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Tropical Storm Chris Forecast Discussion Number 10

2018-07-09 04:44:11| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Sun Jul 08 2018 000 WTNT43 KNHC 090244 TCDAT3 Tropical Storm Chris Discussion Number 10 NWS National Hurricane Center Miami FL AL032018 1100 PM EDT Sun Jul 08 2018 Chris is on a strengthening trend. Deep convection has been expanding over the center and recent microwave images show an improved structure with tightly curved bands, especially on the north and east sides of the circulation. The NOAA Hurricane Hunters are currently investigating Chris and so far they have found a minimum pressure of 1005 mb and maximum flight-level winds of 57 kt, which would support a 50-kt intensity. The initial intensity is increased to 50 kt, but this is a little lower than the latest Dvorak estimates. Chris has not moved much today as it remains caught in very weak steering currents between two mid-level highs and a mid- to upper-level trough to its northeast. Since this pattern is not expected to change much during the next day or so, Chris is likely to continue to drift around during that time period. On Tuesday, however, a deep-layer trough is expected to approach the storm and that should finally cause Chris to pull away to the northeast. A very fast northeastward motion is forecast toward the end of the period when the cyclone becomes embedded in strong mid-latitude flow. The NHC track forecast is not too different than the previous one and lies near the various consensus aids. Additional strengthening is expected during the next 2 to 3 days as Chris remains over the warm Gulf Stream waters and in a moderate wind shear environment. The global models suggest that Chris could also benefit from baroclinic enhancements ahead of the approaching trough. The NHC intensity forecast follows the HCCA and ICON models and brings Chris to hurricane strength on Monday with additional strengthening into Tuesday. Steady weakening should begin shortly after 72 hours, and extratropical transition should be complete by 96 hours when Chris crosses the north wall of the Gulf Stream and is over very chilly 10 degree C waters. The NHC intensity forecast is slightly higher than the previous one during the next few days to be in better agreement with the latest guidance. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 32.5N 74.5W 50 KT 60 MPH 12H 09/1200Z 32.4N 74.5W 60 KT 70 MPH 24H 10/0000Z 32.3N 74.5W 70 KT 80 MPH 36H 10/1200Z 32.3N 74.5W 75 KT 85 MPH 48H 11/0000Z 33.5N 73.2W 80 KT 90 MPH 72H 12/0000Z 37.5N 68.2W 80 KT 90 MPH 96H 13/0000Z 43.6N 61.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 14/0000Z 49.5N 52.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi

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Remnants of Beryl Forecast Discussion Number 15

2018-07-09 04:40:41| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Sun Jul 08 2018 000 WTNT42 KNHC 090240 TCDAT2 Remnants Of Beryl Discussion Number 15 NWS National Hurricane Center Miami FL AL022018 1100 PM AST Sun Jul 08 2018 The remains of the center of Beryl have crossed Dominica during the past few hours, accompanied by a disorganized area of convection. Radar and surface observations continue to show that the system is an open wave. There have been no observations of sustained tropical-storm-force winds from Dominica or Guadeloupe, so the initial intensity is decreased to a probably generous 35 kt. In the short term, increasing vertical wind shear should cause continued weakening of the system, with the remains of the center dissipating in the next 12 h. Between 72-120 h, there may be an opportunity for the remnants of Beryl to regenerate into a tropical cyclone when the system moves through the Bahamas and into the southwestern Atlantic. However, due to a lack of agreement by the dynamical models and the uncertainty about how the tropical wave will be disrupted by passage over Hispaniola, the chances of regeneration are currently in the low category. The initial motion estimate is 290/23 kt. The remnants of Beryl should maintain this rapid west-northwestward motion for the next 12 hours as they move through the northeastern Caribbean Sea to the south of Puerto Rico and the Virgin Islands. This is the last advisory on this system by the National Hurricane Center. Additional information on this system can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and available on the Web at http://ocean.weather.gov/shtml/NFDHSFAT1.shtml. Key Messages: 1. As the tropical wave moves across the northeastern Caribbean Sea, strong gusty winds and locally heavy rains are possible across the Leeward Islands tonight and Monday, and these conditions expected to spread across the Virgin Islands, Puerto Rico, and Hispaniola by Monday night. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 15.8N 62.4W 35 KT 40 MPH...TROPICAL WAVE 12H 09/1200Z...DISSIPATED $$ Forecaster Beven

