000 WTPZ43 KNHC 031439 TCDEP3 TROPICAL STORM BLAS DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016 900 AM MDT SUN JUL 03 2016 Satellite imagery indicates a marked increase in organization of the Blas' cloud pattern overnight, suggesting that the cyclone is quickly intensifying. The center is located underneath a ball of deep convection, the latter which appears to be a formative central dense overcast. The large-envelope cyclone also has a lengthening band that consists of very cold-topped convection in the shape of a figure six. Satellite classifications are T3.0/45 kt and T3.5/55 kt from SAB and TAFB at 1200 UTC, respectively. The initial intensity is raised to 50 kt, based on a blend of the two intensity estimates. The initial motion estimate is 285/11. Blas is forecast to move along the southern periphery of a deep-layer subtropical ridge centered over northern Mexico throughout the forecast period, which should keep the cyclone on a general west-northwesterly course. The model guidance is in very good agreement through 72 hours, but diverges after that time. The GFS and its ensemble mean lie near the previous forecast and is on the northern side of the guidance envelope, while the ECMWF and its ensemble mean are much farther south. The differences between the two models appear related to subtle variations in the strength and position of the subtropical ridge forecast after day 3. The NHC track forecast is adjusted a bit south of the previous one, on the southern side of the guidance envelope through 72 hours and near the multi-model consensus after that time. There does not appear to be anything obvious on the large-scale to impede intensification over the next few days, except that the cyclone will be very gradually departing the warmest waters over the basin. The light-easterly-shear, moist environment and warm waters should allow Blas to strengthen into a major hurricane as indicated in about 48 hours. The official NHC forecast through that time is heavily weighted toward the statistical guidance which is performing well, considering the current developmental trend. By 96 hours, even though the shear is forecast to remain low, the cyclone should be moving over steadily cooler waters and entering a drier and more stable environment. This should foster a weakening trend, though the weakening will likely occur only gradually. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 11.6N 110.3W 50 KT 60 MPH 12H 04/0000Z 12.1N 112.0W 60 KT 70 MPH 24H 04/1200Z 12.6N 114.1W 75 KT 85 MPH 36H 05/0000Z 13.1N 116.4W 90 KT 105 MPH 48H 05/1200Z 13.6N 118.7W 100 KT 115 MPH 72H 06/1200Z 14.6N 123.3W 105 KT 120 MPH 96H 07/1200Z 16.0N 127.7W 95 KT 110 MPH 120H 08/1200Z 17.3N 131.3W 85 KT 100 MPH $$ Forecaster Kimberlain