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Hurricane Larry Forecast Discussion Number 37
2021-09-09 22:59:46| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Sep 09 2021 000 WTNT42 KNHC 092059 TCDAT2 Hurricane Larry Discussion Number 37 NWS National Hurricane Center Miami FL AL122021 500 PM AST Thu Sep 09 2021 A faint eye is still discernible on visible satellite images along with some banding features. On the Bermuda radar, the eyewall is partially open over the southern semicircle of the hurricane. Larry still has a prominent upper-tropospheric outflow pattern, especially over the northern portion of the circulation. The advisory intensity is held at 80 kt, just above the latest Dvorak Current Intensity Numbers from TAFB and SAB. Larry is now heading a little west of north at an increasing forward speed, and the initial motion is 345/17 kt. The hurricane has been moving around the western side of a large deep-layer high pressure area centered over the central Atlantic. By Friday, the system should accelerate northeastward ahead of a strong mid-tropospheric trough over the northeastern United States, and pass near or over southeastern Newfoundland within 36 hours. Thereafter, post-tropical cyclone Larry should move over the far North Atlantic. The official track forecast again lies close to the various consensus model predictions. The hurricane is expected to remain over warm waters with weak vertical shear for another 12 to 24 hours. Thereafter, Larry is forecast to move over the cooler waters north of the Gulf Stream and the shear will increase. These factors should induce weakening, but possible baroclinic forcing associated with the trough to the west of the cyclone could result in Larry maintaining some strength over the next few days. The NHC intensity forecast is similar to the latest NOAA corrected-consensus guidance, HCCA. Global model predictions indicate that Larry will merge with a front, and therefore become an extratropical cyclone, in 48 hours. These models also show the system merging with another large extratropical low over the north Atlantic in 3 to 4 days. Key Messages: 1. Larry is forecast to move near or over portions of southeastern Newfoundland Friday night or early Saturday morning as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions and dangerous storm surge are expected in portions of southeastern Newfoundland where a Hurricane Warning in effect. 2. Large swells generated by Larry will continue to affect the Leeward Islands, portions of the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through the end of the week. These swells will cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the guidance of lifeguards and local officials. 3. Tropical storm conditions are expected on Bermuda through this evening, along with a risk of coastal flooding. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 33.9N 62.2W 80 KT 90 MPH 12H 10/0600Z 36.8N 61.8W 80 KT 90 MPH 24H 10/1800Z 42.2N 59.0W 75 KT 85 MPH 36H 11/0600Z 48.4N 52.9W 70 KT 80 MPH 48H 11/1800Z 55.0N 46.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 60H 12/0600Z 59.5N 42.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 12/1800Z 61.5N 40.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 13/1800Z...MERGED $$ Forecaster Pasch
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Hurricane Olaf Forecast Discussion Number 9
2021-09-09 22:46:16| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Thu Sep 09 2021 000 WTPZ45 KNHC 092046 TCDEP5 Hurricane Olaf Discussion Number 9 NWS National Hurricane Center Miami FL EP152021 300 PM MDT Thu Sep 09 2021 Olaf is quickly strengthening. An eye is now apparent in visible and satellite imagery. For most of the morning and early afternoon, a large and very symmetric eyewall was also apparent in radar data from Cabo San Lucas. Dvorak intensity estimates at 1800 UTC were 4.5/77 kt from both TAFB and SAB at 1800 UTC, and estimates from the U-W CIMSS ADT have increased to 80 kt since then. The initial intensity has been set at 80 kt, in close agreement with all available estimates. Olaf has moved consistently to the right of the forecast track for the past 12 hours, and the NHC track forecast has been shifted in that direction again. Olaf is now forecast to move very near or over southern Baja California Sur tonight. Regardless of the hurricane's exact track, it is very likely that a portions of southern Baja California Sur will get direct impacts from the eyewall of Olaf tonight. A large ridge centered over the southwestern U.S. is still expected to cause Olaf to make a slight turn toward the northwest tonight or early Friday. The hurricane should then make a westward turn by early Saturday as it weakens and the ridge extends westward. Despite the recent adjustments required to the NHC forecast, this forecast is still generally supported by all of the typically-reliable track guidance. By around 60 h, Olaf will likely have lost all of its deep convection and become a shallow post-tropical low, steered primarily southwestward by low-level flow. The environment should support additional intensification during the next 12 h as Olaf