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Tropical Storm Sergio Forecast Discussion Number 43

2018-10-10 04:37:02| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Tue Oct 09 2018 000 WTPZ41 KNHC 100236 TCDEP1 Tropical Storm Sergio Discussion Number 43 NWS National Hurricane Center Miami FL EP212018 800 PM PDT Tue Oct 09 2018 The GOES-15 satellite presentation and an earlier ATMS polar orbiter microwave image revealed little change in Sergio's cloud pattern during the past 6 hours. Deep convection persists in the north semicircle in the form of a rather large curved band while the southern portion is comprised of fragmented bands. A blend of the Dvorak satellite classifications, which haven't changed much, supports holding the initial intensity at 60 kt for this advisory. Very little change in strength is forecast during the next 6-12 hours, as Sergio traverses relatively warm oceanic temperatures and remains in a low shear surrounding environment. Afterward, statistical and dynamical intensity guidance shows weakening through the 48 period, or prior to landfall, as the cyclone moves over cooler waters and into a region of increasing southwesterly vertical shear. Over the weekend, after quickly moving over Baja California Sur, Sergio will weaken further over the state of Sonora in northwestern Mexico, degenerate into a remnant low by day 4, and dissipate over the Southern Plains of the United States. The initial motion is estimated to be east-northeastward, or 060/10 kt, within the deep-layer southwesterly flow produced by a mid-latitude trough stretching southwestward over the eastern Pacific from the southwestern United States. Sergio should continue to accelerate toward the east-northeast or northeast over the next few days, moving over Baja California Sur on Friday, and over the Gulf of California and into northwestern Mexico Friday night and Saturday. The primary threat associated with Sergio and its remnants will likely be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico state of Sonora, the U.S. Southern Plains and the Ozarks through the weekend. For more information about this potential hazard, see products from the Weather Prediction Center and your local weather forecast office. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 17.5N 125.6W 60 KT 70 MPH 12H 10/1200Z 18.2N 124.2W 60 KT 70 MPH 24H 11/0000Z 19.6N 121.9W 55 KT 65 MPH 36H 11/1200Z 21.7N 119.3W 50 KT 60 MPH 48H 12/0000Z 24.1N 116.5W 50 KT 60 MPH 72H 13/0000Z 28.7N 110.0W 35 KT 40 MPH...INLAND 96H 14/0000Z 33.0N 101.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 15/0000Z...DISSIPATED $$ Forecaster Roberts

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Hurricane Michael Forecast Discussion Number 13

