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Tropical Storm NICOLE Forecast Discussion Number 30

2016-10-11 16:47:26| National Hurricane Center (Atlantic)

Issued at 1100 AM AST TUE OCT 11 2016 000 WTNT45 KNHC 111447 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 30 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 AM AST TUE OCT 11 2016 Nicole's cloud pattern has improved this morning, with several bands of convection wrapping around the center. Recent microwave imagery has revealed a well-defined low-level eye feature and there are hints of a ragged banding eye forming in last few visible satellite pictures. Based on the increase in organization the initial intensity is increased to 55 kt, which is in agreement with a Dvorak estimate from SAB. An Air Force Reserve Hurricane Hunter aircraft is currently en route to investigate Nicole, and the data they collect should provide a better estimate of the cyclone intensity and size this afternoon. The shear that has been plaguing Nicole during the past several days has weakened, and is expected to remain low during the next day or so. This, along with warm waters along the forecast track, should allow for strengthening during the 36 to 48 hours, and Nicole is predicted to become a hurricane later today or tonight. Later in the forecast period, some weakening is predicted due to cooler waters and increasing shear, but Nicole is expected to become a powerful extratropical cyclone over the North Atlantic. The new NHC intensity forecast is a little higher than the previous advisory, and is closest to the SHIPS and GFDL model guidance. The tropical storm is moving north-northwestward at about 4 kt. Nicole is forecast to turn northward into a break in the subtropical ridge that is being caused by a mid-latitude trough that is currently passing to the north of Bermuda. As Nicole approaches Bermuda, it will reach the mid-latitude westerly flow, which should cause a turn toward the northeast and some increase in forward speed. The track guidance has come into much better agreement on this scenario since yesterday, and the updated NHC track forecast is near the middle of the now tightly clustered guidance. A Hurricane Warning will likely be required for Bermuda this afternoon. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 27.3N 65.9W 55 KT 65 MPH 12H 12/0000Z 27.7N 66.4W 65 KT 75 MPH 24H 12/1200Z 28.6N 66.9W 75 KT 85 MPH 36H 13/0000Z 30.2N 66.6W 80 KT 90 MPH 48H 13/1200Z 32.2N 65.4W 85 KT 100 MPH 72H 14/1200Z 36.8N 60.5W 80 KT 90 MPH 96H 15/1200Z 40.5N 55.0W 75 KT 85 MPH...POST-TROP/EXTRATROP 120H 16/1200Z 41.8N 53.0W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Tropical Storm NICOLE Forecast Discussion Number 29

2016-10-11 10:35:24| National Hurricane Center (Atlantic)

Issued at 500 AM AST TUE OCT 11 2016 000 WTNT45 KNHC 110835 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 29 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 AM AST TUE OCT 11 2016 The cloud pattern has not become any better organized during the past several hours. The low-level center is located on the northwestern edge of the thunderstorm activity and the Dvorak estimates have remained steady. On this basis, the initial intensity is kept at 50 kt. The wind radii were decreased based on recent ASCAT passes. Nicole is expected to move over warm waters and into weaker shear conditions during the next 48 hours. This environment should result in strengthening and Nicole is expected to become a hurricane during the next 24 hours. The NHC forecast follows the intensity consensus, which is not as aggressive as the GFS and the ECMWF intensity forecasts. After that time, the cyclone should become embedded within very strong wind shear, and a gradual weakening process should begin. By the end of the forecast period, Nicole should have become a large extratropical low. The best estimate of the initial motion is toward the north- northwest or 335 degrees at 4 kt. The steering currents are weak and Nicole should turn toward the north and move slowly around the western edge of a subtropical ridge. By 48 hours, the cyclone will become embedded within the mid-latitude westerly flow and should turn to the northeast with a some increase in forward speed. The NHC forecast is just a little to the left of the previous one, and is basically on top of the multi-model consensus TVCN and TVCX. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 27.1N 65.9W 50 KT 60 MPH 12H 11/1800Z 27.5N 66.4W 55 KT 65 MPH 24H 12/0600Z 28.5N 67.0W 65 KT 75 MPH 36H 12/1800Z 29.5N 67.0W 70 KT 80 MPH 48H 13/0600Z 31.5N 66.0W 80 KT 90 MPH 72H 14/0600Z 36.0N 62.0W 80 KT 90 MPH 96H 15/0600Z 40.0N 56.5W 75 KT 85 MPH 120H 16/0600Z 42.0N 53.5W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ Forecaster Avila

