Tropical Storm Kevin

Post Tropical Storm Kevin Track 0800 Hours August 12 2021
Post Tropical Storm Kevin Track 0800 Hours August 12 2021

Tropical Storm Kevin Wind Speed FieldTropical Storm KevinNWS National Hurricane Center Miami FL 800 AM PDT Thu Aug 12, 2021 (see Tuesday video below)

A little bit of convection continues to persist about 200 n mi to the southwest of Kevin’s center, but at that distance, it is not considered organized in relation to the cyclone. In fact, Kevin has had this structure for a good 18 hours or so, and it has therefore degenerated into a remnant low. Based on last evening’s ASCAT passes, it is assumed that winds as high as 30 kt are still occurring within the circulation. However, the center will be moving over waters colder than 23 degrees Celsius very soon, so a gradual decrease in the winds is expected over the next couple of days. Dissipation of the remnant low in expected in about 3 days.

Kevin is moving toward the west-northwest, or 300/12 kt. The remnant low is expected to move along the southwestern periphery of a low- to mid-level ridge centered over the United States and Mexico, which should cause a west-northwestward or northwestward motion until dissipation. There is very little spread in the track guidance, and this last NHC track forecast is just an update of the previous one.

This is the last advisory being issued for Kevin.

FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 23.2N 120.6W   30 KT  35 MPH - Post Tropical (WSW Punta San Carlos, MX)
 12H  13/0000Z 24.2N 122.5W   25 KT  30 MPH - Post Tropical (WSW Punta San Carlos, MX)
 24H  13/1200Z 25.5N 124.9W   25 KT  30 MPH - Post Tropical (WSW Punta San Carlos, MX)
 36H  14/0000Z 27.0N 126.9W   20 KT  25 MPH - Post Tropical (WNW Punta San Carlos, MX)
 48H  14/1200Z 28.7N 128.6W   20 KT  25 MPH - Post Tropical (WNW Punta San Carlos, MX)
 60H  15/0000Z 30.2N 129.8W   20 KT  25 MPH - Post Tropical (WSW San Diego,CA)
 72H  15/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 PM PDT Wed Aug 11, 2021

The center of Kevin this evening consists of a broad low-level swirl, with a decaying area of convection that has become increasingly detached from the circulation in the southwestern quadrant. The 0000 UTC subjective Dvorak estimates were both T2.5/35 kt from SAB and TAFB, while the most recent UW-CIMSS SATCON estimate was a bit higher at 38 kt. Given the degradation in convective structure from the previous advisory, the initial intensity is lowered to 35 kt for this advisory.

After an earlier westward jog, the initial motion has resumed a more northwest heading at 305/11 kt. The track philosophy remains unchanged, as Kevin’s broad circulation will continue to be steered to the west-northwest or northwest along the southwestern side of a deep tropospheric ridge for the next 48-60 hours. The latest track forecast is essentially an update from the previous advisory, and lies nearly along the HCCA consensus aid, just a shade west of the previous forecast track.

As Kevin continues to move into cooler sea-surface temperatures and a drier air-mass, the storm is expected to continue weakening as the remaining organized convection ceases. The latest intensity forecast weakens Kevin to a tropical depression tomorrow morning and degenerates the cyclone into a remnant low by Friday morning, in good agreement with the model guidance that shows the remaining convection dissipating by tomorrow night.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 22.0N 118.2W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  12/1200Z 22.9N 119.9W   30 KT  35 MPH - Depression (WSW Puerto Vallarta, MX)
 24H  13/0000Z 24.1N 122.3W   30 KT  35 MPH - Depression (WSW Puerto Vallarta, MX)
 36H  13/1200Z 25.5N 124.6W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 48H  14/0000Z 27.1N 126.7W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 60H  14/1200Z 28.7N 128.2W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 72H  15/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Wed Aug 11, 2021

Shortwave infrared images show that the center of Kevin’s broad circulation is exposed to the northeast of a persistent cluster of deep convection, resulting from 15-20 kt of east-northeasterly shear over the system. With Dvorak T-numbers holding steady at T3.0 from TAFB and T2.5 from SAB, the initial intensity remains 40 kt.

