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Hurricane Ophelia Forecast Discussion Number 21

2017-10-14 10:58:25| National Hurricane Center (Atlantic)

Issued at 500 AM AST Sat Oct 14 2017 000 WTNT42 KNHC 140858 TCDAT2 Hurricane Ophelia Discussion Number 21 NWS National Hurricane Center Miami FL AL172017 500 AM AST Sat Oct 14 2017 Ophelia's 20-nmi-diameter eye has continued to become more distinct and cloud-free, with the eye temperature now reaching 15 deg C. Satellite intensity estimates range from T4.5/77 kt from TAFB to T5.0/90 kt from SAB and T5.5/102 kt from UW-CIMSS ADT. For now, the initial intensity will remain at 85 kt, which is an average of the available intensity estimates. The initial motion estimate is 060/21 kt. Ophelia is embedded within deep-layer southwesterly flow on the east side of a broad mid-latitude trough. The global and regional models remain in excellent agreement on the trough amplifying over the next 3-4 days, which will cause the hurricane to accelerate toward the northeast at forward speeds near 30 kt by 48 hours. The tight clustering of the NHC model guidance, which shows very little cross-track or along-track spread, increases the confidence in the official track. As a result, no significant changes were made to the previous advisory, and the new forecast track remains near the middle of the guidance envelope, close to the HCCA and TVCX consensus models. Ophelia is expected to remain in relatively low vertical wind shear environment for the next 12 hours or so, which should help the hurricane retain much of its current intensity during that time, even though SSTs are only going to be 24-25C. However, upper-level temperatures that are still about 2 deg C cooler than normal, which will help to create sufficient instability to continue to drive the development of inner-core convection. By 36 hours or so, the shear is forecast to increase to 30-40 kt and the troposphere is expected to become stable as sea-surface temperatures decrease to less than 20 deg C. However, even those SST values are about 2 deg C warmer than normal for this time of the year. Those above-average ocean temperatures are forecast to combine with strong baroclinic energy associated with a potent, negatively tilted, upper-level trough, causing Ophelia to transition into a powerful extratropical low pressure system. By 48 hours, the post-tropical cyclone is forecast to maintain sustained hurricane-force winds as it approaches Ireland, with stronger winds expected over higher terrain. Given that Ophelia is forecast to become extratropical, the wind field should expand, resulting in impacts over portions of the British Isles regardless of its exact location or strength. By 96 hours, Ophelia should have weakened due to the interaction with land, causing the surface circulation to become ill-defined, and dissipation is expected shortly thereafter. Although the center of Ophelia is not forecast to reach Ireland or the UK for another 48-60 hours, wind and rain effects will arrive well in advance of the cyclone center. Individuals in those locations should consult products from their local meteorological service for more information on local impacts. Tropical-storm-force winds are possible throughout the Azores beginning tonight, primarily due to an approaching cold front. However, any track deviation to the west could bring stronger winds associated with Ophelia's circulation to those islands. Interests in the Azores should refer to products issued by the Azores Weather Forecast and Watch Center. KEY MESSAGES: 1. Ophelia is expected to become a hurricane-force post-tropical cyclone by Monday before it moves near Ireland and the United Kingdom. Direct impacts from wind and heavy rain in portions of these areas are likely, along with dangerous marine conditions. For more details on the magnitude, timing, and location of impacts from post-tropical Ophelia, residents in Ireland should refer to products issued by Met Eireann, and residents in the United Kingdom should refer to products issued by the Met Office. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 33.9N 28.6W 85 KT 100 MPH 12H 14/1800Z 35.3N 25.4W 80 KT 90 MPH 24H 15/0600Z 38.3N 20.4W 80 KT 90 MPH 36H 15/1800Z 43.0N 16.0W 75 KT 85 MPH...POST-TROP/EXTRATROP 48H 16/0600Z 48.4N 12.5W 75 KT 85 MPH...POST-TROP/EXTRATROP 72H 17/0600Z 57.4N 6.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 18/0600Z 63.1N .5W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 19/0600Z...DISSIPATED $$ Forecaster Stewart

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Hurricane Ophelia Forecast Discussion Number 20

