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Hurricane Kenneth Forecast Discussion Number 12

2017-08-21 10:46:15| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Mon Aug 21 2017 000 WTPZ43 KNHC 210846 TCDEP3 Hurricane Kenneth Discussion Number 12 NWS National Hurricane Center Miami FL EP132017 200 AM PDT Mon Aug 21 2017 Kenneth has continued to rapidly intensify since the previous advisory. The satellite presentation of the hurricane is quite impressive, as a 15-nmi wide eye has become better defined while the cloud tops of the surrounding ring of convection has cooled. Dvorak intensity estimates range from T5.5 (102 kt) from SAB, T6.0 (115 kt) from TAFB, to T6.3 (122 kt) from UW/CIMSS. Using a blend of these estimates, the initial wind speed has been increased to 115 kt, making Kenneth a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. The hurricane is expected to peak in intensity very soon as it will be moving over cooler waters and into a more stable air mass later today. After that time, cooler sea surface temperatures and less favorable thermodynamic conditions should cause steady weakening. In 3 to 4 days, increasing southwesterly shear from an upper-level trough along 140W and sub 23C SSTs should cause Kenneth's deep convection to dissipate, resulting in the system becoming a post-tropical cyclone. The NHC intensity forecast is slightly higher than the previous one at 12 and 24 h due to the higher initial intensity. After that time, the forecast is fairly similar to the previous advisory, and is a blend of the various intensity aids. The initial motion estimate is west-northwest or 300 degrees at 9 kt. The track forecast reasoning remains the same as the previous advisory, as Kenneth is expected to turn northwestward today, then north-northwestward on Tuesday between a mid-level ridge to its east and a developing cut-off low to the west. Kenneth should slow down considerably later in the period when it becomes a vertically shallow system and is steered by the weaker low-level flow. There is very little spread in the track guidance, and the updated official forecast is near the middle of the guidance envelope, and very close to the previous NHC forecast. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 17.4N 130.0W 115 KT 130 MPH 12H 21/1800Z 18.2N 131.2W 115 KT 130 MPH 24H 22/0600Z 19.7N 132.3W 105 KT 120 MPH 36H 22/1800Z 21.3N 133.3W 85 KT 100 MPH 48H 23/0600Z 23.1N 134.1W 65 KT 75 MPH 72H 24/0600Z 26.6N 135.5W 45 KT 50 MPH 96H 25/0600Z 29.0N 136.3W 35 KT 40 MPH...POST-TROPICAL 120H 26/0600Z 30.5N 137.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Hurricane Kenneth Forecast Discussion Number 11

2017-08-21 04:52:13| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sun Aug 20 2017 000 WTPZ43 KNHC 210252 TCDEP3 Hurricane Kenneth Discussion Number 11 NWS National Hurricane Center Miami FL EP132017 800 PM PDT Sun Aug 20 2017 Kenneth has rapidly intensified into a major hurricane this evening, as the eye has dramatically warmed and the surrounding cloud tops of the eyewall have cooled. At 00Z, a blend of TAFB, SAB, and ADT Dvorak classifications averaged maximum winds of 95 kt. However, the continued convective development in the last three hours suggests that the advisory intensity be boosted to 100 kt, and even that may be conservative. While the hurricane has shown an impressive evolution in the last day, this should not continue much longer. Kenneth will reach the 26C SST isotherm with drier, less unstable air late Monday, and it is anticipated that Kenneth will peak by then. In about three days, the vertical shear will go up appreciably due to Kenneth approaching an upper-level trough. The combination of the hostile thermodynamics and shear should cause a steady weakening through the forecast period. Kenneth's deep convection is likely to dissipate in three to four days, signaling the system's transformation to a post-tropical cyclone. The official intensity forecast is substantially higher than previously in the short-term due to the unanticipated rapid intensification, but similar for 36 hours and beyond. This prediction is closest to a blend of the HMON dynamical model and the LGEM/SHIPS statistical models. The hurricane is moving toward the west-northwest at 9 kt, steered by a weak mid-level ridge to its northeast. Kenneth should gradually turn toward the north-northwest during the next couple of days at about the same rate of forward speed, as it rounds the mid-level ridge and is impacted by a cut-off mid- to upper-level low farther north. Once Kenneth becomes a post-tropical cyclone in about 4 days, its forward speed should slow as it reaches a weaker steering flow. The official track forecast is nearly unchanged through day 2 and is farther north beyond that time, based upon the HFIP Corrected Consensus Approach. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 16.8N 129.1W 100 KT 115 MPH 12H 21/1200Z 17.4N 130.4W 110 KT 125 MPH 24H 22/0000Z 18.7N 131.7W 100 KT 115 MPH 36H 22/1200Z 20.3N 132.7W 85 KT 100 MPH 48H 23/0000Z 22.1N 133.6W 70 KT 80 MPH 72H 24/0000Z 25.5N 135.0W 50 KT 60 MPH 96H 25/0000Z 28.5N 136.0W 40 KT 45 MPH...POST-TROPICAL 120H 26/0000Z 30.0N 136.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Landsea

