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Hurricane Hilary Forecast Discussion Number 12

2017-07-24 10:47:58| National Hurricane Center (East Pacific)

Issued at 400 AM CDT Mon Jul 24 2017 000 WTPZ44 KNHC 240847 TCDEP4 Hurricane Hilary Discussion Number 12 NWS National Hurricane Center Miami FL EP092017 400 AM CDT Mon Jul 24 2017 Hilary's overall cloud pattern continues to become better organized, although inner-core convection is still fluctuating somewhat. There is well-defined upper-level outflow, particularly over the northwest and northeast quadrants of the circulation. Dvorak T-numbers from both TAFB and SAB are now 4.0, which supports upgrading the system to the fourth hurricane of the 2017 eastern North Pacific season. Hilary is expected to continue traversing a warm ocean with weak vertical shear for the next couple of days, which favors continued strengthening. Rapid intensification is a distinct possibility, since the SHIPS Rapid Intensification Index (RII) shows a 60 percent chance of a 30 kt increase in intensity during the next 24 hours. The NHC forecast is in line with the RII guidance, and is close to the HFIP Corrected Consensus intensity forecast through 72 hours, and a little below it thereafter when SSTs beneath the cyclone are expected to cool below 26 deg C. A west-northwestward motion continues, near 300/7 kt. The flow on the southern periphery of a large 500 mb ridge that extends westward from the southwestern United States should be the main steering mechanism for the next several days. A slight strengthening of the flow should lead to some increase in the forward speed of Hilary over the next few days. There is still the possibility of some binary interaction with Tropical Storm Irwin to the west, but for now this interaction is not expected to be very significant within the forecast period. The official track forecast is similar to the previous one and is a blend of the simple and corrected dynamical model consensus predictions. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 14.0N 103.8W 65 KT 75 MPH 12H 24/1800Z 14.4N 104.8W 80 KT 90 MPH 24H 25/0600Z 15.1N 106.3W 95 KT 110 MPH 36H 25/1800Z 15.8N 108.0W 110 KT 125 MPH 48H 26/0600Z 16.4N 110.0W 115 KT 130 MPH 72H 27/0600Z 17.5N 114.0W 105 KT 120 MPH 96H 28/0600Z 18.5N 117.5W 90 KT 105 MPH 120H 29/0600Z 19.5N 121.0W 75 KT 85 MPH $$ Forecaster Pasch

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Tropical Storm Greg Forecast Discussion Number 27

2017-07-24 04:57:50| Tropical Depression LIDIA

Issued at 800 PM PDT Sun Jul 23 2017

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Tropical Storm Hilary Forecast Discussion Number 11

2017-07-24 04:50:31| National Hurricane Center (East Pacific)

