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Hurricane NICOLE Forecast Discussion Number 40

2016-10-14 04:34:46| National Hurricane Center (Atlantic)

Issued at 1100 PM AST THU OCT 13 2016 000 WTNT45 KNHC 140234 TCDAT5 HURRICANE NICOLE DISCUSSION NUMBER 40 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 PM AST THU OCT 13 2016 The satellite presentation of Nicole has degraded substantially this evening, with the area of cold convective tops shrinking in size and become less symmetric. The low-level center is difficult to locate in geostationary imagery, but recent microwave data suggest it is located to the southwest of the coldest convective tops. This structure is consistent with the 40-45 kt of southwesterly shear analyzed over Nicole by the SHIPS model and UW-CIMSS. The initial intensity has been lowered to 85 kt, which is between the latest Dvorak estimates from TAFB and SAB. Nicole should continue to weaken in the next 12 hours due to the persistent strong shear and cooling SSTs. However, from 24-48 hours, forcing associated with a shortwave trough should cause Nicole to remain a powerful cyclone, and the intensity is maintained at 75 kt through that time. After the shortwave moves past Nicole, slow decay is expected late in the period. The new NHC intensity forecast is lower than the previous one in the first 12-24 hours, following the trend of the latest hurricane intensity guidance. After that time, the intensity forecast is based on global model guidance. Note that the structure of Nicole is quite uncertain during the forecast period, since the cyclone does not appear to complete extratropical transition, with the global models showing the cyclone acquiring a warm seclusion structure. A 2201Z WindSat pass suggested that the center of Nicole was located a little south of previous estimates. The initial motion is estimated to be 060/18, as Nicole is now embedded in the mid- latitude southwesterly flow ahead of a longwave trough moving off the U.S. east coast. This pattern should steer Nicole generally east-northeastward for the next 48 hours, although the forward speed will decrease by 36 hours as Nicole interacts with the aforementioned shortwave. The trough moves east of Nicole by 72 hours, leaving the cyclone in a region of weaker steering flow until a high-latitude trough approaches from the northwest in 4-5 days, and cause Nicole to accelerate northeastward by the end of the forecast period. The new NHC track forecast is a little south of the previous one due to the initial position and is close to a blend of the GFS and ECMWF models through the period. The post-tropical portion of Nicole's track, intensity, and wind radii forecast has been coordinated with the NOAA Ocean Prediction Center. Note that swells from Nicole will affect Bermuda and portions of the U.S. east coast and Atlantic Canada during the next couple of days. By early next week, wave models suggest that long-period swell from Nicole will radiate outward and affect much of the North Atlantic basin. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 34.4N 61.2W 85 KT 100 MPH 12H 14/1200Z 35.6N 58.5W 75 KT 85 MPH 24H 15/0000Z 36.9N 54.3W 75 KT 85 MPH 36H 15/1200Z 38.1N 51.0W 75 KT 85 MPH 48H 16/0000Z 38.6N 49.0W 75 KT 85 MPH...POST-TROPICAL 72H 17/0000Z 39.0N 47.0W 65 KT 75 MPH...POST-TROPICAL 96H 18/0000Z 41.0N 44.0W 65 KT 75 MPH...POST-TROPICAL 120H 19/0000Z 47.0N 37.0W 60 KT 70 MPH...POST-TROPICAL $$ Forecaster Brennan

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Hurricane NICOLE Forecast Discussion Number 39

2016-10-13 22:33:45| National Hurricane Center (Atlantic)

Issued at 500 PM AST THU OCT 13 2016 000 WTNT45 KNHC 132033 TCDAT5 HURRICANE NICOLE DISCUSSION NUMBER 39 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 PM AST THU OCT 13 2016 Satellite imagery indicates that Nicole is weakening as it moves away from Bermuda, most likely due to increasing southwesterly vertical shear. The eye has mostly disappeared since the last advisory, and there has been some warming of the cloud tops near the center. Subjective satellite intensity estimates from TAFB and SAB are 102 and 90 kt, respectively, while the latest CIMSS ADT estimate is 112 kt. The initial intensity is reduced to 95 kt based mainly on the subjective estimates and continuity from earlier aircraft data. As mentioned in the previous advisory, increasing southwesterly shear and slightly lower sea surface temperatures along the forecast track should cause a gradual decrease in intensity during the next 24 to 36 hours. After that time, baroclinic forcing forecast by the dynamical models should keep Nicole as an intense low pressure area over the north Atlantic through early next week. What structure the cyclone might have later in the forecast period is uncertain, with the GFS and UKMET suggesting that the tropical cyclone warm core could become secluded with no cold air reaching the center. Based on this, the forecast continues to call for a post-tropical cyclone and not a fully extratropical/frontal cyclone. The intensity forecast is mainly an update of the previous forecast, and the 3-5 day intensity forecast is in agreement with guidance provided by the NOAA Ocean Prediction Center. The initial motion is now 040/18. The hurricane will continue northeastward as it becomes embedded within southwesterly flow ahead of a mid-latitude trough. The dynamical guidance continues to forecast that the trough should bypass Nicole in a couple of days, which is expected to cause the cyclone to slow down and meander well southeast of Newfoundland late in the forecast period. The track guidance remains in remarkably good agreement, and the NHC is again near the multi-model consensus and the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 33.6N 63.2W 95 KT 110 MPH 12H 14/0600Z 35.0N 60.7W 90 KT 105 MPH 24H 14/1800Z 36.4N 56.8W 80 KT 90 MPH 36H 15/0600Z 37.8N 53.0W 75 KT 85 MPH 48H 15/1800Z 38.8N 50.5W 75 KT 85 MPH...POST-TROPICAL 72H 16/1800Z 39.0N 48.5W 70 KT 80 MPH...POST-TROPICAL 96H 17/1800Z 39.6N 46.5W 65 KT 75 MPH...POST-TROPICAL 120H 18/1800Z 42.0N 41.5W 65 KT 75 MPH...POST-TROPICAL $$ Forecaster Beven

