I am always digging into the past to make a better forecast for the future. Simply put, that is what using analogs is all about: finding past years that have many similarities to the current year, and using the weather that occurred then, to make a projection into the future. In a previous article I listed the following years as likely analogs: 1957-58, 1976-77, 1986-87, 2002-03, and 2009-10. Recently, I have been looking for additional years and came across 1941-42. Lets look at the what the oceans were doing at that time:
Several things about it stand out about the image above.
PDO Phase: Strongly positive as it is now
AMO Phase: Strongly positive as it is now
ENSO Phase: El Nino in progress as it is now
While the El Nino that was occurring in the fall of 1941 was better organized than the weak El Nino that is present now, we will likely continue to see the current El Nino strengthen a bit. Here is a look at the current sea surface temperature structure:
What did the average sea surface temperature anomaly look like from November 1941 through May 1942? See below:
Here is a fresh look at what the JAMSTEC model has for a sea surface temperature anomaly forecast through May:
To its credit, the JAMSTEC has not changed the sea surface temperature anomaly outlook. The sea surface temperature anomaly forecast from the JAMSTEC looks very similar to that of what occurred from November 1941 through May of 1942. The most interesting part is that the warmest water in the fall of 1941 was centered from the west coast of South America westward through ENSO regions. However, that warm pool eventually reorganized into more of a hybrid or Central Pacific based El Nino. Likely not quite meeting Modoki criteria, because of the lack of cooling immediately off the west coast of South America. See the differences between traditional and Modoki El Nino below:
So what was the winter/spring of 1941-42 like for Denver? Lets take a look…
Looks pretty normal in terms of snowfall for Denver, but it was certainly distributed in a different way. Very little snowfall through November, then things started to take off with the most snow in February. Nearly 20” of snow in February is pretty unusual as the monthly normal is only 7.5” Bottomline, December through February saw 37.8” of snow, which is 15.5” above normal for that 90 day period. Here’s what occurred nationally during that time in terms of precipitation and temperature:
Overall, Colorado was cooler and wetter than normal from November 1941 through May of 1942. This doesn’t mean that this type of snowfall/temperature or monthly distribution will occur, I am just showing you what happened during that particular time.
New JAMSTEC Model info…
Temperature Outlook ( Blue = Cooler Than Normal Red = Warmer Than Normal White = Normal )
December - Feburary
March - May
Precipitation Outlook ( Green = Wetter Than Normal Brown = Drier Than Normal White = Normal )
December - February
March - May
Based on the new JAMSTEC model, one could infer that Denver would have normal snowfall with above normal temperatures for December through February. March through May would then have normal to slightly above normal moisture, with cooler than normal temperatures. This still fits with our thinking that the best snowfall and coldest temperatures for Denver will likely favor the latter part of winter into early spring. Overall, the forecast doesn’t look to change much, except maybe warming things up a bit during the first half of winter.
So, I am sure you are asking, “which analog fits us the best?” That is a tough question, as there are so many different variables. However, I like the analogs that best fit what the oceans are doing right now. 1) Positive/warm PDO 2) Positive/warm AMO 3) Weak, but likely to intensify a bit El Nino. And another oscillation that you have heard me talk about before is the MJO, which is fixing to get increasingly active. All of that adds up to my liking the analogs from best to least in this order:
Please reference my previous article to see how those years stacked up. Remember this isn’t an exact science, but is used to provide a roadmap to where we think we are going. I do think the first four on that list are all very close, with the latter two distancing themselves somewhat but not a great deal. I still think locations east of the mountains in southern Colorado will see more snow than locations east of the mountains in northern Colorado this year. This is due to southern Colorado likely being influenced by the southern storm track more than the northern part of the state. To be honest, I hope that works out as drought recovery continues…