Highlight: East trends less warm, tropics stay busy well-offshore.
Fig. 1: The prevailing upper air pattern across the U.S. for the remainder of September into early October.
U.S. pattern discussion: The prevailing upper air pattern across the U.S. the next 15 days (Fig. 1) according to ECM ENS finds a mean-trough location in the Ohio Valley/Southeast U.S. which spawns wet weather along the trough axis and into the Northeast U.S. especially over the next 7 days (Fig. 2). Along the southern periphery of the trough an upper shear axis should keep any Atlantic tropical cyclones from nearing the U.S. East Coast (Fig. 3).
The mean ridge position of the next 2 weeks extends from the 4-Corners region into South-central Canada where a warmer and drier than normal climate persists. Drying of soils in the central and southern Great Plains encourages drought development.
California is beneath an upper trough and a period of wet weather is possible although forecast models vary and confidence is below average. A Pacific storm track is emerging and brings occasional rains to the coastal Northwest U.S.
In 15 days, the mega-cluster ensemble is very confidence (75%) projecting a North-central/central North America upper ridge pattern sustaining anomalous warmth and dryness while tropical cyclone risk emerges off the Florida East Coast (Fig. 4).
The population weight CDD forecast trends to the (cool) 30-yer normal for Sep. 24-30 recovering to warmer than normal in early October (Fig. 5).
Fig. 2: The ECM ENS rainfall forecast for this week identifies wet weather in the Upper Midwest to Midwest to Southeast States early-to-middle week and into the East late week.
Fig. 3: Weather satellite view of the North Atlantic basin which contains two tropical cyclones each likely to stay out-to-sea and not approach the East Coast.
Fig. 4: The mega-cluster ensemble projection of the North America upper air pattern in 15 days is very confident!
Fig. 5: The population weight CDD forecast by all models, their consensus, comparing with 24 hours ago and the 30-year/10-year normal.