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Post-Tropical Cyclone IAN Forecast Discussion Number 17
2016-09-16 16:54:45| National Hurricane Center (Atlantic)
Issued at 1100 AM AST FRI SEP 16 2016 000 WTNT45 KNHC 161454 TCDAT5 POST-TROPICAL CYCLONE IAN DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016 1100 AM AST FRI SEP 16 2016 Ian has transitioned into an extratropical low this morning. Any of the remaining weak-to-moderate convection is the northern side of the circulation, with cold air wrapping into the center of the cyclone as it is overtaken by a cold front. The initial intensity of 55 kt is based on ASCAT data. Ian should move quickly northeastward and gradually weaken before a larger extratropical low absorbs it in about 2 days. The track, intensity, and wind radii forecasts are based largely on guidance from the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 48.8N 36.2W 55 KT 65 MPH...POST-TROP/EXTRATROP 12H 17/0000Z 54.0N 30.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 17/1200Z 59.5N 22.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 18/0000Z 64.5N 14.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 18/1200Z...DISSIPATED $$ Forecaster Blake
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Tropical Storm KARL Forecast Discussion Number 9
2016-09-16 16:52:09| National Hurricane Center (Atlantic)
Issued at 1100 AM AST FRI SEP 16 2016 000 WTNT42 KNHC 161451 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 1100 AM AST FRI SEP 16 2016 Karl remains a sheared tropical cyclone this morning with all of its deep convection in the northeastern quadrant due to shear related to its interaction with a mid- to upper-level trough. The initial wind speed is kept at 40 kt for this advisory, a compromise between lower Dvorak estimates and higher, but noisy, scatterometer values. Vertical shear is expected to decrease in about 36 hours, and, despite a somewhat dry environment, warming sea surface temperatures should allow for at least gradual strengthening. The intensity models continue to trend higher at the end of the forecast period, and the official forecast follows this trend. This forecast is remains close to the SHIPS and LGEM models. The center of Karl has become a little distorted due to the shear and convection, but it still seems to be moving about 280/11. Karl is forecast to turn more to the west and south-of-west this weekend as the subtropical ridge strengthens to the north of the cyclone. However, the current interaction of Karl with the mid- to upper-level trough has not been well forecast, and Karl probably will not get as far to the south as expected yesterday. In a few days, the storm should move to the west-northwest and eventually more to northwest around day 5 as it reaches the edge of the ridge. The new forecast is close to a blend of the ECMWF and GFS, plus their respective ensemble means, ending up a little north of the previous NHC prediction at long range. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 18.4N 34.3W 40 KT 45 MPH 12H 17/0000Z 18.5N 36.2W 40 KT 45 MPH 24H 17/1200Z 18.4N 38.8W 40 KT 45 MPH 36H 18/0000Z 17.9N 41.5W 40 KT 45 MPH 48H 18/1200Z 17.7N 44.0W 45 KT 50 MPH 72H 19/1200Z 18.3N 49.0W 50 KT 60 MPH 96H 20/1200Z 20.0N 54.0W 60 KT 70 MPH 120H 21/1200Z 22.5N 58.5W 70 KT 80 MPH $$ Forecaster Blake
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Tropical Storm ORLENE Forecast Discussion Number 23
2016-09-16 16:51:05| National Hurricane Center (East Pacific)
Issued at 800 AM PDT FRI SEP 16 2016 000 WTPZ41 KNHC 161450 TCDEP1 TROPICAL STORM ORLENE DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL EP162016 800 AM PDT FRI SEP 16 2016 Convection associated with Orlene has decreased significantly during the past six hours, with only a small area of shower activity remaining southwest of the center. The initial intensity is reduced to 40 kt based on various satellite intensity estimates and continuity from the previous advisory. A combination of marginal sea surface temperatures and entrainment of very dry air should cause continued weakening through the forecast period even though Orlene is in a light vertical shear environment. The intensity forecast calls for the cyclone to weaken to a tropical depression in about 24 hours and degenerate to a remnant low in about 48 hours. If the convection does not return, both of these events could happen earlier. The initial motion is 270/10. A low- to mid-level ridge to the north of Orlene should steer it generally westward for 72 hours or so, followed by a northwestward motion as the remnants approach a weakness in the ridge. The new forecast track is similar to the previous track and close to the tightly clustered dynamical and consensus models. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 19.8N 125.9W 40 KT 45 MPH 12H 17/0000Z 19.8N 127.5W 35 KT 40 MPH 24H 17/1200Z 19.8N 129.6W 30 KT 35 MPH 36H 18/0000Z 19.9N 132.1W 25 KT 30 MPH 48H 18/1200Z 20.0N 134.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 19/1200Z 20.5N 139.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 20/1200Z 22.5N 142.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 21/1200Z...DISSIPATED $$ Forecaster Beven
