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Hurricane MATTHEW Forecast Discussion Number 42
2016-10-08 17:01:09| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT SAT OCT 08 2016 000 WTNT44 KNHC 081500 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 42 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 AM EDT SAT OCT 08 2016 Aircraft reconnaissance and land-based radar data indicate that the center of circulation has crossed the coast of South Carolina near the Cape Romain National Wildlife Refuge. The cloud pattern associated with Matthew is beginning to acquire some extratropical characteristics. The wind field is expanding, and the area of heavy rains is now northwest of the center. Data from NOAA and Air Force reconnaissance aircraft around 1200 UTC indicated that the surface winds have decreased to around 65 kt. (Very recent SFMR winds of 78 kt were taken over shallow water where the instrument is affected by shoaling and provides unreliable output). Most of the global models, primarily the GFS and the UKMET, forecast that Matthew will become entangled with a cold front, and the new NHC forecast calls for Matthew to become absorbed within this frontal system within the next couple of days. During the next 12 to 24 hours, while the Matthew is hugging the US coast and taking on a more extratropical structure, the tropical-storm-force winds are expected to expand and strengthen in the western semicircle and continue to affect portions of the coast within the warning area. Matthew is already embedded in the mid-latitude westerly flow and is moving toward the northeast or 050 degrees at 10 kt. The steering pattern is forecast to persist for the next day or two, and on this basis the NHC forecast moves the cyclone eastward until it becomes absorbed. Previous NHC official forecasts followed the EMCWF in keeping the cyclone a distinct entity longer and looping it southward, but even if this the case the system will likely be only a broad area of low pressure. Due to the degradation of Matthew's radar signature, the hourly Tropical Cyclone Updates will not longer be issued. KEY MESSAGES: 1. As Matthew's structure changes, the system's strongest winds will shift to the back side of the circulation. These winds will persist over land even after the center begins to move away from the coastline, and has also increased the threat of storm surge in portions of the North Carolina Outer Banks. Please see the Prototype Storm Surge Watch/Warning Graphic for a depiction of the areas at risk. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 33.0N 79.4W 65 KT 75 MPH 12H 09/0000Z 33.6N 78.0W 60 KT 70 MPH 24H 09/1200Z 34.0N 75.5W 60 KT 70 MPH 36H 10/0000Z 34.0N 73.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 10/1200Z 33.0N 72.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 11/1200Z...DISSIPATED $$ Forecaster Avila
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Tropical Storm NICOLE Forecast Discussion Number 18
2016-10-08 16:39:33| National Hurricane Center (Atlantic)
Issued at 1100 AM AST SAT OCT 08 2016 000 WTNT45 KNHC 081438 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 AM AST SAT OCT 08 2016 Nicole's cloud pattern has further deteriorated this morning. The low-level center has been exposed, with generally only shallow convection on the southern and eastern periphery of the cyclone's circulation. A new burst of deeper convection has developed southeast of the center in the last couple of hours, however. Dvorak Final-T numbers continue to decrease, and a blend of those data and CI-numbers support lowering the initial intensity estimate to 35 kt. Nicole is moving just west of due south or 190/06. A blocking high north of the cyclone should continue to push it southward for about 24 hours. Nicole should then reverse its heading and turn north- northwestward, when the mid-level high shifts to its northeast. A potential complication to the track forecast is the degree to which Nicole interacts with Matthew or its remnants, beginning in 2 to 3 days through the latter part of the forecast period. The ECMWF shows a stronger binary interaction and draws Nicole much farther west than the GFS after 72 hours, and the differences in the models by 96 hours become extreme. The track forecast philosophy continues to closely follow a blend of the ECMWF and GFS model solutions, though slightly more