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Hurricane BLAS Forecast Discussion Number 23

2016-07-08 16:50:12| National Hurricane Center (East Pacific)

Issued at 800 AM PDT FRI JUL 08 2016 000 WTPZ43 KNHC 081450 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 800 AM PDT FRI JUL 08 2016 Despite being over cool water, the convection associated with Blas remains deep with cloud tops below -70C. Recent microwave data show that the eye of Blas is still intact and it has occasionally been evident in infrared satellite imagery this morning. Subjective and objective Dvorak T-numbers are gradually decreasing and a blend of the latest estimates yields an initial wind speed of 85 kt. The hurricane will be moving over waters below 24C and into a more stable atmospheric environment during the next 12 to 24 hours. This is expected to cause rapid weakening and Blas is forecast to weaken to a tropical storm by early Saturday, and become post-tropical in about 48 hours. Blas is still moving west-northwestward or 300/9 kt. The cyclone is expected to turn northwestward very soon between a mid-level ridge extending westward off the coast of Mexico and a mid- to upper-level low northeast of Hawaii. As Blas weakens and becomes a more vertically shallow system, it should turn back westward, then west-southwestward in the low level trade wind flow in 48 to 72 hours. The bulk of the track guidance has shifted a bit southward at 48 hours and beyond, and the NHC forecast has been adjusted in that direction. The updated track is near the center of the model envelope through 72 hours, but is north of the multi-model consensus after that time out of respect for the GFS, GFS ensemble mean, and continuity with the previous NHC track. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 17.8N 130.0W 85 KT 100 MPH 12H 09/0000Z 19.0N 130.9W 70 KT 80 MPH 24H 09/1200Z 20.3N 132.2W 55 KT 65 MPH 36H 10/0000Z 21.3N 133.6W 40 KT 45 MPH 48H 10/1200Z 21.7N 135.3W 35 KT 40 MPH...POST-TROPICAL 72H 11/1200Z 21.5N 139.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 12/1200Z 20.3N 144.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 13/1200Z 19.5N 147.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Hurricane BLAS Forecast Discussion Number 22

2016-07-08 10:46:10| National Hurricane Center (East Pacific)

Issued at 200 AM PDT FRI JUL 08 2016 000 WTPZ43 KNHC 080846 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 200 AM PDT FRI JUL 08 2016 The eye of Blas is no longer apparent in infrared imagery, but cold cloud tops persist in a CDO over the center. The initial intensity is lowered to 90 kt based on a blend of the latest subjective and objective Dvorak estimates. Rapid weakening is expected during the next 48 hours as Blas moves over much cooler waters and into a drier and more stable airmass, and the NHC forecast during this time is close to the latest LGEM guidance. Blas is expected to become post-tropical by 48 hours and then continue a slow spin down through the remainder of the forecast period. The initial motion estimate is 300/09, as Blas is beginning to gain some latitude as it moves around the southwestern edge of a subtropical ridge centered well to the east over Mexico. The track model guidance shows Blas turning northwestward between 12 to 36 h as it moves into a weakness ahead of a large upper-level low northeast of the Hawaiian Islands. After that time a weakening Blas should turn westward and then west-southwestward under the influence of the low-level trade wind flow. The new NHC forecast is a bit north of the previous one through 48 hours following the latest guidance trend. Late in the period the guidance has shifted southward, and the new NHC track is south of the previous one. This forecast is little south of the latest GFS track and ends up a bit north of the multi-model consensus by day 5. The initial and forecast wind radii were adjusted based on a pair of timely ASCAT-A and ASCAT-B passes over Blas between 0530 and 0630 UTC. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 17.4N 129.4W 90 KT 105 MPH 12H 08/1800Z 18.3N 130.3W 75 KT 85 MPH 24H 09/0600Z 19.7N 131.5W 60 KT 70 MPH 36H 09/1800Z 21.0N 132.8W 45 KT 50 MPH 48H 10/0600Z 21.8N 134.4W 35 KT 40 MPH...POST-TROPICAL 72H 11/0600Z 22.0N 138.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 12/0600Z 21.0N 143.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 13/0600Z 20.0N 147.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan

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Tropical Depression FOUR-E Forecast Discussion Number 7

2016-07-08 10:38:42| National Hurricane Center (East Pacific)

