WEATHERAmerica Newsletter, Saturday, July 5, 2025; MEDIUM RANGE OUTLOOK

[Larry Cosgrove]

MEDIUM RANGE OUTLOOK

(Four To Ten Days From Now)

 

Air Mass Alignment: Changeable Canada, Hot North, Warm/Humid South

ECMWF (4)

PivotalWeather.Com (4)

The hottest day of the year in North America is typically around July 23. Modified polar air masses could lower readings to seasonal averages in the northern tier and across southern Canada, with repeated severe thunderstorm threats which could bring the IcP/cTw>mTw boundary as far south as Interstate 70 on some days. But the arc fromCcalifornia to Texas to New York will have repeated cases of hot weather, air pollution alerts and high energy usage. There most likely will be some diurnal convection in parts of Dixie, but the power of the two hot antiyclones will suppress the kinds of cloud and rian development that would limit daytime heating.

Merging Heat Ridges May Usher In More Active Tropical Cyclone Development

UQAM Meteocentre (4)

TrueWx.Com (4)

TwisterData.Com (4)

College Of DuPage Weather Laboratory

It may not be readily visible on the various numerical model interpretations in the medium range, but chances for tropical cyclone development should start to pick up in the Atlantic Basin. Just as risks for storm incursions in Central America and Mexico on the equatorial Pacific shoreline are likely to decrease (while the monsoonal moisture fetch organizes again along the Cordillera), the Saharan Air Layer may bump a bit further north in latitude as upper westerlies recede. The hyperactive ITCZ will eject disturbances toward the Lesser Antilles and Caribbean Sea. This being a neutral-negative ENSO (verging on weak/moderate La Nina by the end of summer), what starts out as weakly organized impulses will transition to depressions and named storms. I repeat my forecast of 22 named storms, 12 hurricanes, 6 of which will likely be major, and 4 will target the coastline of the USA between Brownsville TX and Eastport ME.