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Tropical Storm PAINE Forecast Discussion Number 4

2016-09-18 22:35:24| Tropical Depression LIDIA

Issued at 300 PM MDT SUN SEP 18 2016

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Tropical Depression JULIA Forecast Discussion Number 20

2016-09-18 22:32:58| National Hurricane Center (Atlantic)

Issued at 500 PM EDT SUN SEP 18 2016 000 WTNT41 KNHC 182032 TCDAT1 TROPICAL DEPRESSION JULIA DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 500 PM EDT SUN SEP 18 2016 Julia's low-level circulation has continued to improve despite the lack of organized deep convection near the well-defined center. However, some tight curved banding features consisting of shallow to moderate convection have developed within 100 nmi of the center during the past few hours, a hint that the mid-level moisture is beginning to increase. The initial intensity remains 25 kt based on on a TAFB intensity estimate of T1.5/25 kt, and a 1535Z ASCAT pass that showed some surface winds near 25 kt just north of the center. Julia is moving northwestward or 330/06 kt. The cyclone is forecast to slow down and gradually turn toward the north-northwest and north later tonight. A northward motion is then expected to persist, ahead of a strong shortwave trough that is forecast to move toward the western Carolinas, until Julia moves near or just onshore the the southeastern coast of North Carolina on Tuesday. After that time, it is uncertain whether or not a weakening Julia will lift out to the northeast and merge with a frontal boundary, or drift southwestward as a remnant low. Regardless of the status of Julia by 72 hours, the models are in good agreement that the system will not be a tropical cyclone at that time or thereafter due to strong vertical wind shear and land interaction. The official track forecast is similar to the previous advisory, which is a compromise of the various global and regional model solutions. Julia has a narrow window of opportunity to strengthen tonight and Monday morning when the vertical wind shear is forecast to weaken significantly and the upper-level flow is expected to become more anticyclonic. These more conducive dynamics are forecast to coincide with the nighttime convective maximum period and also during the time when Julia will be over the Gulf Stream where SSTs are 29-30C. Buoy reports offshore the South Carolina coast indicate that surface dew points have increased to near 80F, a further indication that the atmosphere surrounding Julia is becoming more conducive for regeneration of convection near the center later tonight. By Monday afternoon and evening, increasing southwesterly shear ahead of the aforementioned shortwave trough should induce steady weakening, which is expected to continue as the cyclone approaches the coast of North Carolina. The intensity forecast remains unchanged is a little below the consensus model IVCN. However, due to the possibility that Julia could be a little stronger than currently expected, an Air Force Reserve Hurricane Hunter aircraft has tentatively been tasked to investigate the cyclone Monday afternoon. The primary threat from Julia will be locally heavy rainfall from eastern North Carolina northward to the Mid-Atlantic states and the northeastern U.S. when moisture from the cyclone, or its remnants, will interact with an approaching frontal system. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 32.3N 78.0W 25 KT 30 MPH 12H 19/0600Z 33.0N 78.0W 25 KT 30 MPH 24H 19/1800Z 34.0N 77.7W 30 KT 35 MPH 36H 20/0600Z 34.6N 77.5W 30 KT 35 MPH...INLAND 48H 20/1800Z 34.9N 77.5W 25 KT 30 MPH...INLAND 72H 21/1800Z 34.2N 78.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 22/1800Z...DISSIPATED $$ Forecaster Stewart

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Tropical Storm KARL Forecast Discussion Number 17

2016-09-18 16:54:20| National Hurricane Center (Atlantic)

