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Tropical Depression FOUR-E Forecast Discussion Number 5

2016-07-07 22:34:08| National Hurricane Center (East Pacific)

Issued at 300 PM MDT THU JUL 07 2016 000 WTPZ44 KNHC 072034 TCDEP4 TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 300 PM MDT THU JUL 07 2016 Recent ASCAT data indicate that the tropical depression has an elongated circulation and is still producing maximum winds around 30 kt. Although deep convection has been increasing in coverage during the day, it is not all that organized and is primarily confined to the eastern and southern semicircles. In addition, dry air appears to be wrapping into the western part of the circulation. Since the cyclone's structure has not yet improved, and the system is about to move over the cold wake of Hurricane Blas, it may take a little more time before significant strengthening can occur. In fact, the GFS and ECMWF models, which should have a good handle on the ambient environment, do not show significant deepening of the cyclone for another 48 hours or so. Therefore, the NHC official intensity forecast has been adjusted downward during the first couple of days, with the depression possibly not becoming a tropical storm until tomorrow. More significant strengthening is expected after 48 hours, but even that could be tempered by interaction with Blas's cold wake. The NHC intensity forecast is at the low end of the guidance through 48 hours and then near the IVCN intensity consensus thereafter. The scatterometer data showed that the low-level center is located a little farther south than previously estimated, and the initial motion is now 275/7 kt. A strong mid-tropospheric ridge extending westward from northern Mexico is forecast to keep the cyclone on a westward course for the next 3 days. By days 4 and 5, the ridge is expected to weaken a bit, which will allow the cyclone to turn west-northwestward. The NHC official track forecast was shifted slightly southward during the first three days to account for the updated initial position. Otherwise, the guidance remains tightly clustered, and there is high confidence in the track forecast. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 12.4N 111.7W 30 KT 35 MPH 12H 08/0600Z 12.6N 112.8W 30 KT 35 MPH 24H 08/1800Z 12.9N 114.4W 35 KT 40 MPH 36H 09/0600Z 13.0N 116.1W 40 KT 45 MPH 48H 09/1800Z 13.1N 118.0W 50 KT 60 MPH 72H 10/1800Z 12.9N 121.8W 75 KT 85 MPH 96H 11/1800Z 14.0N 125.5W 85 KT 100 MPH 120H 12/1800Z 16.0N 129.0W 85 KT 100 MPH $$ Forecaster Berg

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Hurricane BLAS Forecast Discussion Number 19

2016-07-07 16:39:35| National Hurricane Center (East Pacific)

Issued at 800 AM PDT THU JUL 07 2016 000 WTPZ43 KNHC 071439 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 800 AM PDT THU JUL 07 2016 Satellite imagery indicates that Blas is beginning to weaken. The eye has become a little less distinct this morning, and the surrounding ring of deep convection has warmed over the northwestern portion of the circulation. A blend of the various Dvorak T- and CI-numbers from SAB, TAFB, and UW-CIMSS yields an initial wind speed of 105 kt. Blas is currently moving over gradually decreasing SSTs, which should result in continued weakening, however, given the annular hurricane characteristics of Blas the rate of weakening is expected to be gradual today. A more rapid spin down should begin tonight or Friday when Blas moves over even cooler water and into a more stable environment. The hurricane is forecast to become post-tropical in about 72 hours, and weaken to a remnant low by day 5. Blas is moving west-northwestward or 290/9. The hurricane is expected to continue moving west-northwestward today, but is forecast to turn northwestward on Friday between a mid-level ridge over northern Mexico and a mid-/upper-level low to the northeast of the Hawaiian Islands. The track guidance has come into better agreement through this time period, and the NHC forecast is near the middle of the guidance envelope through 72 hours. After Blas weakens and becomes a shallower system, the ECMWF takes the cyclone west-southwestward while the remainder of the guidance shows a more westward track. The NHC forecast favors the latter scenario and remains north of the ECMWF solution at days 4 and 5. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 16.2N 127.1W 105 KT 120 MPH 12H 08/0000Z 16.8N 128.2W 95 KT 110 MPH 24H 08/1200Z 17.7N 129.6W 80 KT 90 MPH 36H 09/0000Z 18.9N 131.0W 65 KT 75 MPH 48H 09/1200Z 20.1N 132.4W 50 KT 60 MPH 72H 10/1200Z 21.9N 135.5W 35 KT 40 MPH...POST-TROPICAL 96H 11/1200Z 22.0N 139.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 12/1200Z 22.0N 144.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Hurricane BLAS Forecast Discussion Number 18