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Remnants of Beryl Forecast Discussion Number 14

2018-07-08 22:35:39| National Hurricane Center (Atlantic)

Issued at 500 PM AST Sun Jul 08 2018 000 WTNT42 KNHC 082035 TCDAT2 Remnants Of Beryl Discussion Number 14 NWS National Hurricane Center Miami FL AL022018 500 PM AST Sun Jul 08 2018 Satellite imagery and ASCAT scatterometer wind data confirm the sharp open-trough pattern that was indicated by earlier aircraft reconnaissance wind data. Although Beryl has a well-defined, tight vortex noted in GOES-16 hi-res visible satellite imagery, that feature appears to be located above the surface. The latest radar data from Martinique also shows little if any rotation in the most recent convective burst that has developed just north of the aforementioned vortex. Given that the remnants of Beryl are now moving at a forward speed of at least 23 kt, it is highly unlikely that the very small circulation is closed at the surface. The intensity remains at 40 kt based on the earlier reconnaissance 56-kt flight-level wind data and the latest burst of convection that has developed in the same general location as those earlier winds. Now that Beryl is no longer considered to be a tropical cyclone, the reconnaissance mission for this evening has been canceled. On days 3-5, there appears to be an opportunity for the remnants of Beryl to regenerate into a tropical cyclone when the system moves through the Bahamas and into the southwestern Atlantic. Vertical wind shear conditions are forecast by most of the models to be light, with even the possibility of the development of a weak upper-level anticyclone across the Bahamas. The combination of the favorable upper-level wind flow pattern in conjunction with sea-surface temperatures of 28-29 deg C should yield conditions conducive for the reformation of a tropical cyclone, although Beryl's low-level remnants are likely to be significantly disrupted by Hispaniola and could take some time to reform. The initial motion estimate is 290/23 kt. The remnants of Beryl should maintain this rapid west-northwestward motion for the next 12 hours, passing over the Leeward Islands tonight and moving into the northeastern Caribbean Sea Monday morning. Although Beryl is no longer a tropical cyclone, advisories will continue to be issued on this system until the tropical storm watch for Dominica has been discontinued. Key Messages: 1. Tropical storm conditions are possible for Dominica tonight. Elsewhere across the Leeward Islands, strong gusty winds and locally heavy rains are possible tonight and Monday, and these conditions are expected to spread across the Virgin Islands, Puerto Rico, and Hispaniola on Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 15.2N 60.3W 40 KT 45 MPH...REMNANTS 12H 09/0600Z 16.2N 63.3W 35 KT 40 MPH...TROPICAL WAVE 24H 09/1800Z...DISSIPATED $$ Forecaster Stewart

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Tropical Storm Chris Forecast Discussion Number 9

2018-07-08 22:32:08| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Sun Jul 08 2018 000 WTNT43 KNHC 082032 TCDAT3 Tropical Storm Chris Discussion Number 9 NWS National Hurricane Center Miami FL AL032018 500 PM EDT Sun Jul 08 2018 Satellite images indicate that the cloud pattern continues to become better organized, and T-numbers from TAFB and SAB have increased to 3.0 on the Dvorak scale. This was confirmed by data from an Air Force reconnaissance plane which reported flight-level winds of 51 kt on the eastern semicircle. The initial intensity is set at 45 kt in this advisory. Chris is expected to be over a pool of warm water for the next 2 days and embedded within an environment of low shear. On this basis, the NHC forecast continues to call for Chris to become a hurricane in about 36 hours. This is in agreement with the dynamical guidance and the HCCA model consensus which strengthen Chris to a hurricane in a couple of days. In about 4 days, Chris will be over 13 degree C Canadian waters, and this should encourage extratropical transition. The steering currents have collapsed, and the cyclone has barely moved all day. These currents are foreast to remain light, so little motion is anticipated during the next 2 days. A mid-level trough forecast to swing eastward across the eastern United States will provide enough forcing to kick Chris northeastward with increasing forward speed over the Atlantic beyond 72 hours. The NHC forecast continues to be in the middle of the track guidance envelope and follows closely the corrected consensus. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 32.7N 74.6W 45 KT 50 MPH 12H 09/0600Z 32.5N 74.6W 55 KT 65 MPH 24H 09/1800Z 32.3N 74.5W 60 KT 70 MPH 36H 10/0600Z 32.3N 74.5W 65 KT 75 MPH 48H 10/1800Z 33.0N 74.0W 75 KT 85 MPH 72H 11/1800Z 36.5N 69.5W 75 KT 85 MPH 96H 12/1800Z 43.5N 61.5W 55 KT 65 MPH 120H 13/1800Z 50.0N 52.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Avila

