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Tropical Storm Kevin Forecast Discussion Number 8
2021-08-09 10:36:43| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Mon Aug 09 2021 320 WTPZ41 KNHC 090836 TCDEP1 Tropical Storm Kevin Discussion Number 8 NWS National Hurricane Center Miami FL EP112021 300 AM MDT Mon Aug 09 2021 Kevin is a sheared tropical cyclone. Satellite imagery indicates the low-level center lies near the edge of the dense overcast, which has a sharp border in the northeastern quadrant of the cyclone. The associated deep convection is displaced well to the southwest of Kevin's partially exposed center. Recent scatterometer data only show 25 to 30-kt winds near the center, but the full southwestern quadrant where the most intense convection is occurring was not sampled. The initial intensity is lowered to 45 kt for this advisory, in best agreement with the subjective final Dvorak T-numbers from TAFB and SAB. This estimate could still be generous, however. The cyclone has turned west-northwestward during the past 12 h, and its estimated motion is now 290/6 kt. The track forecast reasoning is unchanged, as Kevin is expected to move west-northwestward for most of the forecast period along the southwestern periphery of a mid-level ridge. The official NHC track forecast has been adjusted a bit northward again this cycle, following the trend of the latest multi-model consensus aids. Although Kevin has been embedded within a favorable thermodynamic environment, 15 to 20 kt of northeasterly shear has thus far limited its rate of strengthening. This shear is expected to persist for the next couple of days, so it seems likely that Kevin will continue to struggle intensifying, despite warm SSTs and a moist, unstable environment. By the time the vertical wind shear diminishes, Kevin will have gained enough latitude that the underlying SSTs will be unfavorable for further strengthening. The new intensity guidance is much lower than previous cycles, and so the latest NHC intensity forecast has been reduced by 5 to 10 kt at all forecast hours. Thus, Kevin is no longer forecast to become a hurricane. By day 5, the system is expected to become a post-tropical remnant low over sub-22 deg C waters. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 16.3N 110.9W 45 KT 50 MPH 12H 09/1800Z 16.8N 111.9W 50 KT 60 MPH 24H 10/0600Z 17.6N 113.3W 50 KT 60 MPH 36H 10/1800Z 18.4N 115.0W 55 KT 65 MPH 48H 11/0600Z 19.2N 116.5W 55 KT 65 MPH 60H 11/1800Z 20.1N 118.2W 50 KT 60 MPH 72H 12/0600Z 21.0N 120.2W 45 KT 50 MPH 96H 13/0600Z 22.5N 124.5W 30 KT 35 MPH 120H 14/0600Z 24.0N 129.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Reinhart/Pasch
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Tropical Storm Kevin Forecast Discussion Number 7
2021-08-09 04:34:11| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Sun Aug 08 2021 000 WTPZ41 KNHC 090234 TCDEP1 Tropical Storm Kevin Discussion Number 7 NWS National Hurricane Center Miami FL EP112021 900 PM MDT Sun Aug 08 2021 Satellite images indicate that Kevin has been relatively steady in strength over the past several hours. Deep convection is most organized near the center and over the western half of the circulation, with microwave images showing the center partially exposed. This asymmetric cloud pattern is due to about 15 kt of northeasterly wind shear. The Dvorak classifications from TAFB, SAB, and CIMSS at the University of Wisconsin are largely unchanged and range from 45 to 55 kt, and based on that data the initial intensity is once again held at 50 kt. Kevin is moving westward at a relatively slow pace of 7 kt. There has been little change in the track forecast rationale. A general west-northwestward motion is expected during the next several days as Kevin moves in the flow on the southwest side of a mid-level ridge. The track models have trended a little to the north this cycle, and the NHC track forecast has been nudged in that direction. Despite being over warm 29 degree C waters and embedded in a moist air mass, northeasterly shear has limited the amount of strengthening during the past day or so. Since the shear is expected to continue, Kevin is only forecast to strengthen slowly during the next day or two. After that time, however, progressively cooler waters and a more stable environment should cause a gradual decay. The NHC intensity forecast is a little lower than the previous one, following the HCCA and IVCN consensus aids. The cyclone will likely become a remnant low by the end of the forecast period when it is expected to be over cool 22 C waters. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 16.0N 110.3W 50 KT 60 MPH 12H 09/1200Z 16.4N 111.3W 55 KT 65 MPH 24H 10/0000Z 17.2N 112.7W 60 KT 70 MPH 36H 10/1200Z 18.0N 114.4W 65 KT 75 MPH 48H 11/0000Z 18.7N 115.8W 65 KT 75 MPH 60H 11/1200Z 19.6N 117.5W 60 KT 70 MPH 72H 12/0000Z 20.6N 119.6W 50 KT 60 MPH 96H 13/0000Z 22.1N 123.5W 40 KT 45 MPH 120H 14/0000Z 23.5N 128.1W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi
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Tropical Storm Kevin Forecast Discussion Number 6
2021-08-08 22:35:07| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Sun Aug 08 2021 000 WTPZ41 KNHC 082034 TCDEP1 Tropical Storm Kevin Discussion Number 6 NWS National Hurricane Center Miami FL EP112021 300 PM MDT Sun Aug 08 2021 The earlier burst of deep convection almost completely dissipated, leaving the core of the low-level circulation briefly exposed. However, over the past couple of hours new convection has redeveloped over the center of Kevin. This disruption, possibly aided by moderate northeasterly shear, put a temporary pause on the cyclone's strengthening. The latest Dvorak T-numbers from TAFB and SAB have decreased to 3.0 (45 kt), while the CI-values remain at 3.5 (55 kt). Based on a blend of these numbers, the estimated initial advisory intensity remains 50 kt. Kevin is forecast to remain over warm waters while embedded in a moist and unstable atmospheric environment for the next 48 h or so. The main inhibiting factor for intensification is the persistent vertical wind shear, which is forecast to persist for the next few days. Kevin is forecast by all of the intensity guidance to overcome this shear, and slowly strengthen over the next two days. After 60 h, Kevin should begin to move over decreasing SSTs and into a more stable atmospheric environment, which should cause the cyclone to steadily weaken. By 120 h, the system is forecast to be over waters of less than 23 degrees C, likely causing the cyclone to become devoid of deep convection. The only notable change in the latest NHC forecast from the previous one was to introduce the mention of the system as post-tropical by day 5. Otherwise, the latest forecast remains near the IVCN consensus aid. Kevin continues to move westward, or 270/7 kt. There is no change to the forecast track reasoning. A mid- to upper-level trough west of the Baja California peninsula is expected to weaken the western portion of the ridge that is currently steering Kevin westward. This should cause the cyclone to turn west-northwestward overnight and this west-northwestward heading is then expected to continue for the remainder of the forecast period. The latest track guidance is in very good agreement on this scenario, and the NHC track forecast is little changed from the previous one. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 15.8N 109.7W 50 KT 60 MPH 12H 09/0600Z 16.0N 110.8W 55 KT 65 MPH 24H 09/1800Z 16.6N 112.0W 60 KT 70 MPH 36H 10/0600Z 17.3N 113.5W 65 KT 75 MPH 48H 10/1800Z 18.1N 115.0W 70 KT 80 MPH 60H 11/0600Z 19.0N 116.8W 65 KT 75 MPH 72H 11/1800Z 19.8N 118.4W 60 KT 70 MPH 96H 12/1800Z 21.5N 122.3W 50 KT 60 MPH 120H 13/1800Z 23.0N 126.8W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Latto
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Tropical Storm Kevin Forecast Discussion Number 4