2016-07-07 10:45:05| National Hurricane Center (East Pacific)

Issued at 200 AM PDT THU JUL 07 2016 000 WTPZ43 KNHC 070844 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 200 AM PDT THU JUL 07 2016 Blas continues to maintain an impressive satellite presentation, with a distinct 20 n mi wide eye surrounded by a ring of cold convective tops. Overall, the cyclone has been steady-state for the last 24 hours or so, consistent with some annular hurricane characteristics such as minimal convective banding and a large eye. The initial intensity remains 110 kt based on the latest Dvorak classifications of T5.5/6.0 from TAFB and SAB. The hurricane will be moving over cooler waters and into a more stable atmospheric environment during the next 12 to 24 hours, which should result in the onset of weakening. Weakening should continue after that time, with Blas expected to move over SSTs of about 24C in 48 hours. Deep convection is expected to dissipate late in the period, and Blas should become post-tropical in 4 days, or perhaps a bit sooner. The official forecast is close to the latest IVCN intensity consensus aid. The initial motion estimate is 290/09, as Blas continues to be steered around the southwestern periphery of a distant mid-level ridge centered over northern Mexico. The hurricane is forecast to turn northwestward in 24-36 hours as it reaches the western edge of the ridge, and the track model guidance is in good agreement on this scenario. Through 48 hours the NHC track has been shifted a bit north of the previous one following the latest trend in the guidance. Afterward, most of the guidance shows a continued west-northwestward or northwestward motion through 72 hours as Blas interacts with an upper-level closed low northeast of the Hawaiian Islands, followed by the shallow post-tropical Blas turning westward. The ECMWF continues to show less interaction with the upper-level low, and turns Blas westward and west-southwestward at days 4 and 5. Compared to 24 hours ago, the GFS-based guidance has shifted southward and the ECMWF has trended a bit northward, suggesting that a consensus approach is still the best solution. The new NHC track at days 3 through 5 is close to the previous one and near the middle of the guidance envelope. This track is a little south of the latest multi-model consensus but well north of the ECMWF. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 15.9N 126.4W 110 KT 125 MPH 12H 07/1800Z 16.4N 127.6W 100 KT 115 MPH 24H 08/0600Z 17.2N 129.1W 85 KT 100 MPH 36H 08/1800Z 18.3N 130.4W 70 KT 80 MPH 48H 09/0600Z 19.5N 131.8W 60 KT 70 MPH 72H 10/0600Z 21.5N 135.0W 40 KT 45 MPH 96H 11/0600Z 22.0N 139.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 12/0600Z 22.0N 143.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan

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Tropical Depression FOUR-E Forecast Discussion Number 3

2016-07-07 10:44:05| National Hurricane Center (East Pacific)

