What were the climate drivers in October just-ahead of today’s onset of the cold season? We begin off the Northwest Coast of Africa and southwest of Europe where a strong marine heatwave evolved during 2023 (No. 1).

A Freeze Warning is in effect for North Texas. Dallas dips to 31F tomorrow morning. During the past 10 years the earliest <32F morning in Dallas was Oct. 31 in 2019. Tomorrow will be second earliest of the past 10 years. Interestingly, both early and late dates for <32F in Dallas have been followed by warm winter seasons.

Oceanic El Nino 2023 remains moderate to strong. However, atmospheric El Nino is weaker. As an example of the weaker El Nino climate in place, the 500 MB relative humidity anomalies are somewhat wetter than normal across the entire equatorial Pacific rather than consolidated east of the Dateline typical of stronger El Nino episodes.

The subsurface warming in the East Pacific equatorial region peaked during July. Since that time, much of the subsurface warmth has shifted to the surface as oceanic El Nino has blossomed. The subsurface trend of late is a warmer westward push toward the Dateline.