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Tropical Storm ULIKA Forecast Discussion Number 7

2016-09-28 04:33:58| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE SEP 27 2016 000 WTPZ44 KNHC 280233 TCDEP4 TROPICAL STORM ULIKA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192016 800 PM PDT TUE SEP 27 2016 Ulika continues to maintain a small but well organized central dense overcast. Geostationary satellite images indicate that the inner core of the cyclone has become a little better organized during the last several hours, and there are some hints of an eye feature in the imagery. An ASCAT-B pass from several hours ago revealed maximum winds in the 50 to 55 kt range. Based on that data and a Dvorak classification from TAFB, the initial wind speed is increased to 55 kt. Ulika is expected to remain in generally favorable environmental conditions for another 12 to 24 hours, and the system could be near hurricane strength overnight and early Wednesday. Beyond that time, a significant increase in southwesterly or westerly shear should cause a steady weakening trend. Ulika is forecast to become a remnant low in about 4 days, but some of the models suggest that the system could open up into a trough by then. This intensity forecast is largely an update of the previous one. Ulika is moving northeastward at about 6 kt on the east side of a mid- to upper-level low. The upper low is expected to move slowly westward, which should cause the storm to turn northward on Wednesday and northwestward on Thursday. After that time, Ulika is expected to become a shallow cyclone, and it will likely turn west-northwestward or westward in the low-level trade wind flow. The models are in fair agreement on this overall scenario, and only a small shift to the right was made in the new NHC track forecast. This prediction is in best agreement with the latest consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 13.3N 139.1W 55 KT 65 MPH 12H 28/1200Z 14.2N 138.8W 60 KT 70 MPH 24H 29/0000Z 15.1N 138.7W 60 KT 70 MPH 36H 29/1200Z 15.9N 139.1W 50 KT 60 MPH 48H 30/0000Z 16.5N 139.6W 45 KT 50 MPH 72H 01/0000Z 17.5N 142.0W 35 KT 40 MPH 96H 02/0000Z 17.7N 146.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 03/0000Z 17.9N 150.2W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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Tropical Storm ROSLYN Forecast Discussion Number 9

2016-09-27 16:39:30| National Hurricane Center (East Pacific)

Issued at 800 AM PDT TUE SEP 27 2016 000 WTPZ43 KNHC 271439 TCDEP3 TROPICAL STORM ROSLYN DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182016 800 AM PDT TUE SEP 27 2016 Roslyn continues to be affected by strong southwesterly shear, with the center of the tropical cyclone exposed to the southwest of the associated deep convection. The initial intensity remains 40 kt for this advisory, which is an average of Dvorak estimates of 45 kt and 35 kt, from TAFB and SAB, respectively. Roslyn should slowly weaken due to increasing southwesterly shear, gradually decreasing SSTs, and dry mid-level air that is wrapping around the western portion of the circulation. The updated NHC intensity forecast is unchanged from the previous advisory and calls for Roslyn to become a remnant low in 36 hours, and dissipate in 3 to 4 days. Recent satellite fixes indicate that Roslyn is moving northeastward or 045/7 kt. The tropical storm is forecast to turn northward by tonight around the eastern portion of a mid- to upper-level trough extending southwestward from a large cut-off low over northwestern Mexico. By late Wednesday, a weaker and more vertically shallow Roslyn is expected to turn northwestward. There is more spread in the track models this morning, but little change was required to the NHC forecast which is located near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 18.3N 117.3W 40 KT 45 MPH 12H 28/0000Z 19.3N 116.9W 35 KT 40 MPH 24H 28/1200Z 20.6N 116.7W 30 KT 35 MPH 36H 29/0000Z 21.8N 117.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 29/1200Z 22.6N 118.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 30/1200Z 23.5N 120.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 01/1200Z...DISSIPATED $$ Forecaster Brown

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Tropical Depression NINETEEN-E Forecast Discussion Number 2

2016-09-26 23:38:56| National Hurricane Center (East Pacific)

Issued at 200 PM PDT MON SEP 26 2016 000 WTPZ44 KNHC 262138 CCA TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 2...CORRECTED NWS NATIONAL HURRICANE CENTER MIAMI FL EP192016 200 PM PDT MON SEP 26 2016 CORRECTED NINETEEN TO NINETEEN-E The depression's cloud pattern is a little less organized than it was earlier today. Visible satellite imagery shows the low-level center near the western edge of a small mass of deep convection whose convective tops have warmed, presumably due to some northwesterly shear. Dvorak satellite classifications are T2.0 and T2.5 from SAB and TAFB, respectively. The initial intensity estimate is held at 30 kt, on the lower end of these values. The large-scale factors influencing the intensity of the depression over the next few days are less conducive than previously assessed. Even though the cyclone will be moving over waters around 28 deg C and will encounter an increasingly diffluent flow aloft, some west- northwesterly shear is forecast to persist. A marginally moist environment surrounding the tropical cyclone is also forecast to dry further. The NHC intensity forecast is reduced some over the previous one in line with the current guidance and much below the dynamical guidance. Once the cyclone gains enough latitude in 3 to 4 days, westerly shear of 30 to 40 kt is expected to reduce the system to a remnant low. The cyclone's heading has been more westerly than previously estimated, and a longer-term average of satellite fixes yields an initial motion estimate of 285/05. Global models show the cyclone turning abruptly northward within the next 24 hours and then north- northeastward as it rotates around a mid-tropospheric cyclone slowly retrograding near 18N 140W. When the cyclone decouples in 3 to 4 days, a turn toward the west is likely as the remnant low is steered by the low-level trade wind flow. The new track forecast is shifted toward the left of the previous track because of the more westerly initial motion and lies well west of the multi-model consensus, closest to the leftmost ECMWF model. The next advisory will be issued issued by the Central Pacific Hurricane Center. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 11.6N 140.4W 30 KT 35 MPH 12H 27/0600Z 12.3N 140.3W 35 KT 40 MPH 24H 27/1800Z 13.0N 140.0W 40 KT 45 MPH 36H 28/0600Z 13.9N 139.3W 45 KT 50 MPH 48H 28/1800Z 15.0N 139.1W 45 KT 50 MPH 72H 29/1800Z 16.3N 139.5W 40 KT 45 MPH 96H 30/1800Z 17.1N 141.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/1800Z 17.2N 144.4W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Kimberlain