Issued at 300 AM MDT THU JUL 07 2016 000 WTPZ44 KNHC 070843 TCDEP4 TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 300 AM MDT THU JUL 07 2016 Tropical Depression Four-E has changed little overnight. A 0458Z ASCAT-B overpass indicated a broad, weak inner-core wind field with the low-level center located at or south of 12N latitude. However, passive microwave satellite data indicate a fairly well-developed mid-level circulation displaced more than 30 nmi north-northwest of the low-level center due to southeasterly vertical wind shear. The ASCAT data also indicated a couple of 35-kt surface wind vectors. However, convection near the center has noticeably weakened and become less organized since that pass, so the cyclone is being maintained as a 30-kt depression, which is supported by a blend of satellite intensity estimates from TAFB, SAB, and UW-CIMSS. The initial motion estimate is still 285/07 kt, based primarily on a blend of microwave and scatterometer fix positions of the low-level and mid-level circulation centers. Despite the difficulty in locating the exact center of the depression, the NHC model guidance is in remarkably good agreement on the future track of the cyclone. The strong subtropical ridge to the north of the depression is forecast to remain nearly stationary throughout the forecast period, and even amplify somewhat in 24-72 hours, driving the cyclone in a general westward motion. After that time, the cyclone is expected to turn toward the west-northwest as the system moves around the southwestern periphery of the ridge. The NHC official forecast track essentially lies down the middle of the guidance envelope, and closely follows the multi-model consensus TVCE. The depression is experiencing mid-level dry air entrainment and modest mid-level shear conditions, which have combined to disrupt the inner-core wind field somewhat. However, the overall environment is quite favorable for strengthening to occur, so once the inner-core region recovers later today, steady strengthening is expected through 36 h. However, around 48 h or so, the cyclone is expected to pass near or just south of a pronounced cold wake left behind by Hurricane Blas when it traversed this same area a couple of days ago. This could produce a slightly more stable environment, so the intensification trend at that time is leveled off some. From 72 hours and beyond, however, conditions become quite favorable for at least steady strengthening, and some of the models are even calling for the cyclone to become a major hurricane by 120 h. The official intensity forecast is similar to the previous advisory, and closely follows a blend of the SHIPS and LGEM models through 72 hours, but is a little lower than those models on days 4 and 5. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 12.6N 110.2W 30 KT 35 MPH 12H 07/1800Z 12.7N 111.2W 35 KT 40 MPH 24H 08/0600Z 12.8N 112.6W 45 KT 50 MPH 36H 08/1800Z 12.9N 114.2W 55 KT 65 MPH 48H 09/0600Z 13.1N 115.9W 60 KT 70 MPH 72H 10/0600Z 13.1N 119.4W 75 KT 85 MPH 96H 11/0600Z 14.0N 123.6W 85 KT 100 MPH 120H 12/0600Z 15.6N 127.4W 95 KT 110 MPH $$ Forecaster Stewart

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Hurricane BLAS Forecast Discussion Number 17

2016-07-07 04:35:05| National Hurricane Center (East Pacific)

Issued at 800 PM PDT WED JUL 06 2016 000 WTPZ43 KNHC 070234 TCDEP3 HURRICANE BLAS DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 800 PM PDT WED JUL 06 2016 The satellite presentation of Blas remains quite impressive. The eye of the hurricane is about 20-25 n mi wide with evidence of mesovorticies within it. The convective structure has changed little throughout the day and remains fairly symmetric around the center. A blend of the latest Dvorak classifications from TAFB, SAB, and the automated technique from CIMSS at the University of Wisconsin suggest that the intensity of Blas is holding steady at around 110 kt. The major hurricane is not far away from cool water, and it will likely be crossing the 26 C isotherm in about 12 hours. These anticipated unfavorable oceanic conditions combined with a progressively more stable air mass should promote a steady weakening trend during the next several days. The NHC intensity forecast is an update of the previous one and is fairly close to the intensity model consensus. The system is forecast to become a post-tropical cyclone in about 4 days when sea surface temperatures beneath the cyclone will likely be around 24 C. Blas is moving west-northwestward at about 10 kt on the southwestern periphery of a sprawling mid-level ridge. This general motion should continue for the next couple of days as the ridge remains the primary steering influence. Beyond that time, the forecast track is less certain as the model spread remains quite large with the GFS-based guidance showing a northwestward motion around the east side of a mid- to upper-level low northeast of the Hawaiian Islands. Conversely, the ECMWF and UKMET models show less interaction with the upper low, resulting in a more westward track. The NHC track forecast remains near the middle of the guidance envelope and is in best agreement with the consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 15.7N 125.4W 110 KT 125 MPH 12H 07/1200Z 16.1N 126.8W 100 KT 115 MPH 24H 08/0000Z 16.7N 128.4W 90 KT 105 MPH 36H 08/1200Z 17.5N 129.8W 75 KT 85 MPH 48H 09/0000Z 18.7N 131.2W 65 KT 75 MPH 72H 10/0000Z 20.8N 134.1W 50 KT 60 MPH 96H 11/0000Z 22.1N 138.2W 35 KT 40 MPH...POST-TROPICAL 120H 12/0000Z 22.2N 142.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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