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Tropical Storm NICOLE Forecast Discussion Number 25
2016-10-10 10:39:52| National Hurricane Center (Atlantic)
Issued at 500 AM AST MON OCT 10 2016 000 WTNT45 KNHC 100839 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 25 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 AM AST MON OCT 10 2016 Nicole's overall convective pattern has changed little since the previous advisory, with most of the convection located in the eastern semicircle. However, during the past hour or two, a small burst of deep convection with tops to -80C has developed just east of the exposed low-level circulation center, signaling that dry air entrainment into the center of the cyclone has abated somewhat. Satellite current intensity (CI) estimates from TAFB and SAB remain 55 kt, and a late-arriving ASCAT-A pass indicated 45-kt surface winds in the western semicircle where no convection was present. Based on these data, the initial intensity remains 55 kt. Nicole is moving slowly northward and the initial motion estimate is 360/05 kt. The cyclone is expected to move slowly at around 5 kt for the next 72 hours, beginning with a motion toward the north today, followed by a turn to the north-northwest tonight, and a turn toward the northwest on Tuesday. By 36-48 hours, a break in the ridge to the north of Nicole is forecast to develop as a shortwave trough moves off of the U.S. east coast and erodes the blocking ridge. This should allow Nicole to move northward by 48 hours and turn toward the north-northeast and northeast by 72 hours. By 96 hours and beyond, the aforementioned shortwave trough is forecast to capture the cyclone and accelerate Nicole to the northeast over the north Atlantic. The global models are now in excellent agreement on this developing track scenario, but have unfortunately shifted farther west and are now much closer to Bermuda. The new NHC track forecast has been shifted westward as a result, but still lies east of the consensus model TVCN and the GFS-ECMWF solutions, which bring Nicole over or just west of Bermuda in about 84 hours. The combination of northerly shear and some additional modest dry air entrainment is expected to inhibit development today. However, by Tuesday the vertical wind shear is forecast by the GFS and ECMWF models to decrease to less than 10 kt, and remain low until about 72 hours. The low shear conditions and developing upper-level outflow pattern as depicted in the global and regional models, along with Nicole's already robust low- to mid-level circulations, should allow the cyclone to strengthen and regain hurricane status during that time. By 96 hours and beyond, southwesterly shear ahead of the shortwave trough is forecast to increase to 30-40 kt, which should induce steady weakening. Extratropical transition is possible by 120 hours, but most of the intensity guidance maintains Nicole as a tropical cyclone, which is reflected in the official forecast. The new intensity forecast closely follows the SHIPS intensity model, which appears to have a good handle on the timing of the reduction of the vertical shear and associated strengthening, and also remains above the intensity consensus model IVCN. The 34-kt wind radius was expanded in the northeastern quadrant based on 31-33 kt winds recently reported by NOAA Buoy 41049. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 25.0N 65.2W 55 KT 65 MPH 12H 10/1800Z 25.8N 65.3W 55 KT 65 MPH 24H 11/0600Z 26.6N 65.7W 60 KT 70 MPH 36H 11/1800Z 27.2N 66.2W 65 KT 75 MPH 48H 12/0600Z 27.8N 66.8W 75 KT 85 MPH 72H 13/0600Z 30.5N 66.0W 85 KT 100 MPH 96H 14/0600Z 34.5N 62.2W 80 KT 90 MPH 120H 15/0600Z 38.5N 56.3W 70 KT 80 MPH $$ Forecaster Stewart
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Tropical Storm NICOLE Forecast Discussion Number 24
2016-10-10 04:43:47| National Hurricane Center (Atlantic)
Issued at 1100 PM AST SUN OCT 09 2016 000 WTNT45 KNHC 100243 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 24 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 PM AST SUN OCT 09 2016 Depp convection associated with Nicole has decreased since the last advisory, with the primary convection now confined to an area south of the center. It is unclear whether this is due to the normal diurnal convective minimum, entrainment of dry air seen near the center in water vapor imagery, or the result of cooling sea surface temperatures under the stationary storm. Satellite intensity estimates from TAFB and SAB remain 55 kt, while the latest satellite consensus estimate from CIMSS is 51 kt. Based on these data, the initial intensity remains 55 kt. Nicole is now drifting northward, and this motion should continue for the next 12-24 hours as a blocking ridge of high pressure north of the cyclone weakens. A deep-layer trough associated with former Hurricane Matthew is forecast to pass north of Nicole, with a second ridge passing north of the storm after 24 hours. This should cause a northwestward turn, and the guidance during this stage of the forecast has shifted left since the previous advisory. After 72 hours, a new trough moving eastward from the United States should cause Nicole to recurve