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Hurricane Juliette Forecast Discussion Number 22

2019-09-06 16:37:09| National Hurricane Center (East Pacific)

Issued at 500 AM HST Fri Sep 06 2019 000 WTPZ41 KNHC 061437 TCDEP1 Hurricane Juliette Discussion Number 22 NWS National Hurricane Center Miami FL EP112019 500 AM HST Fri Sep 06 2019 Deep convection associated with Juliette has decreased in coverage over the past 24 hours, however, the remaining convection still wraps completely around the center. Subjective and objective raw T-numbers from TAFB and UW/CIMSS have fallen below 4.0, however the current intensity (CI) numbers are still at 4.5. Using a blend of these T- and CI-numbers, as NHC typically does during the weakening phase, yields an initial wind speed of 65 kt for this advisory. Juliette is currently over SSTs of around 24.5 degrees Celsius, with even cooler waters and a more stable and drier air mass along the predicted path of the storm. These conditions should cause gradual weakening over the next day or so, and Juliette is forecast to become post-tropical in 36 to 48 hours. Recent fixes show that Juliette has turned west-northwestward or 300/10 kt. A subtropical ridge to the north of the cyclone should continue to steer Juliette west-northwestward during the next 24 hours. After that time, the cyclone should turn westward within the low-level tradewind flow. The dynamical models are in better agreement today on the both the track and forward speed of the cyclone, and the NHC forecast is near the middle of the envelope. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 22.8N 123.4W 65 KT 75 MPH 12H 07/0000Z 23.4N 125.2W 60 KT 70 MPH 24H 07/1200Z 23.8N 127.3W 50 KT 60 MPH 36H 08/0000Z 23.9N 129.4W 40 KT 45 MPH 48H 08/1200Z 23.8N 131.5W 35 KT 40 MPH...POST-TROPICAL 72H 09/1200Z 23.5N 135.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 10/1200Z 23.5N 139.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 11/1200Z 24.0N 142.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Tropical Storm Gabrielle Forecast Discussion Number 12

2019-09-06 16:35:39| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Fri Sep 06 2019 000 WTNT43 KNHC 061435 TCDAT3 Tropical Storm Gabrielle Discussion Number 12 NWS National Hurricane Center Miami FL AL082019 1100 AM AST Fri Sep 06 2019 Although Gabrielle was without organized deep convection for most of the past 24 hours, deep convection has quickly re-developed near and to the north of the center this morning. In addition, recent ASCAT data indicate that the winds have increased since last night, suggesting that tropical-cyclone intensification processes are ongoing. While normally we would wait a little longer to restart the cyclone, since the previous advisory and this one show the potential for significant strengthening, advisories are being re-initiated so that marine warnings that were already in place could remain. The initial intensity is set to 40 kt, in agreement with the ASCAT winds. The storm is moving faster to the northwest this morning, or 320/15. A large ridge to the northeast of Gabrielle is forecast to build to the north, forcing the tropical cyclone to turn west- northwestward on Saturday. After that time, southwesterly flow ahead of Hurricane Dorian should turn Gabrielle quickly northward and northeastward by early next week. Model guidance is in remarkably good agreement, and little change was made to the previous NHC track forecast. Gabrielle is currently still experiencing strong southerly shear due to the winds around an upper-level low. However that low is forecast to drop southwestward, causing the storm to enter a low-shear region by tomorrow at the same time water temperatures rise to near 29C. This is a recipe for at least steady strengthening, and all of the models are much higher than the previous cycle. The new NHC prediction is increased at long-range as much as continuity allows and is still below many of the model forecasts. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 27.3N 38.7W 40 KT 45 MPH 12H 07/0000Z 28.9N 40.4W 45 KT 50 MPH 24H 07/1200Z 30.7N 43.3W 50 KT 60 MPH 36H 08/0000Z 32.1N 46.1W 55 KT 65 MPH 48H 08/1200Z 33.4N 48.2W 60 KT 70 MPH 72H 09/1200Z 37.6N 47.7W 70 KT 80 MPH 96H 10/1200Z 42.6N 41.7W 75 KT 85 MPH 120H 11/1200Z 50.0N 29.5W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake

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Hurricane Juliette Forecast Discussion Number 21

2019-09-06 11:26:05| National Hurricane Center (East Pacific)

Issued at 1100 PM HST Thu Sep 05 2019 000 WTPZ41 KNHC 060925 CCA TCDEP1 Hurricane Juliette Discussion Number 21...Corrected NWS National Hurricane Center Miami FL EP112019 1100 PM HST Thu Sep 05 2019 Corrected motion in third paragraph. This evening's satellite presentation is showing a considerable amount of deterioration of Juliette's inner core. The eastern portion of the eyewall has eroded, cloud tops have continue to warm, and it appears as though some drier mid-level air is intruding from the northwest. Subjective satellite intensity estimates from TAFB and SAB, and the UW-CIMSS Objective T-number supports lowering the initial intensity to 70 kt. Although the upper-level winds are expected to remain in a favorable pattern during the next couple days, the hurricane will be moving over decreasing sea surface temperatures and into increasingly stable thermodynamic conditions. Subsequently, gradual weakening should continue through the entire forecast period, and Juliette is expected to become a remnant low in 3 days, or less. The intensity forecast is basically a compromise of the NOAA HFIP HCCA and the global models beyond the 48-hour period. The initial motion continues to be northwestward, or 305/9 kt. A mid-level ridge extending from the southwestern United States over the eastern Pacific should induce a west-northwestward turn on Friday, and this general motion should continue through the next couple of days. Toward the end of the period, a westward motion should commence as Juliette degenerates into a vertically shallow depression, and eventually, a remnant low, and becomes steered by the low-level tradewind flow. The track forecast is an update of the previous advisory and sides with the TVCE model consensus. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 22.4N 122.7W 70 KT 80 MPH 12H 06/1800Z 23.0N 124.2W 60 KT 70 MPH 24H 07/0600Z 23.6N 126.4W 50 KT 60 MPH 36H 07/1800Z 23.8N 128.5W 40 KT 45 MPH 48H 08/0600Z 23.8N 130.6W 35 KT 40 MPH...POST-TROPICAL 72H 09/0600Z 23.4N 135.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 10/0600Z 23.4N 138.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 11/0600Z 23.8N 141.7W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts

