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Hurricane BLAS Forecast Discussion Number 16

2016-07-06 22:35:05| National Hurricane Center (East Pacific)

Issued at 200 PM PDT WED JUL 06 2016 000 WTPZ43 KNHC 062034 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 200 PM PDT WED JUL 06 2016 Blas has a very impressive satellite presentation this afternoon. The hurricane has a large, distinct eye in visible satellite images that is surrounded by a very symmetric ring of deep convection. Dvorak T-numbers are virtually unchanged since this morning so the initial intensity of 110 kt has been maintained. The hurricane is expected to begin to weaken tonight as it moves over gradually decreasing sea surface temperatures. Blas should cross the 26C isotherm in about 24 hours, which is expected to cause a faster rate of decay. The cyclone is forecast to become post-tropical in about 96 hours, and weaken to a remnant low by day 5. The NHC intensity forecast is between the SHIPS and LGEM guidance and close to the multi-model intensity consensus. The initial motion remains 285/10 kt. Blas should continue moving west-northwestward during the next day or so while it moves around the southwestern portion of a mid-level ridge over northern Mexico. After that time, the hurricane is expected to turn northwestward between the western portion of the ridge and a large mid- to upper-level low to the northeast of the Hawaiian Islands. The spread of the guidance remains fairly large at 72 hours and beyond, however, the models have moved a little closer together with the GFS-based guidance shifting southward while the ECMWF has nudged northward. As a result, little change has been made to the NHC track prediction, which lies closest to the GFS/ECMWF (GFEX) consensus aid. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 15.2N 124.7W 110 KT 125 MPH 12H 07/0600Z 15.7N 126.2W 100 KT 115 MPH 24H 07/1800Z 16.2N 127.9W 90 KT 105 MPH 36H 08/0600Z 17.0N 129.5W 80 KT 90 MPH 48H 08/1800Z 18.0N 131.0W 65 KT 75 MPH 72H 09/1800Z 20.2N 134.0W 50 KT 60 MPH 96H 10/1800Z 21.8N 137.5W 35 KT 40 MPH...POST-TROPICAL 120H 11/1800Z 22.5N 141.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Tropical Depression FOUR-E Forecast Discussion Number 1

2016-07-06 22:35:05| National Hurricane Center (East Pacific)

Issued at 300 PM MDT WED JUL 06 2016 000 WTPZ44 KNHC 062034 TCDEP4 TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 300 PM MDT WED JUL 06 2016 Satellite imagery indicates that the low pressure area located well southwest of the coast of Mexico now has a well-defined circulation and sufficient organized convection to be designated a tropical depression. Thus, advisories are initiated on Tropical Depression Four-E with an initial intensity of 30 kt. The depression is moving westward or 280 degrees at 7 kt. A weak low- to mid-level ridge should steer the cyclone westward at a less than climatological forward speed for the next 3-4 days, followed by a west-northwestward motion by day 5. The track forecast guidance is in good agreement with this scenario, and the track forecast is in the center of the guidance envelope. The dynamical models forecast that the cyclone will be in an environment of light vertical wind shear for the next five days. However, it is forecast to cross an area of cooler water, possibly a cold wake left by Hurricane Blas, during the next 72 hours. This is expected to allow only slow intensification during that time. Subsequently, the cyclone should move over warmer water and strengthen at a faster rate. The intensity forecast is in best agreement with the SHIPS model, and it calls for the cyclone to become a tropical storm in about 24 hours and a hurricane in about 96 hours. An alternative scenario is that the cyclone strengthens faster than currently forecast due to the conducive shear environment. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 12.2N 109.1W 30 KT 35 MPH 12H 07/0600Z 12.3N 110.1W 30 KT 35 MPH 24H 07/1800Z 12.3N 111.4W 35 KT 40 MPH 36H 08/0600Z 12.5N 112.6W 40 KT 45 MPH 48H 08/1800Z 12.5N 114.2W 45 KT 50 MPH 72H 09/1800Z 12.5N 117.5W 55 KT 65 MPH 96H 10/1800Z 13.0N 120.5W 75 KT 85 MPH 120H 11/1800Z 14.5N 123.5W 90 KT 105 MPH $$ Forecaster Beven

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Hurricane BLAS Forecast Discussion Number 15

2016-07-06 16:42:59| National Hurricane Center (East Pacific)

Issued at 800 AM PDT WED JUL 06 2016 000 WTPZ43 KNHC 061442 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 800 AM PDT WED JUL 06 2016 The overall satellite appearance of Blas has changed little since early this morning. Blas has characteristics of an annular hurricane with a large 25 to 30 n mi wide eye surrounded by a symmetric convective ring with little outer banding features. The initial intensity remains 110 kt, and is a blend of the various objective and subjective Dvorak satellite intensity estimates. Blas is currently in a low shear environment and over SSTs of 27-28 degrees Celsius. Although the shear is forecast to remain low for the next several days, decreasing sea surface temperatures along the forecast track should result in gradual weakening of the hurricane during the next 24 to 36 hours. After that time, Blas will be moving over SSTs below 26C which should cause a faster rate of weakening, and the cyclone is forecast to become post-tropical in about 4 days. The NHC intensity forecast is similar to the previous advisory and lies between the SHIPS and LGEM models. Blas is moving west-northwestward or 285 degrees at 10 kt, and should continue on this general motion during the next 36 to 48 hours while it moves around the southwestern portion of a mid-level ridge over northern Mexico. By 72 hours, the model guidance begins to diverge with the GFS, HWRF, GFDL, and GFS ensemble mean taking Blas northwestward around the eastern portion of a large mid- to upper-level low to the northeast of Hawaii. The ECMWF and UKMET models show a more westward track, with less interaction between the upper-low and the hurricane. This appears to be the result of the size, location, and orientation of the upper-low in the various models. Given the large spread in the guidance, there is low confidence in the the track forecast late in the period, and the NHC forecast track remains near the GFS/ECMWF consensus at days 3-5. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 15.0N 123.6W 110 KT 125 MPH 12H 07/0000Z 15.4N 125.2W 105 KT 120 MPH 24H 07/1200Z 16.0N 127.1W 95 KT 110 MPH 36H 08/0000Z 16.6N 128.8W 85 KT 100 MPH 48H 08/1200Z 17.5N 130.4W 70 KT 80 MPH 72H 09/1200Z 19.6N 133.3W 50 KT 60 MPH 96H 10/1200Z 21.8N 137.0W 35 KT 40 MPH...POST-TROPICAL 120H 11/1200Z 22.5N 140.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Hurricane BLAS Forecast Discussion Number 14