Recent geostationary images and a 0943 UTC GCOM overpass warranted a slight adjustment to the initial position, which now makes the initial motion northwestward at 325/9 kt. A mid-tropospheric high located over northern Mexico is expected to keep Kevin on a northwestward to west-northwestward path for the next several days, which is shown by all the track models. Most differences among the models are speed related, with the ECMWF being one of the fastest models and the GFS one of the slowest. In general, the NHC track forecast is close to the consensus aids, but the initial position adjustment required a fairly noteworthy northeastward shift in the forecast track compared to the previous advisory.

Kevin’s center is just about ready to move over waters cooler than 26 degrees Celsius and should be over waters as cold as 21 degrees in a couple of days. Also, the shear affecting the storm is only expected to diminish gradually, and these conditions should induce imminent weakening. In line with the latest intensity guidance, Kevin is likely to weaken to a tropical depression within 24 hours and then become a remnant low in about 48 hours when it loses all of its deep convection. This scenario is shown by the GFS and ECMWF simulated satellite imagery.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 21.0N 116.8W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  12/0000Z 22.0N 118.2W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  12/1200Z 23.2N 120.2W   30 KT  35 MPH - Depression (WSW Puerto Vallarta, MX)
 36H  13/0000Z 24.4N 122.5W   25 KT  30 MPH - Depression (WSW Puerto Vallarta, MX)
 48H  13/1200Z 25.6N 124.9W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 60H  14/0000Z 27.0N 126.9W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 72H  14/1200Z 28.3N 128.4W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 96H  15/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 PM PDT Tue Aug 10, 2021 

Tracking the center of Kevin this evening has been a challenge, as multiple low-level swirls appear to be rotating cyclonically around a broader mean circulation. The deeper convection remains mostly south of the estimated circulation center, though some cooler cloud tops did attempt to build northward, following a mesovortex seen on visible satellite imagery. Subjective Dvorak intensity estimates from SAB and TAFB at 0000 UTC were T2.5/35 kt and T3.0/45 kt, respectively, and the latest UW-CIMSS SATCON estimate was hovering between these values at 42 kt. The initial intensity is held at 45 kt for this advisory, favoring the higher intensity estimates given the earlier ASCAT data.

The initial motion is estimated at 315/7 kt, attempting to follow the mean center that has several mesovorticies rotating around. A general northwest to west-northwestward motion is expected to continue over the next several days as the large cyclone is steered by a deep-layer ridge located to its northeast. The latest track guidance was a bit more poleward compared to the previous cycle, and the latest NHC track forecast has been shifted a bit more poleward in the short term, choosing to remain close to the track guidance consensus.

Moderate to strong northeasterly wind shear continues to keep Kevin’s deepest convection downshear in the southern semicircle of the large circulation envelope. Over the next 24 hours, Kevin will also be crossing a sharp sea-surface temperature (SST) gradient, with sub 26 C SSTs not far away to the north. As the cyclone moves over these progressively cooler waters, gradual weakening should commence. Simulated IR brightness temperature data from both the GFS and ECMWF suggest that Kevin will lose its remaining organized convection by 48-60 hours, and the latest NHC intensity forecast shows Kevin becoming a remnant low by that time.

FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 19.5N 115.4W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  11/1200Z 20.7N 116.5W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  12/0000Z 21.9N 118.3W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  12/1200Z 23.0N 120.3W   30 KT  35 MPH - Depression (WSW Puerto Vallarta, MX)
 48H  13/0000Z 24.0N 122.5W   25 KT  30 MPH - Depression (WSW Puerto Vallarta, MX)
 60H  13/1200Z 25.1N 124.7W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 72H  14/0000Z 26.3N 126.8W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 96H  15/0000Z 28.4N 130.0W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)
120H  16/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 900 AM MDT Tue Aug 10, 2021

Kevin remains a sheared tropical cyclone, with the bulk of the deep convection located southwest of its center, while the center itself was exposed for a few hours earlier this morning. The structure of the cyclone has changed little since yesterday, and remains somewhat elongated. The estimated initial intensity is being held at 40 kt, using a blend of the latest Dvorak T-numbers from TAFB and SAB.

Kevin continues to make its jog to the northwest, and the initial motion is 315/08 kt. A general northwestward to west-northwestward motion is expected over the next several days as Kevin moves along the southwestern periphery of a deep-layer ridge. Model guidance has continued to make a gradual shift to the north for the past several runs, and thus the latest NHC track forecast has been nudged a little northward as well, lying just south of the consensus models.