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Post-Tropical Cyclone Gabrielle Forecast Discussion Number 11

2019-09-06 10:50:36| National Hurricane Center (Atlantic)

Issued at 500 AM AST Fri Sep 06 2019 000 WTNT43 KNHC 060850 TCDAT3 Post-Tropical Cyclone Gabrielle Discussion Number 11 NWS National Hurricane Center Miami FL AL082019 500 AM AST Fri Sep 06 2019 Poorly defined Gabrielle has not produced any organized deep convection since Thursday morning, and what remains of the showers and thunderstorms, is displaced nearly 200 miles north of the elongated surface circulation. Consequently, Gabrielle can no longer be classified as a tropical cyclone and has degenerated into a 35 kt post-tropical cyclone. Statistical-dynamical models, as well as the large-scale guidance, show that strong shear, along with mid-tropospheric dry air intrusion, should continue to inhibit convective development during the next 24 h or so, and cause further weakening into a remnant low. Around mid-period, the shear is forecast to decrease and the upper wind pattern becomes more diffluent. Additionally, Post-Tropical Cyclone Gabrielle will be traversing significantly warmer oceanic sea surface temperatures. As a result, the cyclone is forecast to redevelop organized deep convection, and more than likely, re-strengthen. In fact, some of the intensity guidance shows Gabrielle becoming a hurricane in 4 days before transitioning into an extratropical cyclone at the end of the period. The NHC intensity forecast is based on a blend of the HFIP HCCA, and the deterministic guidance beyond day 3. The initial motion is estimated to be an accelerating northwestward motion, or 315/10 kt. The global and regional models are in rather good agreement that the post-tropical cyclone will gradually turn toward the west-northwest during the next 48 hours, before recurving northward and then northeastward early next week in response to an approaching major shortwave mid-latitude trough from the northwest. The official forecast track is just a little to the left of the previous one, and is very close to the TVCA simple multi-model guidance. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 25.5N 37.6W 35 KT 40 MPH...POST-TROPICAL 12H 06/1800Z 27.1N 39.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 07/0600Z 29.2N 41.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 07/1800Z 30.7N 44.8W 35 KT 40 MPH...TROPICAL CYCLONE 48H 08/0600Z 31.9N 47.4W 45 KT 50 MPH 72H 09/0600Z 35.6N 48.6W 55 KT 65 MPH 96H 10/0600Z 40.4N 44.3W 60 KT 70 MPH 120H 11/0600Z 47.0N 34.5W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ Forecaster Roberts

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Hurricane Dorian Forecast Discussion Number 52

2019-09-06 10:48:32| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Fri Sep 06 2019 000 WTNT45 KNHC 060848 TCDAT5 Hurricane Dorian Discussion Number 52 NWS National Hurricane Center Miami FL AL052019 500 AM EDT Fri Sep 06 2019 The center of the eye of Hurricane Dorian is located just off the coast of North Carolina not far from Cape Lookout. Based on data from the Air Force Hurricane Hunters and Doppler radar velocities, the initial intensity is set at 80 kt. This estimate is a compromise between the flight-level winds and SFMR values. The minimum pressure remains quite low, 956 mb, based on surface observations and aircraft fixes. There have been several reports in eastern North Carolina of sustained tropical-storm-force winds and hurricane-force gusts, with the strongest winds being reported in the northern eyewall. Dorian is moving northeastward at 12 kt. A faster northeastward motion is expected during the next few days as a mid- to upper-level trough, currently over the U.S. Great Lakes, approaches the system and accelerates the steering flow. This track forecast takes the hurricane along the coast of North Carolina during the next several hours and near or over Atlantic Canada this weekend. The models are tightly clustered, and the NHC track forecast lies near the middle of the guidance envelope. The hurricane is expected to gradually weaken during the next couple of days due to an increase in wind shear and drier air. Dorian is expected to cross the north wall of the Gulf Stream current in about 36 hours, and head over much colder waters after that. These atmospheric and oceanic conditions should cause the cyclone to become a powerful hurricane-force extratropical in about 2 days. As the system gains latitude, the tropical-storm-force winds are expected to expand significantly. The NHC intensity forecast is largely an update of the previous one and in line with the various consensus aids. Key Messages: 1. Life-threatening storm surge and dangerous winds are expected to continue along portions of the North Carolina coast, portions of southeast Virginia and the southern Chesapeake Bay. Water levels could rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 2. Flash flooding is occurring, and will continue to become more widespread across the eastern Carolinas and far southeast Virginia this morning. There is a high risk of flash flooding over these areas, where significant, life-threatening flash flooding is expected. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 34.6N 76.2W 80 KT 90 MPH 12H 06/1800Z 36.0N 74.1W 75 KT 85 MPH 24H 07/0600Z 38.8N 69.9W 75 KT 85 MPH 36H 07/1800Z 42.5N 65.4W 70 KT 80 MPH 48H 08/0600Z 46.7N 61.6W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 09/0600Z 53.0N 52.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 10/0600Z 58.0N 36.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 11/0600Z...DISSIPATED $$ Forecaster Cangialosi

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