weight has been placed on the GFS-based guidance since a sizable number of ECMWF ensemble members are east of its deterministic run. Admittedly, the forecast on days 4 and 5 are of low confidence. The shear is forecast to be so strong in the short term that one might be tempted to call for Nicole to degenerate to a remnant low, especially given its current satellite appearance. However, the shear is forecast to nominally decrease, when the tail of a mid- to upper-level trough over the central Atlantic fractures and becomes co-located with the tropical cyclone during the next day or so. How the merger of the two affects Nicole's intensity and structure remains unclear. Nonetheless, the large-scale conditions are shown to become less hostile in 2 to 4 days, and it seems plausible that some re-intensification of the cyclone could occur before becoming less favorable again by day 5. The new intensity forecast is somewhat lower than the previous one and below the multi-model consensus, and continues to show a modest recovery after 72 hours. The intensity forecast continues to be of low confidence in the long range. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 25.2N 65.7W 35 KT 40 MPH 12H 09/0000Z 24.6N 65.7W 35 KT 40 MPH 24H 09/1200Z 24.2N 65.8W 35 KT 40 MPH 36H 10/0000Z 24.8N 65.9W 35 KT 40 MPH 48H 10/1200Z 25.7N 66.0W 35 KT 40 MPH 72H 11/1200Z 28.3N 66.6W 40 KT 45 MPH 96H 12/1200Z 30.5N 67.0W 45 KT 50 MPH 120H 13/1200Z 33.4N 64.6W 45 KT 50 MPH $$ Forecaster Kimberlain
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Hurricane MATTHEW Forecast Discussion Number 41
2016-10-08 10:59:15| National Hurricane Center (Atlantic)
Issued at 500 AM EDT SAT OCT 08 2016 000 WTNT44 KNHC 080858 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 41 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT SAT OCT 08 2016 Coastal Doppler weather radars this morning continue to depict a 40-nmi wide eye with a band of intense convection located in the northwestern quadrant along the coasts of extreme eastern Georgia and South Carolina from Tybee Island northeast to near the entrance of Charleston Harbor. Air Force Reserve and NOAA reconnaissance wind data, along with Doppler radar velocity data and surface observations, indicate that hurricane-force wind gusts in excess of 80 kt are occuring along the aforementioned coastal areas. Based on 700-mb maximum flight-level winds of 108 kt, peak SFMR surface winds of 83 kt, and Doppler velocities of 100-102 kt between 8000-11000 ft, the initial intensity will remain at 90 kt for this advisory. The initial motion estimate is 015/10 kt. Matthew made a northward jog since the previous advisory, but now appears to moving north-northeastward based on the latest radar and recon fixes. However, the more northward motion earlier has increased the possibility that the center of Matthew's eye will move onshore the coast of South Carolina later this morning or early afternoon as the cyclone turns northeastward ahead of a strong shortwave trough. Regardless of whether or not the center makes landfall, hurricane-force winds in the northern eyewall will lash much of the coast of South Carolina today as the center moves to a position just east of Charleston Harbor in about 12 hours. After that, the models are in fair agreement on Matthew turning eastward through 36 hours as the cyclone briefly gets captured by the aforementioned shortwave trough. However, by 48 hours and beyond, Matthew is expected to turn southeastward and southward as the cyclone moves around the eastern periphery of an amplifying ridge located east of Florida. In the 48-72 hours time period, some erratic motion could occur as Matthew and Tropical Storm Nicole briefly undergo some binary interaction before separating by 96 hours. The official forecast track closely follows a blend of the GFS and ECMWF solutions. The vertical wind shear is forecast to increase to more than 30 kt by 12 hours, which should induce steady weakening. At 48 hours and beyond, the SHIPS model is forecasting the shear to increase to more than 40 kt, resulting in rapid weakening to remnant low status by 120 hours. However, the shear forecast appears to be overdone since both the GFS and ECMWF models indicate that Matthew and Nicole will both be moving underneath a narrow 200 mb ridge axis, which should act to reduce the shear across the two cyclones in the 48-96 hour period. The official intensity forecast closely follows the consensus model IVCN, and maintains Matthew as a tropical cyclone throughout the forecast period. KEY MESSAGES: 1. The western eyewall of Matthew, which contains hurricane-force winds, is now moving over the northern coast of Georgia and the southern coast of South Carolina and should spread up the coast during the day. 2. Hurricane winds increase very rapidly with height, and occupants of high-rise buildings along the coast are at particular risk of strong winds. Winds at the top of a 30-story building will average one Saffir-Simpson category higher than the winds near the surface. 