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Tropical Depression Nineteen Forecast Discussion Number 3

2017-11-06 21:31:46| National Hurricane Center (Atlantic)

Issued at 500 PM AST Mon Nov 06 2017 000 WTNT44 KNHC 062031 TCDAT4 Tropical Depression Nineteen Discussion Number 3 NWS National Hurricane Center Miami FL AL192017 500 PM AST Mon Nov 06 2017 The depression has changed little in structure during the past several hours. The low-level center remains exposed to the west of the main area of deep convection due to the influence of westerly shear and dry air. The initial intensity is held at 30 kt based on the earlier ASCAT data and a Dvorak classification of 2.0/30 kt from TAFB. Satellite fixes indicate that the system has been moving slowly and erratically during the past 6 to 12 hours. Smoothing through the wobbles yields an initial motion of 020/5 kt. The combined influences of a mid-level ridge to the east of the depression and a shortwave trough to its west should cause the system to move progressively faster toward the north or north-northeast during the next couple of days. Beyond that time, an even faster northeastward motion is expected when the system becomes embedded in the mid- latitude westerlies. The latest track guidance is notably slower than the previous cycles, and the new NHC track forecast has been adjusted in that direction. The cyclone is expected to remain in an environment of moderate westerly shear while it moves toward cooler waters. Although these conditions typically would not favor strengthening, the models do show the depression deepening during the next couple of days, likely due to some baroclinic forcing and the expected increase in forward speed of the system. The cyclone will likely complete extratropical transition Wednesday night or early Thursday when it merges with a cold front. Overall the intensity guidance has changed little this cycle, and no change was made to the previous NHC intensity prediction. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 29.9N 50.0W 30 KT 35 MPH 12H 07/0600Z 31.4N 49.8W 35 KT 40 MPH 24H 07/1800Z 34.2N 49.3W 40 KT 45 MPH 36H 08/0600Z 37.6N 48.4W 45 KT 50 MPH 48H 08/1800Z 41.1N 46.6W 50 KT 60 MPH 72H 09/1800Z 48.8N 37.4W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 10/1800Z 56.0N 14.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 11/1800Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Depression Nineteen Forecast Discussion Number 2

2017-11-06 15:37:04| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Mon Nov 06 2017 000 WTNT44 KNHC 061433 TCDAT4 Tropical Depression Nineteen Discussion Number 2 NWS National Hurricane Center Miami FL AL192017 1100 AM AST Mon Nov 06 2017 The depression has a sheared appearance with the low-level center exposed to the west of the mid-level center and the convective bands. A very recent ASCAT-B overpass indicated that maximum winds are near 30 kt, which is also in agreement with a Dvorak classification from TAFB. Based on these data, the initial wind speed is held at 30 kt. The depression has slowed down and turned to the left, with the initial motion estimated to be 015/3 kt. A faster north to north-northeast motion is expected during the next couple of days while the system moves in the flow on the west side of a mid-level ridge. Thereafter, an even faster motion toward the northeast is forecast when the cyclone becomes embedded in the mid-latitude westerlies. The model guidance is in good agreement, and the NHC track forecast is nudged to the west of the previous one to come into agreement with the latest consensus models. Although the environment ahead of the depression is not expected to be particularly conducive for strengthening as a tropical system, baroclinic enhancements and the expected faster forward speed should cause the cyclone to gain some strength during the next couple of days. The global models agree that the cyclone should merge with a cold front by Wednesday evening, causing extratropical transition. The extratropical cyclone is expected to gradually weaken and dissipate in 4 to 5 days. The guidance has trended a little higher this cycle, and the NHC intensity forecast follows that trend and lies near the IVCN and HCCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 29.5N 50.4W 30 KT 35 MPH 12H 07/0000Z 30.8N 50.2W 35 KT 40 MPH 24H 07/1200Z 33.6N 49.8W 40 KT 45 MPH 36H 08/0000Z 37.3N 49.0W 45 KT 50 MPH 48H 08/1200Z 41.4N 46.6W 50 KT 60 MPH 72H 09/1200Z 51.0N 33.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 10/1200Z 57.0N 14.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 11/1200Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Depression Nineteen Forecast Discussion Number 1

