Mountain West Discussion

[raindancewx]

^^  I went with the following for my winter analogs:

1932: x2, 1943: x3, 1944: x3, 1996: x3, 2005: x3, 2007: x3, 2008: x2, 2012: x1

1932 Atlantic hurricane season is very similar to 2017: Irma=Fl/AL Hurricane, Nate= Tropical Storm 11, Maria = San Ciprian, Harvey = Freeport, similar attempt at an El Nino in Summer before cooling, had a big time volcanic eruption (Agung as a VEI 5 in 2017?) before winter, similar PDO values, two years after a big El Nino in 1930-31, which itself followed an El Nino like 2014-2015 (1929-30). Winter 1931-32 temperature anomalies were similar to 2016-17 as well. I pray to god the similarities break - this is not a good time globally for a dust-bowl pattern (1933-34) to re-emerge. I have 2007 in there to cancel out the Neutral years, and 2012 is in there because of how warm it was in the SW.

All analog years (except 2012) had low solar activity. Mean of the analogs is a La Nina following a La Nina. PDO is near 0 in the mean. Structure of the La Nina mean is Modoki-ish, but less so than last year, with Nino 1.2 expected much colder. The blend of the years also matches well to observed Monsoon rainfall totals, as a sanity check on the weighting. Globally, I was pretty pleased with the look of the oceans v. what the models have for winter. Atlantic has warm anomalies north of the cooler anomalies in the tropics, which is what we have now and what we should see in winter. Pacific looks OK in the La Nina zone, with similar PDO features. 

Main issue is the Indian Ocean is cold now, unusual for a La Nina, and the analogs don't have that. So the MJO will probably screw up the timing of the cold shots and heat waves in the winter, but overall it looks close to me. The relatively huge cold shots in the West in late Sept & Oct (valleys in Western NM were in the mid-20s in Sept) are consistent with some of the big time cold shots in the analogs. Not expecting a cold winter here, but much colder than last year. The structure of Summer heat here corresponds well to winter cold - we had 96 days at 87F or hotter here, but only 21 at 95F or hotter. Last year, 83 days at 87F or hotter, but 33(!) at 95 or hotter. To me, implies the warm days this winter are less warm, even though there will be still be a lot of them. July was nearly 4F colder for highs v. 2016, and July corresponds fairly well to Dec here as well. I see people like 1999-00 for this winter, but that was a super cold Summer in the West and then a super hot winter nationally, it was a strong La Nina following a strong La Nina, 1999 had very high solar activity, which we don't have at all, and the PDO was super negative.

Some years I considered for analogs but didn't use: 1933, 1954, 1962, 1984, 1985, 1995, 2011. 

I have an analog system that automatically selects best years to a wide variety of independent conditions. It had 1984 as the best match to the winter pattern, but I threw it out because the AMO was so cold that year. If you use super-warm AMO years though, you can blend in 1984 with it:

1932: x1, 1933: x1, 1943: x3, 1944: x4, 1984: x1, 1996: x1, 2005: x1, 2007: x1, 2008: x1, 2012: x1

I went with the first blend ultimately, because I don't think the cold AMO years really have any place in helping with the current pattern. Blends aren't super different though -

 

I put out my winter forecast a week ago if anyone is curious - https://t.co/ZnvyQletct

 

[Chinook]

Your analogs have given kind of a weird lack of precipitation in the Pac NW, given some sort of La Nina status.

[raindancewx]

That's kind of what happened last year though (decent match to 1942) - pretty dry for a La Nina in Washington, and Montana didn't really see a huge year either.

I think the blend has a pretty big Spring in parts of the NW though.

To me, there are 27 La Ninas (July-June basis) since 1930: 1933, 1938, 1942, 1949, 1950, 1954, 1955, 1956, 1964, 1970, 1971, 1973, 1974, 1975, 1983, 1984, 1988, 1995, 1998, 1999, 2000, 2005, 2007, 2008, 2010, 2011, 2016. You had substantial dryness in parts or all of the NW in 1938, 1942, 1954, 1956, 1975, 1983, 1984, 1988, 2000, 2008, 2011, 2016

The NW seems to be drier in La Ninas after La Ninas - that's factored in the analog system I have - since I use ENSO order as a variable.

 

[raindancewx]

Also, for what it's worth, this is the latest CFS run. We're close enough to winter that it probably isn't completely out to lunch for the season. I'm not a huge fan of the models for temps/precip, but I do try to look at them. I think they are much better at forecasting ocean temps v. anything else.