2016-07-06 10:36:27| National Hurricane Center (East Pacific)

Issued at 200 AM PDT WED JUL 06 2016 000 WTPZ43 KNHC 060836 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 200 AM PDT WED JUL 06 2016 The satellite presentation of Blas has degraded since the previous advisory, as the convective ring surrounding the eye had warmed and shrunk. The eye, however, remains distinct in infrared imagery. The initial intensity has been lowered to 110 kt, which is a little above a blend of the latest Dvorak CI and Final-T numbers from TAFB and SAB. Sea surface temperatures gradually cool along the forecast track, which should result in weakening, albeit at a slow pace during the first day or so. After 24 hours the rate of weakening should increase as SSTs fall below 27C. Blas is expected to become a post-tropical cyclone in about 4 days and a remnant low by day 5. The new NHC intensity forecast is close to or a little above the latest LGEM and IVCN intensity consensus. The initial motion estimate is 280/10, as Blas has begun to gain some latitude. Blas should move west-northwestward for the next 48 hours while being steered around the southwestern periphery of a mid-level ridge centered over Mexico. After that time the model spread increases. The GFS based guidance, including the HWRF and GFDL, shows Blas turning northwestward late in the period as it interacts with an upper-level low northeast of the Hawaiian Islands. The ECMWF continues to show less interaction between Blas and the upper-level low and has the cyclone turning westward at days 4-5. Given the continued spread in the guidance, the NHC track forecast will stay in the middle of the two extremes and shows a northwestward to west-northwestward motion at days 4-5. This forecast is a little south of the latest GFS/ECMWF consensus. Given the uncertainty, there is low confidence in the details of the track forecast late in the period. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 14.7N 122.7W 110 KT 125 MPH 12H 06/1800Z 15.1N 124.2W 105 KT 120 MPH 24H 07/0600Z 15.7N 126.3W 100 KT 115 MPH 36H 07/1800Z 16.3N 128.1W 90 KT 105 MPH 48H 08/0600Z 16.9N 129.7W 75 KT 85 MPH 72H 09/0600Z 18.8N 132.6W 55 KT 65 MPH 96H 10/0600Z 21.0N 136.0W 35 KT 40 MPH...POST-TROPICAL 120H 11/0600Z 22.5N 140.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan

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Hurricane BLAS Forecast Discussion Number 13

2016-07-06 04:33:58| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE JUL 05 2016 000 WTPZ43 KNHC 060233 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 800 PM PDT TUE JUL 05 2016 Blas continues to intensify. Satellite images indicate that Blas has a typical appearance of a major hurricane with a distinct eye surrounded by a fairly symmetric ring of deep convection. The Dvorak CI-numbers at 0000 UTC were 6.0/115 kt from TAFB and SAB, and recent ADT values from CIMSS at the University of Wisconsin are a little higher. Based on these estimates and the continued improvement in organization since the time of the classifications, the initial wind speed is set at 120 kt. This makes Blas a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. The hurricane has slowed a little in forward speed, and the latest initial motion estimate is 275/11 kt. The models are in very good agreement for the next 3 days or so in showing Blas continuing westward to west-northwestward on the southwest side of a mid-level ridge centered over Mexico and the eastern Pacific Ocean. After that time, however, the model solutions diverge with the bulk of the guidance showing a northwestward motion due to the cyclone interacting with a cut-off low northeast of the Hawaiian Islands. The ECMWF model has a notably different solution showing little involvement with the cut-off low, which results in Blas continuing westward. No significant changes were made to the previous prediction and this track forecast lies close to a consensus of the GFS and ECMWF models. It should be noted that there is low confidence at the latter forecast points. Blas still has another 12-18 hours of favorable conditions for strengthening. Beyond that time, the cyclone is expected to move over cool water and into a progressively drier air mass. These conditions should end the strengthening phase and cause a steady weakening trend. The official NHC intensity forecast lies at the upper end the guidance in the short term, but then falls in line with the intensity model consensus from 36-120 h. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 14.4N 121.7W 120 KT 140 MPH 12H 06/1200Z 14.8N 123.4W 130 KT 150 MPH 24H 07/0000Z 15.4N 125.5W 120 KT 140 MPH 36H 07/1200Z 16.0N 127.4W 100 KT 115 MPH 48H 08/0000Z 16.6N 129.0W 85 KT 100 MPH 72H 09/0000Z 18.2N 132.1W 65 KT 75 MPH 96H 10/0000Z 20.2N 135.7W 45 KT 50 MPH 120H 11/0000Z 21.6N 139.8W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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