2021-08-08 10:39:33| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Sun Aug 08 2021 000 WTPZ41 KNHC 080839 TCDEP1 Tropical Storm Kevin Discussion Number 4 NWS National Hurricane Center Miami FL EP112021 300 AM MDT Sun Aug 08 2021 Kevin has changed little overnight. Microwave data and infrared satellite imagery reveal that its convective bands are still somewhat fragmented with only modest curvature. Recent UW-CIMSS objective estimates and subjective Dvorak classifications from TAFB and SAB range from 35 to 45 kt, so the initial intensity is held at 40 kt for this advisory. Unfortunately, no recent scatterometer passes were available to better assess the cyclone's current intensity. The cyclone continues moving westward, or 270 degrees, at around 9 kt. This motion is expected for another 12 to 24 h, before a mid- to upper-level trough weakens the steering ridge and causes Kevin to move west-northwestward through midweek. Kevin is forecast to pass near or just south of Clarion Island on Tuesday. The track guidance is in good agreement for much of the forecast period, and the latest official NHC forecast lies near the previous one and generally follows the multi-model consensus aids. Kevin appears primed for some strengthening, as the cyclone will remain in a moist, unstable environment with ample oceanic heat content for the next couple of days. However, persistent northeasterly wind shear of 15-20 kt will likely curtail rapid intensification in an otherwise favorable environment. Despite the shear, the guidance supports strengthening in the near-term, and the official NHC forecast shows Kevin becoming a hurricane on Monday. The cyclone's intensity is forecast to level off by Tuesday, with weakening thereafter as Kevin moves over cooler waters and continues to battle moderate shear. The latest NHC intensity forecast is a little lower than the previous one, but remains near or slightly above the HFIP corrected consensus approach (HCCA) and IVCN aids. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 15.8N 108.7W 40 KT 45 MPH 12H 08/1800Z 15.8N 109.6W 50 KT 60 MPH 24H 09/0600Z 16.1N 110.8W 60 KT 70 MPH 36H 09/1800Z 16.7N 112.0W 65 KT 75 MPH 48H 10/0600Z 17.5N 113.3W 70 KT 80 MPH 60H 10/1800Z 18.2N 114.8W 70 KT 80 MPH 72H 11/0600Z 19.1N 116.5W 65 KT 75 MPH 96H 12/0600Z 20.8N 120.0W 55 KT 65 MPH 120H 13/0600Z 22.5N 124.0W 40 KT 45 MPH $$ Forecaster Reinhart/Pasch
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Tropical Storm Kevin Forecast Discussion Number 3
2021-08-08 04:32:25| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Sat Aug 07 2021 000 WTPZ41 KNHC 080232 TCDEP1 Tropical Storm Kevin Discussion Number 3 NWS National Hurricane Center Miami FL EP112021 900 PM MDT Sat Aug 07 2021 Kevin appears to be gradually gaining strength. Satellite images show that the storm has a central dense overcast feature that is surrounded by fragmented curved bands. The latest Dvorak classifications from TAFB, SAB, and CIMSS at the University of Wisconsin range from 35 to 45 kt, and based on that data, the initial intensity is nudged up to 40 kt. The cyclone is moving westward, or 270 degrees, at 10 kt. Kevin is expected to continue westward for about another day or so while it remains on the south side of a mid-level ridge to its north. After that time, a turn to the west-northwest is forecast as a mid- to upper-level trough erodes the western portion of the ridge, allowing Kevin to gain more latitude. The models are in fairly good agreement, and the NHC track forecast is essentially an update of the previous one and lies near the middle of the guidance envelope. The tropical storm is currently over warm 29 C waters and embedded in a very moist air mass. These conditions support strengthening, but there could be a moderate amount of northeasterly shear that will likely prevent rapid intensification. Nonetheless, steady strengthening is expected during the next couple of days, and Kevin is forecast to become a hurricane during that time period. Beyond that time, however, progressively cooler waters and drier air should cause Kevin to level off in strength and then begin to weaken. The NHC intensity forecast lies close to the HCCA and IVCN consensus models. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 15.8N 107.7W 40 KT 45 MPH 12H 08/1200Z 15.7N 108.8W 50 KT 60 MPH 24H 09/0000Z 15.7N 110.0W 60 KT 70 MPH 36H 09/1200Z 16.1N 111.0W 70 KT 80 MPH 48H 10/0000Z 16.9N 112.3W 75 KT 85 MPH 60H 10/1200Z 17.7N 113.6W 75 KT 85 MPH 72H 11/0000Z 18.6N 115.2W 70 KT 80 MPH 96H 12/0000Z 20.5N 118.7W 60 KT 70 MPH 120H 13/0000Z 22.2N 123.1W 45 KT 50 MPH $$ Forecaster Cangialosi
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