2017-11-06 09:49:33| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Nov 06 2017 000 WTNT44 KNHC 060849 TCDAT4 Tropical Depression Nineteen Discussion Number 1 NWS National Hurricane Center Miami FL AL192017 500 AM AST Mon Nov 06 2017 GOES-16 night-time visible and infrared satellite imagery indicate that convection associated with the well-defined low pressure system located over the central Atlantic Ocean has increased and become better organized during the past several hours. Satellite intensity estimates were T1.5/25 kt from both TAFB and SAB at 0600Z. Since that time, however, a burst of deep convection has developed over the previously partially exposed low-level circulation center, which had been located near the northwestern edge of the large convective cloud mass. Given that the center is now located farther into the deep convection, NHC objective intensity estimates have increased to more than 30 kt. As a result, advisories have been initiated on the nineteenth tropical depression of the 2017 Atlantic hurricane season. The initial motion estimate is 095/05 kt. The center of the cyclone has been moving slowly eastward within the larger cyclonic gyre for the past 12-18 hours, most likely due to the deep convection being sheared toward the east. However, the latest NHC model guidance indicates that the recent eastward motion should be short-lived since the larger gyre is forecast to begin moving northward within the next 6 h or so. As the wind field contracts over the next 24 hours, the motion of the cyclone should stabilize and become less erratic as deep-layer southerly steering flow becomes established on the west side of a large-scale subtropical ridge. By 48 h and beyond, southwesterly flow ahead of mid-latitude trough is forecast to accelerate the system toward the northeast through 96 h. By 120 h, the cyclone should have merged with a frontal system or have dissipated over the cold waters of the far north Atlantic. The official track forecast lies close to a blend of the TVCN, TVCX, and GFEX consensus track models. The cyclone is currently embedded within a low-shear environment in the col region between a weakening upper-level low located to the southeast and a trough to the northwest. The vertical wind shear is forecast by the GFS and ECMWF models to remain relatively low for the next 36 h or so, which should allow for some modest strengthening to occur despite sea-surface temperatures only being around 25-26 deg C. Temperatures of 2-3 deg C colder-than-normal in the mid- and upper-levels of the troposphere, however, should act to offset the cooler SSTs, providing sufficient instability to allow for deep convection to continue to develop. Model soundings and the FSU Cyclone Phase-Space diagram indicate that extratropical transition should begin shortly after 48 h when the cyclone reaches about 40N latitude and moves over much cooler water. The NHC intensity closely follows the HCCA and IVCN consensus models. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 28.9N 50.2W 30 KT 35 MPH 12H 06/1800Z 30.0N 49.9W 35 KT 40 MPH 24H 07/0600Z 32.0N 49.6W 40 KT 45 MPH 36H 07/1800Z 35.4N 49.4W 45 KT 50 MPH 48H 08/0600Z 39.4N 48.2W 45 KT 50 MPH 72H 09/0600Z 49.0N 38.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 10/0600Z 59.0N 15.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 11/0600Z...DISSIPATED $$ Forecaster Stewart

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Transcribed Discussion Notes

2017-10-30 23:21:29| PortlandOnline

Minutes from the October 14, 2017 listening session PDF Document, 713kbCategory: October 14, 2017 Listening and Learning Session

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Remnants of Philippe Forecast Discussion Number 9

2017-10-29 21:32:34| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Sun Oct 29 2017 000 WTNT43 KNHC 292032 TCDAT3 Remnants Of Philippe Discussion Number 9 NWS National Hurricane Center Miami FL AL182017 500 PM EDT Sun Oct 29 2017 During the past few hours, strong vertical wind shear in excess of 50 kt, plus merger with a cold front, has taken its toll on Philippe's previously well-defined low-level circulation. The system has become elongated north-to-south within the frontal zone, and a new low-level center may have developed about 150 nmi farther north along the frontal boundary near NOAA buoy 41002. Now that Philippe has lost any tropical or subtropical characteristics due to merger with a synoptic-scale cold front, the system is declared to have dissipated. Much of the latent heat and deep convection associated with Philippe's remnants will likely be drawn into a larger extratropical low pressure that is developing near the outer banks of North Carolina, aiding in that intensification process. Although the developing powerful low near the Outer Banks is not directly associated with Philippe, interests along the mid-Atlantic and southern New England coasts should closely monitor forecast products issued by the NOAA Weather Prediction Center, NOAA Ocean Prediction Center, and your local National Weather Service forecast office. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 31.0N 75.0W 50 KT 60 MPH 12H 30/0600Z...ABSORBED BY FRONTAL SYSTEM $$ Forecaster Stewart

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