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Hurricane GASTON Forecast Discussion Number 29

2016-08-29 22:44:37| National Hurricane Center (Atlantic)

Issued at 500 PM AST MON AUG 29 2016 000 WTNT42 KNHC 292044 TCDAT2 HURRICANE GASTON DISCUSSION NUMBER 29 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 500 PM AST MON AUG 29 2016 Gaston's satellite presentation continues to slowly degrade, with the latest microwave data suggesting it could be undergoing an eyewall replacement. The initial wind speed is lowered to 90 kt in accordance with the latest satellite estimates. Little change in intensity is expected for the next couple of days while Gaston remains over warm waters with light-to-moderate shear, although the eyewall cycle adds a wrinkle to the forecast. In a couple of days, a gradual increase in shear, along with a decrease in SSTs, should cause a more significant weakening. Intensity guidance is a bit lower than 6 hours ago, and the latest NHC intensity forecast follows that trend. Gaston appears to be moving a bit faster, now north-northeastward at 3 kt. Due to a ridge becoming established to the southeast of the cyclone, Gaston should accelerate to the east-northeast over the next few days. The end of the forecast is tricky, with some uncertainties over how Gaston interacts with the mid-latitude westerlies and the strength of an eastern Atlantic ridge. While the overall guidance suite has shifted somewhat to the north at days 4 and 5, the ECMWF has been more consistent during the past few days and has stayed farther south. Thus, the new forecast is on the southern side of the guidance envelope, to the south of the model consensus at long range. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 31.2N 55.2W 90 KT 105 MPH 12H 30/0600Z 31.6N 54.5W 90 KT 105 MPH 24H 30/1800Z 32.2N 52.8W 85 KT 100 MPH 36H 31/0600Z 33.2N 50.7W 85 KT 100 MPH 48H 31/1800Z 34.6N 48.0W 85 KT 100 MPH 72H 01/1800Z 37.7N 39.6W 75 KT 85 MPH 96H 02/1800Z 38.5N 32.0W 55 KT 65 MPH 120H 03/1800Z 40.0N 28.0W 40 KT 45 MPH $$ Forecaster Blake

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Hurricane GASTON Forecast Discussion Number 28

2016-08-29 16:48:44| National Hurricane Center (Atlantic)

Issued at 1100 AM AST MON AUG 29 2016 000 WTNT42 KNHC 291447 TCDAT2 HURRICANE GASTON DISCUSSION NUMBER 28 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 1100 AM AST MON AUG 29 2016 Over the past few hours, the satellite presentation of Gaston has become slightly less organized, with decreasing convection noted in the eyewall. Satellite estimates are a bit lower, so the initial wind speed is reduced to 95 kt. Little change in intensity is expected for the next couple of days while Gaston remains over warm waters with light-to-moderate shear. Thereafter, a gradual increase in shear, along with a decrease in SSTs, should cause a more significant weakening. The latest NHC intensity forecast is simply an update of the previous one since the guidance continues to be in fairly good agreement. Gaston is still drifting northward. The steering currents should become better defined tomorrow as a ridge becomes established to the south of the cyclone. The ridge should cause Gaston to accelerate to the east-northeast over the next few days, although the cyclone stays south of the main belt of mid-latitude westerlies. Guidance is coming into better agreement on the system approaching the Azores in about 5 days, although there are some speed differences. No significant changes were made to the previous forecast, which lies near or just south of the model consensus. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 31.0N 55.4W 95 KT 110 MPH 12H 30/0000Z 31.3N 55.1W 95 KT 110 MPH 24H 30/1200Z 31.9N 53.7W 95 KT 110 MPH 36H 31/0000Z 32.6N 51.7W 90 KT 105 MPH 48H 31/1200Z 33.7N 49.2W 90 KT 105 MPH 72H 01/1200Z 36.7N 42.5W 80 KT 90 MPH 96H 02/1200Z 38.0N 35.0W 65 KT 75 MPH 120H 03/1200Z 39.0N 30.5W 50 KT 60 MPH $$ Forecaster Blake

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Tropical Depression EIGHT Forecast Discussion Number 5

2016-08-29 16:44:34| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT MON AUG 29 2016 000 WTNT43 KNHC 291444 TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082016 1100 AM EDT MON AUG 29 2016 The Air Force Reserve Hurricane Hunter aircraft did not find many changes to the depression this morning, with maximum believable SFMR winds of about 30 kt. This value will remain the initial wind speed. Satellite images indicate the cyclone continues to struggle to produce convection, likely due to moderate shear and plentiful dry air aloft. The environment is forecast to become more conducive over the next 24 hours, with a slight decrease in shear and an increase in moisture. Thus, the latest forecast still shows the depression becoming a tropical storm by Tuesday. Most of the guidance suggests the cyclone will strengthen in a couple of days while it moves northeastward away from the Carolinas as it moves right along the Gulf Stream. Since the previous forecast is almost identical to the new model consensus, no significant changes are made to the final NHC intensity forecast. The depression is moving northwestward, now at about 6 kt. The cyclone should slow down and begin to turn to the north as it reaches a weakness in the subtropical ridge near the North Carolina coast. In 36 to 48 hours, a mid-latitude shortwave trough moving through the northeastern United States is forecast to erode the ridge and cause the cyclone to recurve northeastward into the westerlies. The guidance is in fairly good agreement, and the latest NHC track forecast is close to the previous one. The cyclone should be absorbed within a large extratropical cyclone in about 4 days. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 33.2N 73.5W 30 KT 35 MPH 12H 30/0000Z 33.8N 74.3W 30 KT 35 MPH 24H 30/1200Z 34.4N 75.0W 35 KT 40 MPH 36H 31/0000Z 35.1N 75.0W 35 KT 40 MPH 48H 31/1200Z 36.2N 73.5W 40 KT 45 MPH 72H 01/1200Z 39.0N 68.0W 45 KT 50 MPH 96H 02/1200Z...DISSIPATED $$ Forecaster Blake

