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Tropical Storm FRED Forecast Discussion Number 15

2015-09-02 16:37:17| National Hurricane Center (Atlantic)

Issued at 1100 AM AST WED SEP 02 2015 000 WTNT41 KNHC 021437 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 1100 AM AST WED SEP 02 2015 Fred has been without deep convection for about 12 hours and consists of a tight swirl of low- to mid-level clouds. The circulation remains fairly strong and the initial wind speed is maintained at 40 kt, which is in agreement with data from a recent ASCAT overpass. If organized deep convection does not return very soon, which appears unlikely, Fred will become a post-tropical cyclone this afternoon. Strong westerly shear, marginal sea surface temperatures, and dry mid-level air should cause the circulation to gradually spin down during the next few days. Very late in the forecast period, the remnant low could be over slightly warmer SSTs and in an area of lower shear. Redevelopment appears unlikely, however, due to a dry and stable air mass over the east-central Atlantic. Fred is moving west-northwestward at about 9 kt. The forecast calls for the cyclone to continue on a west-northwestward heading over the next 72 hours to the south of a low- to mid-level ridge over the eastern Atlantic. After that time, the remnant low is predicted to turn turn northwestward, and then north-northwestward while it moves around the western periphery of a low-level high pressure area centered south of the Azores. The new NHC track forecast is in good agreement with the latest ECMWF, which is along the southern edge of the model envelope. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 19.8N 30.9W 40 KT 45 MPH 12H 03/0000Z 20.2N 32.0W 35 KT 40 MPH...POST-TROPICAL 24H 03/1200Z 20.9N 33.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 04/0000Z 21.5N 35.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 04/1200Z 21.9N 36.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 05/1200Z 22.7N 39.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 06/1200Z 24.2N 41.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 07/1200Z 26.5N 42.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Tropical Depression FOURTEEN-E Forecast Discussion Number 8

2015-09-02 16:36:13| National Hurricane Center (East Pacific)

Issued at 800 AM PDT WED SEP 02 2015 000 WTPZ44 KNHC 021436 TCDEP4 TROPICAL DEPRESSION FOURTEEN-E DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP142015 800 AM PDT WED SEP 02 2015 Enhanced IR and shortwave imagery continues to depict a relatively shapeless, asymmetric, convective mass sheared to the northeast of the surface circulation. Although deep convection has increased somewhat since yesterday, objective and subjective satellite intensity estimates still yield an initial intensity of 30 kt. The global models and the statistical-dynamical intensity guidance are indicating a small window of opportunity during the next 24-36 hours for some strengthening. Through the remaining portion of the period, weakening to a remnant low by day 3 is expected as the cyclone enters a region of high static stability and begins to traverse cooler sea surface temperatures. The official intensity forecast is based on a blend of the IVCN and FSSE forecasts and is quite similar to the previous advisory. A fortuitous 0849 UTC AMSR2 microwave overpass helped immensely in locating the surface center and estimating the current motion of the depression which now appears to be northward or, 350/8 kt. The cyclone should continue moving in this general direction during the next 36 hours or so. After that time, a turn toward the north-northeast is forecast through day 3. By that point in time, the tropical cyclone should degenerate into a shallow swirl of low-level clouds and basically drift within the weak steering flow created by an existing deep-layer trough west of the Baja California peninsula. The NHC forecast continues to follow closely to the multi-model consensus and the GFEX (GFS/ECMWF blend) model. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 16.2N 115.0W 30 KT 35 MPH 12H 03/0000Z 17.2N 115.2W 35 KT 40 MPH 24H 03/1200Z 18.5N 115.4W 35 KT 40 MPH 36H 04/0000Z 19.6N 115.2W 35 KT 40 MPH 48H 04/1200Z 20.6N 114.9W 30 KT 35 MPH 72H 05/1200Z 22.1N 114.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/1200Z 23.1N 115.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 07/1200Z...DISSIPATED $$ Forecaster Roberts

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Tropical Depression FOURTEEN-E Forecast Discussion Number 7

2015-09-02 10:34:10| National Hurricane Center (East Pacific)

Issued at 200 AM PDT WED SEP 02 2015 000 WTPZ44 KNHC 020834 TCDEP4 TROPICAL DEPRESSION FOURTEEN-E DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP142015 200 AM PDT WED SEP 02 2015 Deep convection has increased somewhat during the past few hours, but it is oriented linearly north to south, displaced to the east of the low-level center. Unfortunately ASCAT missed the circulation tonight, and Dvorak final-T numbers from SAB and TAFB were steady or decreased from six hours ago. Therefore, the cyclone is being maintained as a 30-kt depression. The depression is located just to the east of a sharp upper-level trough, which is producing about 15 kt of southwesterly shear over the cyclone. The trough is expected to weaken soon, which should allow the shear to decrease slightly during the next 36 hours. However, dry mid-level air is located just to the west of the depression, and the shear will likely not relax enough to prevent an asymmetric convective pattern. The new NHC intensity forecast continues to show the possibility of the depression reaching tropical storm strength during the next 36 hours, but the peak intensity is a little bit lower than in the previous advisory. An increase in shear after 36 hours should cause deep convection to become significantly displaced from the center, leading to the depression degenerating to a remnant low by day 3. Although the center has still been tough to pinpoint, the depression appears to have turned north-northwestward with an initial motion of 335/9 kt. A subtropical ridge over Mexico and a deep-layer trough west of the Baja California peninsula should steer the depression generally northward through day 3. Once it becomes a shallow remnant low, it will likely meander or drift westward in the low-level flow. There are considerable speed differences between the track models, presumably a result of how soon each depicts the cyclone becoming sheared. The updated NHC track forecast is again a little slower than the previous one and is close to the GFS-ECMWF model consensus. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 15.2N 115.1W 30 KT 35 MPH 12H 02/1800Z 16.4N 115.5W 35 KT 40 MPH 24H 03/0600Z 17.8N 115.9W 35 KT 40 MPH 36H 03/1800Z 18.9N 115.8W 35 KT 40 MPH 48H 04/0600Z 20.0N 115.4W 30 KT 35 MPH 72H 05/0600Z 21.6N 115.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/0600Z 22.6N 115.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 07/0600Z...DISSIPATED $$ Forecaster Berg

