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Tropical Storm Jose Forecast Discussion Number 2

2017-09-05 22:34:08| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Sep 05 2017 000 WTNT42 KNHC 052033 TCDAT2 Tropical Storm Jose Discussion Number 2 NWS National Hurricane Center Miami FL AL122017 500 PM AST Tue Sep 05 2017 A distinct curved band of deep convection wraps more than half way around the center of Jose in its southern semicircle. Due to the improved structure, the Dvorak Current Intensity numbers from TAFB and SAB have increased to a 3.0 and 2.0, respectively. A blend of these input gives a 40 kt intensity for the initial time. Jose's current motion is assessed to be west at 11 kt, though this is uncertain due to not knowing the initial position with much confidence. Jose should move toward the west or west-northwest for the next three to four days at a slightly faster rate of forward speed as it moves south of the deep-layer Azores-Bermuda high. In about four to five days, Jose should turn toward the northwest and slow as it reaches the southwestern periphery of the high. The official track forecast is primarily based upon a blend of the ECMWF-UKMET model output and is nearly unchanged from the previous advisory. The environment in which Jose is located in appears to be quite conducive for development for the next three days as the SSTs are very warm, the vertical shear is very low, and there is abundant mid-level moisture. By days four and five, however, the vertical shear may increase in part due to the outflow from Hurricane Irma to its west. Thus the official intensity forecast shows steady intensification until day three, then decreases slightly to day five. This forecast is based upon the IVCN multi-model consensus technique, but has the usual - large - uncertainties at the long forecast ranges. No new observations have been available, so I have let it ride for the initial tropical-storm-wind radii. The official size forecast indicates a gradual increase in size, based upon the RVCN multi-model consensus approach. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 12.5N 40.6W 40 KT 45 MPH 12H 06/0600Z 12.9N 42.5W 45 KT 50 MPH 24H 06/1800Z 13.6N 45.3W 55 KT 65 MPH 36H 07/0600Z 14.3N 48.1W 65 KT 75 MPH 48H 07/1800Z 14.9N 51.2W 75 KT 85 MPH 72H 08/1800Z 16.5N 56.2W 95 KT 110 MPH 96H 09/1800Z 18.7N 59.8W 90 KT 105 MPH 120H 10/1800Z 22.0N 63.0W 85 KT 100 MPH $$ Forecaster Landsea

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Tropical Storm Jose Forecast Discussion Number 1

2017-09-05 16:55:37| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Tue Sep 05 2017 000 WTNT42 KNHC 051455 TCDAT2 Tropical Storm Jose Discussion Number 1 NWS National Hurricane Center Miami FL AL122017 1100 AM AST Tue Sep 05 2017 Deep convection associated with the disturbance in the central Atlantic has become more organized overnight. Banding features are starting to develop as seen in the first-light visible pictures from the GOES and METEOSAT imagery. Additionally, the ASCAT scatterometers sampled the system at 1140Z and 1234Z, showing that a well-defined - though slightly elongated - center had formed. The maximum believable winds from ASCAT were 35 kt. Thus advisories are being started on Tropical Storm Jose, the 10th named storm of the Atlantic season. With no history on the center location, the motion is estimated to be west-northwest at 11 kt. Jose should move toward the west or west-northwest for the next three to four days at a slightly faster rate of forward speed as it moves south of the deep-layer Azores-Bermuda high. In about four to five days, Jose should turn toward the northwest and slow as it reaches the southwestern periphery of the high. The model guidance is in good agreement with this scenario and the official forecast is based upon a blend of the ECMWF-GFS-UKMET deterministic and ensemble model output. The environment in which Jose is located in appears to be quite conducive for development for the next three days as the SSTs are very warm, the vertical shear is very low, and there is abundant mid-level moisture. By days four and five, however, the vertical shear may increase in part due to the outflow from Hurricane Irma to its west. Thus the official intensity forecast show steady intensification until day three, then remains flat through day five. This forecast is based upon the IVCN multi-model consensus technique, but has the usual - large - uncertainties at the long forecast range. The ASCAT observations indicate that the tropical-storm-force winds extend out about 40 nm from the center in the southeastern quadrant. The official size forecast suggests a gradual increase in size, based upon the RVCN multi-model consensus approach. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 12.3N 39.1W 35 KT 40 MPH 12H 06/0000Z 12.8N 40.8W 40 KT 45 MPH 24H 06/1200Z 13.4N 43.4W 50 KT 60 MPH 36H 07/0000Z 13.9N 46.2W 60 KT 70 MPH 48H 07/1200Z 14.4N 49.2W 70 KT 80 MPH 72H 08/1200Z 16.0N 55.0W 90 KT 105 MPH 96H 09/1200Z 18.5N 59.0W 90 KT 105 MPH 120H 10/1200Z 21.5N 62.5W 90 KT 105 MPH $$ Forecaster Landsea

