ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Genevieve Discussion Number 4 NWS National Hurricane Center Miami FL EP122020 400 AM CDT Mon Aug 17 2020 Genevieve's infrared satellite presentation continues to improve in organization, with the center embedded beneath a Central Dense Overcast and strong convection occurring in two bands to the southwest and northwest of the center. There has been a dearth of microwave data over the cyclone during the past few hours, so it's difficult to know how the internal structure has changed, but subjective and objective satellite estimates all support raising the intensity to 55 kt. Genevieve's motion has not changed--still west-northwestward (290 degrees) at 16 kt. The cyclone will be moving along the periphery of a strong mid-level ridge which extends from the southwestern United States southeastward into Mexico. This ridge should steer Genevieve toward the west-northwest or northwest for the entire 5-day forecast period, but small variations in the strength and orientation of the ridge will play a role in how close Genevieve gets to the southern portion of the Baja California peninsula. The track models are showing a slight bend to the storm's forecast path in 2-3 days, with the most recent run of the GFS showing a much closer approach to the Baja California peninsula. At this stage, however, that model is a bit of an outlier compared to the other guidance. Still, given the new set of models, the updated NHC track forecast has been shifted north and east of the previous track prediction, and it lies very close to the ECMWF, HWRF, and HCCA model solutions. Some of the intensity guidance for Genevieve is incredible. Due to low shear, very warm water, and high atmospheric moisture, several of the various SHIPS Rapid Intensification (RI) indices for the 12-, 24-, and 36-hour forecast periods are between 95 and 100 percent--numbers that suggest there is little doubt that Genevieve will go through a period of significant RI during the next couple of days. RI is explicitly shown in the NHC intensity forecast, which is very near the HCCA and Florida State Superensemble solutions and shows Genevieve peaking as a category 4 hurricane in about 48 hours. Amazingly, the LGEM and COAMPS-TC models are even higher than what is indicated in the official forecast, showing a peak intensity of 125-130 kt. A combination of cooler waters and increasing shear (especially at the end of the forecast period) is expected to cause weakening on days 3 through 5. Large swells generated by Genevieve are expected to begin affecting portions of the coast of southern Mexico today and will spread northward along the coast of Mexico to the Baja California peninsula by Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 17/0900Z 13.3N 101.7W 55 KT 65 MPH 12H 17/1800Z 14.4N 104.0W 75 KT 85 MPH 24H 18/0600Z 16.0N 106.7W 95 KT 110 MPH 36H 18/1800Z 17.4N 108.7W 110 KT 125 MPH 48H 19/0600Z 18.7N 110.1W 120 KT 140 MPH 60H 19/1800Z 20.0N 111.2W 115 KT 130 MPH 72H 20/0600Z 21.3N 112.3W 100 KT 115 MPH 96H 21/0600Z 23.5N 115.0W 70 KT 80 MPH 120H 22/0600Z 25.5N 118.5W 45 KT 50 MPH $$ Forecaster Berg NNNN