2018-10-09 22:55:30| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Tue Oct 09 2018 000 WTNT44 KNHC 092055 TCDAT4 Hurricane Michael Discussion Number 13 NWS National Hurricane Center Miami FL AL142018 400 PM CDT Tue Oct 09 2018 The eye of Michael became very distinct in both visible and infrared satellite pictures early this afternoon, but has been a little more cloud filled since that time. Very deep convection has continue to develop over the southeastern and eastern portion of the eyewall and rotate around the north and west sides. An Air Force Reserve reconnaissance aircraft measured a peak 700-mb flight-level wind of 109 kt in the northeast eyewall as it exited the storm just prior to 1800 UTC, and another Air Force Hurricane Hunter very recently made its first pass through the eye and reported similar flight-level winds in the southeast quadrant, and a minimum pressure of 957 mb, down about 8 mb over the past few hours. Based on these observations and Dvorak satellite classifications of 115 kt and 102 kt from SAB and TAFB, respectively, the initial intensity has been increased to 105 kt for this advisory. The environment ahead of Michael is expected to remain conducive for additional strengthening during the next 12 to 18 hours. There may be some increase in southwesterly shear as the hurricane nears the Gulf Coast, but it is not likely to result in a significant decrease in intensity before landfall. The global models continue to deepen the cyclone over the Gulf, increasing the confidence that some additional intensification will occur. The new NHC intensity forecast brings Michael up to 110 kt, and is in best agreement with the SHIPS and HCCA models. After landfall, significant weakening should occur while Michael moves over the southeastern United States, but the cyclone is predicted to re-strengthen over the western Atlantic due to baroclinic processes after it merges with a front and becomes extratropical on Friday. Michael is still moving north-northwestward to northward at about 10 kt. The hurricane should turn due northward this evening, then northeastward on Wednesday as a trough moves into the central United States. Michael should become embedded within the westerlies in 48 to 72 hours, and then accelerate northeastward to east- northeastward over the western and central-north Atlantic over the weekend. There is not much spread in the dynamical model guidance, and little change was required to the official forecast. Although the NHC forecast brings the center onshore Wednesday afternoon, conditions will deteriorate along the northeastern Gulf Coast tonight. Tropical storm watches and warnings have been expanded northward along the U.S. East Coast from northeastern Florida to North Carolina. Non-tropical watches, warnings, and advisories will be issued by local NWS offices for wind hazards north of Duck, North Carolina, as Michael is expected to be post-tropical when it affects those areas. Key Messages: 1. Life-threatening storm surge is likely along portions of the coasts of the Florida Panhandle, Big Bend, and Nature Coast, where a storm surge warning is in effect. The worst storm surge is expected between Mexico Beach and Keaton Beach, where 9 to 13 feet of inundation is possible. Water levels will rise well in advance of the center of Michael, and residents within the storm surge warning area should finish preparations to protect life and property today. 2. Everyone in the hurricane warning area along the Florida Gulf Coast should prepare for life-threatening major hurricane winds associated with the core of Michael. Hurricane force winds will also extend well inland across portions of the Florida Panhandle, southern Georgia, and southeast Alabama as Michael moves inland. 3. Heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions of Georgia, the Carolinas, and southeast Virginia. 4. Tropical storm conditions will likely affect portions of the southeast U.S. coast from northeast Florida through North Carolina, and tropical storm watches and warnings have been issued for these areas. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 26.0N 86.4W 105 KT 120 MPH 12H 10/0600Z 27.6N 86.6W 110 KT 125 MPH 24H 10/1800Z 29.7N 85.9W 110 KT 125 MPH 36H 11/0600Z 31.8N 84.1W 60 KT 70 MPH...INLAND 48H 11/1800Z 33.9N 81.0W 45 KT 50 MPH...INLAND 72H 12/1800Z 39.0N 70.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 13/1800Z 45.5N 51.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 14/1800Z 50.0N 30.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Tropical Storm Sergio Forecast Discussion Number 42

2018-10-09 22:55:30| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Tue Oct 09 2018 000 WTPZ41 KNHC 092055 TCDEP1 Tropical Storm Sergio Discussion Number 42 NWS National Hurricane Center Miami FL EP212018 200 PM PDT Tue Oct 09 2018 Days of slow movement and cold water upwelling appear to have finally taken a toll on Sergio. Cloud top temperatures on the west side of the cyclone have warmed considerably since this morning, and microwave imagery indicates that Sergio's eyewall is no longer fully closed. Dvorak-based intensity estimates have decreased accordingly and now support an initial intensity of only 60 kt. A recent partial ASCAT overpass also showed maximum winds of only 50-55 kt in the eastern semicircle of the cyclone, and these data also support making Sergio a tropical storm. The tropical storm is moving east-northeastward, or 060/8 kt. No important changes were made to the track forecast, which is merely an update of the previous advisory. The tropical storm will likely continue to accelerate toward the east-northeast or northeast over the next few days, before approaching the Baja California peninsula on Friday. The NHC forecast remains near the track consensus at all times and confidence in the track forecast is high. Now that Sergio is moving a little faster, it has a chance to move over slightly warmer waters during the next few hours. The intensity guidance is in fairly good agreement that little additional weakening is likely for the next day or so. Beyond 36 h, faster weakening is still possible as the storm reaches much colder waters and the shear over the tropical storm increases. Rapid weakening and dissipation is expected after Sergio makes its final landfall along the coast of mainland Mexico, though a 96 h point remnant low is maintained again in this advisory to represent the inland movement of Sergio. The NHC forecast is essentially an average of the HCCA and IVCN consensus aids at all forecast hours. The biggest hazard associated with Sergio and its remnants will likely be heavy rain that will affect portions of northwestern Mexico and the U.S. Southern Plains through Sunday. For more information about this potential hazard, see products from the Weather Prediction Center and your local weather forecast office. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 16.9N 126.5W 60 KT 70 MPH 12H 10/0600Z 17.5N 125.4W 60 KT 70 MPH 24H 10/1800Z 18.7N 123.4W 55 KT 65 MPH 36H 11/0600Z 20.3N 121.0W 55 KT 65 MPH 48H 11/1800Z 22.7N 118.2W 50 KT 60 MPH 72H 12/1800Z 27.3N 112.0W 40 KT 45 MPH 96H 13/1800Z 31.0N 105.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 14/1800Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Storm Leslie Forecast Discussion Number 54

