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Tropical Depression Andres Forecast Discussion Number 7

2021-05-10 22:36:51| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Mon May 10 2021 000 WTPZ41 KNHC 102036 TCDEP1 Tropical Depression Andres Discussion Number 7 NWS National Hurricane Center Miami FL EP012021 300 PM MDT Mon May 10 2021 Hostile environmental conditions are taking a toll on Andres this afternoon. After a small area of convection persisted downshear of the cyclone's partially exposed low-level center earlier today, recent satellite images show rapidly warming cloud tops in the northeast quadrant with no signs of new convection anywhere near the center. Additionally, the low-level center now appears to be completely exposed. Although T2.5 18Z Dvorak classifications were received from SAB and TAFB, recent satellite trends and UW-CIMSS ADT estimates indicate the system has weakened since that time. Therefore, the intensity is lowered to 30 kt with this advisory, making Andres a tropical depression. Andres appeared to take a bit of a northward jog earlier today, but the current estimated motion is 330/06 kt. The weakening, shallow cyclone is expected to turn more west-northwestward and westward on Tuesday and Wednesday under the influence of a building low-level ridge to its north. The latest track forecast is close to the center of the guidance envelope, with just a slight adjustment to the right of track from the previous forecast. An upper-level ridge to the northwest of the cyclone is producing increasing vertical wind shear over Andres. This, combined with some drier mid-level air encroaching on the cyclone from the west, will continue weakening Andres through its dissipation by midweek. Simulated satellite imagery from the GFS and ECMWF suggest the system will struggle to generate any new convection overnight, and this forecast shows Andres becoming a remnant low on Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 16.0N 109.8W 30 KT 35 MPH 12H 11/0600Z 16.5N 110.2W 30 KT 35 MPH 24H 11/1800Z 16.8N 111.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 12/0600Z 17.0N 112.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 12/1800Z 16.9N 113.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 13/0600Z...DISSIPATED $$ Forecaster Reinhart/Cangialosi

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Tropical Storm Andres Forecast Discussion Number 6

2021-05-10 16:48:46| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Mon May 10 2021 000 WTPZ41 KNHC 101448 TCDEP1 Tropical Storm Andres Discussion Number 6 NWS National Hurricane Center Miami FL EP012021 900 AM MDT Mon May 10 2021 Andres continues to battle vertical wind shear this morning. Early visible satellite imagery indicates the broadened circulation of the cyclone is exposed and displaced to the southwest of a recent burst of deep convection. Overall, the convective coverage has noticeably decreased during the past several hours, with warming infrared cloud top temperatures noted where a convective band wrapped around the eastern semicircle overnight. A blend of the objective ADT and SATCON estimates with subjective Dvorak classifications from SAB and TAFB supports holding the initial intensity at 35 kt. Hopefully, scatterometer data will become available this afternoon to better assess the intensity of Andres. The center of the cyclone was adjusted a bit northward this morning based on recent visible imagery, and its estimated motion is now 330/05 kt. A general northwestward motion is expected today as Andres moves around the western edge of a deep-layer subtropical ridge. As the cyclone spins down and becomes more vertically shallow, it should turn more west-northwestward and then westward under the influence of a building low-level ridge to its north. The forecast track has been nudged to the right of the previous forecast to account for the center adjustment, and the new track lies closer to the reliable consensus aids including HCCA. Increasing southwesterly vertical wind shear, along with drier and more stable low- to mid-level air approaching from the west, suggest a weakening trend is imminent. Andres is expected to become a tropical depression later today and then continue weakening through midweek as environmental conditions become increasingly hostile. GFS and ECMWF simulated satellite imagery suggest the cyclone will become devoid of convection by tonight, and so this forecast shows Andres becoming a remnant low by Tuesday morning. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 15.4N 109.4W 35 KT 40 MPH 12H 11/0000Z 15.8N 109.7W 30 KT 35 MPH 24H 11/1200Z 16.1N 110.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 12/0000Z 16.4N 111.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 12/1200Z 16.3N 112.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 13/0000Z 16.2N 113.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 13/1200Z...DISSIPATED $$ Forecaster Reinhart/Pasch

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Tropical Storm Andres Forecast Discussion Number 5

