Cooler U.S. CDD Forecast for Later June

Climate Impact Company U.S. Medium Range Report

Issued: Thursday June 11, 2026

Highlight: MJO shift eastward through the America Tropics spawns stronger negative East/West Pacific oscillation and Central U.S. trend is cooler.

CIC ENSO Outlook: Using RONI, El Nino climate may not be as strong as oceanic El Nino; La Nina back next year.

Charts of the day: Latest CDD forecasts.

Discussion: Much cooler June 19-25 is forecast by all models.

Medium-range 6-10 Day Forecast Valid June 16-20, 2026 (AIFS ENS and 24-hour change)

Discussion: Yesterday, +GLAAM was mentioned as a climate signal implying U.S. forecasts were too amplified in the medium range. However, a forceful eastward shift of the MJO through the America Tropics causes a stronger mid-continent trough pattern as supported by a stronger -EPO/-WPO forecast in the medium-range supporting cooler changes in the Central U.S./Great Lakes region. Most models (also) diminish the +GLAAM regime. Returning to AIFS ENS which stays hot in the West (but not Southwest Canada) and is cooler in the Midwest.

Medium-range 11-15 Day Forecast Valid June 21-25, 2026 (AIFS ENS and 24-hour change)

Discussion: Prefer the cooler (AIFS ENS) change for the Central U.S. and Southern Canada due to stronger -EPO/-WPO projections.

U.S. Medium-range Precipitation Forecast

Discussion: The heavy rain on the Gulf Coast is due to entrainment of a tropical system. Parts of Cristina’s energy has shifted across Old Mexico emerging as a tropical wave which crosses the Yucatan Peninsula late week and could generate into a tropical system in the Bay of Campeche this weekend. The tropical moisture entrainment of that system causes the 6-10-day heavy rain. The Mid-south States stay wet in the 11-15-day period.

Days 16-20 Extended range Temperature Forecast valid June 26-30, 2026

Discussion: Strongly favor the ECM solution of rebuilding heat across the southern 2/3 of the U.S. during late June.