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Hurricane Irma Forecast Discussion Number 26

2017-09-05 16:47:03| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Tue Sep 05 2017 000 WTNT41 KNHC 051446 TCDAT1 Hurricane Irma Discussion Number 26 NWS National Hurricane Center Miami FL AL112017 1100 AM AST Tue Sep 05 2017 Irma is an extremely impressive hurricane in both infrared and visible satellite images. Experimental GOES-16 one-minute visible satellite pictures show a distinct 25-30 n mi wide eye with several mesovortices rotating within with eye. The aircraft have not sampled the northeastern eyewall where the strongest winds were measured shortly before 1200 UTC this morning, but the Air Force plane will be entering the eye in that quadrant momentarily. A peak SFMR wind of 154 kt was reported, with a few others of 149-150 kt. Based on these data the initial intensity is set at 155 kt for this advisory. This makes Irma the strongest hurricane in the Atlantic basin outside of the Caribbean Sea and Gulf of Mexico in the NHC records. Irma is expected to remain within low vertical wind shear, a moist mid-level atmosphere, and high upper-ocean heat content as it moves west-northwestward during the next several days. These conditions should allow the hurricane to remain very intense throughout much of the forecast period, however, fluctuations in intensity are likely to occur as eyewall replacement cycles take place. The NHC intensity forecast is near the upper-end of the guidance and assumes little overall interaction of Irma with the islands of the Greater Antilles. Irma continues to move westward at about 12 kt, and a strong subtropical ridge centered over the central Atlantic should steer Irma generally westward today. The ridge is expected to remain in place over the western Atlantic during the next several days and Irma is forecast to move west-northwestward throughout the most of remainder of the forecast period. Around day 5, a shortwave trough dropping southward over the central United States is expected to begin eroding the western portion of the ridge, allowing a Irma to gain some latitude. The new NHC track forecast is close to the HFIP corrected consensus model and is very similar to the previous forecast. Since Irma is a large hurricane, users are reminded to not focus on the exact forecast track since tropical-storm and hurricane-force winds and life-threatening storm surge extend far from the center. Residents in the Leeward Islands should complete their preparations very soon as the weather will begin to deteriorate over the easternmost Leeward Islands later this afternoon. KEY MESSAGES: 1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northeastern Leeward Islands beginning later today and the Virgin Islands and Puerto Rico beginning tomorrow. Preparations should be rushed to completion before the arrival of tropical-storm force winds later today in the Leeward Islands and tomorrow morning in Virgin Islands and Puerto Rico. 2. Hurricane watches have been issued for portions of the Dominican Republic and Haiti, the southeastern Bahamas and Turks and Caicos, and Irma could bring dangerous wind, storm surge, and rainfall to those areas on Thursday and Friday. 3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. The chance of direct impacts from Irma later this week and this weekend is increasing in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of the impacts. Elsewhere, it is too early to determine what direct impacts Irma might have on the continental United States. Everyone in hurricane-prone areas should ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 16.8N 58.4W 155 KT 180 MPH 12H 06/0000Z 17.2N 60.3W 155 KT 180 MPH 24H 06/1200Z 18.1N 63.0W 150 KT 175 MPH 36H 07/0000Z 19.1N 65.9W 145 KT 165 MPH 48H 07/1200Z 20.1N 68.7W 140 KT 160 MPH 72H 08/1200Z 21.4N 74.0W 135 KT 155 MPH 96H 09/1200Z 22.7N 78.3W 130 KT 150 MPH 120H 10/1200Z 24.4N 81.2W 125 KT 145 MPH $$ Forecaster Brown

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Hurricane Irma Forecast Discussion Number 25

2017-09-05 14:00:34| National Hurricane Center (Atlantic)