Issued at 300 AM MDT FRI JUL 08 2016 000 WTPZ44 KNHC 080838 TCDEP4 TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 300 AM MDT FRI JUL 08 2016 The cloud pattern of the depression is showing signs of becoming better organized. There has been an increase in central convection near the estimated center location and in convective banding to the north and southeast of the center. The initial intensity remains 30 kt based on a blend of the latest TAFB and SAB Dvorak estimates. Slow strengthening is forecast during the next 24 hours, while the cyclone moves over a cool patch of SSTs in the wake of Hurricane Blas. After that time, the intensification rate should increase as the cyclone will be moving over warm SSTs in a low shear environment. In 4 to 5 days, the shear is expected to increase and SSTs cool along the track, which should result in weakening. The new NHC intensity forecast is a little below the consensus aid IVCN during the first 24 hours and then close to the consensus through 48 hours. Beyond that time the official forecast is higher than the consensus but not as aggressive as the SHIPS model. The initial motion estimate is a rather uncertain 275/05 given the uncertainty in the exact center location. The cyclone should be steered more quickly westward by a building subtropical ridge to the north through the next 2 to 3 days. After that time, a west- northwestward turn is forecast as the system reaches the southwestern edge of the ridge. The guidance has shifted northward this cycle in the short term, in particular the ECMWF, which is now well north of the rest of the models through 48 hours. The new NHC track has been adjusted to the north this cycle, but still lies a little south of the multi-model consensus. Confidence in the details of the track forecast is lower than normal given that the system is still organizing. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 12.5N 112.0W 30 KT 35 MPH 12H 08/1800Z 12.7N 113.1W 35 KT 40 MPH 24H 09/0600Z 13.0N 115.0W 40 KT 45 MPH 36H 09/1800Z 13.2N 116.7W 50 KT 60 MPH 48H 10/0600Z 13.5N 119.0W 60 KT 70 MPH 72H 11/0600Z 14.2N 123.3W 85 KT 100 MPH 96H 12/0600Z 15.7N 127.5W 85 KT 100 MPH 120H 13/0600Z 17.3N 131.2W 75 KT 85 MPH $$ Forecaster Brennan

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Hurricane BLAS Forecast Discussion Number 21

2016-07-08 04:33:40| National Hurricane Center (East Pacific)

Issued at 800 PM PDT THU JUL 07 2016 000 WTPZ43 KNHC 080233 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 800 PM PDT THU JUL 07 2016 The eye feature has become less discernible in enhanced infrared imagery this evening, and the inner core cloud top temperatures have warmed considerably. A compromise of all available subjective and objective Dvorak intensity estimates yields an initial intensity of 95 kt. Blas is expected to accelerate its spin down as the cyclone continues to traverse a rather sharp sea surface temperature gradient and reaches sub-24C waters by the 36 hour period. Blas is forecast to weaken to a tropical storm by that time, and ultimately become a remnant low in 3 days, or earlier. The official forecast intensity is basically an update of the previous advisory and is close to the Florida State Superensemble. The initial motion is west-northwestward or 295/8, within the southwestern peripheral steering flow of a mid-level ridge originating over eastern Mexico. Large-scale models all show the cyclone gradually turning northwestward in 12 hours as Blas enters a growing weakness produced by a large cut-off low northeast of the Hawaiian Islands. As the weakening trend accelerates and Blas becomes a vertically shallower system, the post-tropical remnant low is expected to turn westward in the easterly flow of the trades. The NHC forecast is based on a blend of the previous forecast and a consensus of the ECMWF and GFS (GFEX). FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 16.9N 128.6W 95 KT 110 MPH 12H 08/1200Z 17.6N 129.7W 85 KT 100 MPH 24H 09/0000Z 18.8N 131.0W 65 KT 75 MPH 36H 09/1200Z 20.2N 132.4W 55 KT 65 MPH 48H 10/0000Z 21.5N 133.9W 40 KT 45 MPH 72H 11/0000Z 22.5N 137.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 12/0000Z 22.3N 142.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 13/0000Z 21.7N 146.9W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts

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Hurricane BLAS Forecast Discussion Number 20

2016-07-07 22:38:35| National Hurricane Center (East Pacific)

Issued at 200 PM PDT THU JUL 07 2016 000 WTPZ43 KNHC 072038 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 200 PM PDT THU JUL 07 2016 The eye of Blas has become cloud filled in visible satellite imagery today, but the convective ring surrounding the center has changed little since this morning. Recent microwave imagery indicates that the southwestern portion of the eyewall has eroded somewhat. Although the subjective Dvorak current intensity estimates have not changed much since 1200 UTC, the objective T-numbers have decreased and the initial wind speed has been reduced to 100 kt. Blas will be moving over cooler water and into a more stable environment during the next several days. This should result in a faster rate of weakening and Blas is forecast to weaken to a tropical storm in about 36 hours, and become post-tropical in about 72 hours. The updated NHC intensity forecast is between the SHIPS/LGEM guidance and close to the multi-model intensity consensus. Blas continues to move west-northwestward or 290/9. The track forecast reasoning remains unchanged. The hurricane is expected to turn northwestward on Friday between a mid-level ridge over northern Mexico and a mid- to upper-level low to the northeast of the Hawaiian Islands. In 2 to 3 days, a weaker and more shallow Blas should turn westward in the low-level easterly flow. The GFS and ECMWF continue to converge on this solution, and the updated NHC track is near a consensus of those models. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 16.6N 127.8W 100 KT 115 MPH 12H 08/0600Z 17.1N 128.9W 90 KT 105 MPH 24H 08/1800Z 18.2N 130.3W 75 KT 85 MPH 36H 09/0600Z 19.5N 131.6W 60 KT 70 MPH 48H 09/1800Z 20.9N 132.9W 45 KT 50 MPH 72H 10/1800Z 22.2N 136.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 11/1800Z 22.2N 140.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 12/1800Z 21.8N 145.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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