Hello everyone! This blog will cover just a few of the pattern drivers we are watching for the upcoming winter season and how they will play a role in our weather. Don’t forget will be hosting a FREE winter weather webinar next Wednesday, October 17th at 11AM! ***Don’t worry if you can’t watch the webinar live – if you sign-up you will receive an e-mail of the recorded webinar afterwards!*** Sign-up at bamwx.com/webinar!
Oceans remain a major factor when it comes to the winter forecast!! (Over 70% of our planet is covered in water). You hear us so often refer to ENSO, which is the El Nino Southern Oscillation, and this refers to the ocean temperatures in the equatorial Pacific. Remember last year we dealt with a weak La Niña that gradually faded late in the season. The waters have steadily warmed in our ENSO regions are we are now seeing weak El Niño conditions setting up. Looking at the different ENSO regions in the Pacific, we note these areas have steadily warmed especially from just mid-September to now.
To keep things simple, we can look at the correlation between warmer than normal equatorial water temps and temperatures across the U.S. during the winter season. We tend to find a connection to cooler than normal temps in the southern half of the country, with warmer risks north and west.
Data has struggled with the evolution of ENSO, but we can take a look at the ENSO forecasts from multiple models. Note they all converge on a warm-neutral to weak El-Nino threshold for the upcoming winter. We generally use 0.5º as the threshold between a neutral ENSO vs. El Nino.
We also look at solar activity, which has been on a decline in recent years. This year we are nearing a solar minimum with very low sunspot activity. Not surprising, we tend to find colder winters with low sunspot activity.
If you followed us last year, you probably remember us discussing the QBO – Quasi-Biennal Oscillation. This is essentially a measure of winds over the equator in the stratosphere. If the phase is negative, this tends to result in more sudden-stratospheric warming events which can break down the polar vortex and lead to increased cold air outbreaks. This year, the QBO is actually coming out of the negative and likely goes positive for the winter. This tends to lead to a stronger, more “in tact” polar vortex leading to less breakdowns and arctic intrusions.
Here is what some of our analogs featured for the winter based on years with similar atmospheric conditions to this year based on the factors mentioned above plus several other signals which we discuss in the webinar. Our actual analog years will be revealed in our webinar next week!
We will dive deeper into these pattern drivers in our webinar next Wednesday and answer any questions you may have!! It will be a fun discussion! Sign-up at bamwx.com/webinar! It is free! Have a great rest of your day!
-Nathan