Issued at 800 AM AST Tue Sep 05 2017 000 WTNT41 KNHC 051200 TCDAT1 Hurricane Irma Special Discussion Number 25 NWS National Hurricane Center Miami FL AL112017 800 AM AST Tue Sep 05 2017 This special advisory is being issued to increase the initial and forecast intensity of Irma. NOAA and U.S. Air Force Hurricane Hunter aircraft have recently measured peak flight-level winds of around 170 kt and SFMR winds of around 150 kt. Based on these data the initial intensity has been increased to 150 kt, making Irma an extremely dangerous category 5 hurricane. Some additional strengthening is still possible, but fluctuations in intensity are likely during the next couple of days due to eyewall replacement cycles. No change was made to the previous track or wind radii forecast. KEY MESSAGES: 1. Irma is expected to affect the northeastern Leeward Islands as an extremely dangerous category 5 hurricane, accompanied by life-threatening wind, storm surge, and rainfall. Hurricane warnings are in effect for portions of the Leeward Islands. Preparations should be rushed to completion, as tropical-storm force winds are expected to first arrive in the hurricane warning area later today. 2. Irma is also expected to affect the British and U.S. Virgin Islands and Puerto Rico as a dangerous major hurricane beginning tomorrow, with life-threatening wind, storm surge, and rainfall. Hurricane warnings have been issued for these areas, and tropical- storm-force winds are expected to arrive in these areas by early tomorrow. 3. Irma could directly affect Hispaniola, the Turks and Caicos, the Bahamas, and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. There is an increasing chance of seeing some impacts from Irma in the Florida Peninsula and the Florida Keys later this week and this weekend. Otherwise, it is still too early to determine what direct impacts Irma might have on the continental United States. However, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 05/1200Z 16.7N 57.7W 150 KT 175 MPH 12H 05/1800Z 17.0N 58.9W 155 KT 180 MPH 24H 06/0600Z 17.7N 61.5W 150 KT 175 MPH 36H 06/1800Z 18.6N 64.2W 145 KT 165 MPH 48H 07/0600Z 19.6N 67.0W 140 KT 160 MPH 72H 08/0600Z 21.2N 72.5W 135 KT 155 MPH 96H 09/0600Z 22.4N 77.2W 135 KT 155 MPH 120H 10/0600Z 24.0N 81.0W 130 KT 150 MPH $$ Forecaster Brown

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Hurricane Irma Forecast Discussion Number 24

2017-09-05 10:49:05| National Hurricane Center (Atlantic)

Issued at 500 AM AST Tue Sep 05 2017 000 WTNT41 KNHC 050848 TCDAT1 Hurricane Irma Discussion Number 24 NWS National Hurricane Center Miami FL AL112017 500 AM AST Tue Sep 05 2017 The cloud pattern on satellite is spectacular with a clear eye surrounded by a ring of very deep convection. An Air Force plane was in the eye of the hurricane a few hours ago and measured surface winds of 126 kt with the SFMR. Since the plane left, the could pattern has become even more impressive and objective T-numbers have been oscillating around 7.0 on the Dvorak scale. Based on the average of these estimates, the initial intensity is adjusted upward to 130 kt. The hurricane will be moving through an environment of low vertical wind shear, a moist mid-level atmosphere, and increasing upper-ocean heat content, and this is ideal for some additional intensification. However, given that the SHIPS models do not show any significant change in the intensity, the NHC forecast keeps Irma a powerful hurricane through five days. Recon and satellite fixes indicate that Irma is moving toward the west or 270 degrees at 12 kt. The hurricane is moving around the periphery of the Atlantic subtropical ridge, which in fact is quite strong at this time. This persistent pattern should keep Irma on a general westward track for the next 24 hours, with a west-northwest track thereafter. The guidance envelope and many of the ensemble members of the GFS and the ECMWF models have shifted slightly westward since the previous run. The NHC forecast also shifted slightly westward, and it is on top of the multi-model consensus. The confidence in the forecast beyond 3 days is lower, since the guidance spreads out more. Users are reminded to not focus on the exact forecast track, especially at the longer ranges, since the average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively. KEY MESSAGES: 1. Irma is expected to affect the northeastern Leeward Islands as a dangerous major hurricane, accompanied by life-threatening wind, storm surge, and rainfall impacts. Hurricane warnings are in effect for portions of the Leeward Islands. Preparations should be rushed to completion, as tropical-storm force winds are expected to first arrive in the hurricane warning area later today. 2. Irma is also expected to affect the British and U.S. Virgin Islands and Puerto Rico as a dangerous major hurricane later this week. Hurricane warnings have been issued for these areas, and tropical-storm-force winds could arrive in these areas by early Wednesday. 3. Irma could directly affect Hispaniola, the Turks and Caicos, the Bahamas, and Cuba as a dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. There is an increasing chance of seeing some impacts from Irma in the Florida Peninsula and the Florida Keys later this week and this weekend. Otherwise, it is still too early to determine what direct impacts Irma might have on the continental United States. However, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 16.6N 57.0W 130 KT 150 MPH 12H 05/1800Z 17.0N 58.9W 130 KT 150 MPH 24H 06/0600Z 17.7N 61.5W 130 KT 150 MPH 36H 06/1800Z 18.6N 64.2W 130 KT 150 MPH 48H 07/0600Z 19.6N 67.0W 125 KT 145 MPH 72H 08/0600Z 21.2N 72.5W 120 KT 140 MPH 96H 09/0600Z 22.4N 77.2W 115 KT 130 MPH 120H 10/0600Z 24.0N 81.0W 115 KT 130 MPH $$ Forecaster Avila

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