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Hurricane Kenneth Forecast Discussion Number 10

2017-08-20 22:33:42| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Sun Aug 20 2017 000 WTPZ43 KNHC 202033 TCDEP3 Hurricane Kenneth Discussion Number 10 NWS National Hurricane Center Miami FL EP132017 200 PM PDT Sun Aug 20 2017 Kenneth has been strengthening rapidly during the last several hours. An eye has appeared in geostationary satellite images and deep convection has been increasing in intensity, especially to the east of the center. The latest Dvorak classifications have increased, and an average of the intensity estimates from TAFB, SAB, and ADT values from CIMSS at the University of Wisconsin support raising the initial wind speed to 80 kt. The hurricane is still not gaining much latitude, and the initial motion is 280/11 kt, which is a little slower than before. The track forecast reasoning is unchanged from earlier. A decrease in forward speed and a turn to the northwest is expected on Monday as the hurricane moves on the southwestern side of a mid-level ridge. After that time, Kenneth is expected to move north-northwestward and slow down even more as it moves into a break in the ridge caused by a cut off low near the California coast. The track models have shifted a little to the east beyond 48 hours, and the NHC forecast has been nudged in that direction. Kenneth has already intensified more than expected, and it still has about another 24 hours in favorable environmental conditions. Therefore, additional strengthening is anticipated, and the NHC intensity forecast lies at the high end of the guidance in the short term, in best agreement with the HCCA model. Beyond 24 hours, Kenneth is expected to move over waters cooler than 26 deg C and into a progressively drier and more stable air mass. These unfavorable conditions combined with an increase in southerly shear beginning in about 72 hours should cause a steady weakening trend. Kenneth is now forecast to become a post-tropical cyclone by day 4, when it will be over SSTs near 23 deg C and in wind shear conditions of nearly 30 kt. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 16.2N 128.4W 80 KT 90 MPH 12H 21/0600Z 17.0N 129.9W 90 KT 105 MPH 24H 21/1800Z 18.1N 131.4W 95 KT 110 MPH 36H 22/0600Z 19.4N 132.6W 85 KT 100 MPH 48H 22/1800Z 21.0N 133.4W 70 KT 80 MPH 72H 23/1800Z 24.5N 135.0W 55 KT 65 MPH 96H 24/1800Z 27.0N 136.2W 40 KT 45 MPH...POST-TROPICAL 120H 25/1800Z 28.7N 136.6W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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Hurricane Kenneth Forecast Discussion Number 9