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Tropical Storm NICOLE Forecast Discussion Number 28

2016-10-11 04:37:56| National Hurricane Center (Atlantic)

Issued at 1100 PM AST MON OCT 10 2016 000 WTNT45 KNHC 110237 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 28 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 PM AST MON OCT 10 2016 The vertical wind shear that has been hampering the development of Nicole has diminished during the past 6-12 hours. In response, the cyclone's convective pattern has become better organized and now is comprised of a curved band over the eastern semicircle. Satellite intensity estimates have not changed significantly since the last advisory, so the initial intensity remains 50 kt. The initial motion is now 350/5. During the next 12-24 hours, a mid-latitude shortwave trough currently seen in water vapor imagery north of Nicole is going to move eastward with a shortwave ridge taking its place north of the tropical cyclone. This should cause Nicole to turn northwestward for a time. After that, the ridge moves eastward in advance of a second mid-latitude trough moving eastward from the United States. This evolution should lead to Nicole turning northward and then northeastward with an increase in forward speed as it recurves into the westerlies. The forward motion may slow near the 120 hour time as Nicole becomes a large cut-off extratropical low over the northern Atlantic. The track guidance is in good agreement with this scenario, and the new track forecast is essentially an update of the previous track. The new forecast has the center of Nicole passing near or over Bermuda between 48 and 72 hours. Nicole is forecast to be in a light shear environment over increasing sea surface temperatures for the next 36-48 hours, and at the moment none of the low-level cooler air brought southward in the wake of Post-Tropical Cyclone Matthew is entraining into the system. However, water vapor imagery shows a lot of dry air just northwest of the tropical cyclone, and this could slow intensification in an otherwise favorable environment. After 48 hours, Nicole is likely to weaken due to increasing shear, although the dynamical models forecast increasing values of upper-level divergence that should slow the weakening. Extratropical transition is expected to occur at about 120 hours. The new intensity forecast is almost the same as the previous forecast and lies near the upper edge of the intensity guidance. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 26.8N 65.5W 50 KT 60 MPH 12H 11/1200Z 27.4N 66.0W 55 KT 65 MPH 24H 12/0000Z 28.0N 66.6W 65 KT 75 MPH 36H 12/1200Z 28.9N 66.8W 70 KT 80 MPH 48H 13/0000Z 30.5N 66.3W 80 KT 90 MPH 72H 14/0000Z 34.5N 63.0W 80 KT 90 MPH 96H 15/0000Z 39.5N 57.0W 75 KT 85 MPH 120H 16/0000Z 42.0N 53.5W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven

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Tropical Storm NICOLE Forecast Discussion Number 27

2016-10-10 22:36:08| National Hurricane Center (Atlantic)

Issued at 500 PM AST MON OCT 10 2016 000 WTNT45 KNHC 102035 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 27 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 PM AST MON OCT 10 2016 While Nicole's convective organization has not changed much over the last several hours, satellite data indicate that the cyclone is maintaining a well-defined inner-core structure. Several bands have also developed over the eastern half of the circulation. An ASCAT pass received after the previous advisory's issuance indicated a couple of reliable 50-kt wind vectors, and the initial intensity estimate is set to this value in basic agreement with satellite classifications. Nicole appears to have turned slightly west of due north, and the initial motion estimate is 355/05. This general motion is expected to continue through tonight or early Tuesday while a shortwave trough treks across Atlantic Canada and bypasses the storm to the north. In the wake of this weather system, a weak low- to mid-level ridge is forecast to build north and west of Nicole for a short time, allowing the track to bend more toward the left. The ECMWF continues to predict a greater westerly component motion than the other guidance for the next 3 days, with still about half of the the 0000 UTC ensemble members left of the current forecast. Before Nicole reaches 30N, it should encounter a stronger mid-latitude flow and recurve into the westerlies with increasing forward speed over the next few days. The new track forecast continues to place greater weight on the ECMWF guidance suite, which results in the track being adjusted slightly left of the previous one through the forecast period. It is in the middle of the 0000 UTC ECMWF ensemble output and to the left of the latest multi-model consensus. Nicole is still struggling partially from mid- to upper-level dry air associated with a lobe of vorticity from a mid-latitude shortwave trough that has been wrapping around the cyclone's circulation. In addition, oceanic upwelling beneath the cyclone has also likely contributed to the cyclone's lack of convective vigor. Once Nicole starts to move farther west over untapped waters and its interaction with the above-mentioned feature ends, the strong northerly shear affecting Nicole for days will have decreased significantly. With the tropical cyclone moving over near-record warm SSTs at that time, in a reasonably moist large-scale environment, and under a diffluent flow at upper levels, a significant intensification is likely. Global models maintain the theme of showing substantial deepening over the next few days. By 72 hours, or shortly thereafter, strong southwesterly shear could bring the predicted intensification to a close unless baroclinic processes counteract the shear enough to allow for some further increase in strength. Extratropical transition in shown by day 5. The new intensity forecast is an update of the previous one and generally near or just above the model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 26.3N 65.4W 50 KT 60 MPH 12H 11/0600Z 26.9N 65.7W 55 KT 65 MPH 24H 11/1800Z 27.5N 66.3W 65 KT 75 MPH 36H 12/0600Z 28.2N 66.7W 70 KT 80 MPH 48H 12/1800Z 29.5N 66.7W 80 KT 90 MPH 72H 13/1800Z 33.2N 64.3W 80 KT 90 MPH 96H 14/1800Z 38.1N 58.3W 80 KT 90 MPH 120H 15/1800Z 42.0N 54.2W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Kimberlain