3. The water hazards remain, even if the core of Matthew remains offshore. These include the danger of life-threatening inundation from storm surge, as well as inland flooding from heavy rains from Florida to North Carolina. 4. The National Hurricane Center is issuing Potential Storm Surge Flooding Maps, and Prototype Storm Surge Watch/Warning Graphics for Matthew. It is important to remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario -- the amount of inundation that has a 10 percent chance of being exceeded. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 32.0N 80.5W 90 KT 105 MPH 12H 08/1800Z 32.9N 79.4W 80 KT 90 MPH 24H 09/0600Z 33.7N 77.1W 70 KT 80 MPH 36H 09/1800Z 33.4N 75.1W 60 KT 70 MPH 48H 10/0600Z 32.6N 73.5W 50 KT 60 MPH 72H 11/0600Z 29.0N 73.5W 40 KT 45 MPH 96H 12/0600Z 26.0N 75.3W 30 KT 35 MPH 120H 13/0600Z 25.0N 76.2W 30 KT 35 MPH $$ Forecaster Stewart
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Tropical Storm NICOLE Forecast Discussion Number 17
2016-10-08 10:40:13| National Hurricane Center (Atlantic)
Issued at 500 AM AST SAT OCT 08 2016 000 WTNT45 KNHC 080839 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 AM AST SAT OCT 08 2016 Nicole's structure has changed dramatically just within the past six hours due to about 45 kt of northerly shear. The deep convection is now oriented linearly from east to west and is displaced more than 100 n mi to the south of the exposed low-level center. Dvorak Current Intensity numbers have dropped to 3.0 from TAFB, SAB, and the UW-CIMSS ADT, and Nicole's initial intensity is lowered to 45 kt. Deep-layer northerly flow continues to push Nicole southward, and the initial motion is estimated to be 190/6 kt. The winds on the west side of a mid-level low should continue forcing Nicole generally southward for the next 24-36 hours until these two systems become collocated with one another. After 36 hours, Nicole is expected to be steered back toward the north, ahead of Hurricane Matthew's remnant mid-level circulation. There are some differences among the track models associated with exactly how the interaction between Nicole and Matthew will play out. The notable outlier is the ECMWF model, which swings Nicole northwestward and then westward around the north side of Matthew after 48 hours. In deference to this model, the new NHC track forecast is a little west and slower than the previous forecast, and it lies very close to an average of the GFS and ECMWF models. The vertical shear affecting Nicole is expected to remain high for several more days, possibly not dropping below 20 kt until after 72 hours. Still, sea surface temperatures will remain between 29 and 30C, so Nicole may be able to continue producing bursts of deep convection that will prevent its intensity from decreasing much. Some restrengthening at the end of the forecast period is possible, although trends are suggesting that the shear may once again increase by day 5. Based on the latest guidance, the official intensity forecast is lowered by 5 kt for much of the forecast period. If the shear wins out, however, then Nicole's intensity could end up being lower than shown in the forecast. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 25.9N 65.6W 45 KT 50 MPH 12H 08/1800Z 25.2N 65.6W 45 KT 50 MPH 24H 09/0600Z 24.7N 65.6W 40 KT 45 MPH 36H 09/1800Z 24.8N 65.7W 40 KT 45 MPH 48H 10/0600Z 25.4N 65.9W 40 KT 45 MPH 72H 11/0600Z 28.0N 66.5W 40 KT 45 MPH 96H 12/0600Z 30.0N 67.5W 45 KT 50 MPH 120H 13/0600Z 32.5N 66.0W 50 KT 60 MPH $$ Forecaster Berg
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Hurricane MATTHEW Forecast Discussion Number 40
