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Tropical Depression TWO Forecast Discussion Number 4

2016-05-28 16:48:02| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT SAT MAY 28 2016 000 WTNT42 KNHC 281447 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 1100 AM EDT SAT MAY 28 2016 Satellite and NOAA WSR-88D radar data indicate that deep convection has increased in the northern semicircle of the depression's circulation since the previous advisory. However, the depression remains a sheared tropical cyclone due to southeasterly upper-level winds of 20-25 kt. An Air Force Reserve reconnaissance aircraft investigated the cyclone this morning and obtained reliable SFMR surface winds of at least 30 kt. Satellite intensity estimates were also T2.0/30 kt from both TAFB and SAB, so the intensity is being maintained at 30 kt for this advisory. Microwave satellite and recon fix positions indicate that the cyclone has made a jog toward the west-northwest during the past six hours. However, smoothing through these short-term wobbles yields a 12-hour motion of 310/11 kt. The ECMWF and GFS models actually did quite well in predicting this recent short-term wobble, and both models turn the depression more toward the right, accompanied by a steady decrease in forward speed over the next 24 hours as the cyclone nears the South Carolina coast. As a result, the new NHC forecast track lies slightly to the left of the previous advisory track through 12 hours, primarily to account for the more westward initial position, and then is near the previous track and a blend of the GFS-ECMWF model consensus track at 24 hours and beyond. The depression is beginning to move over the eastern wall of the Gulf Stream where sea-surface temperatures are 27-28 deg C. Outer convective bands have also developed over the slightly cooler shelf waters between the South Carolina coast and the Gulf Stream, which implies that there might not be as much of a weakening effect by those cooler waters as previously anticipated. However, southerly vertical wind shear is forecast by the SHIPS model to increase to more than 20 kt before the cyclone reaches the coast, and that is expected to inhibit any significant strengthening. It is possible that the cyclone could peak at around 40 kt while it is over the Gulf Stream this afternoon and evening, followed by slight weakening just before it reaches the coast. The official intensity forecast is similar to the previous advisory and closely follows the Decay-SHIPS intensity model. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 30.3N 78.5W 30 KT 35 MPH 12H 29/0000Z 31.3N 79.5W 35 KT 40 MPH 24H 29/1200Z 32.4N 80.3W 35 KT 40 MPH 36H 30/0000Z 32.7N 80.3W 30 KT 35 MPH...INLAND 48H 30/1200Z 33.0N 79.7W 30 KT 35 MPH...INLAND 72H 31/1200Z 33.6N 78.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 01/1200Z 34.4N 76.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 02/1200Z 34.9N 75.8W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Tropical Depression TWO Forecast Discussion Number 3

2016-05-28 10:36:30| National Hurricane Center (Atlantic)

Issued at 500 AM EDT SAT MAY 28 2016 000 WTNT42 KNHC 280836 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 500 AM EDT SAT MAY 28 2016 The depression has not become any better organized since yesterday. The convection is located to the northwest of the low-level center due to southeasterly shear, and it is also limited due to the fact that the cyclone has been moving over cooler waters. Dvorak T-numbers have not changed, and the initial intensity is kept at 30 kt based on continuity. The depression has a small opportunity to strengthen a little during the next 24 hours while it moves over the warmer waters of the Gulf Stream, although the shear is not favorable for intensification. This is consistent with most of the intensity guidance, which do not show any notable increase of the winds. In between 24 and 36 hours, the circulation will be interacting with land, and weakening should begin. By 72 hours or sooner, the depression is forecast to become a remnant low. Although the low-level center is difficult to locate on satellite imagery, the best estimate of the initial motion is 310 degrees at 12 kt. The depression is currently located on the southwestern edge of a mid-level ridge, and this pattern will continue to steer the cyclone on the same track for the next 24 to 36 hours. Thereafter, a short wave trough is forecast to approach from the west and force the cyclone to turn to the east-northeast at a very slow pace. The NHC forecast is an extrapolation of the previous one, and it follows the trend of the GFS and the ECMWF models very closely. The NHC forecast brings the center of the cyclone near the South Carolina coast between 24 and 36 hours. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 29.9N 77.0W 30 KT 35 MPH 12H 28/1800Z 31.0N 78.4W 30 KT 35 MPH 24H 29/0600Z 32.4N 79.7W 35 KT 40 MPH 36H 29/1800Z 32.8N 80.0W 30 KT 35 MPH...INLAND 48H 30/0600Z 33.0N 79.5W 30 KT 35 MPH...INLAND 72H 31/0600Z 33.5N 78.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 01/0600Z 34.5N 76.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 02/0600Z 35.0N 75.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Avila

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Tropical Depression TWO Forecast Discussion Number 2

