Overall, I look for summer temperatures to average cooler than last summer with closer to normal temperatures to slightly above normal /-1.0 to +2.0 degrees/. Local analogue data for this summer generally shows a variable summer temperature pattern as would be expected with negligible Pacific effects. More importantly for this summer are recent upper wind developments and projections for these upper wind patterns. Several models (see below) suggest the ridging over the High Plains eastward into the Mississippi Valley; will periodically expand east across the Great Lakes and East bringing heat into the region. In spite of the strong upper ridge however; will be the occasional influence of the upper level low and trough that made itself known this spring over eastern Canada when it still was able to penetrate; albeit infrequently, well south into the Great Lakes and Ohio Valley eastward to the East Coast.
Overall; the strong ridge is expected to continue to be a dominant player and will oscillate from the center part of the country to the east; bringing the periods of heat. Normal to below trends will be brought about by the dubious North Atlantic Oscillation /NAO/ cycling lower into neutral to possible negative phases (more below) which would aid in emphasizing the upper low and troughing over central and eastern Canada. Look for the number of 90 degree days this summer to closer to the normal /8 -14/.
Overall rainfall this summer is challenging due to this past spring’s variable pattern. Recent patterns have been drier than normal conditions across the Ann Arbor into metro Detroit area. Wetter than average weather from the center part of Southeast Lower Michigan (around Flint into Port Huron) with about normal rainfall across the Saginaw Valley and Thumb Region. As I look into the summer; I feel this basic pattern will continue with normal to above rainfall from the I-69 corridor north; but normal to below south. Storm trends and severe weather are discussed under summer analogues.
Note: The number 2 on some years denotes the Neutral conditions came after a second La Nina. The general cycle was: La Nina-Neutral-La Nina-Neutral. Also; the 1971-2000 norms were used reflective of less contamination of the heat island affect (DTW). They are closer to the century average used in composite maps norms of 1895-2000 and recently used in previous La Nina to Neutral analogue patterns.
Analogue Summer Trends
- High-frequency (denoted HF) composites
- Trend adjusted (denoted TA) composites
SUMMER BEGINS: JUNE 20th at 709 PM EDT
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian