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Tropical Storm DARBY Forecast Discussion Number 8

2016-07-13 16:32:56| National Hurricane Center (East Pacific)

Issued at 900 AM MDT WED JUL 13 2016 000 WTPZ45 KNHC 131432 TCDEP5 TROPICAL STORM DARBY DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016 900 AM MDT WED JUL 13 2016 About 10-15 kt of northeasterly shear continues to affect Darby, keeping it just below hurricane strength. Microwave data from a few hours ago revealed that the cyclone has a closed mid-level ring, which is offset a bit from the low-level center. In addition, the bulk of the deep convection is displaced to the south of the center. Given the current structure, and that Dvorak estimates range from 55 kt to 65 kt, the initial intensity is held at 60 kt for now. Ocean temperatures near Darby are between 28 and 29 degrees Celsius, and based on the forecast track, it appears that the cyclone will skirt along the northern edge of the cold wake left behind by previous hurricanes. The SSTs will be sufficiently warm to support intensification for the next three days or so, and vertical shear is still expected to decrease later today. Therefore, strengthening is anticipated, with the NHC official forecast close to the high end of the intensity guidance for the entire forecast period. Darby has been moving south of due west, or 265/9 kt, due to a strengthening subtropical ridge extending west of northern Mexico. The ridge is forecast to remain firmly in place through the next 5 days, keeping Darby on a generally westward path. The GFS continues to show a weaker ridge compared to the other global models at the end of the forecast period, but the spread in the guidance envelope is actually fairly low. There is high confidence in the NHC track forecast, which remains near the southern extent of the model suite and close to a consensus of the GFS and ECMWF. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 15.2N 112.4W 60 KT 70 MPH 12H 14/0000Z 15.3N 114.1W 70 KT 80 MPH 24H 14/1200Z 15.6N 116.5W 80 KT 90 MPH 36H 15/0000Z 15.9N 119.0W 90 KT 105 MPH 48H 15/1200Z 16.2N 121.3W 90 KT 105 MPH 72H 16/1200Z 16.8N 125.4W 80 KT 90 MPH 96H 17/1200Z 17.5N 129.5W 70 KT 80 MPH 120H 18/1200Z 18.5N 133.5W 60 KT 70 MPH $$ Forecaster Berg

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Tropical Storm DARBY Forecast Discussion Number 7

2016-07-13 10:57:44| National Hurricane Center (East Pacific)

Issued at 300 AM MDT WED JUL 13 2016 000 WTPZ45 KNHC 130857 TCDEP5 TROPICAL STORM DARBY DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016 300 AM MDT WED JUL 13 2016 Darby continues to strengthen. The satellite appearance has changed from a shear pattern to a central dense overcast, with a larger and deeper area of convection than 6 hours ago. In addition, a WindSat 37 GHz microwave pass at 0104 UTC showed the development of a low-level ring feature. The initial wind speed is raised to 60 kt, a bit above the satellite classifications in deference to the improved inner-core structure. Somewhat surprisingly, Darby has been rapidly intensifying during the past 24 hours, with a 30-kt wind increase during that time. Given the recently observed microwave ring feature and a generally conducive environment, it makes sense to be on the high side of the guidance in the near-term. After 24 hours, SSTs should drop to around 27C, but the shear is expected to stay low. Thus, the forecast intensities are leveled off from days 1-3 in agreement with much of the guidance. A slow decrease in wind speed is predicted at long range due to gradually falling SSTs. The NHC intensity forecast is most similar to a consensus of the HWRF, SHIPS and LGEM models. The storm is moving generally westward at about 10 kt. This general motion is expected for the next several days while Darby remains on the southern side of a strong ridge over the eastern Pacific. The cyclone could turn toward the west-northwest by the end of the period with a weaker ridge possible over the western portion of the basin. Only small changes were made to the previous forecast, and the latest NHC prediction is on the southern side of the well-clustered guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 15.3N 111.5W 60 KT 70 MPH 12H 13/1800Z 15.3N 113.1W 70 KT 80 MPH 24H 14/0600Z 15.5N 115.4W 85 KT 100 MPH 36H 14/1800Z 15.7N 117.9W 90 KT 105 MPH 48H 15/0600Z 16.0N 120.2W 90 KT 105 MPH 72H 16/0600Z 16.7N 124.5W 85 KT 100 MPH 96H 17/0600Z 17.5N 128.5W 75 KT 85 MPH 120H 18/0600Z 18.5N 132.5W 65 KT 75 MPH $$ Forecaster Blake

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Tropical Storm CELIA Forecast Discussion Number 27

2016-07-13 10:57:17| National Hurricane Center (East Pacific)

