ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NORA DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182015 800 AM PDT SAT OCT 10 2015 The satellite appearance of Nora has improved slightly during the past several hours with deeper convection near the center and increased banding features in the northwestward quadrant. The initial intensity is raised to 40 kt as a compromise between the TAFB and SAB satellite estimates. Further strengthening seems likely over the next couple of days while Nora remains in a low shear, warm water environment. The models, however, generally show a lower peak intensity with Nora, perhaps due to drier air in the mid-levels, so the new forecast will reflect this trend. The most notable change to the forecast is at day 3 and beyond when the global models are predicting the vertical wind shear to increase earlier and be much stronger than predicted yesterday for the cyclone. Intensity guidance is notably lower during that period, with only the GFDL showing hurricane strength. The latest NHC prediction is similar to the previous one through 48 hours, then is reduced afterward by about 10 kt. That's about the largest change I feel comfortable making at long range due to continuity concerns, but most of the historically reliable guidance is still below my new forecast. Nora is moving westward at roughly 12 kt. The cyclone should move to the west or west-northwest for the next couple of days while it is steered by a ridge over the east-central Pacific. This ridge is forecast to weaken during that time, which should result in Nora slowing down and gradually gaining latitude. A mid-latitude trough should help the ridge break down in a few days and turn Nora northward, although there remains some spread in the guidance when Nora will recurve. The GFS and HWRF models have joined the ECMWF model in predicting a weaker Nora, which results in a delayed northward turn. The official forecast is similar to the previous one through 72 hours, then is shifted westward at long range in accordance with the new guidance. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 11.7N 137.2W 40 KT 45 MPH 12H 11/0000Z 11.9N 139.0W 45 KT 50 MPH 24H 11/1200Z 12.1N 140.9W 50 KT 60 MPH 36H 12/0000Z 12.3N 142.5W 60 KT 70 MPH 48H 12/1200Z 12.6N 143.7W 65 KT 75 MPH 72H 13/1200Z 13.6N 145.3W 65 KT 75 MPH 96H 14/1200Z 15.9N 145.4W 55 KT 65 MPH 120H 15/1200Z 18.0N 144.5W 45 KT 50 MPH $$ Forecaster Blake NNNN