northeastward into the westerlies. The new forecast track is shifted to the left between 24-72 hours, but still lies to the east of the various consensus models. After 72 hours, the track lies a little north of the previous track. A combination of the above mentioned dry air, possible cooler waters, and continuing strong northerly shear should limit intensification for the next 12 hours or so. After that, the shear should gradually subside and allow Nicole to intensify if the cyclone does not entrain too much low-level dry air brought southward due to Matthew. The environment is most favorable at about 72 hours, and the new intensity forecast calls for a slightly increased peak intensity of 85 kt in best agreement with the SHIPS model. After that time, the cyclone is expected to encounter the mid-latitude westerlies with increased shear partly compensated for by increased upper-level divergence. This environment should lead to gradual weakening with extratropical transition beginning near 120 hours. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 24.4N 65.3W 55 KT 65 MPH 12H 10/1200Z 25.1N 65.3W 55 KT 65 MPH 24H 11/0000Z 26.0N 65.5W 60 KT 70 MPH 36H 11/1200Z 26.6N 65.9W 65 KT 75 MPH 48H 12/0000Z 27.1N 66.4W 70 KT 80 MPH 72H 13/0000Z 28.5N 66.5W 85 KT 100 MPH 96H 14/0000Z 32.0N 64.0W 85 KT 100 MPH 120H 15/0000Z 37.0N 58.0W 70 KT 80 MPH $$ Forecaster Beven
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Tropical Storm NICOLE Forecast Discussion Number 23
2016-10-09 22:40:49| National Hurricane Center (Atlantic)
Issued at 500 PM AST SUN OCT 09 2016 000 WTNT45 KNHC 092040 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 PM AST SUN OCT 09 2016 Nicole's cloud pattern has become better organized this afternoon. Deep convection has been pulsing but, unlike yesterday, it has not diminished. The cyclone's maintenance of deep convection suggests that the vertical shear has decreased, which is supported by the SHIPS analyses. In addition, the low-level center is underneath but on the northwestern side of a formative and expanding central dense overcast, consisting of cold cloud tops. Dvorak classifications are T3.5 from TAFB and SAB, and the initial intensity estimate is therefore raised to 55 kt. Nicole has been nearly stationary during the last several hours. A slow motion generally toward the north or north-northwest is expected to commence soon, now that the blocking high north of it has slid to the northeast of Nicole. A shortwave trough currently over the northeastern United States is shown in global model solutions bypassing Nicole in about 2 days. The ECMWF has stronger ridging in the wake of this feature than the GFS, and thus carries Nicole farther to the west as did the 0000 UTC ECMWF ensembles. A turn toward the north and northeast is likely after 72 hours once Nicole reaches a belt of stronger mid-latitude southwesterly flow. The new track forecast is adjusted slightly to the left of the previous one and is slower, and it is shifted again toward the ECMWF. The NHC track is close to an average of the ECMWF and GFS models and to the west of the other model consensus aids. Northerly vertical shear of 20 to 25 kt over Nicole will continue for about another 24 hours, which should prevent significant intensification from occurring. After that time, the shear is forecast to gradually diminish and remain relatively low until about 3 days. The reduction of shear, in combination with near-record warm SSTs, a relatively moist environment, and an increasingly diffluent flow aloft, suggest that intensification is likely. The only caveat involves much a cooler and drier air mass in the wake of Post-Tropical Cyclone Matthew would affect Nicole. The new intensity forecast is increased again, much more than in the previous advisory, and is near the high end of the guidance in closest agreement with the SHIPS model. It is worth mentioning that global models continue to show significant deepening in 2 to 3 days, still more than indicated in the current forecast. The guidance shows a sharp increase in shear by 96 hours, which ordinarily would curb any further intensification. However, baroclinic forcing could offset the negative effects of the shear and Nicole should at a minimum maintain its intensity if not intensify a bit further. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 24.2N 65.3W 55 KT 65 MPH 12H 10/0600Z 25.0N 65.2W 60 KT 70 MPH 24H 10/1800Z 25.9N 65.3W 65 KT 75 MPH 36H 11/0600Z 26.6N 65.5W 70 KT 80 MPH 48H 11/1800Z 27.2N 65.9W 75 KT 85 MPH 72H 12/1800Z 28.4N 66.4W 80 KT 90 MPH 96H 13/1800Z 31.3N 65.0W 80 KT 90 MPH 120H 14/1800Z 35.4N 59.0W 75 KT 85 MPH $$ Forecaster Kimberlain
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Tropical Storm NICOLE Forecast Discussion Number 22
2016-10-09 17:03:15| National Hurricane Center (Atlantic)