Issued at 1100 AM AST SUN SEP 18 2016 000 WTNT42 KNHC 181454 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 1100 AM AST SUN SEP 18 2016 The overall appearance of Karl has changed little in satellite imagery since the previous advisory. However, recent water vapor imagery suggest that the strong southwesterly shear that has been plaguing the cyclone for the past few days is beginning to relax. The initial wind speed is held at 35 kt based on a TAFB satellite estimate of T2.5/35 kt. Ship BATFR18, which has been skirting the eastern portion of Karl's circulation the past 12 hours, has reported winds as high as 32 kt. That data has been helpful in determining the extent of the 34-kt wind radius in the northeastern quadrant. Karl has trended westward and the initial motion estimate is now 270/11 kt. A deep-layer subtropical ridge over the central Atlantic to the north of Karl is expected to keep the cyclone moving in a general westward direction for the next 48 hours or so, followed by west-northwestward motion during the remainder of the forecast period. The new NHC track forecast is similar to the previous advisory, and lies close to the various consensus model solutions. Although Karl's convective pattern is currently somewhat disheveled due to the hostile shear and dry mid-level conditions that the cyclone has been encountering the past several days, the surface wind field has remained remarkably robust, including a tight inner-core. The GFS and ECMWF models are forecasting the vertical wind shear to decrease to less than 5 kt from 24-120 hours, which favors a strengthening trend, especially since Karl will be moving 29-30C SSTs during that time. However, only a marginally moist mid-level environment is expected, a condition that could slow down the intensification process. The official intensity forecast follows the trend of the previous advisory, showing gradual strengthening throughout the forecast period, and remains on the conservative side close to the intensity consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 18.0N 43.4W 35 KT 40 MPH 12H 19/0000Z 18.2N 45.5W 35 KT 40 MPH 24H 19/1200Z 18.6N 48.2W 40 KT 45 MPH 36H 20/0000Z 19.3N 50.9W 45 KT 50 MPH 48H 20/1200Z 20.2N 53.3W 50 KT 60 MPH 72H 21/1200Z 22.3N 58.4W 55 KT 65 MPH 96H 22/1200Z 24.7N 63.2W 65 KT 75 MPH 120H 23/1200Z 27.3N 66.7W 75 KT 85 MPH $$ Forecaster Stewart

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Tropical Depression JULIA Forecast Discussion Number 18

2016-09-18 10:50:19| National Hurricane Center (Atlantic)

Issued at 500 AM EDT SUN SEP 18 2016 000 WTNT41 KNHC 180850 TCDAT1 TROPICAL DEPRESSION JULIA DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 500 AM EDT SUN SEP 18 2016 Surprisingly, Julia is attempting a comeback. Thunderstorm activity has fired near and southeast of the center, with the cyclone looking considerably better organized than any time in the last day or so. The initial wind speed is kept at 25 kt in line with the TAFB satellite classification. The future of Julia looks less clear than it did yesterday. While there is currently strong shear affecting the cyclone, this shear is forecast to relax in about 24 hours as a mid- to upper-level trough moves over the southeastern United States. Considering the current appearance of Julia and the more favorable environment ahead of it, Julia is no longer forecast to become a remnant low. Instead, a more likely scenario is that Julia holds its own or strengthens some while it moves slowly northward near the Gulf Stream. It is best to be conservative with the intensity forecast at this stage, since this overnight convective trend could be misleading. Nonetheless, the intensity forecast is raised from the previous one, on the low side of the guidance near the LGEM model. Julia has started moving north-northwestward overnight at about 4 kt. A slow motion toward the north is expected for the next couple of days while the cyclone moves between a weak west Atlantic subtropical ridge and the southeastern United States trough. The model guidance has shifted northward near the North Carolina coast, although the GFDL and ECMWF remain offshore. Given the uncertainty and continuity constraints, it would be preferable to wait another model cycle before making a larger northward change, and hence the current forecast is on the southern side of the guidance envelope. It would not be surprising if further northward changes have to be made later today. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 31.3N 76.7W 25 KT 30 MPH 12H 18/1800Z 31.8N 77.0W 25 KT 30 MPH 24H 19/0600Z 32.4N 77.1W 25 KT 30 MPH 36H 19/1800Z 33.3N 76.9W 30 KT 35 MPH 48H 20/0600Z 33.7N 77.0W 30 KT 35 MPH 72H 21/0600Z 33.5N 77.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 22/0600Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm PAINE Forecast Discussion Number 2

2016-09-18 10:37:47| Tropical Depression LIDIA

Issued at 300 AM MDT SUN SEP 18 2016

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