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Tropical Storm JULIA Forecast Discussion Number 11
2016-09-16 16:41:08| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT FRI SEP 16 2016 000 WTNT41 KNHC 161440 TCDAT1 TROPICAL STORM JULIA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 1100 AM EDT FRI SEP 16 2016 Julia continues to feel the impact of 25 to 35 kt of westerly vertical wind shear, as the main deep convection remains about 40 to 60 n mi east of the low-level center. Various subjective and objective satellite intensity estimates are near 35 kt, and that remains the initial intensity. It is noted that buoy 41002 located about 55 n mi northeast of the center is reporting winds of less than 30 kt, so it is possible that initial intensity is a little generous. There is decreasing confidence in the intensity forecast. While Julia is expected to stay in a strong shear environment for the next 60 hours or so, the dynamical models suggest that the upper-level winds over the cyclone may be less than forecast yesterday. After 60 hours, all guidance suggests that the shear should decrease, and at that time the Canadian and UKMET models show re-intensification. On the other hand, the GFS and ECMWF forecast Julia to continue to weaken even in the more favorable upper-level winds. The new intensity forecast stays with the scenario of the previous forecast in calling for the shear to cause the cyclone's demise. However, this forecast is on the low edge of the intensity guidance, and the chances that Julia will survive and re-intensify are higher than they were 24 hours ago. Julia continues to move erratically east-southeastward with an initial motion of 105/6. The cyclone is expected to meander for the next 2 days or so in weak steering flow. In 3-4 days, a mid- to upper-level trough moving into the northeastern United States should steer the cyclone or its remnants northeastward. There remains a considerable amount of uncertainty in the track forecast due somewhat to the uncertainties in the intensity. A weaker Julia should be slower to move northeastward as shown by the GFS and ECMWF, while a stronger Julia will move somewhat more quickly toward the northeast as shown by the Canadian. Overall, the new forecast track goes with the slower scenario and and is an update of the previous track. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 31.1N 75.6W 35 KT 40 MPH 12H 17/0000Z 30.9N 75.4W 35 KT 40 MPH 24H 17/1200Z 30.8N 75.5W 30 KT 35 MPH 36H 18/0000Z 30.9N 75.9W 30 KT 35 MPH 48H 18/1200Z 31.2N 76.1W 30 KT 35 MPH 72H 19/1200Z 32.5N 76.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 20/1200Z 33.0N 74.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 21/1200Z...DISSIPATED $$ Forecaster Beven
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Tropical Storm JULIA Forecast Discussion Number 10
2016-09-16 10:40:25| National Hurricane Center (Atlantic)
Issued at 500 AM EDT FRI SEP 16 2016 000 WTNT41 KNHC 160839 TCDAT1 TROPICAL STORM JULIA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 500 AM EDT FRI SEP 16 2016 Deep convection continues to burst 60 to 70 n mi east of the center of Julia and is then pushed farther to the east by 25 to 30 kt of westerly shear affecting the cyclone. The initial intensity is held at 35 kt based on the latest Dvorak estimate from TAFB, and this could be a little generous. The shear will remain strong for the next 2-3 days, and the cyclone is expected to remain in a dry mid-level environment, which should result in a gradual spin down to remnant low status. The new NHC forecast is similar to the previous one and reflects this thinking. Julia has been moving southeastward tonight, and the initial motion estimate is 135/04. The cyclone is expected to meander erratically for the next 2-3 days in weak steering flow, while late in the period the remnant low should begin to move northeastward. Not surprisingly, the track model guidance shows a lot of spread in the direction of motion and the forward speed, so the uncertainty in the track forecast remains large. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 31.1N 76.4W 35 KT 40 MPH 12H 16/1800Z 30.8N 76.3W 35 KT 40 MPH 24H 17/0600Z 30.9N 76.3W 30 KT 35 MPH 36H 17/1800Z 31.0N 76.3W 30 KT 35 MPH 48H 18/0600Z 31.2N 76.8W 30 KT 35 MPH 72H 19/0600Z 32.0N 76.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 20/0600Z 32.5N 75.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 21/0600Z...DISSIPATED $$ Forecaster Brennan
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