approaches the Baja California peninsula, so any fluctuations in intensity will likely be driven by internal dynamics at this point. The appearance of Olaf's eyewall in radar imagery has degraded a little during the past couple of hours, but it is possible this is due to attenuation of the radar signal and not fully representative of the hurricane's structure. Regardless, Olaf should begin to weaken once it interacts with land or moves inland. By late Friday, the rate of weakening is forecast to increase due to a combination of continued land interactions and cool sea surface temperatures. Olaf should quickly weaken over the weekend as it continues to move over cold water, and it will likely become a post-tropical cyclone on Sunday. The NHC intensity forecast is above the consensus at 12 h to allow for additional short-term strengthening, but follows the consensus closely at 36 h and beyond. Key Messages: 1. Olaf is forecast to move very near or over the southern portion of Baja California Sur tonight and Friday. Hurricane conditions are expected to begin within the southern portion of the hurricane warning area tonight and will spread northward through Friday. 2. Heavy rains associated with Olaf are expected across portions of southern Baja California Sur through Friday. This will pose a threat of significant and life-threatening flash flooding and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 22.2N 108.9W 80 KT 90 MPH 12H 10/0600Z 23.1N 110.0W 85 KT 100 MPH...INLAND 24H 10/1800Z 24.2N 111.5W 70 KT 80 MPH...OVER WATER 36H 11/0600Z 24.6N 112.9W 60 KT 70 MPH 48H 11/1800Z 24.5N 114.1W 50 KT 60 MPH 60H 12/0600Z 23.9N 115.3W 40 KT 45 MPH...POST-TROPICAL 72H 12/1800Z 23.2N 116.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 13/1800Z 22.0N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 14/1800Z 21.5N 122.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster D. Zelinsky
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Tropical Depression Mindy Forecast Discussion Number 5
2021-09-09 22:39:12| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Thu Sep 09 2021 000 WTNT43 KNHC 092039 TCDAT3 Tropical Depression Mindy Discussion Number 5 NWS National Hurricane Center Miami FL AL132021 500 PM EDT Thu Sep 09 2021 The latest infrared satellite imagery indicates that Mindy has been devoid of convection near its center since about the time it emerged over the Atlantic this morning. Deep convection is present well to the northeast of Mindy along a surface trough that extends northeastward from the cyclone. A late morning ASCAT pass showed a large area of 25 to 30 kt winds southeast of the center. The initial intensity is set to 30 kt based on this data. The ASCAT data and surface observations indicate that the circulation has become less well-defined, with barely any east winds observed on the north side. Mindy is located in an environment of strong south to southwesterly vertical wind shear. Over the next 24 h, the shear is expected to become even stronger. The latest forecast calls for Mindy to become post-tropical on Friday and dissipate Friday night. However, based on the lack on convection and the deteriorating wind structure, it is quite possible that dissipation could occur much sooner than forecast. Mindy continues moving quickly off to the east-northeast, with a motion of 075/20 kt. There has been no change to the track forecast philosophy. Mindy is forecast to continue moving east-northeastward at a similar speed for the next 24 h near the southern portion of a deep-layer trough moving across the eastern United States. Once the trough begins to lift northeastward, Mindy should slow down a little on Friday. The NHC forecast is a little south of and slightly faster than the previous forecast, mainly due to the farther south initial position. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 32.0N 78.3W 30 KT 35 MPH 12H 10/0600Z 32.9N 74.9W 30 KT 35 MPH 24H 10/1800Z 33.8N 71.2W 30 KT 35 MPH...POST-TROPICAL 36H 11/0600Z...DISSIPATED $$ Forecaster D. Zelinsky/Hagen
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Hurricane Larry Forecast Discussion Number 36
2021-09-09 17:00:37| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Thu Sep 09 2021 000 WTNT42 KNHC 091500 TCDAT2 Hurricane Larry Discussion Number 36 NWS National Hurricane Center Miami FL AL122021 1100 AM AST Thu Sep 09 2021 Larry continues to feature a banding-type eye on satellite images, and the eye is clearly evident on the Bermuda radar. Satellite and radar data also show a moat-like area of low precipitation between the eyewall and a large band of convection farther removed from the center. This outer band is expected to affect Bermuda or the waters just east of the island over the next several hours. Observations from an Air Force Hurricane Hunter aircraft indicate that the central pressure has changed little since yesterday. Flight-level winds from the aircraft were as high as 95 kt, but the peak SFMR-observed surface winds were only 69 kt. This again indicates that in this case the strong winds aloft are not being transported to the surface as effectively as in a typical hurricane at