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Tropical Storm Nora Forecast Discussion Number 17
2021-08-29 22:52:12| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Sun Aug 29 2021 000 WTPZ44 KNHC 292052 TCDEP4 Tropical Storm Nora Discussion Number 17 NWS National Hurricane Center Miami FL EP142021 300 PM MDT Sun Aug 29 2021 Visible satellite imagery and surface observations along the west-central coast of Mexico suggest that the center of Nora has re-formed closer to a mass of deep convection that has persisted today over the southern Gulf of California. Various satellite data sets indicate that Nora is weakening. The latest SSMIS microwave data reveal that the structure of Nora has degraded since this morning, especially in the mid-levels where an eyewall structure is no longer evident. Additionally, a 15 UTC ASCAT-A pass shows the winds are substantially weaker than previously estimated. Thus, the initial intensity has been lowered to 50 kt for this advisory. The initial motion is somewhat uncertain given the earlier center relocation, but it is estimated to be north-northwestward, or 330/10 kt. The global models suggest the tropical cyclone will move generally northwestward over the next couple of days, between an upper-level low offshore the Baja California peninsula and a mid-level ridge to the east of Nora. This motion should keep the center of Nora along the coast, or just inland over mainland west-central or northwestern Mexico. The official NHC track forecast is once again shifted a little to the right based on the latest track guidance, which brings the cyclone further inland by Tuesday. Nora is forecast to gradually weaken over the next few days as the system continues to interact with the coastline of Mexico. Despite warm SSTs in the Gulf of California and weak environmental shear, it appears unlikely that Nora will move far enough away from the coast to take advantage of this favorable environment. In fact, it is certainly plausible that the center of Nora could move well inland earlier than forecast and weaken more rapidly. The NHC intensity forecast has been adjusted about 10 kt weaker at all forecast hours based on today's data supporting a much weaker initial intensity. Key Messages: 1. Nora is forecast to be at or near tropical storm strength while it moves near the coast of Sinaloa and southern Sonora through early Tuesday, and tropical storm warnings and watches are in effect for portions of that coastline. Interests in these areas should closely monitor the progress of Nora. 2. Heavy rain associated with Nora is expected across the west coast of Mexico from the states of Colima northward to southern Sonora. This rain will likely result in life-threatening flash flooding and mudslides across these regions. Rainfall from Nora is likely to spread into the southwestern U.S. and central Rockies during the middle to latter portion of the week bringing the potential for flash flooding to the region. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 24.3N 107.5W 50 KT 60 MPH...NEAR THE COAST 12H 30/0600Z 25.1N 108.2W 45 KT 50 MPH...NEAR THE COAST 24H 30/1800Z 25.8N 108.8W 40 KT 45 MPH...NEAR THE COAST 36H 31/0600Z 26.5N 109.3W 40 KT 45 MPH...NEAR THE COAST 48H 31/1800Z 27.2N 109.9W 35 KT 40 MPH...INLAND 60H 01/0600Z 28.2N 110.6W 30 KT 35 MPH...INLAND 72H 01/1800Z 28.9N 111.1W 30 KT 35 MPH...INLAND 96H 02/1800Z...DISSIPATED $$ Forecaster Reinhart
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