000 WTPZ42 KNHC 090854 TCDEP2 Tropical Storm Kay Discussion Number 20 NWS National Hurricane Center Miami FL EP122022 200 AM PDT Fri Sep 09 2022 After moving back offshore yesterday evening, Kay has been roughly paralleling the northwestern coastline of the Baja California peninsula. The satellite presentation is not all that impressive, with the majority of the deep convective activity firing over the warm waters of the Gulf of California and adjacent mountainous terrain, well removed from Kay's center. An Air Force Reserve Hurricane Hunter aircraft was able to reach the center earlier this morning, and found that Kay's circulation is largely intact, with peak 700-mb flight-level winds of 62 kt and a minimum central pressure of 990 mb. While the standard wind reduction at that flight level would still typically support 55 kt, the SFMR-derived winds in that area were much lower, which better match a dropsonde also launched in the area. South of the center, there were some significant winds observed, with a sustained wind of 44 kt at Isla Cedros at 0630 UTC. Based on a combination of all these data, the initial intensity was reduced to 50 kt for this advisory. Additional weakening over the next 24-36 hours is expected as Kay will be traversing sub-23 C sea-surface temperatures and approaching even cooler waters in the cold California Current. The GFS, ECMWF, and HWRF models all indicate that Kay will cease to produce organized deep convection near its center in about 36 hours, marking its transition to a post-tropical remnant low off the coast of Southern California. The low should spin down further and dissipate sometime in the 4-5 day forecast. The latest NHC intensity forecast is in good agreement with the intensity guidance suite. From the two recon fixes, Kay continues to move off to the north-northwest at 330/11 kt. A narrowing mid-level ridge draped along the northeast side of the storm is expected to maintain this motion with a gradual turn to the northwest and west-northwest today into tonight. As Kay loses its remaining deep convection and becomes more shallow, the weak low-level ridging in the Eastern Pacific should result in the remnant low making a slow cyclonic turn away from the western U.S. coastline. The latest track guidance has shifted a bit more leftward this cycle, and the latest NHC track forecast was also shifted in that direction, towards the track consensus aids. Although Kay's maximum sustained winds are lower, the tropical cyclone 34-kt wind radii remain quite large on its eastern side, as seen in recent scatterometer data showing these tropical-storm-force winds extending up to the northern Gulf of California coast. Wind, surf, and rainfall impacts continue to extend far from the center so users should not focus on the exact forecast track of Kay. KEY MESSAGES: 1. Heavy rainfall could lead to flash flooding, including landslides, across the Baja California peninsula and portions of mainland northwestern Mexico through Saturday morning. Flash, urban, and small stream flooding is likely across Southern California beginning today, especially in and near the peninsular ranges. Flash, urban, and small stream flooding is possible beginning later today in Southwest Arizona. 2. Tropical storm conditions are occurring over portions of the Baja California peninsula, and these conditions extend all the way to the northern Gulf of California coastline, where a Tropical Storm Warning is in effect. 3. Strong winds not directly associated with Kay's core wind field are expected across portions of southern California and extreme southwestern Arizona later today. For information on this wind hazard, users should see High Wind Warnings and other products from their local NWS Weather Forecast Office. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 29.4N 116.0W 50 KT 60 MPH 12H 09/1800Z 30.5N 117.3W 40 KT 45 MPH 24H 10/0600Z 31.3N 119.0W 35 KT 40 MPH 36H 10/1800Z 31.5N 120.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 11/0600Z 31.3N 121.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 11/1800Z 30.6N 121.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 12/0600Z 29.9N 121.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 13/0600Z 28.6N 120.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 14/0600Z...DISSIPATED $$ Forecaster Papin