2016-05-28 04:36:55| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT FRI MAY 27 2016 000 WTNT42 KNHC 280236 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 1100 PM EDT FRI MAY 27 2016 The cloud pattern of the depression has not changed much during the past few hours, and the associated deep convection is confined to a somewhat linear band north and northwest of the center. The initial intensity remains 30 kt, consistent with a blend of the latest TAFB and SAB Dvorak estimates. The biggest positive factor for the cyclone intensifying in the next 12 to 36 hours is its movement over the Gulf Stream, where SSTs are above 27C. However, moderate to strong vertical shear and dry air argue against significant strengthening. Given these competing factors, the official forecast continues to show modest intensification during the first 24-36 hours. This forecast is closest to the SHIPS model. After 36 hours, a track over cooler shelf waters and an increase in shear should result in slow weakening, with the system expected to become a remnant low in about 3 days. The initial motion estimate is 300/10, with the depression currently situated between a mid/upper-level low over the northwest Bahamas and a narrow mid-level ridge extending east of the North Carolina coast. These features should result in a continued west- northwestward track for the next 24 hours. After that time, both of these synoptic steering features weaken while a broad mid/upper- level trough moves into the eastern United States. This pattern suggests that the cyclone will slow down and gradually turn northward and then northeastward in 2-3 days. Through day 3 the NHC track is close to a blend of the GFS and ECMWF models, and lies a bit to the right of the previous official forecast, especially at 48 and 72 hours. After that time the global model spread is larger. The ECMWF shows the remnant low moving more quickly northeastward, while the GFS and GEFS ensemble mean show a motion back toward the west at days 4-5. The NHC forecast late in the period still favors the ECMWF track, but is slower given the latest GFS/GEFS trend. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 29.0N 75.9W 30 KT 35 MPH 12H 28/1200Z 30.0N 77.3W 35 KT 40 MPH 24H 29/0000Z 31.3N 78.9W 40 KT 45 MPH 36H 29/1200Z 32.2N 79.7W 40 KT 45 MPH 48H 30/0000Z 32.7N 79.7W 35 KT 40 MPH 72H 31/0000Z 33.5N 78.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 01/0000Z 34.0N 77.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 02/0000Z 34.5N 76.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan

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Tropical Depression TWO Forecast Discussion Number 1

2016-05-27 22:57:55| National Hurricane Center (Atlantic)

Issued at 500 PM EDT FRI MAY 27 2016 000 WTNT42 KNHC 272057 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 500 PM EDT FRI MAY 27 2016 An Air Force Reserve reconnaissance aircraft investigating the low pressure system located about 400 n mi southeast of Charleston, South Carolina, indicated that the system has developed a well-defined closed circulation. With this afternoon's increase in convection near the center, the system is now a tropical cyclone and advisories have been initiated. The strongest reliable SFMR surface wind measured was 30 kt, and that is the intensity set for this advisory. The initial motion estimate is 300/11 kt. A strong deep-layer ridge to the northeast of the depression is forecast to remain oriented northwest-southeast across the Carolinas through 36 hours or so, which should keep the depression moving in a general west-northwestward direction during that time. By 48 hours, however, a mid-level shortwave trough ejecting northeastward out of the south-central United States is forecast to erode the ridge, resulting in a significant weakening of the steering currents and a sharp decrease in forward speed as the cyclone is approaching the coast of South Carolina. By day 3 and beyond, the cyclone is forecast to move slowly northeastward or eastward off of the coast of North Carolina as a weakening system. The models are in good agreement on this track scenario, with only small differences in forward speed. The official track forecast is close to the consensus model TVCN and has incorporated the slightly slower speed of the ECMWF model. The depression will be moving over somewhat cooler sea surface temperatures of near 25C during the next 24 hours or so before moving over the warmer Gulfstream by 36 hours, where SSTs are 27C-28C. Over the next day or so, the cyclone will also be moving into weaker vertical wind shear conditions. The net result is expected to be slow strengthening to tropical storm status prior to landfall. The NHC intensity forecast is similar to the SHIPS model through 48 hours, and then closely follows the Decay-SHIPS model after that. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 28.5N 74.7W 30 KT 35 MPH 12H 28/0600Z 29.5N 76.4W 35 KT 40 MPH 24H 28/1800Z 30.7N 78.3W 40 KT 45 MPH 36H 29/0600Z 32.0N 79.7W 40 KT 45 MPH 48H 29/1800Z 32.8N 80.2W 40 KT 45 MPH...INLAND 72H 30/1800Z 33.6N 78.7W 30 KT 35 MPH...OVER WATER 96H 31/1800Z 34.0N 77.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/1800Z 34.7N 75.6W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Compiled Comments on the Discussion Draft

2016-05-24 20:26:16| PortlandOnline

Individuals and organizations comments on the Discussion Draft with staff responses PDF Document, 441kbCategory: Public comments on the Discussion Draft

Tags: comments discussion draft compiled

 

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