Both Tropical and Non-Tropical Heavy Rains/Flash Flooding Southwest and Southeast This Weekend

Highlight: Hurricane Early heading northeastward. Excessive rain/flash flooding California/Arizona/Nevada and the Southeast to Mid-Atlantic U.S.

Fig. 1: Morning satellite view of the North Atlantic basin.

Discussion: Hurricane Earl is forecast to continue a northeastward drift the next 2-3 days slowly becoming a post-tropical storm over cooler waters. However, the trek into cooler waters does not prevent this storm from further intensification. ECM indicates a 938 MB storm well southeast of Nova Scotia tomorrow. Earl becomes an extratropical storm early next week and will eventually turn northward and accelerate. Tropical Disturbance 95L is not forecast to become a tropical storm arcing northwestward this weekend to east-northeastward toward the Azores early next week. A potential tropical disturbance in the outer tropical North Atlantic is weakening. In the southeast Gulf of Mexico to just-east of Belize a large mass of thunderstorms is unlikely to organize due to upper shear. However, some of that moisture extends northward to soak Florida over the weekend. ECM indicates another “fish storm” in the outer North Atlantic tropics next week. ALL CLEAR for the western North Atlantic basin.

Weakening Tropical Storm Kay will unload heavy rain and high wind across Southern California today. Risk of blackouts due to the recent heat wave were largely avoided thanks to in-part customer consumption. However, power outages due to high wind caused by the interaction between high terrain and the circulation around “Kay” propels damaging wind today for Southern California and possibly southwest Arizona. NOAA/WPC indicates extreme rain and flash flooding across Southern California today (Fig. 2) expanding to the southern 40% of California tomorrow (Fig. 3). Flash flooding from heavy rain is also likely for Southern Nevada and Arizona the next 2 days. On Sunday, residual moisture leads to more pop-up heavy rains in California (Fig. 4). Also note the evolving rainstorm across the Southeast today shifting to the Mid-Atlantic States this weekend.

Fig. 2-4: NOAA/WPC excessive rainfall/flash flood areas through the weekend.