Issued at 200 AM PDT WED JUL 13 2016 000 WTPZ44 KNHC 130857 TCDEP4 TROPICAL STORM CELIA DISCUSSION NUMBER 27 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 200 AM PDT WED JUL 13 2016 While Celia continues to show an eye in infrared imagery, several recent microwave overpasses indicate this feature is displaced to the north-northeast of the low-level center. Satellite intensity estimates from TAFB and SAB are 65 kt, and a recent CIMSS AMSU estimate is 74 kt. However, a partial ASCAT-B overpass showed maximum winds of 55 kt north of the center. Given these data and the level of disorganization implied by the microwave imagery, Celia is downgraded to a tropical storm with 60-kt winds. The initial motion is 300/10. A mid-level subtropical ridge is predicted by the global models to remain to the north of the cyclone for the next several days. This should result in Celia moving west-northwestward for the next 36-48 hours. After that time, the guidance becomes somewhat divergent. The GFS and UKMET models are on the south side of the guidance envelope and forecast a more westward motion, while the ECMWF is on the north side and forecasts a continued west-northwestward motion. Overall, the consensus models have shifted a little to the south after 36 hours. Based on this, the new forecast track is also shifted a little to the south and shows a just north of due west motion from 48-120 hours. Celia should encounter decreasing sea surface temperatures for the next 48-72 hours. After 72 hours, the cyclone is likely to encounter strong westerly shear even as it moves over slightly warmer water. This evolution should cause Celia to weaken further, with the system forecast to become a tropical depression by 72 hours and a remnant low by 120 hours. The new forecast intensity is an update of the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 18.3N 131.2W 60 KT 70 MPH 12H 13/1800Z 19.3N 132.7W 55 KT 65 MPH 24H 14/0600Z 20.4N 134.8W 50 KT 60 MPH 36H 14/1800Z 21.3N 136.9W 40 KT 45 MPH 48H 15/0600Z 22.0N 139.0W 35 KT 40 MPH 72H 16/0600Z 22.5N 144.0W 30 KT 35 MPH 96H 17/0600Z 23.0N 149.0W 25 KT 30 MPH 120H 18/0600Z 23.5N 153.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven

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Tropical Storm DARBY Forecast Discussion Number 6

2016-07-13 04:39:43| National Hurricane Center (East Pacific)

Issued at 900 PM MDT TUE JUL 12 2016 000 WTPZ45 KNHC 130239 TCDEP5 TROPICAL STORM DARBY DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016 900 PM MDT TUE JUL 12 2016 This evening's satellite presentation shows a considerable amount of improvement in Darby's cloud pattern. It appears as though the northeasterly shear, which was curtailing development, is decreasing. Deep convection has developed over the circulation center with -75C cloud tops, and a strong curved banding feature is evident in the western portion of the cyclone. Dvorak satellite intensity estimates are T3.5 from both agencies, and the initial intensity is increased to 55 kt for this advisory. Further strengthening is expected, and the majority of the intensity guidance indicates that Darby will become a hurricane in 12 hours. Models, particularly the LGEM, Decay SHIPS, and the FSU ensemble, are showing a stronger hurricane in 48-60 hours compared to earlier runs, and the forecast follows suit. Gradual weakening is forecast beyond day 3 as Darby traverses decreasing sea surface temperatures. Darby is moving a little to the left of the previous advisory, now 260/9 kt. The cyclone should continue on a general westward track during the next 48 hours south of a well established mid- to upper level ridge extending from Mexico. The GFDL and the GFS are still indicating a stronger break in the ridge beyond day 3 as a mid-latitude trough approaches the west coast of the United States. The other global models indicate the ridge maintaining strength through day 5. The official forecast basically splits the two solutions and sides with the multi-model consensus and the FSU superensemble. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 15.4N 110.4W 55 KT 65 MPH 12H 13/1200Z 15.3N 111.8W 65 KT 75 MPH 24H 14/0000Z 15.3N 114.1W 75 KT 85 MPH 36H 14/1200Z 15.4N 116.4W 80 KT 90 MPH 48H 15/0000Z 15.5N 118.9W 85 KT 100 MPH 72H 16/0000Z 16.2N 123.3W 85 KT 100 MPH 96H 17/0000Z 16.8N 127.2W 75 KT 85 MPH 120H 18/0000Z 17.7N 131.1W 65 KT 75 MPH $$ Forecaster Roberts

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Hurricane CELIA Forecast Discussion Number 26

2016-07-13 04:36:42| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE JUL 12 2016 000 WTPZ44 KNHC 130236 TCDEP4 HURRICANE CELIA DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 800 PM PDT TUE JUL 12 2016 The convective cloud tops surrounding the large ragged eye of Celia have been gradually warming since earlier today. Based on subjective Dvorak classifications from both TAFB and SAB as well as objective ADT estimates from UW-CIMSS, the intensity is reduced to 65 kt. Since the tropical cyclone will be moving over cooler waters, into a stabler air mass, and westerly shear is forecast to increase, a continued weakening trend is expected. Celia should weaken into a tropical depression by the time it reaches the Central Pacific Hurricane Basin. The official intensity forecast is a little below the latest model consensus and a little above the latest LGEM guidance. The large eye has been moving between west-northwest and northwest at around 10 kt. There is no reason to make any significant changes to the previous NHC forecast track. A mid-level subtropical ridge is predicted by the global models to remain to the north of the cyclone for the next several days. Celia is likely to become an increasingly shallow system, so later in the forecast period, it should turn toward the west following the low-level flow. The official forecast is close to the consensus of the dynamical guidance, which are fairly tightly clustered. This is basically an extension/update of the previous NHC track. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 18.0N 130.3W 65 KT 75 MPH 12H 13/1200Z 18.9N 131.8W 60 KT 70 MPH 24H 14/0000Z 20.0N 133.9W 50 KT 60 MPH 36H 14/1200Z 21.0N 135.9W 45 KT 50 MPH 48H 15/0000Z 21.9N 138.1W 35 KT 40 MPH 72H 16/0000Z 22.7N 142.6W 30 KT 35 MPH 96H 17/0000Z 23.5N 147.5W 25 KT 30 MPH 120H 18/0000Z 24.0N 152.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Pasch

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