2016-10-08 05:00:04| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT FRI OCT 07 2016 000 WTNT44 KNHC 080259 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 40 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 PM EDT FRI OCT 07 2016 Coastal Doppler radar data this evening indicate that Matthew is gradually becoming less organized. The eyewall has broken open with the remaining deep convection in a band just north of the center, and there is now little precipitation in the southeastern quadrant. A combination of radar winds and earlier aircraft data suggests that the intensity has decreased slightly since the last advisory, so the initial intensity is lowered to 90 kt. The initial motion is now 010/10 kt. During the next 36 hours, Matthew should turn more northeastward as it moves along the southern edge of a mid-latitude trough. The forecast track, which lies in the center of the track guidance envelope, has the center moving near the coasts of Georgia and South Carolina during the next 12-18 hours, then near the North Carolina coast from 18-36 hours. While this occurs, the cyclone is forecast to encounter strong vertical wind shear and to entrain dry air associated with an approaching frontal system. This should result in a steady weakening, and Matthew is now forecast to weaken to a tropical storm by 36 hours in agreement with the SHIPS model. It is possible that Matthew could merge with the frontal system at about 36 hours, although none of the available guidance currently forecasts the system to become an extratropical low. The track and intensity forecasts become very low confidence after 36 hours due to a large diversity of model solutions. The GFDL and HWRF forecast Matthew to turn northeastward and become an extratropical low near the Canadian Atlantic provinces. The UKMET moves Matthew eastward and eventually has it absorbed by Tropical Storm Nicole. The ECMWF, NAVGEM, and Canadian models show a southwestward turn, with the cyclone or it remnants near the Bahamas by 120 hours. The GFS is between the UKMET and ECMWF, showing Matthew moving far enough to the east to interact with Nicole, then turning southward. The new track forecast follows the previous advisory in showing a southward/southwestward turn similar to the ECMWF, but is east of the previous track due to an overall eastward trend in the guidance. Regarding the intensity, the GFS suggests that Matthew could decay to a remnant low by 120 hours, while the ECMWF suggests the system could still be a tropical cyclone. Either way, continued weakening is likely due to shear and dry air entrainment, and the official forecast calls for Matthew to weaken to a depression by 96 hours. Due to the degradation of the radar signature of Matthew, the hourly Tropical Cyclone Updates will no longer be issued. KEY MESSAGES: 1. We have been very fortunate that Matthew's strongest winds have remained a short distance offshore of the Florida and Georgia coasts thus far, but this should not be a reason to let down our guard. Only a small deviation to the left of the forecast track could bring these winds onshore. The western eyewall of Matthew, which contains hurricane-force winds, is expected to move over or very near the coasts of Georgia and South Carolina tonight and Friday. 2. Hurricane winds increase very rapidly with height, and occupants of high-rise buildings along the coast are at particular risk of strong winds. Winds at the top of a 30-story building will average one Saffir-Simpson category higher than the winds near the surface. 3. The water hazards remain, even if the core of Matthew remains offshore. These include the danger of life-threatening inundation from storm surge, as well as inland flooding from heavy rains from Florida to North Carolina. 4. The National Hurricane Center is issuing Potential Storm Surge Flooding Maps, and Prototype Storm Surge Watch/Warning Graphics for Matthew. It is important to remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario -- the amount of inundation that has a 10 percent chance of being exceeded. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 31.2N 80.5W 90 KT 105 MPH 12H 08/1200Z 32.5N 79.8W 80 KT 90 MPH 24H 09/0000Z 33.6N 77.8W 70 KT 80 MPH 36H 09/1200Z 33.9N 75.5W 60 KT 70 MPH 48H 10/0000Z 33.0N 74.0W 55 KT 65 MPH 72H 11/0000Z 30.0N 73.5W 40 KT 45 MPH 96H 12/0000Z 27.5N 74.5W 30 KT 35 MPH 120H 13/0000Z 26.0N 75.5W 30 KT 35 MPH $$ Forecaster Beven
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