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Tropical Depression NINE Forecast Discussion Number 4

2016-08-29 16:44:02| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT MON AUG 29 2016 000 WTNT44 KNHC 291443 TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 1100 AM EDT MON AUG 29 2016 Deep convection associated with the tropical cyclone increased this morning, especially around western Cuba where rainfall totals of up to 12 inches may have occurred. A NOAA Hurricane Hunter aircraft investigated the system earlier this morning and did not find winds of tropical storm force. Based on those observations, and Dvorak satellite estimates, the current intensity is held at 30 kt. An Air Force Hurricane Hunter aircraft is scheduled to investigate the depression this afternoon, which should give a better estimate of the strength of the system. Vertical shear should remain modest for the next couple of days, but begin to increase around 72 hours as the environment becomes more baroclinic with strong upper-level westerlies prevailing over northern Florida. This is likely to discourage significant strengthening as the cyclone nears landfall. The official intensity forecast is close to the latest statistical/dynamical LGEM guidance. The center is not easy to locate but is believed to be situated near the northwestern edge of the cloud mass, and the motion is estimated to be 280/6 kt. A mid-tropospheric shortwave trough developing over the southeastern United States is expected to induce a turn toward the north and northeast in 2 to 3 days, followed by acceleration toward the east-northeast late in the forecast period. The official forecast is similar to that from the previous advisory, and is mainly a blend of the latest GFS and ECMWF solutions but leans toward the latter model. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 23.6N 84.3W 30 KT 35 MPH 12H 30/0000Z 23.9N 85.3W 35 KT 40 MPH 24H 30/1200Z 24.4N 86.4W 40 KT 45 MPH 36H 31/0000Z 25.0N 87.0W 45 KT 50 MPH 48H 31/1200Z 26.1N 86.7W 50 KT 60 MPH 72H 01/1200Z 28.6N 83.8W 55 KT 65 MPH 96H 02/1200Z 31.5N 79.0W 50 KT 60 MPH 120H 03/1200Z 34.0N 71.5W 50 KT 60 MPH $$ Forecaster Pasch

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Hurricane LESTER Forecast Discussion Number 20

2016-08-29 16:40:34| National Hurricane Center (East Pacific)

Issued at 800 AM PDT MON AUG 29 2016 000 WTPZ43 KNHC 291440 TCDEP3 HURRICANE LESTER DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132016 800 AM PDT MON AUG 29 2016 Lester's satellite presentation is quite impressive this morning. The cyclone's eye continues to warm and and the inner core cloud top temperatures have cooled considerably. A blend of 1200 UTC satellite intensity estimates of 105 kt, and a recent ADT objective intensity estimate yields an increased initial intensity of 110 kt for this advisory. Lester should remain in a low-shear environment for the next several days, with only some gradual decrease in the oceanic water temperature. The majority of the intensity guidance indicate that the hurricane will peak within the next 12 hours or so, then gradual decrease. It appears that the atmospheric environment and the sea surface temperatures match similar criteria for an annular hurricane manifestation. If Lester acquires annular hurricane characteristics, the cyclone could remain stronger longer than reflected in the official forecast and what the intensity guidance suggests. The NHC forecast is adjusted a bit higher in the short term, then shows gradual weakening and falls in line with the IVCN multi-model consensus. The initial motion estimate remains 270/13. A strong, deep-layer ridge to the north of Lester should steer the cyclone on a continued westward course during the next 3 days. Beyond that period, the large-scale models indicate some interaction with Madeline to the southwest of Lester which induces a gradual turn toward the west-northwest through day 5. The official forecast follows suit and is based on a multi-model consensus and is quite similar to the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 18.1N 129.2W 110 KT 125 MPH 12H 30/0000Z 18.1N 131.2W 115 KT 130 MPH 24H 30/1200Z 18.2N 133.6W 95 KT 110 MPH 36H 31/0000Z 18.2N 135.9W 90 KT 105 MPH 48H 31/1200Z 18.2N 138.3W 85 KT 100 MPH 72H 01/1200Z 18.4N 143.0W 80 KT 90 MPH 96H 02/1200Z 19.3N 147.9W 75 KT 85 MPH 120H 03/1200Z 21.0N 153.0W 70 KT 80 MPH $$ Forecaster Roberts

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