The Ocean/Atmosphere July Pattern Change Affecting Europe Climate

Charts of the day: Explaining the wet/cool AND dry/hot Europe climate.

Discussion: During the past month, SSTA west and northwest of Europe have cooled by 2-3C, a dramatic change over a relatively short timeframe. During late spring, a marine heat wave (MHW) northwest of Africa shifted north to significantly warm the ocean waters west of Europe. Typical of MHW’s, the upper air pattern responded with an upper-level high-pressure ridge across and downstream the anomalous warm region of ocean water well-correlated to an upper ridge that warmed and dried-out much of Europe during early summer. However, in July, a pattern change occurred. An upper trough emerged across the very warm SSTA pattern west of Europe and the rapid cooling of the ocean surface caused latent heat loss that amplified the upper trough to soak and cool much of Europe in late July while a compensating downstream upper ridge strengthened, entrained North Africa heat, and caused harsh hot and dry weather for South/Southeast Europe. Conversely, a new MHW formed off Newfoundland as the ocean surface warmed by 4-5C in this zone during the past 4-6 weeks. Another example of STRONG REGIONAL SSTA well-correlated with extreme climate (and embedded weather) extremes.

Week-2 Ahead Forecast valid August 8-14, 2023: Cool/wet upper trough shifts eastward.

Discussion: The vigorous late July upper trough shifts inland and is weakening. Cool weather lingers while the storminess shifts east to Eastern Europe/Western Russia. Meanwhile, Southwest Europe is drier, and Spain turns hot.

Week-3 Ahead Forecast valid August 15-21, 2023: Most of Europe remains temperate (except Spain); Western Russia is wet.

Discussion: The upper trough continues to shift east, into Western Russia. Wet weather stretches from Ukraine to east of Caspian Sea. Southern Europe remains hot and dry, especially Spain.

Week-4 Ahead Forecast valid August 22-28, 2023: Temperate across most of Europe and Western Russia.

Discussion: During late August, Europe avoids hot weather (except southern sections). Western Russia is also temperate with lingering wet weather east of Black Sea and across previously hot and dry Kazakhstan.