lower latitudes. Blending these data results in an intensity estimate of 80 kt for this advisory. This is just a little higher than the latest subjective Dvorak estimates from TAFB and SAB. The hurricane is gradually turning to the right and the initial motion is 340/14 kt. Larry is currently moving around the western side of a deep-layer subtropical anticyclone over the central Atlantic, and is passing east of Bermuda. The flow on the east side of a strong mid-level trough moving from the northeastern United States to Atlantic Canada will cause Larry to turn toward the northeast and accelerate in 24 to 48 hours. Larry will move near or over southeastern Newfoundland in 36 to 48 hours, and then move over the far north Atlantic around the end of the forecast period. There is very little change to the NHC track forecast from the previous advisory, which remains close to the various consensus model solutions. Larry is likely remain over warm waters with low shear for another 24 hours or so. Thus the system will probably maintain much of its intensity into Friday. By Friday night and over the weekend, cooler SSTs and increasing shear should cause weakening. However, baroclinic forcing associated with the trough to the west of the hurricane could slow the weakening process. The official intensity forecast keeps Larry at hurricane-force through 48 hours even as it undergoes extratropical transition. In 3-4 days, the global models show Larry merging with another large extratropical cyclone over the north Atlantic. Key Messages: 1. Large swells generated by Larry will continue to affect the Leeward Islands, portions of the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through the end of the week. These swells will likely cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the guidance of lifeguards and local officials this week. 2. The center of Larry is forecast to pass east of Bermuda later today, and tropical storm conditions are expected there today, along with a risk of coastal flooding. 3. Larry is forecast to move near or over portions of southeastern Newfoundland Friday night or early Saturday morning as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions are storm surge are possible in portions of southeastern Newfoundland where a hurricane watch is in effect. Interests there should monitor updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 32.0N 61.6W 80 KT 90 MPH 12H 10/0000Z 34.5N 62.2W 80 KT 90 MPH 24H 10/1200Z 39.0N 60.8W 80 KT 90 MPH 36H 11/0000Z 44.8N 56.1W 75 KT 85 MPH 48H 11/1200Z 51.3N 49.1W 65 KT 75 MPH...POST-TROP/EXTRATROP 60H 12/0000Z 57.0N 43.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 12/1200Z 61.0N 40.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 13/1200Z...MERGED $$ Forecaster Pasch
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Tropical Depression Mindy Forecast Discussion Number 4
2021-09-09 16:52:11| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Thu Sep 09 2021 000 WTNT43 KNHC 091452 TCDAT3 Tropical Depression Mindy Discussion Number 4 NWS National Hurricane Center Miami FL AL132021 1100 AM EDT Thu Sep 09 2021 Doppler radar data and surface observations show that the center of Mindy has recently moved offshore the coast of Georgia. Buoy 41008 located off the Georgia coast recently recorded 1-min sustained winds of 29 kt with gusts as high as 33 kt. Thus, 30 kt is maintained as the intensity for this advisory. Mindy is located in an environment of strong south to southwesterly vertical wind shear. Over the next 24 h, the shear is expected to become even stronger. The strong shear should prevent restrengthening and is likely to strip away any remaining convection by Friday or Friday night. Mindy is forecast to become post-tropical Friday evening. Most of the global models suggest that the cyclone will open up into a trough in 36-48 h, but it is possible this could happen sooner, as surface observations already show that easterly winds on the north side have become quite weak. The NHC forecast calls for dissipation Friday night, which is sooner than the previous advisory. Mindy continues moving quickly to the east-northeast or 065/18 kt. There has been no change to the track forecast philosophy. Mindy is forecast to continue moving east-northeastward at a similar speed for the next 24 h near the southern portion of a deep-layer trough moving across the eastern United States. Once the trough begins to lift northeastward, Mindy should slow down a little on Friday. The main adjustment to the NHC track is to show a slightly faster motion toward the east-northeast at the 24-36 h points. Key Messages: 1. Mindy will produce locally heavy rainfall across portions of coastal South Carolina through early this afternoon. This rainfall may produce isolated to scattered flash, urban, and small stream flooding. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 31.5N 80.7W 30 KT 35 MPH 12H 10/0000Z 32.5N 77.5W 30 KT 35 MPH 24H 10/1200Z 33.6N 73.4W 30 KT 35 MPH 36H 11/0000Z 34.3N 70.3W 25 KT 30 MPH...POST-TROPICAL 48H 11/1200Z...DISSIPATED $$ Forecaster D. Zelinsky/Hagen
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