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Subtropical Storm Ernesto Forecast Discussion Number 2

2018-08-15 17:01:37| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Aug 15 2018 805 WTNT45 KNHC 151501 CCA TCDAT5 Subtropical Storm Ernesto Discussion Number 2...Corrected NWS National Hurricane Center Miami FL AL052018 1100 AM AST Wed Aug 15 2018 Convection associated with the subtropical cyclone became better organized after the release of the previous advisory, but cloud tops have warmed recently with the convection becoming somewhat fragmented. An Hebert-Poteat subtropical classification of T2.5 from TAFB suggests that they system is producing gale-force winds, and recent scatterometer data that passed over the far eastern portion of the circulation revealed 30-kt winds. Since the instrument missed the radius of maximum winds, it is assumed that stronger winds exist over the eastern portion of the circulation, and the initial intensity is increased to 35 kt, making the system a subtropical storm. Ernesto has about 24 hours over marginally warm SSTs and in a low- shear environment in which to strengthen. After that time, the cyclone will be moving over much colder water which should cause it to become post-tropical within 48 hours. The post-tropical cyclone is forecast to merge with a frontal zone associated with a larger extratropical cyclone over the North Atlantic in 3 to 4 days. The cyclone is moving northward at about 6 kt. A mid-level trough that is moving off the east coast of the United States should cause Ernesto to turn north-northeastward later today, and the cyclone is forecast to accelerate northeastward by late Thursday as it becomes embedded within the mid-latitude westerlies. The dynamical model guidance continues to be in good agreement, and the new NHC track forecast remains in the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 38.1N 46.0W 35 KT 40 MPH 12H 16/0000Z 39.3N 45.3W 40 KT 45 MPH 24H 16/1200Z 41.3N 43.5W 45 KT 50 MPH 36H 17/0000Z 43.6N 40.3W 45 KT 50 MPH 48H 17/1200Z 46.4N 35.2W 45 KT 50 MPH...POST-TROPICAL 72H 18/1200Z 52.3N 21.0W 40 KT 45 MPH...POST-TROPICAL 96H 19/1200Z...MERGED WITH LARGER EXTRATROPICAL LOW $$ Forecaster Brown

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Tropical Storm Lane Forecast Discussion Number 3

2018-08-15 16:52:08| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Wed Aug 15 2018 781 WTPZ44 KNHC 151452 TCDEP4 Tropical Storm Lane Discussion Number 3 NWS National Hurricane Center Miami FL EP142018 800 AM PDT Wed Aug 15 2018 The latest satellite imagery shows that the cyclone continues to become better organized with a growing central dense overcast along with ample banding features. Dvorak estimates range from 30 to 40 kt, and with the increased organization since the last advisory, the initial wind speed is set to 35 kt. Further intensification is likely over the next few days as Lane encounters a conducive large-scale environment consisting of low shear and fairly warm waters. Rapid strengthening is a distinct possibility after the cyclone forms an inner core, which could take a day or so given that there is still some drier air in the eastern semicircle. The DTOPS rapid intensification index indicates a high probability of significant strengthening over the next 3 days, with over a 70 percent chance of a 65-kt increase during that time. Given that some of the guidance (FSSE and HMON) are even higher than that, this seems like a reasonable forecast and is indicated below. The new NHC forecast is raised from the last advisory, and is close to a blend of the previous forecast and the corrected-consensus guidance. Continuity prevents a higher forecast, but Lane seems destined to eventually become a category-4 hurricane like Hector. The storm continues to move just south of due west at about 12 kt. The subtropical ridge to the north of Lane is forecast to weaken slightly over the next few days, which will likely steer the cyclone to the west or west-northwest throughout the period. There is very little spread in the guidance, with the most notable change since the last advisory being a small shift to the southwest. The latest official track forecast is adjusted in that direction, and is not too far from the latest model consensus. Given the tightly packed guidance, this appears to be a high-confidence forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 10.7N 123.6W 35 KT 40 MPH 12H 16/0000Z 10.6N 125.5W 45 KT 50 MPH 24H 16/1200Z 10.7N 127.7W 55 KT 65 MPH 36H 17/0000Z 11.0N 130.0W 70 KT 80 MPH 48H 17/1200Z 11.5N 132.4W 85 KT 100 MPH 72H 18/1200Z 12.6N 137.6W 100 KT 115 MPH 96H 19/1200Z 13.9N 142.2W 105 KT 120 MPH 120H 20/1200Z 15.0N 146.5W 105 KT 120 MPH $$ Forecaster Blake

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Subtropical Depression Five Forecast Discussion Number 1