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Hurricane NICOLE Forecast Discussion Number 38

2016-10-13 16:55:45| National Hurricane Center (Atlantic)

Issued at 1100 AM AST THU OCT 13 2016 000 WTNT45 KNHC 131455 TCDAT5 HURRICANE NICOLE DISCUSSION NUMBER 38 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 AM AST THU OCT 13 2016 Southwesterly shear is beginning to affect Nicole. Microwave imagery and Bermuda radar indicate that the eye has lost some definition and become open to the south. There is also a significant southwest to northeast tilt between the low-level center as noted between the radar and satellite presentations of the eye, and the Air Force center fix that was located near the extreme western part of the eye seen in satellite imagery. The Air Force Reserve reconnaissance aircraft has not yet sampled the eastern portion of the eyewall where the strongest winds were reported overnight, however, they have reported a minimum pressure 961 mb, which is up several millibars since the previous fix. Based on the most recent aircraft data and satellite intensity estimates, the initial wind speed has been set at 105 kt for this advisory. Although the area of strongest winds in the eastern eyewall are expected to remain offshore of Bermuda, sustained hurricane-force winds have been reported on the island during the past couple of hours. The official observing site at the airport has measured sustained winds of 67 kt with a gust to 90 kt within the past hour. Increasingly southwesterly shear and slightly lower sea surface temperatures along the forecast track of Nicole should cause a gradual decrease in intensity during the next 24 to 36 hours. After that time, baroclinic forcing is forecast by the global models to keep Nicole an intense low pressure area over the north Atlantic through early next week. The days 3-5 intensity forecast is in agreement with guidance provided by the NOAA Ocean Prediction Center. Nicole has turned northeastward as expected. The hurricane will move northeastward with some acceleration in forward speed as it becomes embedded within southwesterly flow ahead of a mid-latitude trough. The trough is forecast to bypass Nicole in a couple of days, which is expected to cause the cyclone to slow down and meander well southeast of Newfoundland late in the forecast period. The track guidance is in remarkably good agreement, and the NHC is again near the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 32.3N 64.6W 105 KT 120 MPH 12H 14/0000Z 33.8N 62.4W 95 KT 110 MPH 24H 14/1200Z 35.5N 58.9W 80 KT 90 MPH 36H 15/0000Z 37.0N 54.5W 75 KT 85 MPH 48H 15/1200Z 38.3N 51.3W 75 KT 85 MPH...POST-TROPICAL 72H 16/1200Z 39.0N 48.7W 75 KT 85 MPH...POST-TROPICAL 96H 17/1200Z 39.0N 47.5W 65 KT 75 MPH...POST-TROPICAL 120H 18/1200Z 41.0N 44.5W 60 KT 70 MPH...POST-TROPICAL $$ Forecaster Brown

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Hurricane NICOLE Forecast Discussion Number 37

2016-10-13 10:40:09| National Hurricane Center (Atlantic)