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Tropical Storm NICOLE Forecast Discussion Number 26

2016-10-10 17:05:20| National Hurricane Center (Atlantic)

Issued at 1100 AM AST MON OCT 10 2016 000 WTNT45 KNHC 101505 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 AM AST MON OCT 10 2016 Nicole's cloud pattern has lost organization since late yesterday. A series of convective bursts over the last 24 hours faded away into a shallow and shapeless cloud mass earlier this morning. Since then, some deep convection has redeveloped over the low-level center but there has been no apparent increase to its organization. A blend of the Final-T and CI-number from the TAFB satellite classification and UW-CIMSS ADT values are used to lower the initial intensity estimate to 50 kt. Nicole has been moving slowly northward or 360/05 as it moves along the southwestern periphery of a mid-level ridge to its northeast. While this general motion should continue today, a shortwave trough trekking across Atlantic Canada is expected to bypass Nicole during the next 24 hours, and allow a weak mid-level ridge to build north and west of the cyclone during the next day or two. This synoptic pattern should result in a leftward bend of the track through about 48 hours. After that time, global models show Nicole turning northward and then northeastward with an increase in forward speed once it reaches a faster-paced westerly flow around 30N. Although the track guidance is in much better agreement than it has been during the last few days, the theme from yesterday of the ECMWF and its 0000 UTC ensemble members showing Nicole with a greater westerly component of motion from 24 to 72 hours persists. In fact, a majority of the ECMWF ensembles members are still, to varying degrees, left of the current forecast. The new track forecast is again adjusted to left of the previous one, closer to the ECMWF, and is west of the model consensus aids. During the last 24 hours, a piece of vorticity that fractured from a central Atlantic shortwave trough has been merging with Nicole. The interaction of this feature with Nicole and a continuation of strong northerly shear could explain the degraded satellite appearance of Nicole since yesterday. Nonetheless, the shear is still forecast to diminish during the next day or two, as the cyclone traverses near-record warm SSTs, finds itself in a reasonably moist environment and an increasingly diffluent flow aloft. These factors suggest that a significant re-intensification is still possible, as the global models continue to show. The only caveat would be to what degree a drier and more stable air in the wake of Post-Tropical Matthew would modify as it is at least partially ingested by Nicole's circulation. SHIPS model output shows the shear greatly increasing by 96 hours, which would likely result in an end to the predicted intensification phase unless baroclinic processes become dominant and result in just a little bit more. The new intensity forecast is similar to the previous one and is close to the multi-model consensus. It should be noted that global models show Nicole becoming a large hurricane in about 3 days, with a wide distribution of strong winds over the central Atlantic. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 25.7N 65.2W 50 KT 60 MPH 12H 11/0000Z 26.4N 65.4W 50 KT 60 MPH 24H 11/1200Z 27.2N 66.0W 60 KT 70 MPH 36H 12/0000Z 27.7N 66.5W 65 KT 75 MPH 48H 12/1200Z 28.5N 66.8W 75 KT 85 MPH 72H 13/1200Z 31.8N 65.2W 80 KT 90 MPH 96H 14/1200Z 36.7N 59.6W 75 KT 85 MPH 120H 15/1200Z 41.2N 53.9W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Kimberlain

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