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Hurricane GASTON Forecast Discussion Number 35

2016-08-31 10:52:43| National Hurricane Center (Atlantic)

Issued at 500 AM AST WED AUG 31 2016 000 WTNT42 KNHC 310851 TCDAT2 HURRICANE GASTON DISCUSSION NUMBER 35 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 500 AM AST WED AUG 31 2016 Gaston's satellite presentation continues to be outstanding. It consists of a large and clear eye surrounded by rings of very deep convection. Dvorak intensity estimates have remained steady and still support and initial intensity of 105 kt. Gaston is over warm waters and the shear is expected to increase just a little during the next day or two. Consequently, only a slight weakening is anticipated during the the day or so. After that time, Gaston should encounter cooler waters resulting in a faster weakening. By the end of the forecast period, Gaston should become absorbed by another extratropical cyclone. The NHC intensity forecast is very similar to the previous one. The initial motion is 050/8 kt. Gaston is already embedded in the mid-latitude westerlies, and this pattern should steer the hurricane toward the northeast and east-northeast with a gradual increase in forward speed. By day 3, the cyclone should reduce its forward speed once it begins to interact with a separate extratropical cyclone. No significant adjustments were made to the previous NHC track forecast and it continues to be close to the multi-model consensus TVCN. Gaston continues to move in the direction of the Azores, and all interests in these islands should monitor the progress of this cyclone. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 33.4N 50.2W 105 KT 120 MPH 12H 31/1800Z 34.5N 48.2W 105 KT 120 MPH 24H 01/0600Z 36.3N 44.5W 95 KT 110 MPH 36H 01/1800Z 37.5N 40.0W 85 KT 100 MPH 48H 02/0600Z 38.5N 35.0W 70 KT 80 MPH 72H 03/0600Z 39.5N 28.0W 45 KT 50 MPH 96H 04/0600Z 41.5N 22.0W 30 KT 35 MPH...POST-TROPICAL 120H 05/0600Z...DISSIPATED $$ Forecaster Avila

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Hurricane LESTER Forecast Discussion Number 26

2016-08-31 04:56:14| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE AUG 30 2016 000 WTPZ43 KNHC 310256 TCDEP3 HURRICANE LESTER DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132016 800 PM PDT TUE AUG 30 2016 Lester has shown a sudden reintensification this evening as a symmetric eyewall with very cold cloud tops is encircling a 25 nm diameter warm eye. Subjective Dvorak classifications from SAB and TAFB are at 6.5 and 6.0 current intensity numbers, respectively, while the CIMSS Advanced Dvorak Technique is at 6.3. A blend of these gives 120 kt maximum winds at the initial time, up considerably from the previous advisory. Lester is anticipated to experience quite low vertical shear for the next few days, though the lukewarm SSTs and 40-50 percent humidity air are only marginally conducive for maintaining high intensities. The current convective structure and its environment suggest that Lester may be evolving into an annular hurricane, which tends to weaken only slowly over time. The NHC intensity forecast is closest to the HWRF and DSHP models, and is above that from the previous advisory due to the higher initial intensity. Lester is moving toward the west-southwest at about 11 kt. A large subtropical ridge to its north is providing the westward steering and low shear environment. The tightly packed model guidance indicate that the system should turn slightly toward the west or west-northwest during the next two days at about the same rate of forward speed. The NHC track forecast is based upon the TVCN multi-model consensus technique and is very close to that from the previous advisory. No new information is available about Lester's initial wind radii, so that is unchanged from the previous advisory. The NHC wind radii forecast is based upon the RVCN consensus technique and nearly the same as that from the last advisory. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 17.8N 136.5W 120 KT 140 MPH 12H 31/1200Z 17.8N 138.1W 115 KT 130 MPH 24H 01/0000Z 17.9N 140.3W 110 KT 125 MPH 36H 01/1200Z 18.2N 142.5W 105 KT 120 MPH 48H 02/0000Z 18.7N 144.7W 100 KT 115 MPH 72H 03/0000Z 20.0N 149.6W 85 KT 100 MPH 96H 04/0000Z 21.8N 155.0W 75 KT 85 MPH 120H 05/0000Z 23.5N 159.5W 65 KT 75 MPH $$ Forecaster Landsea

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Tropical Depression NINE Forecast Discussion Number 10