Issued at 500 AM AST THU OCT 13 2016 000 WTNT45 KNHC 130840 TCDAT5 HURRICANE NICOLE DISCUSSION NUMBER 37 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 AM AST THU OCT 13 2016 Nicole continues to have an impressive satellite presentation with a warm, well-defined eye and strong eyewall convection. The last Air Force Reserve Hurricane Hunter aircraft measured a 700-mb wind of 118 kt and a peak SFMR wind of 114 kt. These values are close to the previous mission, and based on these data, the initial intensity is kept at 115 kt for this advisory. The initial motion estimate is 025/13. All of the guidance show the core of Nicole very close to Bermuda later today, and only a small westward adjustment was made to the first part of the forecast. Nicole is beginning to accelerate generally northeastward ahead of a mid-latitude trough moving across the northern United States. However, this trough is forecast to move away from Nicole in a few days, leaving the cyclone meandering over the North Atlantic well southeast of Newfoundland. A ridge is then forecast to build over the far northeastern Atlantic east of Nicole, which should help the system resume a slow northeastward motion by day 5. The new forecast is basically an update of the previous one and is very close to the multi-model consensus. Southwesterly shear is forecast by all of the global models to increase rapidly today. In combination with a slow decrease in SSTs, these factors will likely cause Nicole to lose strength soon. The steady weakening trend is forecast to level off in about 36 hours as baroclinic forcing from a mid-latitude shortwave trough should help maintain Nicole as a strong cyclone through rest of the forecast period. The new NHC intensity forecast is a blend of the previous forecast, the intensity consensus and the global model fields beyond 48 hours. While no changes were made to the timing of Nicole becoming post-tropical, there is considerable uncertainty on exactly what structure Nicole will have in a few days time. Regardless, all models forecast Nicole to be a large and powerful cyclone for the next several days. The forecast at days 3 through 5 has been coordinated with the NOAA Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 31.1N 65.8W 115 KT 130 MPH 12H 13/1800Z 32.7N 64.3W 105 KT 120 MPH 24H 14/0600Z 34.8N 61.1W 90 KT 105 MPH 36H 14/1800Z 36.4N 57.3W 80 KT 90 MPH 48H 15/0600Z 37.7N 53.2W 75 KT 85 MPH 72H 16/0600Z 39.0N 49.5W 75 KT 85 MPH...POST-TROPICAL 96H 17/0600Z 38.5N 49.0W 65 KT 75 MPH...POST-TROPICAL 120H 18/0600Z 40.5N 47.0W 60 KT 70 MPH...POST-TROPICAL $$ Forecaster Blake/Avila

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Hurricane NICOLE Forecast Discussion Number 36

2016-10-13 05:01:08| National Hurricane Center (Atlantic)

Issued at 1100 PM AST WED OCT 12 2016 000 WTNT45 KNHC 130301 TCDAT5 HURRICANE NICOLE DISCUSSION NUMBER 36 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 PM AST WED OCT 12 2016 Nicole's satellite presentation has improved, with a warm, distinct, 30 n mi wide eye surrounded by cloud tops of -70C. The large eye is also now visible on the Bermuda radar. An Air Force Reserve Hurricane Hunter aircraft just measured a 700-mb wind of 119 kt and a peak SFMR wind of 118 kt. Based on these data, the initial intensity is set to 115 kt for this advisory. The latest extrapolated minimum pressure from the aircraft is around 950 mb, a decrease of 20 mb since this morning. The aircraft data also showed an expansion of the hurricane force wind field in the northwest and southeast quadrants. The shear is expected to increase quickly, reaching 25-30 kt by 12 h and 45-50 kt by 36 hours. This increase in shear and a gradual decrease in SSTs should result in some weakening in the first 36 to 48 hours, but baroclinic forcing from a mid-latitude shortwave trough should maintain Nicole as a powerful cyclone through the forecast period. The amount of tropical characteristics Nicole will have late in the forecast period remains uncertain, as the cyclone will not undergo a classical extratropical transition. Post-tropical status is shown at days 3 through 5, but confidence in this part of the forecast remains low. The NHC intensity forecast is close to the latest intensity consensus through 48 hours and is based on global models after that time. The initial motion estimate is 020/10, as Nicole is beginning to recurve into the mid-latitude flow ahead of a broad longwave trough moving offshore of the U.S. east coast. This synoptic pattern should result in Nicole accelerating northeastward and then east-northwestward in the next 24 to 48 hours. After 72 hours, the trough moves away from Nicole, and leaves the cyclone meandering in a region of weak steering currents to the south of a high-latitude ridge, and only a a slow eastward to northeastward drift is expected at days 4 and 5. The new NHC track forecast is an update of the previous one through 24 hours, and continues to take the core of Nicole near or over Bermuda on Thursday. After 24 hours, the new NHC track has been shifted a bit to the right, and lies to the right of the multi-model consensus, favoring a blend of the global models and their ensemble means. The forecast at days 3 through 5 has been coordinated with the NOAA Ocean Prediction Center. Note that while hurricanes often affect Bermuda, a hurricane this strong is rare. There have only been seven major hurricanes that have passed within 40 n mi of Bermuda in the Atlantic hurricane database, which goes back to 1851. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 30.1N 66.4W 115 KT 130 MPH 12H 13/1200Z 31.6N 65.3W 105 KT 120 MPH 24H 14/0000Z 33.8N 62.7W 90 KT 105 MPH 36H 14/1200Z 35.7N 59.0W 80 KT 90 MPH 48H 15/0000Z 37.3N 55.0W 75 KT 85 MPH 72H 16/0000Z 38.5N 50.5W 75 KT 85 MPH...POST-TROPICAL 96H 17/0000Z 38.5N 50.0W 65 KT 75 MPH...POST-TROPICAL 120H 18/0000Z 40.0N 49.0W 65 KT 75 MPH...POST-TROPICAL $$ Forecaster Brennan

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