity forecast with Elsa also continues to be challenging this evening. While the GFS-based SHIPS guidance indicates that the current 200-850-hPa vertical wind shear is only 5-10 kt, the strong east-southeasterly low-level flow Elsa is embedded in is resulting in stronger 15-20 kt of west-northwesterly mid-level shear. This mid-level shear has thus far prevented deep convection from wrapping around the circulation and helping to align the low- and mid-level vortex like the GFS/HWRF models have been forecasting over the past day. Despite this convective structure, the fast east-southeasterly low-level flow will likely continue to enhance the winds on the north side of the circulation. For this reason, the intensity forecast still shows intensification in the short term to 55 kt. However, additional intensification beyond that will likely require a better vertically aligned vortex. This structure may be difficult to achieve as moderate mid-level shear continues, counter to the motion vector of the storm. After 48 hours, the intensity forecast shows slight weakening given the possibility of land interaction over the Greater Antilles. The latest intensity forecast continues remain on the conservative side relative to the guidance, especially the HWRF/HMON regional hurricane models, and is also low confidence. Key Messages: 1. Tropical storm conditions are expected to begin early Friday in portions of the Windward and southern Leeward Islands, and are possible over portions of southern Hispaniola on Saturday, and are also possible over Jamaica beginning Saturday night. 2. Heavy rainfall from Elsa will move quickly across the Windward and southern Leeward Islands, including Barbados, on Friday. Outer rain bands will impact Puerto Rico on Friday and southern Hispaniola by early Saturday. Flooding and mudslides are possible. 3. There is a risk of wind and rainfall impacts in portions of Cuba, the Turks and Caicos, and the Bahamas through early next week. Interests in these areas should monitor Elsa's progress and updates to the forecast. 4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa's potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa's progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 11.8N 55.9W 45 KT 50 MPH 12H 02/1200Z 12.8N 59.7W 55 KT 65 MPH 24H 03/0000Z 14.5N 64.8W 55 KT 65 MPH 36H 03/1200Z 16.2N 69.8W 55 KT 65 MPH 48H 04/0000Z 17.7N 73.3W 55 KT 65 MPH 60H 04/1200Z 19.4N 76.5W 50 KT 60 MPH 72H 05/0000Z 21.2N 78.8W 50 KT 60 MPH 96H 06/0000Z 23.9N 81.7W 50 KT 60 MPH 120H 07/0000Z 28.2N 83.1W 50 KT 60 MPH $$ Forecaster Papin/Brown

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Tropical Storm Elsa Forecast Discussion Number 5

2021-07-01 22:47:12| National Hurricane Center (Atlantic)

Issued at 500 PM AST Thu Jul 01 2021 000 WTNT45 KNHC 012047 TCDAT5 Tropical Storm Elsa Discussion Number 5 NWS National Hurricane Center Miami FL AL052021 500 PM AST Thu Jul 01 2021 The structure of Elsa has changed little since the last advisory, with the low-level center partly exposed to the northwest of the somewhat-ragged primary convective band. Various subjective and objective satellite intensity estimates have changed little during the last 6 h, so the initial intensity is held at 40 kt. The initial motion is now 285/25. There is little change to the track forecast philosophy from the previous advisory. A rapid west-northwestward motion is likely for the next 48 h or so as Elsa is steered by the strong subtropical ridge to the north. After that time, the storm is expected to approach a weakness in the ridge caused by a mid-latitude trough over the eastern United states. The guidance becomes rather divergent as this happens, as the ECWMF and the ECMWF ensembles forecast a turn toward the north while the GFS and UKMET are forecasting a continued west- northwestward to northwestward motion. In addition, the GFS ensemble members are spread from a continued west-northwestward motion toward the Yucatan Peninsula on one side to a northward motion east of the northern Bahamas on the other. The latter part of the new NHC forecast track will still lean more toward the deterministic GFS/UKMET solutions, but the confidence remains low. The new official forecast track again has only minor adjustments from the previous forecast. The intensity forecast and its high uncertainty are also little changed from the last advisory. Some strengthening is expected during the next day or so as Elsa is expected to be in an environment of warm sea-surface temperatures, light vertical wind shear, and high mid-level relative humidity. However, as mentioned earlier, the fast forward motion could result in the upper and lower parts of the storm being unable to stay together, and this could limit strengthening. The latter part of the intensity forecast also has the issues of possible land interaction and disagreements among the global models on how favorable the upper-level winds will be, although the latest model runs trended toward less favorable conditions north of about 22N. This uncertainty is highlighted by the UKMET forecasting Elsa to weaken to a trough near western Cuba while the GFS forecasts it to be a hurricane in the same area and time. Based on these factors, the NHC intensity forecast continues to be on the lower end of the intensity guidance suite. Key Messages: 1. Tropical storm conditions are expected beginning early Friday in portions of the Windward and southern Leeward Islands, and are possible over portions of southern Hispaniola on Saturday. 2. Heavy rainfall from Elsa will move quickly across the Windward and southern Leeward Islands, including Barbados, on Friday. Outer rain bands will impact Puerto Rico on Friday and southern Hispaniola by early Saturday. Flooding and mudslides are possible. 3. There is a risk of wind and rainfall impacts in portions of Cuba, Jamaica, the Turks and Caicos, and the Bahamas through early next week. Interests in these areas should monitor Elsa's progress and updates to the forecast. 4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa's potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa's progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 11.2N 53.8W 40 KT 45 MPH 12H 02/0600Z 12.1N 57.5W 45 KT 50 MPH 24H 02/1800Z 13.5N 62.4W 50 KT 60 MPH 36H 03/0600Z 15.1N 67.3W 50 KT 60 MPH 48H 03/1800Z 16.7N 71.6W 50 KT 60 MPH 60H 04/0600Z 18.3N 75.0W 50 KT 60 MPH 72H 04/1800Z 19.8N 77.9W 50 KT 60 MPH 96H 05/1800Z 22.5N 82.0W 50 KT 60 MPH 120H 06/1800Z 26.5N 83.5W 50 KT 60 MPH $$ Forecaster Beven