2018-10-09 22:41:57| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Oct 09 2018 000 WTNT43 KNHC 092041 TCDAT3 Tropical Storm Leslie Discussion Number 54 NWS National Hurricane Center Miami FL AL132018 500 PM AST Tue Oct 09 2018 Leslie's appearance on visible imagery has improved through the afternoon, and multiple microwave overpasses show the development of a small mid-level eye. The intensity has been increased to 60 kt based on an average of the most recent Dvorak classifications from TAFB and SAB. Leslie is moving over warmer waters and the wind shear is expected to be low, so additional strengthening is anticipated and Leslie is forecast to become a hurricane overnight. Given the relatively favorable environment and the recent organization of Leslie's inner-core, it is possible that Leslie could intensify a little faster than currently indicated by the NHC forecast. Beyond day 2, there is particularly low confidence in the intensity forecast since the track of Leslie is highly uncertain, and the NHC forecast essentially follows the intensity consensus. It is likely that the farther south and west Leslie remains, the stronger it will be. Unfortunately the track forecast has not become any clearer. Recent GFS and ECMWF ensemble forecasts still indicate that a range of possibilities exist, from Leslie becoming extratropical and heading toward the extreme northeast Atlantic, to Leslie turning back west in a few days and persisting as a tropical cyclone. No large changes were made to the track forecast at this time, since I see no reason to commit to a new solution at this time. The NHC forecast is close to HCCA at all forecast hours, but confidence is low to say the least. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 30.3N 43.0W 60 KT 70 MPH 12H 10/0600Z 29.0N 42.6W 65 KT 75 MPH 24H 10/1800Z 28.0N 42.2W 70 KT 80 MPH 36H 11/0600Z 28.1N 41.4W 75 KT 85 MPH 48H 11/1800Z 29.2N 38.9W 75 KT 85 MPH 72H 12/1800Z 32.0N 29.5W 75 KT 85 MPH 96H 13/1800Z 33.0N 22.0W 60 KT 70 MPH 120H 14/1800Z 31.0N 20.0W 45 KT 50 MPH $$ Forecaster Zelinsky

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Tropical Storm Nadine Forecast Discussion Number 3

2018-10-09 22:31:39| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Oct 09 2018 000 WTNT45 KNHC 092031 TCDAT5 Tropical Storm Nadine Discussion Number 3 NWS National Hurricane Center Miami FL AL152018 500 PM AST Tue Oct 09 2018 Nadine is a sheared tropical cyclone this afternoon with the center partially exposed on the southwestern side of an increasing area of convection. Dvorak estimates are unchanged since earlier, so the initial wind speed remains 35 kt. The shear is forecast to remain low enough to support strengthening during the next day or so, along with sufficiently warm waters. However, Nadine should encounter a large upper trough after that time, which should cause weakening to begin on Thursday. Later on, cooler SSTs and strong shear are expected to cause Nadine to degenerate into a trough of low pressure by the weekend. Model guidance is in fair agreement on this scenario, and the new NHC prediction is close to the previous one and the model consensus. Satellite imagery today shows that Nadine has turned rightward and is moving 300/7. A northwestward track should begin overnight and continue for the next few days due to steering from a mid-level ridge near the Cabo Verde Islands. A westward turn is expected beyond day 3 as Nadine becomes a shallow system and dissipates. The track forecast isn't super confident because it is somewhat dependent on the intensity. For example, a stronger cyclone like the GFS shows would have the potential to move more toward the north- northwest as it attempts to remain a vertically coherent system. Since Nadine isn't expected to get very strong, the official forecast will stay near or just south of the model consensus, which results in no significant change to the previous track forecast. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 10.9N 30.6W 35 KT 40 MPH 12H 10/0600Z 11.6N 31.5W 40 KT 45 MPH 24H 10/1800Z 12.6N 32.5W 45 KT 50 MPH 36H 11/0600Z 13.7N 33.4W 40 KT 45 MPH 48H 11/1800Z 15.0N 34.7W 35 KT 40 MPH 72H 12/1800Z 17.0N 37.5W 25 KT 30 MPH 96H 13/1800Z...DISSIPATED $$ Forecaster Blake

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