Moderate to strong northeasterly wind shear is forecast to persist over Kevin for the next 24 h, which should limit the cyclone’s ability to strengthen despite favorable SSTs and abundant mid-level moisture. By 24 h, the cyclone will begin to pass over progressively cooler waters and into a drier, more stable environment. Based on this scenario, the latest NHC intensity forecast shows no change in strength through much of tonight, followed by weakening beginning Wednesday morning. By 72 h, CMC and ECMWF model simulated satellite imagery suggest that Kevin will be devoid of organized convection, and so the official NHC forecast shows Kevin as a remnant low by that time.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 19.1N 114.3W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  11/0000Z 19.9N 115.2W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  11/1200Z 21.0N 116.7W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  12/0000Z 22.1N 118.4W   30 KT  35 MPH - Depression (WSW Puerto Vallarta, MX)
 48H  12/1200Z 23.1N 120.5W   25 KT  30 MPH - Depression (WSW Puerto Vallarta, MX)
 60H  13/0000Z 24.1N 122.8W   25 KT  30 MPH - Depression (WSW Cabo San Lucas, MX)
 72H  13/1200Z 25.2N 125.0W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 96H  14/1200Z 27.2N 128.8W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)
120H  15/1200Z 28.7N 131.8W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 900 PM MDT Mon Aug 09, 2021 

Kevin remains a sheared tropical cyclone with most of the convection displaced to the southwest of the elongated inner-core wind field due to strong northeasterly vertical wind shear. However, some small curved bands of shallow convection have recently developed in the eastern semicircle, suggesting that the shear might be starting to abate somewhat. The initial intensity has been decreased to 40 kt, more in line with earlier ASCAT surface wind data that showed peak surface winds near 40 kt.

The initial motion estimate remains west-northwestward, or 295/08 kt. There is no change to the previous track forecast reasoning. Kevin is expected to continue moving west-northwestward through the 120-h forecast period along the southwestern periphery of a deep-layer ridge. The new NHC track forecast is just a tad to the right or north of the previous track, but remains near the southern portion of the track model envelope, between the ECMWF model to the south and the consensus models to the north.

Kevin is forecast remain under the influence of at least modest northeasterly to easterly wind shear for the next 48 h. Thus little change in strength is expected despite he warm sea-surface temperatures (SST) exceeding 28C and a very moist mid-level environment exceeding 80 percent relative humidity. Thereafter the shear is forecast to decrease to less than 10 kt, which would normally favor intensification. However, Kevin will be moving over near-22 deg C SSTs at that time, so weakening rather than strengthening is forecast in the 72-120 period. The latest official intensity forecast is similar to the previous advisory, and closely follows a blend of the consensus models HCCA and IVCN, and the Navy COAMPS-TC model.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 17.4N 112.9W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  10/1200Z 18.1N 114.0W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  11/0000Z 19.0N 115.3W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  11/1200Z 20.0N 116.8W   40 KT  45 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  12/0000Z 21.0N 118.6W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 60H  12/1200Z 21.8N 120.8W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, MX)
 72H  13/0000Z 22.7N 123.0W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
 96H  14/0000Z 24.6N 127.7W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
120H  15/0000Z 26.2N 132.3W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 300 PM  MDT Mon Aug 09, 2021 

Visible satellite imagery and satellite wind data have revealed today that Kevin is a poorly organized tropical cyclone. The circulation is elongated from northeast-to-southwest, with one dominant, exposed low-level cloud swirl pivoting around the larger cyclonic gyre. The center has been initialized a little to the southwest of the exposed swirl, closer to a generalized mean cyclonic center. Satellite wind data also indicate that tropical-storm-force winds are confined to the southern semicircle, with a swath of 35-41 kt winds covering an area up to 110 n mi from the estimated center. Assuming some instrument undersampling, and based on the latest pair of 3.0 (45 kt) T-numbers from TAFB and SAB, the initial intensity remains at 45 kt.

