ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Norma Discussion Number 1 NWS National Hurricane Center Miami FL EP172023 300 PM MDT Tue Oct 17 2023 Satellite imagery this afternoon depicts that the area the National Hurricane Center has been monitoring offshore of the southwestern coast of Mexico (EP90) has become better organized. Showers and thunderstorms have been consolidating, with curved band features developing around a recently well-defined low-level center. Subjective Dvorak satellite intensity estimates are T2.5/T3.0 from TAFB and SAB, respectively. Given the improved satellite presentation and these intensity estimates, advisories are being initiated on Tropical Storm Norma with an initial intensity of 35 kt. Norma is in a fairly conducive environment for intensification. Low vertical wind shear, warm sea surface temperatures, and favorable upper-level diffluence will likely lead to steady to rapid strengthening for the next few days. DTOPS and SHIPS rapid intensification (RI) indices are between 60 to 70 percent for a 55 kt increase over the next 48 hours, and the NHC forecast is near that value, explicitly forecasting RI between 12 to 36 hours. Towards the end of the forecast, increasing vertical wind shear and potential drier air intrusions could cause the system to gradually weaken. The NHC forecast lies just below the HCCA HFIP corrected consensus aids, and it is noted that the HAFS-A/B hurricane regional models show a higher, but still plausible, peak intensity. Norma is moving west-northwestward at an estimated motion of 285/9 kt. The system is expected to turn more northwestward at a slightly slower forward speed during the next few days around the western periphery of a mid-level ridge. Towards the end of the forecast period as the system moves toward the Baja peninsula, there is a notable divergence among the model suite. A stronger vortex, as depicted in the GFS/CMC model, would be picked up by an approaching trough from the northwest and move the system northeastward towards the Baja peninsula. However, a weaker vortex would tend to meander south of the peninsula and be missed by the approaching trough, like the ECMWF/UKMET solutions. Since the NHC intensity forecast is on the strong side of the guidance, the official track is closer to the right side of the guidance envelope, more similar to the GFS and HCCA models. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 13.2N 107.3W 35 KT 40 MPH 12H 18/0600Z 13.8N 108.0W 45 KT 50 MPH 24H 18/1800Z 15.0N 108.4W 60 KT 70 MPH 36H 19/0600Z 16.0N 108.6W 75 KT 85 MPH 48H 19/1800Z 16.9N 108.8W 85 KT 100 MPH 60H 20/0600Z 17.8N 109.1W 95 KT 110 MPH 72H 20/1800Z 18.7N 109.6W 95 KT 110 MPH 96H 21/1800Z 20.9N 110.3W 90 KT 105 MPH 120H 22/1800Z 22.5N 110.0W 85 KT 100 MPH $$ Forecaster Kelly NNNN