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Tropical Storm Beryl Forecast Discussion Number 13

2018-07-08 16:49:35| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Sun Jul 08 2018 000 WTNT42 KNHC 081449 TCDAT2 Tropical Storm Beryl Discussion Number 13 NWS National Hurricane Center Miami FL AL022018 1100 AM AST Sun Jul 08 2018 An Air Force Reserve reconnaissance aircraft investigating Beryl earlier this morning was unable to find a closed low-level center. However, the wind data from the aircraft indicated that a sharp through did exist northeastward of the deep convection located in the northeastern quadrant of the larger circulation. Since that time, a stronger burst of convection has developed over the sharp trough, and the assumption is that the convection could have spun up a new center. For that reason, the system is still being considered as a tropical cyclone for this advisory. The highest 850-mb flight-level wind measured was 56 kt in the northeast quad, which equates to about a 45-kt surface wind. However, the advisory intensity is being maintained at 40 kt in case the recent convective development doesn't persist. Another reconnaissance mission into Beryl is scheduled for this evening. The initial motion estimate is 290/20 kt. Beryl is expected to maintain this quick west-northwestward motion through dissipation due to the strong and broad deep-layer ridge that extends east-to-west across most of the subtropical Atlantic Ocean. The latest model guidance remains tightly packed about the previous advisory track, so no significant changes were required. For now, Beryl seems to have found a sweet spot where the vertical wind shear is a little lower and more difluent based on water vapor imagery. However, this localized favorable upper-level wind flow pattern is expected to be short-lived and give way to more hostile shear conditions by 12 hours and beyond when the shear is forecast to increase to more than 25 kt from the west. The result should be a rapid degeneration of the cyclone into an open wave by 24 h when the system will be moving over the eastern Caribbean Sea. However, the system will likely produce strong gusty winds and locally heavy rainfall across the Leeward Islands, the Virgin Islands, and Puerto Rico during the next couple of days. On days 3-5, there appears to be an opportunity for the remnants of Beryl to regenerate into a tropical cyclone when the system moves through the Bahamas and into the southwestern Atlantic. Vertical wind shear conditions are forecast by most of the models to be light, with even the possibility of the development of a weak upper-level anticyclone across the Bahamas. The combination of the favorable upper-level wind flow pattern in conjunction with sea-surface temperatures of 28-29 deg C should yield conditions conducive for the reformation of a tropical cyclone, although Beryl's low-level remnants are likely to be significantly disrupted by Hispaniola and could take some time to reform. Key Messages: 1. Tropical storm warnings and watches are in effect for portions of the Lesser Antilles where Beryl is forecast to bring impacts from wind and rainfall to some of the islands beginning late today or tonight. 2. Although Beryl is forecast to degenerate into a trough of low pressure over the eastern Caribbean, the system is likely to produce strong gusty winds and locally heavy rainfall across the remainder of the Leeward Islands, the Virgin Islands, Puerto Rico, and Hispaniola through Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 14.4N 57.9W 40 KT 45 MPH 12H 09/0000Z 15.4N 60.8W 40 KT 45 MPH 24H 09/1200Z 16.8N 64.9W 35 KT 40 MPH...TROPICAL WAVE 36H 10/0000Z 18.4N 68.8W 30 KT 35 MPH...TROPICAL WAVE 48H 10/1200Z...DISSIPATED $$ Forecaster Stewart

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