000 WTPZ43 KNHC 271434 TCDEP3 HURRICANE LESTER DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132016 800 AM PDT SAT AUG 27 2016 Lester has been slowly strengthening. Since the last advisory, the eye has cleared out, warmed and become better defined. The cyclone has also been maintaining a compact and fairly symmetric central dense overcast but with no prominent banding features. Satellite classifications are T4.5/77 kt and T5.0/90 kt from TAFB and SAB, respectively. A blend of these is used to raise the initial intensity estimate to 80 kt. Lester's heading has become more westerly during the past several hours, and the initial motion estimate is 275/08. A strong subtropical ridge should hold sway to the north of Lester for at leastthe next 3 days, keeping the cyclone on a nearly due-west course. The track guidance is tightly clustered during this time, resulting in a high confidence forecast. After 72 hours, the model spread increases, with the GFS-based solutions on the northern side of the guidance envelope and the ECMWF to the south. The differences between the models are related to their handling of a mid-latitude trough approaching the California coast, which could weaken the ridge to the north of Lester. The ECMWF maintains a stronger ridge and thus depicts a more westerly track, while the GFS-based guidance shows Lester gaining more latitude as a result of a weaker ridge. The new NHC track foreast is adjusted slightly north of the previous one from 72-120 hours and is close to a consensus of these models. Global models forecast a nearly uniform easterly flow at all levels over Lester throughout the forecast period, implying a low-shear environment for the foreseeable future. Sea surface temperatures should gradually decrease along Lester's track but be warm enough to support additional intensification, except perhaps when it encounters a pocket of somewhat cooler waters between 130W and 140W in 2 to 4 days. The main issue governing Lester's intensity is likely to be the dryness of the air surrounding it, with both the GFS and ECMWF models indicating unusually dry air affecting the cyclone during the period. The NHC intensity forecast calls for only modest intensification the next day or two, during a time when environmental conditions appear most optimal. After that time, the extremely dry conditions and more marginal SSTs suggest that a slow weakening would be the best forecast. The new intensity forecast is lower than the previous one throughout the period. The NHC forecast is above the multi-model consensus in the short term and generally near it after 72 hours. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 18.0N 118.4W 80 KT 90 MPH 12H 28/0000Z 18.0N 119.9W 85 KT 100 MPH 24H 28/1200Z 18.1N 122.4W 90 KT 105 MPH 36H 29/0000Z 18.2N 125.1W 90 KT 105 MPH 48H 29/1200Z 18.4N 128.0W 85 KT 100 MPH 72H 30/1200Z 18.6N 133.7W 80 KT 90 MPH 96H 31/1200Z 18.6N 138.7W 75 KT 85 MPH 120H 01/1200Z 18.7N 143.5W 70 KT 80 MPH $$ Forecaster Kimberlain