Issued at 1000 PM CDT Sun Jul 23 2017 000 WTPZ44 KNHC 240250 TCDEP4 Tropical Storm Hilary Discussion Number 11 NWS National Hurricane Center Miami FL EP092017 1000 PM CDT Sun Jul 23 2017 Hilary has continued to become better organized with a curved convective band now wrapping nearly all the way around the low-level center, and a banding eye of about 10 n mi in diameter evident in recent SSMI/S microwave satellite data. The intensity estimate was 55 kt by TAFB at 0000Z, but since the overall convective and inner-core patterns have improved during the past few hours, the initial intensity is increased to 60 kt for this advisory. The initial motion estimate is 300/08 kt. There is no significant change to the previous forecast track or reasoning. Hilary is expected to move west-northwestward along the southern periphery of a deep-layer ridge to its north for the next several days, with a slight increase in forward speed expected in about 48 hours or so. The new model guidance is tightly packed around the previous NHC advisory track through 96 h, so the new forecast track is just an update of the previous one, and closely follows the HCCA and TVCN models. Given the improving inner-core structure, coupled with very low vertical shear values and a moist unstable environment, continued rapid intensification appears likely for the next 36-48 hours while the small cyclone remains over SSTs greater than 28C. By 72 hours, SSTs cool to near 27C and the upper-ocean heat content decreases to less than 10 units, suggesting that cold upwelling will probably begin around that time. The new intensity forecast follows the previous advisory by showing rapid strengthening of about 15 kt every 12 hours for the next 36 hours, followed by a slightly slower rate of strengthening since an eyewall replacement cycle could begin in the 36-48 h period. After that, increasing shear and cooler water temperatures should induce gradual weakening. The official intensity forecast is similar to the corrected-consensus model HCCA, which brings Hilary to a 116-kt, category-4 hurricane in 48 hours. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 13.6N 103.5W 60 KT 70 MPH 12H 24/1200Z 14.0N 104.5W 70 KT 80 MPH 24H 25/0000Z 14.7N 106.0W 85 KT 100 MPH 36H 25/1200Z 15.4N 107.6W 100 KT 115 MPH 48H 26/0000Z 16.1N 109.5W 110 KT 125 MPH 72H 27/0000Z 17.2N 113.4W 105 KT 120 MPH 96H 28/0000Z 18.3N 117.1W 90 KT 105 MPH 120H 29/0000Z 19.2N 120.8W 80 KT 90 MPH $$ Forecaster Stewart

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Tropical Storm Irwin Forecast Discussion Number 7

2017-07-24 04:32:54| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sun Jul 23 2017 000 WTPZ45 KNHC 240232 TCDEP5 Tropical Storm Irwin Discussion Number 7 NWS National Hurricane Center Miami FL EP102017 800 PM PDT Sun Jul 23 2017 Irwin is gradually gaining strength. Deep convection has increased over the center during the past several hours, and the cloud pattern now consists of a central dense overcast with fragmented curved bands over the southern portion of the circulation. The Dvorak classifications from TAFB and SAB were both 3.0/45 kt, and the initial wind speed is increased to that value. This intensity estimate is also in agreement with an ASCAT-A pass from around 1800 UTC that showed maximum winds in the 40-45 kt range. Irwin is moving westward at 7 kt to the south of a relatively weak low- to mid-level ridge. This ridge is expected to guide Irwin slowly westward during the next few days. After that time, the forecast track becomes much more uncertain as the path of Irwin depends upon the degree of interaction it has with Hilary to its east. The global models all show Irwin slowing down significantly in a few days and then moving north or northeast as it becomes embedded in the circulation of Hilary. Conversely, the hurricane regional models HWRF, HMON, and COAMPS-TC show Irwin continuing generally westward. The NHC track forecast has been shifted a little to the north and west at days 4 and 5, but continues to lie to the east of the consensus aids favoring the global model solutions. The tropical storm is located in an environment of moderate shear, relatively moist conditions, and over 28 degree C water. These conditions are expected to change little during the next couple of days, and should allow for gradual intensification. Beyond that time, an increase in wind shear associated with the outflow of Hilary would likely cause Irwin to weaken some. The NHC intensity forecast is a little higher than the previous one, trending closer to the latest consensus models HCCA and IVCN. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 14.9N 117.3W 45 KT 50 MPH 12H 24/1200Z 14.8N 118.0W 55 KT 65 MPH 24H 25/0000Z 14.8N 118.8W 60 KT 70 MPH 36H 25/1200Z 14.8N 119.6W 65 KT 75 MPH 48H 26/0000Z 14.7N 120.6W 70 KT 80 MPH 72H 27/0000Z 14.2N 122.8W 65 KT 75 MPH 96H 28/0000Z 14.0N 124.2W 60 KT 70 MPH 120H 29/0000Z 14.5N 124.5W 60 KT 70 MPH $$ Forecaster Cangialosi

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Tropical Storm GREG Forecast Discussion Number 26

2017-07-23 22:47:17| Tropical Depression LIDIA

Issued at 200 PM PDT Sun Jul 23 2017

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