Kevin has not been able to get its act together over warm waters and within the favorable thermodynamic environment, likely due to moderate northeasterly shear and a subsequent lack of persistent deep convection over the center. The overall environment that the storm is interacting with is not expected to change much over the next 36 h. And, since the structure of the cyclone is not conducive for imminent strengthening, additional intensification is no longer anticipated. After 36 h, Kevin will begin to move over decreasing SSTs and into a more stable atmospheric environment. These unfavorable thermodynamic conditions should cause the cyclone to begin weakening. By 96 hours, the system is forecast to be over water temperatures of less than 22 degrees C, which should result in the cyclone degenerating into a remnant low. The latest NHC intensity forecast was adjusted slightly lower once again, and is in good agreement with the latest consensus intensity guidance.

Kevin continues to move to the west-northwest, or 300/08 kt, along the southwestern periphery of a mid-level ridge. This steering pattern is forecast by all of the forecast models to remain intact for the next several days, resulting in a continued west-northwestward motion. The track guidance has once again shifted slightly northward after 24 h. Therefore, the latest NHC track forecast was also nudged a little to the north, and lies on the southern end of the tightly clustered track guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 17.0N 112.2W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  10/0600Z 17.7N 113.3W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  10/1800Z 18.5N 114.7W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  11/0600Z 19.3N 116.1W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  11/1800Z 20.4N 117.8W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 60H  12/0600Z 21.2N 119.7W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 72H  12/1800Z 22.0N 121.9W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, MX)
 96H  13/1800Z 23.6N 126.6W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)
120H  14/1800Z 25.5N 131.5W   20 KT  25 MPH - Post Tropical (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 900 AM MDT Mon Aug 09, 2021

Kevin has been successfully battling moderate northeasterly wind shear overnight, as a large convective mass with cloud tops colder than -80 degrees C has persisted for several hours over the center and southwestern portion of the cyclone’s large circulation. The latest Dvorak intensity estimates have a large spread, ranging from 55 kt from TAFB to 35 kt from the UW-CIMSS ADT. A mean of 45 kt from these values suggest that the storm’s initial intensity remains the same as 6 h ago, which seems reasonable as the overall appearance of Kevin has changed little this morning.

The storm is moving to the west-northwest at 300/07 kt along the southwestern periphery of a mid-level ridge. This steering pattern is forecast by all of the forecast models to remain in tact for the next several days, resulting in a continued west-northwestward motion. The only notable change in the track guidance was a slight shift to the north, and the latest NHC track forecast lies in between the previous one and the tightly clustered track guidance.

The favorable thermodynamic environment and warm water have allowed Kevin to maintain deep convection despite the vertical wind shear. With the large amount of convection occurring near and over the center of the cyclone, it is possible for some slight strengthening to occur in the short-term, despite wind shear persisting over the next couple of days. By 48 hours, Kevin will begin to move over decreasing SSTs and into a more stable atmospheric environment. These unfavorable thermodynamic conditions should cause the cyclone to begin weakening. By 96 hours, the system is forecast to be over water temperatures of less than 23 degrees C, which should result in the cyclone degenerating into a remnant low. The latest NHC intensity forecast was decreased slightly from the previous one, and is in good agreement with the various intensity consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 16.6N 111.5W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  10/0000Z 17.3N 112.5W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  10/1200Z 18.1N 114.1W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  11/0000Z 18.9N 115.6W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  11/1200Z 19.7N 117.1W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 60H  12/0000Z 20.6N 119.0W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 72H  12/1200Z 21.4N 121.0W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 96H  13/1200Z 23.0N 125.6W   30 KT  35 MPH - Post Tropical (WSW Cabo San Lucas, MX)
120H  14/1200Z 24.5N 130.6W   25 KT  30 MPH - Post Tropical (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 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 - Tropical Storm (WSW Acapulco, MX)
 12H  09/0600Z 16.0N 110.8W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  09/1800Z 16.6N 112.0W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  10/0600Z 17.3N 113.5W   65 KT  75 MPH - Category 1 (WSW Puerto Vallarta, MX)
 48H  10/1800Z 18.1N 115.0W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta, MX)
 60H  11/0600Z 19.0N 116.8W   65 KT  75 MPH - Category 1 (WSW Puerto Vallarta, MX)
 72H  11/1800Z 19.8N 118.4W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 96H  12/1800Z 21.5N 122.3W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
120H  13/1800Z 23.0N 126.8W   35 KT  40 MPH - Post Tropical (WSW Puerto San Carlos, MX)