2018-08-15 10:39:35| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Aug 15 2018 684 WTNT45 KNHC 150839 TCDAT5 Subtropical Depression Five Discussion Number 1 NWS National Hurricane Center Miami FL AL052018 500 AM AST Wed Aug 15 2018 The low pressure system that the National Hurricane Center has been monitoring over the central Atlantic Ocean has developed sufficently organized deep convection and a well-defined center. Since the system has a large radius of maximum wind and is co-located with an upper-level low, it is being classified as a subtropical depression. The initial intensity is set to a possibly conservative 30 kt based on an earlier ASCAT pass. This value is slightly below the latest satellite intensity estimate from TAFB. It is interesting to note that so far this hurricane season, four of the five systems have been a subtropical cyclone at some point in their lifetimes. Slow strengthening is possible during the next 24 hours or so while the system remains over warm SSTs and in fairly low wind shear conditions. After that time, sharply colder waters, drier air, and a significant increase in wind shear should cause extratropical transition in about 48 hours, or sooner, and a gradual weakening. The models show the post-tropical system merging with a frontal zone in 3 to 4 days. The subtropical depression is moving slowly northward at about 4 kt. A north to north-northeastward motion is expected today as the system moves on the western periphery of a mid-level ridge. A mid- to upper-level trough currently over the northeastern U.S. is anticipated to approach the cyclone, and that feature should cause the system to accelerate northeastward on Thursday and Friday. The models are in good agreement, and the NHC track forecast lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 37.6N 45.6W 30 KT 35 MPH 12H 15/1800Z 38.5N 45.4W 35 KT 40 MPH 24H 16/0600Z 40.2N 44.4W 45 KT 50 MPH 36H 16/1800Z 42.5N 41.9W 45 KT 50 MPH 48H 17/0600Z 45.1N 37.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 18/0600Z 51.0N 24.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 19/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Depression Fourteen-E Forecast Discussion Number 2

2018-08-15 10:34:35| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Wed Aug 15 2018 131 WTPZ44 KNHC 150834 TCDEP4 Tropical Depression Fourteen-E Discussion Number 2 NWS National Hurricane Center Miami FL EP142018 200 AM PDT Wed Aug 15 2018 Satellite images indicate that the depression is gradually getting better organized with deep convection increasing near the center and in curved bands over the western semicircle. The initial intensity remains 30 kt, in agreement with the Dvorak classifications from TAFB and SAB, but it would not be surprising if the system was a little stronger. The depression continues to move just south of due west at about 12 kt. A deep-layer ridge situated to the north of the cyclone should keep the system moving on a general westward path at about the same forward speed during the next couple of days. After that time, the models suggest that a mid- to upper-level low will cut off and cause a break in the ridge. This change in the flow pattern should cause the tropical cyclone to move toward the west-northwest in the 3- to 5-day time frame. The models have generally shifted slightly to the left this cycle, and the NHC forecast has been nudged in that direction. The environmental conditions appear conducive for the cyclone to strengthen during the next several days with the wind shear expected to remain low, less than 10 kt, mid-level humidities fairly high, and SSTs marginally warm. The intensity models respond to these favorable conditions, and all of them now show the system becoming a hurricane within the next few days. The NHC intensity forecast follows that theme, and shows a faster rate of strengthening than the previous forecast. This prediction lies closest to the HCCA and ICON models. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 10.8N 122.3W 30 KT 35 MPH 12H 15/1800Z 10.6N 124.2W 40 KT 45 MPH 24H 16/0600Z 10.6N 126.4W 45 KT 50 MPH 36H 16/1800Z 10.8N 128.6W 55 KT 65 MPH 48H 17/0600Z 11.1N 130.8W 65 KT 75 MPH 72H 18/0600Z 12.3N 135.6W 80 KT 90 MPH 96H 19/0600Z 13.8N 140.1W 90 KT 105 MPH 120H 20/0600Z 15.2N 144.1W 90 KT 105 MPH $$ Forecaster Cangialosi

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Tropical Depression Fourteen-E Forecast Discussion Number 1

2018-08-15 04:39:04| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Tue Aug 14 2018 191 WTPZ44 KNHC 150238 TCDEP4 Tropical Depression Fourteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP142018 800 PM PDT Tue Aug 14 2018 The area of disturbed weather and associated low pressure area that the NHC has been tracking for the past few days has acquired enough organized deep convection for the system to be declared a tropical depression. Although the convection had waned a little during the day, recent satellite imagery indicates that convection near the well-defined center has begun to increase and that outer banding features in the western semicircle have been improving during the past few hours. The initial intensity of 30 kt is based on a Dvorak satellite intensity estimate of T2.0/30 kt from TAFB. The initial motion estimate is 265/12 kt. For the next 72 hours, the tropical cyclone is forecast to move westward or slightly south of due west along the southern periphery of a broad deep-layer ridge that is located to the north of the depression. The ridge is expected to weaken by 96 hours as a mid-latitude low/trough currently located off the coast of southern California digs southward and then westward during the forecast period. This pattern should allow the cyclone to move west-northward into the weakness in the ridge and start gaining latitude. For this initial forecast of the system, the NHC track lies close to a blend of the consensus track models HCCA and TVCE. The vertical wind shear is forecast to remain around 10 kt or less for the next 72 hours or so, with a further decrease on days 4 and 5 when the system moves underneath and/or develops an upper-level anticyclone, conditions that typically favor significant intensification. However, since the circulation envelope is currently elongated northeast-to-southwest, it will take a couple of days for the system to become more symmetrical, which could then enhance the strengthening process. By that time, however, sea- surface temperatures and mid-level humidity values will be marginal for significant intensification to occur. As a result, only slow but steady strengthening is indicated in this first intensity forecast, which closely follows the HCCA intensity consensus model. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 10.9N 121.2W 30 KT 35 MPH 12H 15/1200Z 10.8N 122.9W 35 KT 40 MPH 24H 16/0000Z 10.7N 125.2W 40 KT 45 MPH 36H 16/1200Z 10.8N 127.3W 45 KT 50 MPH 48H 17/0000Z 11.0N 129.5W 50 KT 60 MPH 72H 18/0000Z 12.0N 134.1W 65 KT 75 MPH 96H 19/0000Z 13.8N 138.6W 80 KT 90 MPH 120H 20/0000Z 15.6N 142.8W 90 KT 105 MPH $$ Forecaster Stewart

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