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Tropical Depression FOURTEEN-E Forecast Discussion Number 6

2015-09-02 04:43:10| National Hurricane Center (East Pacific)

Issued at 900 PM MDT TUE SEP 01 2015 000 WTPZ44 KNHC 020243 TCDEP4 TROPICAL DEPRESSION FOURTEEN-E DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP142015 900 PM MDT TUE SEP 01 2015 The depression is no better organized than it was earlier today. Satellite imagery shows the cyclone with a couple of loosely organized bands without much curvature over the eastern half of circulation. This assymetric and disorganized cloud pattern is indicative of southwesterly shear induced by a mid- to upper-level tropospheric trough to the northwest of the depression. The initial intensity estimate is 30 kt, based on a blend of the latest Dvorak estimates. A relative reduction in vertical shear is forecast in 24 to 36 hours, when the trough to the west of the depression shears out. All other factors being equal at that time, this should present the cyclone with a limited opportunity for intensification. After 48 hours, the cyclone should meet a harsh environment of very dry air and southwesterly shear associated with an unusually deep trough digging along the U.S. west coast. The global models indicate that the shear should be strong enough that the low- to mid-level circulations separate in about 72 hours, with dissipation by day 5. The intensity guidance has decreased across the board, and the new intensity forecast shows less intensification but still with a peak in 24 to 36 hours. This new forecast, however, is higher than the statistical-dynamical guidance. The depression's center is difficult to locate, but a blend of the latest fixes and a continuity provide an initial motion estimate of 325/08. A south-southeasterly to southerly steering flow between a subtropical ridge over Mexico and the trough to the west should cause the depression to gradually turn northward in 24 to 36 hours. Once the cyclone crosses 20N, strong southwesterly flow ahead of the amplifying western U.S. trough should cause recurvature. However, the decoupling of the system will leave the low-level center behind, moving slowly northeastward. By day 4, the remnant low should drift erratically and then turn southward in the low-level flow until dissipation. The new track forecast is a little slower than the previous one based on a blend of the GFS and ECWMF model solutions. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 14.3N 114.6W 30 KT 35 MPH 12H 02/1200Z 15.7N 115.1W 35 KT 40 MPH 24H 03/0000Z 17.3N 115.5W 40 KT 45 MPH 36H 03/1200Z 18.8N 115.5W 40 KT 45 MPH 48H 04/0000Z 20.1N 115.0W 35 KT 40 MPH 72H 05/0000Z 22.0N 114.2W 25 KT 30 MPH 96H 06/0000Z 22.8N 114.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 07/0000Z...DISSIPATED $$ Forecaster Kimberlain

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Tropical Storm FRED Forecast Discussion Number 13

2015-09-02 04:41:39| National Hurricane Center (Atlantic)

Issued at 1100 PM AST TUE SEP 01 2015 000 WTNT41 KNHC 020241 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 1100 PM AST TUE SEP 01 2015 The deep convection near the center of Fred has decreased during the past few hours, with the low-level center now partially exposed to the west of the convection. An ASCAT-B overpass near 0000 UTC probed the western side of the circulation and showed 40-kt winds near the center. Based on this, the initial intensity remains 45 kt. The initial motion estimate is now 295/11. There is no change to the track forecast philosophy since the previous advisory. Fred should continue moving west-northwestward to the south of a low- to mid-level ridge over the eastern Atlantic during the next 2 to 3 days. Thereafter, the western portion of the ridge is expected to weaken when a trough deepens over the central Atlantic. This evolution should steer Fred or its remnants generally northwestward. There has been little change in the forecast guidance since the last advisory. Based on this, the new forecast track is an update of the previous track through 72 hours and lies just north of the consensus models. After 72 hours, the track has been adjusted westward, but still lies to the east of the center of the guidance envelope as a compromise between the current guidance and the previous forecast. The intensity forecast philosophy remains unchanged. Fred is over sea surface temperatures of about 26 deg C and is about to encounter strong westerly vertical wind shear. In addition, the cyclone is entraining a drier and more stable air mass. This combination should cause weakening over the next several days. The new intensity forecast is unchanged from the previous forecast, and it calls for Fred to weaken to a depression in 30 to 36 hours and degenerate into a remnant low after 48 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 19.4N 29.1W 45 KT 50 MPH 12H 02/1200Z 19.8N 30.3W 40 KT 45 MPH 24H 03/0000Z 20.4N 31.8W 35 KT 40 MPH 36H 03/1200Z 21.0N 33.3W 30 KT 35 MPH 48H 04/0000Z 21.4N 34.9W 30 KT 35 MPH 72H 05/0000Z 22.0N 38.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/0000Z 23.0N 41.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 07/0000Z 25.0N 43.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven

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