000 WTPZ44 KNHC 250235 TCDEP4 Hurricane Hilary Discussion Number 15 NWS National Hurricane Center Miami FL EP092017 1000 PM CDT Mon Jul 24 2017 Recent microwave satellite images indicate that Hilary has developed a tight banding eye feature with a diameter of less than 10 nmi. Deep convection with cloud tops to -85C within an elongated CDO has continued to pulse since the previous advisory, likely due to some modest high-level shear induced by a large convective complex located a couple hundred nmi southeast of Hilary's center. However, that convective cloud mass has recently been showing signs of waning, so that negative influence will likely begin to abate fairly soon. Dvorak satellite intensity estimates were a consensus T4.5/77 kt from TAFB and SAB at 0000Z. Since that time, the CDO has become more distinct and NHC objective intensity estimates have been ranging between 82-88 kt during the past 2 hours. As a result, the advisory intensity has been increased to 85 kt. The initial motion estimate is 300/08 kt. Hilary is forecast to move generally west-northwestward along the southern periphery of a deep-layer subtropical ridge for the next 5 days. With the exception of the more northerly GFS model -- which had a similar poleward bias with Fernanda -- the rest of the NHC model guidance is tightly clustered around the previous forecast track. As a result, only minor speed adjustments were made to the previous forecast track. Although some binary interaction with TS Irwin is still possible, Hilary is expected to be the larger and more dominant circulation, resulting in Irwin being pulled poleward within Hilary's wake on days 3-5. The small eye and tight inner-core banding features noted in recent microwave imagery, along with large-scale low vertical wind shear conditions and favorable thermodynamics, argues for some rapid intensification to occur during the next 12-24 hours. Thereafter, some adjustment of the eye and inner-core wind field is possible, which has resulted in a leveling off of Hilary's intensity forecast in the 24-to 48-h period. By 72 hours and beyond, the combination of decreasing SSTs to less than 26C along with some modest westerly wind shear should produce steady weakening. The official intensity forecast is similar to the previous advisory, and follows a blend of the HCCA and ECMWF intensity predictions. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 15.0N 105.7W 85 KT 100 MPH 12H 25/1200Z 15.5N 107.0W 95 KT 110 MPH 24H 26/0000Z 16.1N 109.0W 105 KT 120 MPH 36H 26/1200Z 16.5N 111.1W 105 KT 120 MPH 48H 27/0000Z 17.1N 113.0W 100 KT 115 MPH 72H 28/0000Z 18.1N 116.7W 90 KT 105 MPH 96H 29/0000Z 19.1N 120.2W 80 KT 90 MPH 120H 30/0000Z 19.9N 123.4W 65 KT 75 MPH $$ Forecaster Stewart