Issued at 1100 AM AST SUN OCT 09 2016 000 WTNT45 KNHC 091503 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 AM AST SUN OCT 09 2016 Overnight microwave data indicated that Nicole had formed a well-defined low- to mid-level eye, embedded within a significant convective burst. Since then, the shear has caused the new convective growth to diminish and pushed the coldest cloud tops south of the low-level center. Satellite classifications are T3.0 and T3.5 from SAB and TAFB, respectively. A blend of these is used to set the initial intensity estimate to 50 kt. Nicole appears to have drifted southeastward during the last several hours, but is now essentially stationary. The blocking ridge north of Nicole has begun to shift eastward, which should cause the cyclone to begin a slow motion, generally toward the north. Variations in the orientation and strength of this ridge in the GFS and ECMWF solutions result in either a north-northeastward or north-northwestward motion, respectively, during the next couple of days, and these differences could have implications on Nicole's track longer term. A turn toward the northeast is expected late in the period when Nicole reaches the mid-latitude westerly flow. The split in the track guidance over the forecast period is notable this cycle, with the ECMWF and all but a few of its 0000 UTC ensemble members even or left of the previous forecast track. All of the other track guidance is to the east, including the GFS which is the rightmost of the members in this camp. The new forecast track is very near the previous one in deference to the ECMWF and its ensemble output even though the model consensus aids are to the east through 96 hours. The strong northerly shear over Nicole has marginally decreased since yesterday, but is forecast to remain at about the same magnitude for another 24 hours. The shear should then gradually diminish until about day 3, and Nicole is likely to find itself in the lowest-shear environment it has seen in several days. Since the cyclone will be over anomalously warm waters at that time, in a moist environment and under a somewhat diffluent flow aloft, intensification seems likely. The intensity forecast is increased over the previous one and is slightly above the multi-model consensus. It should be noted that the global models show significant deepening of Nicole starting around this time, potentially much more than what is indicated in this forecast. Southwesterly shear should greatly increase by day 4, which could curb any additional intensification after that time unless the cyclone's intensification is being driven by baroclinic forcing. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 24.0N 65.4W 50 KT 60 MPH 12H 10/0000Z 24.4N 65.3W 55 KT 65 MPH 24H 10/1200Z 25.2N 65.3W 55 KT 65 MPH 36H 11/0000Z 26.1N 65.3W 55 KT 65 MPH 48H 11/1200Z 27.0N 65.6W 60 KT 70 MPH 72H 12/1200Z 28.6N 65.9W 65 KT 75 MPH 96H 13/1200Z 31.8N 64.2W 70 KT 80 MPH 120H 14/1200Z 34.9N 59.4W 70 KT 80 MPH $$ Forecaster Kimberlain
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Post-Tropical Cyclone MATTHEW Forecast Discussion Number 46
2016-10-09 16:56:42| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT SUN OCT 09 2016 000 WTNT44 KNHC 091456 TCDAT4 POST-TROPICAL CYCLONE MATTHEW DISCUSSION NUMBER 46 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 AM EDT SUN OCT 09 2016 Satellite data and surface observations indicate that a cold front has wrapped around the southwestern portion of Matthew's circulation and the post-tropical cyclone is now analyzed as an extratropical low. Despite the change in the cyclone's structure over the past 24 hours, Matthew continues to produce an area of very strong winds to the southwest and west of the center. Sustained winds of 55 to 60 kt with gusts above hurricane force were reported at several coastal marine observing stations near the Outer Banks of North Carolina this morning, and a recent dropsonde from the Global Hawk unmanned aircraft reported surface winds of 58 kt. Based on these data, the initial intensity remains 65 kt. The global models indicate that the post-tropical cyclone will gradually weaken during the next 24 to 36 hours, and be absorbed by a frontal boundary in about 48 hours. Matthew is moving eastward at about 13 kt. The low should continue moving eastward within the mid-latitude westerly flow during the next day or so. The NHC forecast track is close to a blend of the ECMWF, GFS, and UKMET models, and is similar to the previous advisory. Strong winds in the Tidewater Region of Virginia are being handled by non-tropical wind warnings. KEY MESSAGES: 1. Tropical-storm-force winds will continue over the North Carolina Outer Banks this afternoon, with gusts to near hurricane force possible during the next hour or two. Storm surge flooding continues over portions of the Outer Banks. Please see the Prototype Storm Surge Watch/Warning Graphic for a depiction of the areas at risk. 2. Although Matthew has become a post-tropical cyclone, NHC will continue to issue its full suite of advisory and warning products as long as the system remains a significant threat to land areas. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 35.2N 73.7W 65 KT 75 MPH...POST-TROP/EXTRATROP 12H 10/0000Z 35.3N 71.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 24H 10/1200Z 35.7N 68.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 11/0000Z 37.0N 64.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 11/1200Z...ABSORBED $$ Forecaster Brown
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