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Tropical Storm Elsa Forecast Discussion Number 4

2021-07-01 16:53:09| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Thu Jul 01 2021 000 WTNT45 KNHC 011453 TCDAT5 Tropical Storm Elsa Discussion Number 4 NWS National Hurricane Center Miami FL AL052021 1100 AM AST Thu Jul 01 2021 Just-received scatterometer data showed 35-40 kt winds to the northeast of the center, so the initial intensity is increased to 40 kt. Some slight revisions were also made to the initial and forecast wind radii. Over all, the organization of the storm has changed little during the past several hours, with the low-level center partly exposed to the north and northwest of the primary convective band. Elsa continues to move a little faster with the initial motion now 280/24. A rapid west-northwestward motion is likely for the next 48 h or so as Elsa is steered by the strong subtropical ridge to the north. After that time, the storm is expected to approach a weakness in the ridge caused by a mid-latitude trough over the eastern United states. The guidance becomes rather divergent as this happens, as the ECWMF and ECMWF ensemble mean forecast a turn toward the north while the GFS and UKMET are forecasting a west-northwestward to northwestward motion. The latter part of the new NHC forecast track will lean more toward the GFS/UKMET solutions at this time, but the large spread in both the deterministic models and the ensembles make this part of the forecast of low confidence. The new official forecast track has only minor adjustments from the previous forecast. Some additional strengthening is expected during the next day or so as Elsa is expected to be in an environment of warm sea-surface temperatures, light vertical wind shear, and high mid-level relative humidity. However, as mentioned earlier, the fast forward motion could result in some decoupling of the lower and upper parts of the storm, and this could limit strengthening. The latter part of the intensity forecast also has high uncertainty due to the possibility of land interaction and disagreements among the global models on how favorable the upper-level winds will be. Based on these factors, the NHC intensity forecast continues to be on the lower end of the intensity guidance suite. Key Messages: 1. Tropical storm conditions are expected beginning early Friday in portions of the Windward and southern Leeward Islands. 2. Heavy rainfall from Elsa will move quickly across the Windward and southern Leeward Islands, including Barbados, on Friday, with outer rain bands impacting Puerto Rico Friday into Saturday. Isolated flash flooding and mudslides are possible. 3. There is a risk of wind and rainfall impacts in portions of Hispaniola, Cuba, the Turks and Caicos and the Bahamas through early next week. Interests in these areas should monitor Elsa's progress and updates to the forecast. 4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the southern Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa's potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa's progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 10.1N 51.4W 40 KT 45 MPH 12H 02/0000Z 11.2N 54.9W 45 KT 50 MPH 24H 02/1200Z 12.6N 59.9W 50 KT 60 MPH 36H 03/0000Z 14.1N 64.9W 50 KT 60 MPH 48H 03/1200Z 15.9N 69.8W 50 KT 60 MPH 60H 04/0000Z 17.6N 73.6W 50 KT 60 MPH 72H 04/1200Z 19.3N 76.5W 45 KT 50 MPH 96H 05/1200Z 22.0N 80.5W 50 KT 60 MPH 120H 06/1200Z 25.6N 82.5W 50 KT 60 MPH $$ Forecaster Beven

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