The NOAA/CPC Sep. 22-28 rainfall amount observation analysis across the U.S. identifies the excessive rain associated with Category-4 Major Hurricane Helene. Note the influence of topography on the observation results.

As early October arrives, the North Atlantic basin observed sea surface temperature anomalies (SSTA) remain much warmer than normal. Clearly, the best place for tropical cyclone generation/intensification is the western and northern Caribbean Sea where upper ocean heat is immense. Moderate to strong upper ocean heat is also present in parts of the Gulf of Mexico, East of the Bahamas, and central North Atlantic tropics.

The immediate forecast issues include risk of another Gulf of Mexico tropical cyclone. NOAA/NHC identifies a tropical wave southwest of Jamaica having a 50% chance of tropical cyclone development after 48 hours. The 12Z GFS indicates the system develops slowly and eventually reaches the north/northeast Gulf of Mexico Coast early in the 6-10-day period.

The U.S. week 2-4 outlook features sprawling high pressure across the West and Central U.S. producing a nationally drier and warmer than normal climate through mid-autumn. The Gulf of Mexico may be tropically active (after Helene) otherwise rainfall in the U.S. is sparse.