NWS National Hurricane Center Miami FL 900 AM MDT Sun Aug 08, 2021

A burst of deep convection with clouds top temperatures of around -80C has developed and expanded over the center of Kevin this morning, however a few microwave overpass have shown that the center is located near the eastern portion of the convective mass. Subjective Dvorak intensity estimates from TAFB and SAB were T3.5 (55 kt) at 12Z, with the latest objective estimates from ADT and SATCON at 53 kt and 44 kt, respectively. Using a blend of these intensity estimates, the initial wind speed has been increased to 50 kt for this advisory. Kevin remains in a generally favorable environment of warm water and a moist, unstable atmosphere, however moderate northeasterly shear is likely to hinder rapid development over the next day or two. The NHC intensity forecast does call for steady strengthening and it brings Kevin to hurricane status on Monday. After 60-72 hours, decreasing SSTs and less favorable thermodynamic conditions should cause weakening during the latter portion of the forecast period. The NHC intensity forecast is similar to the previous advisory and lies near the ICVN consensus aid.

Kevin is moving westward or 270 degrees at about 7 kt, a little slower than before. 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 by Monday morning, and this west-northwestward heading is then expected to continue for the remainder of the forecast period. The track guidance is in relatively good agreement on the overall forecast scenario except there are some differences in Kevin’s forward speed. The new NHC track forecast is similar to the previous advisory and lies near the middle of the guidance envelope, closest to the the HCCA and GFEX consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 15.8N 109.0W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  09/0000Z 15.8N 110.1W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  09/1200Z 16.2N 111.2W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  10/0000Z 16.9N 112.5W   65 KT  75 MPH - Category 1 (WSW Puerto Vallarta, MX)
 48H  10/1200Z 17.7N 114.0W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta, MX)
 60H  11/0000Z 18.5N 115.6W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta, MX)
 72H  11/1200Z 19.4N 117.3W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, MX)
 96H  12/1200Z 21.2N 120.9W   55 KT  65 MPH - Depression (WSW Cabo San Lucas, MX)
120H  13/1200Z 22.7N 125.3W   40 KT  45 MPH - Depression (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 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 - Tropical Storm (WSW Acapulco, MX)
 12H  08/1200Z 15.7N 108.8W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  09/0000Z 15.7N 110.0W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  09/1200Z 16.1N 111.0W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta, MX)
 48H  10/0000Z 16.9N 112.3W   75 KT  85 MPH - Category 1 (WSW Puerto Vallarta, MX)
 60H  10/1200Z 17.7N 113.6W   75 KT  85 MPH - Category 1 (WSW Puerto Vallarta, MX)
 72H  11/0000Z 18.6N 115.2W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, MX)
 96H  12/0000Z 20.5N 118.7W   60 KT  70 MPH - Depression (WSW Cabo San Lucas, MX)
120H  13/0000Z 22.2N 123.1W   45 KT  50 MPH - Depression (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 300 PM MDT Sat Aug 07, 2021 

Visible satellite imagery has continued to show an improvement in the cloud pattern of the tropical cyclone today. Banding has increased over the western and southern portions of the circulation while a small CDO has developed near the center. Scatterometer data from around 1700 UTC revealed an area of 30-kt winds to the northwest of the center, but with the continued increase in organization and Dvorak T-numbers of T2.5 from both TAFB and SAB the initial wind speed has been increased to 35 kt. Kevin becomes the eleventh named storm in the eastern Pacific basin during the 2021 season, which is running about a month ahead of schedule as the eleventh named storm typically does not form until early-to-mid September.

Kevin is located within an environment of low-to-moderate shear, warm sea surface temperatures, and a moist atmosphere. These conditions are expected to support steady strengthening over the next few days, and the cyclone is expected to become a hurricane in about 36 hours. There is some spread in the intensity guidance with the statistical guidance on the more aggressive side as compared to some of the dynamical models. The NHC wind speed forecast lies a little above the various consensus models but slightly below the SHIPS guidance.