2017-10-14 04:33:52| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Fri Oct 13 2017 000 WTNT42 KNHC 140233 TCDAT2 Hurricane Ophelia Discussion Number 20 NWS National Hurricane Center Miami FL AL172017 1100 PM AST Fri Oct 13 2017 The eye of Hurricane Ophelia continues to be remarkably distinct on satellite and remains surrounded by a ring of deep convection. An average of objective and subjective Dvorak numbers still support an initial intensity of 85 kt. The hurricane has managed to move through an area of relatively low shear and maintain its intensity so far. This is about to change in a day or so when a cold front reaches the circulation of the hurricane and the shear increases substantially. By then, any increase in intensity should be triggered by baroclinic forces as the cyclone becomes extratropical. The NHC forecast calls for Ophelia to become extratropical in about 48 hours and dissipate or absorbed by another large low beyond 4 days. Given that the cyclone is forecast to become extratropical, the wind field should expand, resulting in impacts over portions of the British Isles regardless of its exact location or strength. By 96 hours, Ophelia should have weakened due to the interaction with land, causing the surface circulation to become ill-defined, and dissipation is expected shortly thereafter. Now that the cyclone is well embedded in the mid-latitude westerlies, it is moving faster toward the east-northeast or 060 degrees at 17 kt. An additional increase in forward speed is anticipated as a large high-latitude trough accelerates the westerly flow. Track models are in very good agreement and this increases the confidence in the NHC forecast which is in the middle of the tight guidance envelope. Although the center of Ophelia is not expected to reach Ireland or the UK for another 2-3 days, wind and rain effects will arrive well in advance of the cyclone center. Individuals in those locations should consult products from their local meteorological service for more information on local impacts. Tropical-storm-force winds are possible throughout the Azores beginning Saturday night primarily due to an approaching cold front. However, any track deviation to the left could bring stronger winds associated with Ophelia's circulation to the islands. Interests in the Azores should refer to products issued by the Azores Weather Forecast and Watch Center. KEY MESSAGES: 1. Ophelia is expected to become a hurricane-force post-tropical cyclone by Monday before it moves near Ireland and the United Kingdom. Direct impacts from wind and heavy rain in portions of these areas are likely, along with dangerous marine conditions. For more details on the magnitude, timing, and location of impacts from post-tropical Ophelia, residents in Ireland should refer to products issued by Met Eireann, and residents in the United Kingdom should refer to products issued by the Met Office. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 33.0N 30.6W 85 KT 100 MPH 12H 14/1200Z 34.3N 27.9W 80 KT 90 MPH 24H 15/0000Z 36.5N 23.2W 80 KT 90 MPH 36H 15/1200Z 40.3N 17.7W 75 KT 85 MPH 48H 16/0000Z 46.0N 14.0W 75 KT 85 MPH...POST-TROP/EXTRATROP 72H 17/0000Z 56.0N 7.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 18/0000Z 62.0N 1.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 19/0000Z...DISSIPATED $$ Forecaster Avila

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Hurricane Ophelia Forecast Discussion Number 19

2017-10-13 22:42:52| National Hurricane Center (Atlantic)

Issued at 500 PM AST Fri Oct 13 2017 000 WTNT42 KNHC 132042 TCDAT2 Hurricane Ophelia Discussion Number 19 NWS National Hurricane Center Miami FL AL172017 500 PM AST Fri Oct 13 2017 Ophelia's eye has become better defined over the past 6 hours. Although cloud tops near the inner core of the hurricane are warmer than 24 hours ago, a ring of -50 deg C or colder cloud tops still surrounds the eye. Dvorak current intensity estimates have not changed substantially, and a blend of objective and subjective classifications still supports an initial intensity of 85 kt. Little change in strength is expected while Ophelia remains a hurricane, since the relatively cool SSTs along the hurricane's path will likely be offset by low shear and cold upper-level temperatures for the next 36 h. Extratropical transition will likely begin shortly after that time, as Ophelia begins to interact with a large upper-level trough approaching from the west. The dynamical guidance suggests that Ophelia will deepen in response to the trough, and although the forecast does not explicitly show it, I can not rule out that Ophelia will briefly intensify as it undergoes extratropical transition. By 72 hours, the cyclone is expected to occlude and begin weakening, though the expansion of the wind field will result in impacts over portions of the British Isles, regardless of its exact location or strength. By 96 hours, continued weakening and interaction with land will likely cause the surface circulation to become ill-defined, and dissipation is expected shortly thereafter. Ophelia is beginning to accelerate toward the east-northeast and the initial motion estimate is 060/11 kt. Very little change has been made to the official track forecast. Ophelia is still expected to continue picking up speed on an east-northeast heading while passing south of the Azores during the next 24 to 36 hours. By 48 hours, interaction with the aforementioned upper-level trough will cause Ophelia to turn toward the northeast and approach Ireland and the western UK in about 72 h. The track guidance is tightly clustered, especially through 72 h, and the new NHC track forecast is close to the various multi-model consensus aids. Although the center of Ophelia is not expected to reach Ireland or the UK until about day 3, wind and rain effects will arrive well in advance of the cyclone center. Individuals in those locations should consult products from their local meteorological service for more information on local impacts. Tropical-storm-force winds are possible throughout the Azores beginning late Saturday or Saturday night due to an approaching cold front. Any deviation to the left of Ophelia's forecast track could bring stronger winds to the islands. Interests in the Azores should refer to products issued by the Azores Weather Forecast and Watch Center. KEY MESSAGES: 1. Ophelia is expected to become a hurricane-force post-tropical cyclone by Monday before it moves near Ireland and the United Kingdom. Direct impacts from wind and heavy rain in portions of these areas are likely, along with dangerous marine conditions. For more details on the magnitude, timing, and location of impacts from post-tropical Ophelia, residents in Ireland should refer to products issued by Met Eireann, and residents in the United Kingdom should refer to products issued by the Met Office. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 32.3N 31.8W 85 KT 100 MPH 12H 14/0600Z 33.4N 29.5W 80 KT 90 MPH 24H 14/1800Z 35.2N 25.4W 80 KT 90 MPH 36H 15/0600Z 38.2N 20.3W 80 KT 90 MPH 48H 15/1800Z 43.1N 16.0W 80 KT 90 MPH 72H 16/1800Z 53.2N 10.4W 65 KT 75 MPH...POST-TROP/EXTRATROP 96H 17/1800Z 60.5N 2.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 18/1800Z...DISSIPATED $$ Forecaster Zelinsky

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Discussion Guide: Suggested Items for Future Agendas by Theme

2017-10-13 22:13:24| PortlandOnline

PDF Document, 193kbCategory: October 10, 2017 Materials

Tags: items guide future discussion

 

DRAFT Annual Report for Discussion (revised)

2017-10-13 22:11:03| PortlandOnline

PDF Document, 615kbCategory: October 10, 2017 Materials

Tags: report discussion annual revised

 

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