2016-08-31 04:56:14| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT TUE AUG 30 2016 000 WTNT44 KNHC 310256 TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 1000 PM CDT TUE AUG 30 2016 The convective organization of the cyclone has improved markedly since this time yesterday, and especially since the previous advisory, with a large convective cloud mass having developed around the well-defined low-level center. Ship C6FN5 located about 80 nmi south of the center at 00Z reported a 35-kt wind, but at an elevated height of 43 meters, which adjusts down to a 10-meter wind of 30-31 kt. The recent NOAA recon flight also confirmed that winds of about 30 kt existed, so the intensity will remain unchanged at 30 kt for this advisory. Fixes from the NOAA aircraft indicated a west-southwestward motion over the previous 6 hours. However, this is believed to be a temporary motion that was likely just the result of the center redeveloping closer to strongest convection in the southern quadrant. Since that time, little motion or just a slight drift toward the north-northwest at 2 kt is indicated by satellite imagery. The latest 00Z upper-air data showed the depression is now located along or just north of the subtropical ridge axis that is oriented east-west across the Florida Straits, a steering pattern that favors a northward motion during the next 12 hours or so. After that time, the NHC model guidance is in excellent agreement on a shortwave trough currently over the central U.S. digging southeastward to the northeast Gulf coast and lifting out and accelerating the cyclone toward the northeast by 36 hours. Due to the uncertainty in the short term motion, the new official forecast was not shifted as far west as the latest model consensus and instead lies very close to the previous advisory track. Unlike the previous several days, deep convection has finally developed north of the low-level center during the past 6 hours, and more recent satellite trends suggest that some inner-core curved banding features may be developing. The upper-level outflow has been improving and expanding in all quadrants now that the vertical wind shear has decreased to less than 10 kt and has shifted from a northerly to a westerly component. Some additional decrease in the shear is forecast to occur for the next 36 to 48 hours while the cyclone remains in a modestly moist environment. The NHC intensity guidance has increased as a result of the improving environmental conditions, so the official intensity forecast has also been increased, which now shows the cyclone near hurricane strength just prior to landfall at 48 hours. No changes to the existing hurricane and tropical storm watches are required at this time. However, by Wednesday morning, a tropical storm watch may be needed for the coasts of northeast Florida and Georgia. It is important not to focus on the forecast landfall point of this system. Among other reasons, dangerous storm surge flooding is likely along the coast well to the east and south of the path of the center. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 24.3N 87.8W 30 KT 35 MPH 12H 31/1200Z 25.1N 87.7W 40 KT 45 MPH 24H 01/0000Z 26.3N 87.0W 45 KT 50 MPH 36H 01/1200Z 27.8N 85.9W 50 KT 60 MPH 48H 02/0000Z 29.6N 83.9W 60 KT 70 MPH 72H 03/0000Z 33.4N 77.5W 60 KT 70 MPH 96H 04/0000Z 37.1N 70.0W 60 KT 70 MPH 120H 05/0000Z 39.0N 68.2W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart

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Hurricane GASTON Forecast Discussion Number 34

2016-08-31 04:53:34| National Hurricane Center (Atlantic)

Issued at 1100 PM AST TUE AUG 30 2016 000 WTNT42 KNHC 310253 TCDAT2 HURRICANE GASTON DISCUSSION NUMBER 34 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 1100 PM AST TUE AUG 30 2016 Gaston's satellite presentation has continued to improve, with a large clear eye and cloud tops colder than -60C completely surrounding the center. Dvorak intensity estimates have risen to T5.5 from TAFB and SAB and are a little higher from the objective ADT. The initial intensity is therefore raised to 105 kt, making Gaston a major hurricane again. Gaston is expected to remain over waters warmer than 26C for at least the next 36 hours. In addition, vertical shear is not expected to increase any further than what is already affecting the system. Therefore, Gaston should be able to at least maintain its intensity in the short term, but weakening is likely to commence by 24 hours. Due to cooler waters, a rather fast weakening trend is expected after 36 hours, with Gaston likely to weaken to a tropical storm between 48 and 72 hours. The cyclone is now expected to become post-tropical by day 4 since it will be difficult for it to maintain organized, deep convection over cold water, and it should become absorbed by another extratropical cyclone by day 5. The NHC intensity forecast closely follows the ICON intensity consensus for the entire forecast period. The initial motion is 070/9 kt. Gaston is becoming embedded in the mid-latitude westerlies, which should cause it to accelerate toward the east-northeast during the next couple of days. Some reduction in speed is then forecast to start by day 3 once Gaston begins to interact with the separate extratropical cyclone. The track guidance is tightly clustered, and no significant changes were needed from the previous NHC track forecast. The updated NHC forecast continues to show a threat to the Azores in about 3 days. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 32.9N 50.9W 105 KT 120 MPH 12H 31/1200Z 33.7N 49.2W 105 KT 120 MPH 24H 01/0000Z 35.4N 46.0W 95 KT 110 MPH 36H 01/1200Z 36.9N 41.7W 85 KT 100 MPH 48H 02/0000Z 37.9N 36.9W 75 KT 85 MPH 72H 03/0000Z 38.7N 29.5W 50 KT 60 MPH 96H 04/0000Z 40.5N 23.5W 35 KT 40 MPH...POST-TROPICAL 120H 05/0000Z...DISSIPATED $$ Forecaster Berg

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Tropical Depression EIGHT Forecast Discussion Number 11

2016-08-31 04:40:55| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT TUE AUG 30 2016 000 WTNT43 KNHC 310240 TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082016 1100 PM EDT TUE AUG 30 2016 Aircraft fixes from the Air Force Reserve Hurricane Hunters indicate that the center of the depression is located near the southwestern edge of a persistent cluster of deep convection. The plane did not find any stronger winds than in previous missions, and the initial intensity remains 30 kt. Westerly vertical shear affecting the cyclone is not expected to decrease, and in fact it should increase substantially from 24 hours and beyond. Still, if the system can maintain deep convection while it remains over warm sea surface temperatures for the next 36 hours or so, the mere fact that it is expected to accelerate from this point forward could allow the maximum winds to increase. The NHC intensity forecast is very similar to the previous one, but it does allow for possible strengthening to tropical storm strength in about 12 hours. The cyclone should become extratropical by 72 hours, but after that there is some uncertainty whether it will be absorbed by another cyclone or become the dominant system. For now, the forecast continues to show it becoming absorbed, which is in line with the ECMWF. The aircraft fixes indicate that the depression is beginning to move away from the Outer Banks with an initial motion of 040/4 kt. The cyclone is expected to accelerate toward the northeast and then east-northeast through the forecast period. The track models are in very good agreement, and no significant changes were required to the official track forecast. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 34.5N 74.6W 30 KT 35 MPH 12H 31/1200Z 35.4N 73.6W 35 KT 40 MPH 24H 01/0000Z 37.1N 71.0W 40 KT 45 MPH 36H 01/1200Z 39.3N 66.1W 45 KT 50 MPH 48H 02/0000Z 41.5N 59.3W 45 KT 50 MPH 72H 03/0000Z 45.1N 45.3W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 04/0000Z...DISSIPATED $$ Forecaster Berg

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