2021-05-10 10:32:41| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Mon May 10 2021 000 WTPZ41 KNHC 100832 TCDEP1 Tropical Storm Andres Discussion Number 5 NWS National Hurricane Center Miami FL EP012021 300 AM MDT Mon May 10 2021 Andres remains a sheared tropical storm with a small ball of deep convection displaced just east of the partially exposed low-level center. All three scatterometer passes missed Andres. The initial intensity remains 35 kt based on consensus subjective Dvorak satellite intensity estimates of T2.5/35 kt from TAFB and SAB, and objective intensity estimates of 37 kt and 35 kt from UW-CIMSS ADT and SATCON, respectively. The initial motion estimate is 325/04 kt. There are no significant changes to the previous track forecast of reasoning. The latest NHC track model guidance continues to show Andres moving slowly northwestward around the western edge of a deep-layer subtropical ridge while gradually weakening and becoming more vertically shallow. The ridge to the north of the cyclone is forecast to strengthen and build westward over the next few days, which is expected to gradually nudge Andres west-northwestward on Tuesday and westward on Wednesday. The new official track forecast is similar to the previous advisory track, and remains along the southern edge of the guidance envelope between the GFS and GFS-ensemble mean models, and the HCCA and GFEX consensus track models. Despite the ragged looking cloud pattern depicted in infrared satellite imagery, night-viz and passive microwave satellite data indicate that the low-level circulation has actually improved a little since the previous advisory. However, the combination of increasing southwesterly vertical wind shear and entrainment of drier and more stable low- to mid-level air from the west and northwest is expected to induce gradual weakening later today. Additional weakening is forecast on Tuesday and Wednesday as Andres moves over cooler sea-surface temperatures, with the cyclone expected to degenerate into a remnant low on Tuesday and dissipate by Thursday. The latest NHC intensity forecast is essentially just and update of the previous advisory, and closely follows a blend of the IVCN and HCCA intensity consensus models. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 14.7N 109.1W 35 KT 40 MPH 12H 10/1800Z 15.2N 109.7W 30 KT 35 MPH 24H 11/0600Z 15.6N 110.3W 30 KT 35 MPH 36H 11/1800Z 15.9N 111.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 12/0600Z 16.0N 112.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 12/1800Z 16.0N 113.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 13/0600Z...DISSIPATED $$ Forecaster Stewart

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Tropical Storm Andres Forecast Discussion Number 3

2021-05-09 22:35:30| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Sun May 09 2021 000 WTPZ41 KNHC 092035 TCDEP1 Tropical Storm Andres Discussion Number 3 NWS National Hurricane Center Miami FL EP012021 300 PM MDT Sun May 09 2021 The convective cloud pattern of Andres is rather ragged-looking at this time, and the system continues to show little evidence of banding features. However the cyclone is producing some very cold cloud tops over the eastern portion of the circulation. A partial scatterometer pass did not show tropical-storm-force winds, but it is believed that these could be occuring in the strong convection to the east of the center. The current intensity estimate remains at 35 kt in agreement with the latest Dvorak estimates from TAFB and SAB. The environment ahead of Andres looks very hostile, with increasing west-southwesterly shear and dry air in the mid- to lower-troposphere. Therefore, a weakening trend should begin tomorrow and the system is likely to degenerate into a remnant low in about 48 hours which is also indicated by the global model guidance. The scatterometer observations showed that the center was somewhat elongated zonally, but it appears to be a little south of the previously estimated track. Andres should move along the southwestern periphery of a mid-level ridge for the next day or so, and then turn westward in 48-60 hours, following the low-level steering flow. The official track forecast is south of much of the model guidance on account of the more southward center location. This is not far from the latest GFS model solution. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 14.0N 108.5W 35 KT 40 MPH 12H 10/0600Z 14.7N 109.1W 35 KT 40 MPH 24H 10/1800Z 15.2N 109.7W 30 KT 35 MPH 36H 11/0600Z 15.6N 110.2W 30 KT 35 MPH 48H 11/1800Z 15.8N 111.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 12/0600Z 15.9N 112.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 12/1800Z 15.9N 113.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 13/1800Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Andres Forecast Discussion Number 2

2021-05-09 16:54:30| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Sun May 09 2021 000 WTPZ41 KNHC 091454 TCDEP1 Tropical Storm Andres Discussion Number 2 NWS National Hurricane Center Miami FL EP012021 900 AM MDT Sun May 09 2021 Although the system lacks well-defined convective banding features, Dvorak intensity estimates from both TAFB and SAB are 35 kt. This is consistent with a data T-number based on a shear pattern with the low-level center displaced within 3/4 degrees to the west of the edge of the main area of deep convection, as suggested by recent microwave imagery. Since earlier scatterometer data indicated that the system was close to tropical storm strength, and given the latest Dvorak analyses, the cyclone is being named. Andres is the earliest tropical storm on record in the eastern North Pacific basin, just beating out Adrian of 2017. Increasing southwesterly to westerly shear and drier air to the west of the cyclone should prevent any significant additional strengthening. The official forecast generally follows the numerical guidance and shows the system degenerating into a remnant low in 48 hours, as in the previous advisory. The initial motion is slowly northwestward, or 325/5. Andres should move along the southwestern side of a low- to mid-level ridge for the next couple of days and turn westward in the low-level flow as an increasingly shallow circulation. The official track forecast is on the southern side of the model guidance suite. This also close to the latest latest corrected consensus, or HCCA, track. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 14.1N 107.9W 35 KT 40 MPH 12H 10/0000Z 14.8N 108.4W 35 KT 40 MPH 24H 10/1200Z 15.4N 108.9W 35 KT 40 MPH 36H 11/0000Z 15.9N 109.5W 30 KT 35 MPH 48H 11/1200Z 16.2N 110.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 12/0000Z 16.5N 111.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 12/1200Z 16.4N 112.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 13/1200Z 16.3N 115.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 14/1200Z...DISSIPATED $$ Forecaster Pasch

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