000 WTPZ42 KNHC 050857 TCDEP2 Tropical Storm Kay Discussion Number 4 NWS National Hurricane Center Miami FL EP122022 400 AM CDT Mon Sep 05 2022 Deep convection has increased in a band around the southern and eastern portions of the circulation overnight. A couple of ASCAT passes from around 0345-0445 UTC revealed peak winds of 38-41 kt, and a much larger wind field over the northeastern quadrant than previous estimated. The ASCAT data, a TAFB Dvorak classification of T3.0 and UW/CIMSS SATCON all supported a 45 kt intensity around 0600 UTC. Since the convective organization has continued to increase over the past few hours, the initial intensity for this advisory has been set at 50 kt. Although Kay is currently within an area of light to moderate northeasterly shear, it will be moving over SSTs of 28-29 degrees Celsius during the next couple of days which should allow steady strengthening. Most of the dynamical model guidance also predicts significant deepening of Kay during that time, giving more confidence to the forecast. The updated NHC intensity forecast shows a slightly faster rate of strengthening in the short term and now calls for Kay to become a hurricane within 24 hour. The new forecast also calls for a slightly higher peak intensity than before. After 60 h, cooler SSTs along the storm's track are likely to induce gradual weakening, but Kay is forecast to remain a large hurricane when it passes near the southern and central portions of the Baja California peninsula. The latest NHC intensity prediction again lies between the IVCN and HCCA aids. Kay appears to have wobbled back left since the previous advisory, but the longer term motion is 290/13 kt. Kay should remain on a west-northwestward heading through tonight, but by Tuesday a northwestward motion around the western periphery of a mid-level ridge over Mexico is expected to begin. A turn to the north-northwest is forecast by midweek and the guidance is in good agreement that Kay will move in the direction of the southwest and west-central coast of the Baja peninsula. Although there has been some increase in model spread this cycle with the UKMET keeping the system farther offshore, the typically reliable GFS and ECMWF are near the eastern side of the guidance envelope and are in good agreement on Kay moving very close to or over a portion of the west coast of the Baja peninsula. The NHC track forecast is near a blend of those models and is very similar to the previous track. Users are reminded not to focus on the exact details of the long-range forecast as wind and rainfall impacts are likely to extend far from the center of the hurricane. Tropical Storm or Hurricane Watches will likely be required later today for portions of the Baja California peninsula, and interests there should closely monitor the latest forecast updates. KEY MESSAGES: 1. Although the center of Kay is expected to stay offshore of southwest mainland Mexico, heavy rainfall could lead to flash flooding, including landslides, across portions of the Mexican Riviera and western Mexico through Wednesday night. 2. Kay is forecast to strengthen into a hurricane while it moves northward toward the Baja California peninsula later this week. While the details of the long-range track and intensity forecasts are uncertain, there is increasing risk of wind and rainfall impacts in the Baja California peninsula during the middle and latter parts of the week. Interests there should closely monitor updates to the forecast as tropical storm or hurricane watches will likely be required for a portion of that area later today. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 15.7N 105.3W 50 KT 60 MPH 12H 05/1800Z 16.0N 106.8W 60 KT 70 MPH 24H 06/0600Z 17.0N 108.5W 70 KT 80 MPH 36H 06/1800Z 18.1N 110.2W 80 KT 90 MPH 48H 07/0600Z 19.6N 111.7W 90 KT 105 MPH 60H 07/1800Z 21.4N 112.7W 90 KT 105 MPH 72H 08/0600Z 23.3N 113.4W 85 KT 100 MPH 96H 09/0600Z 27.5N 115.1W 65 KT 75 MPH 120H 10/0600Z 29.9N 118.3W 45 KT 50 MPH $$ Forecaster Brown