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Tropical Storm ROSLYN Forecast Discussion Number 6

2016-09-26 22:48:46| National Hurricane Center (East Pacific)

Issued at 200 PM PDT MON SEP 26 2016 000 WTPZ43 KNHC 262048 CCA TCDEP3 TROPICAL STORM ROSLYN DISCUSSION NUMBER 6...CORRECTED NWS NATIONAL HURRICANE CENTER MIAMI FL EP182016 200 PM PDT MON SEP 26 2016 CORRECTED STATUS AT 72H Although the center of Roslyn has become farther separated from the deep convection this afternoon due to strong southwesterly shear, recent ASCAT data indicate that the tropical cyclone is stronger than previously estimated. The 1756 UTC ASCAT overpass revealed 40-45 kt winds, and a much larger area of 34-kt winds than analyzed earlier. Based on these data, the initial intensity has been set at 45 kt, and the 34-kt wind radii have been expanded accordingly. Increasing southwesterly vertical wind shear and gradually decreasing SSTs should cause weakening, but given the large size of the system the spindown process is likely to be more gradual than average. In 24 to 36 hours, much cooler waters and a more stable airmass are expected to cause Roslyn to degenerate into a remnant low and to dissipate in 3 to 4 days. The NHC intensity forecast has been adjusted upward in the early portion of the forecast to account for the higher initial intensity, but is unchanged thereafter. The official forecast shows a slower rate of decay than the SHIPS guidance, but it is general agreement with the trend in the global models. Roslyn has not moved much during the past 24 hours, and the best estimate of the initial motion is 035/2 kt. The models insist that Roslyn will begin moving northeastward within deep layer southwesterly flow between a mid-level ridge to the southeast and a large upper-level low over Baja California. In a couple of days, the cyclone should turn northward, then northwestward once it weakens and is steered by the low-level flow. The new NHC track is similar to the previous advisory and is near a consensus of the ECMWF and GFS models. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 16.8N 118.8W 45 KT 50 MPH 12H 27/0600Z 17.3N 118.4W 40 KT 45 MPH 24H 27/1800Z 18.4N 117.7W 35 KT 40 MPH 36H 28/0600Z 19.8N 117.3W 30 KT 35 MPH 48H 28/1800Z 21.2N 117.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 29/1800Z 23.3N 118.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 30/1800Z...DISSIPATED $$ Forecaster Brown

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Tropical Depression NINETEEN-E Forecast Discussion Number 1

2016-09-26 16:45:18| National Hurricane Center (East Pacific)

Issued at 800 AM PDT MON SEP 26 2016 000 WTPZ44 KNHC 261445 TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192016 800 AM PDT MON SEP 26 2016 Scatterometer data from around 0600 UTC indicated that the area of low pressure located near 140W had a well-defined circulation, with peak reliable wind vectors of 28 kt. Deep convection associated with this system has since become much better organized. Satellite classifications are T2.0 and T2.5, and the low is designated as a tropical depression based on these satellite data. Light northwesterly shear, warm waters of around 28 deg C and an increasingly diffluent flow aloft over the cyclone support intensification during the next 2 to 3 days. The large divergence expected over the depression is related to a mid-level cyclone seen in water vapor imagery near 18N 140W that is forecast to retrograde. The only negative factor is marginal mid-level moisture that is forecast to decrease further. Once the system gains sufficient latitude after 72 hours, it is likely to become vulnerable to much stronger westerly flow aloft. In fact, with 30 to 40 kt of westerly shear forecast over the cyclone by day 4, rapid weakening should occur, and the system is forecast to be a remnant low by that time. The NHC intensity forecast is a blend of the statistical and dynamical guidance through 72 hours and is below both sets of output after that time. The low was moving just south of due west during the last 24 hours, but appears to have recently turned toward the northwest. Given the sudden change in heading, the initial motion estimate of 305/04 is rather uncertain. Global models show the cyclone turning northward within 24 hours and then moving north-northeastward after that for the next few days while it rotates around the mid-level low to the northwest of the cyclone. Once the cyclone weakens appreciably after 72 hours, a turn toward the west is likely when the remnant low is steered by the trade wind flow. The NHC track forecast is a left of the multi-model consensus, close to a consensus without the GFDL model. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 11.6N 139.6W 30 KT 35 MPH 12H 27/0000Z 12.0N 139.8W 40 KT 45 MPH 24H 27/1200Z 12.8N 139.5W 45 KT 50 MPH 36H 28/0000Z 13.6N 138.8W 50 KT 60 MPH 48H 28/1200Z 14.4N 138.2W 55 KT 65 MPH 72H 29/1200Z 16.1N 138.0W 50 KT 60 MPH 96H 30/1200Z 17.2N 139.5W 35 KT 40 MPH...POST-TROP/REMNT LOW 120H 01/1200Z 17.3N 142.3W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Kimberlain

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