The storm is moving westward or 270/9 kt. A mid-tropospheric ridge that extends across the subtropical eastern Pacific is forecast to steer Kevin generally westward during the next 36 hours. After that time, a cut-off low west of the Baja peninsula is expected to erode the western portion of the ridge causing Kevin to turn west- northwestward to northwestward through the remainder of the forecast period. The GFS, which depicts an unrealistic elongation of the system’s low-level vorticity in about 48 hours, shows a much sharper northward or northwestward motion from 48-72 hours. Less weight was placed on that solution with the NHC track remaining closer to the bulk of the guidance and the various consensus aids. The latest track forecast is similar to, but a little slower than previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 15.8N 106.8W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  08/0600Z 15.8N 108.1W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  08/1800Z 15.7N 109.4W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  09/0600Z 15.7N 110.5W   65 KT  75 MPH - Category 1 (WSW Acapulco, MX)
 48H  09/1800Z 16.2N 111.5W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta, MX)
 60H  10/0600Z 17.3N 112.7W   75 KT  85 MPH - Category 1 (WSW Puerto Vallarta, MX)
 72H  10/1800Z 18.2N 114.0W   75 KT  85 MPH - Category 1 (WSW Puerto Vallarta, MX)
 96H  11/1800Z 19.9N 117.6W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, MX)
120H  12/1800Z 21.9N 122.2W   50 KT  60 MPH - Depression (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 1000 AM CDT Sat Aug 07, 2021

Last night’s METOP-A/B scatterometer overpasses indicated that the area of low pressure located a couple hundred miles south-southwest of Manzanillo, Mexico had become a little better defined, and since that time, the system has developed sufficient organized convection to be designated as a tropical depression. The initial intensity is estimated to be 30 kt and is in agreement with the satellite intensity estimates from TAFB and SAB.

Modest northeasterly shear, warm sea surface temperatures and a moist surrounding low- to mid-level environment support steady strengthening during the next few days, and the depression is forecast to become a tropical storm by tonight. The Statistical SHIPS (GFS/ECMWF), and the HCCA/IVCN multi-model intensity aids, all show that the cyclone will become a hurricane in about 48 hours, and the NHC forecast follows suit. The intensity forecast resembles the HCCA and IVCN intensity consensus models, and is just below the Decay SHIPS guidance.

The initial motion is estimated to be westward, or 275/8 kt. The depression is being steered by a mid-tropospheric ridge stretching westward over the subtropical eastern Pacific from high pressure located over the northern Gulf of Mexico. A general westward motion with a similar forward speed is expected through early next week. Through the remaining portion of the forecast, a turn toward the west-northwest to the northwest is expected due to growing weakness in the aforementioned ridge. The official forecast is based on the TVCN multi-model consensus and lies between the GFS and ECMWF global models solutions.

 

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 15.9N 105.5W   30 KT  35 MPH - Depression (WSW Acapulco, MX)
 12H  08/0000Z 15.9N 106.8W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  08/1200Z 15.9N 108.4W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  09/0000Z 15.9N 109.7W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, MX)
 48H  09/1200Z 16.2N 111.1W   65 KT  75 MPH - Category 1 (WSW Acapulco, MX)
 60H  10/0000Z 16.8N 112.3W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta, MX)
 72H  10/1200Z 18.0N 113.7W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, MX)
 96H  11/1200Z 19.9N 117.3W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, MX)
120H  12/1200Z 21.7N 121.4W   50 KT  60 MPH - Tropcal Storm (WSW Cabo San Lucas, MX)

NWS National Hurricane Center Miami FL 500 PM PDT Fri Aug 6, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

Recently downgraded Tropical Depression Jimena has crossed into the Central Pacific basin and is located about 1000 miles east of Hilo, Hawaii. The Central Pacific Hurricane Center in Honolulu, Hawaii, will be issuing the next advisory on Jimena at 500 PM HST.

  • 1. Showers and thunderstorms are beginning to show some signs of organization in association with a broad area of low pressure located a couple of hundred miles south of the coast of southwestern Mexico. Environmental conditions are conducive for additional development, and a tropical depression is expected to form late this weekend or early next week while the system moves west-northwestward at about 10 mph. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…90 percent.
  • 2. An area of low pressure is expected to develop a few hundred miles south of the Gulf of Tehuantepec by early next week. Environmental conditions are forecast to be conducive for gradual development thereafter while the system moves west-northwestward at about 10 mph, parallel to and offshore of the coast of southern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

Recent Tropical Cruise Weather:

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