The preliminary outlook indicates MAY-SEP 2021 is hotter than last year as the average of the U.S. cities CDD forecast is about 112% of the 30-year normal compared to just-under 109% last year. Meteorological summer (JUN/JUL/AUG) is not quite as hot as last year.

Last week southern oscillation index returned to weak positive phase and trade winds off the northwest coast of South America also returned. As a result, the increased trade winds up-welled cool waters to cause all Nino SSTA regions to fall to within La Nina thresholds. However, the subsurface at 75+ meters continue to warm and subsurface cool water supply to sustain La Nina is steadily losing amplitude.

A titanic blocking high-pressure ridge south-southeast of Australia during the past 5+ days forced a deep upper trough to form along the southern Australia Coast this past weekend and into this week. Tropical moisture entrained into the upper trough from a warmer-than-normal water surface north and northeast of the continent lead to the 60-year flooding episode in Sydney and surrounding areas.

Heavy rains have caused widespread flooding across New South Wales this weekend due to a moist onshore tropical flow into a low-pressure trough made more intense by a blocking high-pressure area to the south. A low-pressure area has formed along the low-pressure trough in far northwest New South Wales.