2017-08-20 16:32:11| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Sun Aug 20 2017 000 WTPZ43 KNHC 201432 TCDEP3 Hurricane Kenneth Discussion Number 9 NWS National Hurricane Center Miami FL EP132017 800 AM PDT Sun Aug 20 2017 Kenneth is gradually strengthening. Satellite images show that the cloud pattern consists of a central dense overcast and curved bands beyond that feature, especially to the south of the center. The Dvorak classifications from TAFB and SAB were both 4.0/65 kt, and recent ADT values from CIMSS at the University of Wisconsin are about the same. Based on these data, the initial intensity is increased a little to 65 kt, making Kenneth a category 1 hurricane. The initial motion of the hurricane is the same as before, 280/13 kt. A turn to the northwest with a decrease in forward speed is expected to occur on Monday as a mid-level ridge to the northeast of the system weakens. After that time, Kenneth is expected to move even slower to the north-northwest when it moves into a break in the ridge caused by a cut-off low near the southwestern United States. Overall the models are in fair agreement with this scenario, but they differ in where and when Kenneth begins to recurve. The consensus aids have been quite consistent over the past few cycles, and this forecast is largely just an update of the previous one. The environmental conditions are conducive for Kenneth to strengthen some more during the next 24 to 36 hours. After that time, however, cooler waters along the expected track and drier air should end the strengthening trend and cause weakening. In addition, the global models show a significant increase in southerly shear beginning in about 72 hours, which should aid in the weakening trend. The intensity models are in very good agreement, and little change was made to the previous forecast. Kenneth will likely become a post-tropical cyclone in 4 to 5 days when it will be over SSTs of about 23 deg C. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 16.3N 127.4W 65 KT 75 MPH 12H 21/0000Z 16.8N 129.1W 70 KT 80 MPH 24H 21/1200Z 17.8N 131.0W 75 KT 85 MPH 36H 22/0000Z 19.0N 132.4W 75 KT 85 MPH 48H 22/1200Z 20.4N 133.4W 70 KT 80 MPH 72H 23/1200Z 23.7N 134.8W 55 KT 65 MPH 96H 24/1200Z 26.7N 136.3W 40 KT 45 MPH 120H 25/1200Z 28.0N 137.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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Tropical Storm Kenneth Forecast Discussion Number 8

2017-08-20 10:39:08| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Sun Aug 20 2017 000 WTPZ43 KNHC 200838 TCDEP3 Tropical Storm Kenneth Discussion Number 8 NWS National Hurricane Center Miami FL EP132017 200 AM PDT Sun Aug 20 2017 The overall cloud pattern of Kenneth has changed little since the previous advisory. The center remains embedded with a fairly symmetric central dense overcast, but there has been no evidence of an eye in infrared satellite pictures overnight. Subjective and objective Dvorak T-numbers are between 3.5 and 4.0, which support maintaining an initial wind speed of 60 kt. Kenneth is forecast to remain within a low shear environment and over warm water for another 24 to 36 hours. This should result in strengthening and Kenneth is expected to become a hurricane later today. After that time, decreasing sea surface temperatures and less favorable thermodynamic conditions should cause gradual weakening. Late in the period, increasing southwesterly shear should hasten Kenneth's demise and the system is expected to become a remnant low by day 5. The NHC intensity forecast is close to the SHIPS guidance and the IVCN multi-model consensus through 72 hours, but is a little below this guidance at days 4 and 5. Kenneth has been moving generally westward during the past 24 hours and recent satellite fixes suggest that Kenneth's forward motion has slowed to about 13 kt. The track forecast reasoning remains unchanged from the previous few advisories, with Kenneth expected to move around the western portion of a subtropical ridge over the next couple of days. By Tuesday, a developing weakness in the ridge should cause Kenneth to turn northwestward, then north-northwestward late in the period. The early portion of the track forecast has been shifted a little southward, primarily due to a more southward initial position as noted by recent microwave data. After 72 h, the dynamical models have come into a little better agreement and little change was required to the previous NHC track. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 16.0N 126.1W 60 KT 70 MPH 12H 20/1800Z 16.4N 127.8W 70 KT 80 MPH 24H 21/0600Z 17.2N 129.8W 75 KT 85 MPH 36H 21/1800Z 18.2N 131.5W 75 KT 85 MPH 48H 22/0600Z 19.5N 132.6W 70 KT 80 MPH 72H 23/0600Z 22.7N 134.4W 55 KT 65 MPH 96H 24/0600Z 25.9N 136.0W 40 KT 45 MPH 120H 25/0600Z 27.5N 137.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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