Mountain West Discussion

[raindancewx]

Silly question, but how long has it been since Denver and the surrounding areas had snow in June? 

I can't help but notice that extreme (wet) June precipitation down here is 5x more likely than normal after a very dry Nov-Jan, and its gotta be from one of two sources:

1) Powerful late Spring storms dipping south unusually late OR

2) The monsoon coming on early 

Some of my objective replication techniques imply 1-2" of rain in June here, and if we get it, it'd be cold or at least cooler than last year, and since we're your heat source...if we get multiple cold days in June I'd imagine it snows pretty late in Eastern CO.

[mayjawintastawm]

NWS Boulder climate records look like last trace of snow in June at DEN was in 1974.

We got a generous 6" here, hard to measure exactly, extremely variable from bare ground in a few spots to knee high + drifts in others. Not super windy, but windy enough. First XC ski of the season was quite enjoyable- snow is perfect! Couple rocks here and there though.

[raindancewx]

It looks like June 1951 had measurable snow in Denver. Oct-Dec 1950 is a very similar to Oct-Dec 2017 here - with 0.01" in 1950, and 0.04" in 2017. Nov & Dec both very hot both years. Will keep that in the back of my head. Of course, it was dry here in June 1951...

Have only had 13 Junes since 1931 with >=1" rain, but 5 of them are after the 10 driest Nov-Jan periods, so its about 5x more likely than normal. 

[Chinook]

3 hours ago, raindancewx said:

It looks like June 1951 had measurable snow in Denver. Oct-Dec 1950 is a very similar to Oct-Dec 2017 here - with 0.01" in 1950, and 0.04" in 2017. Nov & Dec both very hot both years. Will keep that in the back of my head. Of course, it was dry here in June 1951...

Have only had 13 Junes since 1931 with >=1" rain, but 5 of them are after the 10 driest Nov-Jan periods, so its about 5x more likely than normal. 

It's pretty hard to tell-- it might be 1951 or 1953, but hail may be recorded as a trace of snow. And hail is common.

Central Nebraska- it must be about a snow rate of 2" per hour there, with winds increasing. Already reports of big snow drifts and blizzard conditions near Goodland KS

[Chinook]

This may have been only 8" for Rocky Mountain National Park

[raindancewx]

Some of the mountain ranges in the north of NM have recovered to 30-35% of normal snow pack with the latest storm.

 

[aggiegeog]

4 minutes ago, raindancewx said:

Some of the mountain ranges in the north of NM have recovered to 30-35% of normal snow pack with the latest storm.

 

Looks like most of the northern resorts got a foot or so. In many cases that is more than they had had in total this season.

[Chinook]

Realistically, the Washington Cascades could get 30" to 60" at higher elevations due to two storm systems in the near future. But it's always fun when you can do this with the weather model web sites

[raindancewx]

237" would be amazing. Euro tops out around 160" I think?

I should note: even down here the mountains occasionally can get 60-100 inches in five days or so. March 1969, March 1968, Feb-Mar 2015, Dec 2006, Dec 1958, Dec 1959, March/April 1973, March 1974, March 1975, Feb 1986, March 1937, March 2005, December 2000, March 1998, March/April 1988, November 1992, all come to mind as candidates when it may have happened.

I've been working on a Spring precipitation calculator for NM that can estimate how wet the wettest month of Spring will be using known/consistent predictor available by ENSO state before mid-February, and the big, late snowy Springs definitely have common elements in each ENSO state. NDJ SST conditions actually seem to be a better indicator for Spring than DJF for whatever reason in Neutrals and La Ninas. El Ninos are easy - you want a cold August and a wet monsoon.

[raindancewx]

It came three weeks late, but the last full week, where the West is cold and the East roasts is pretty close to what I expected for January, in terms of highs relative to normal v. 1951-2010. 

A blend of 1944, 1977, 1980, 1983, 1999, 2002, 2005, 2010 gets at Dec-Jan high temperature anomalies nicely, as it blends in some big PDO+ years with some big La Ninas, and then the warm Atlantic. I've been pleased to see ND will have another warm month for highs, Bismarck, ND >25F or so for the Dec-Jan high is one of the better indicators for a wet March down here. I weighted 1980 x2, 1983 x3, 2002 x3, 2005 x4, and 2010 x2, to get the unique features of the winter - its fairly rare to have warm anomalies north of cold anomalies in the Plains v. TX. The years with extra weight get most of the mid-south down to -3F or so v. 1951-2010 which is about right for Dec-Jan looks like. Large parts of the NE, and other areas east of the Rockies look like they'll be +0 to +2F against 1951-2010 highs through January, which is what I forecast. Been pretty pleased with the precipitation aspect of my forecast for the West too. Its not been great for Western temps and Eastern precip so far.

[AfewUniversesBelowNormal]

What an impressive streak of warm weather coming up! This is actually a good showing of global warming locally, the west coast and mountain west for the next 15 days. 

[Chinook]

There could be some very cold air coming into the Front Range next weekend, with some snow. Some of yesterday's GFS runs were kind of absurd in the 240-hr total QPF. Of course, the Kuchera ratios went nuts with temperatures under 15 or 20 degrees.  We'll have to be patient with the model craziness. Unfortunately, none of these model runs give any hint of moderate snow for the southwest, not even the San Juan Mountains of CO. That's where it has been too dry. And indeed the southwestern areas seem like they may be 5-10F above normal for days!

[raindancewx]

I've been working on my Spring outlook, and basically...Spring could be horrible here for water/snow-pack. It looks 3F above normal for highs, lows a bit less, +1 or +2.

These super dry Nov-Jan periods are almost always (9/10) followed by a dry May, so I've ruled out May, as this Nov-Jan is my driest on record.

April is almost always (9/10) dry if the prior two Aprils were both wet. April 2016/2017 were both wet here. April looks pretty hot actually, with the Nina still in place.

That leaves March. We are disfavored to get above average precipitation (23.8%) in March in Jul-Jun years with <30 sunspots, compared to 50.8% odds in all other years, but years after TX is hit by a major hurricane, Springs after dry NDJ periods, Springs after two-wet Aprils, all favor March as the wettest Spring month.

The question is whether we get something like 0.15" in March, 0.05" in April, 0.03" in May, or more like 0.60" in March, 0.15" in April, 0.20" in May. I lean toward the latter, mainly because based on the 1932-2017 records, the odds of the same month (March) being dry 11-years in a row are 0.44%, and its been dry ten years in a row, but that's relatively common, a 1/100 thing. Around 60% of years when Bismarck has a warm Dec-Jan (high >25.3F) are wet here the following March, there are relationships in precipitation in the SW & Plains I think that are pretty well established in the research. The odds get to 65% or so for >27F (like this year), and remain there in top-20 warm Dec-Jan years in Bismarck.

[finnster]

Raindance's spring outlook is pretty sobering for the NM/southwest region - I hope this doesn't verify .

I am interested in anyone's thoughts regarding the large, persistent high pressure systems that have been causing frequent periods of drought, record high temps - particularly in California and southwest regions of the US.  These systems also negatively impact the weather patterns of the mountain west region by blocking storms from entering into the region - sometimes for long periods of time.

There is a school of thought now these large high pressure systems are a semi-permanent feature of western US climate, perhaps even brought on by shrinking of ice coverage in the polar regions (see the weatherwest.com web site for ore details).  I'm not sure I subscribe to that thinking - I still tend to believe that long-term cycles - such as ocean temps in the Pacific and Atlantic, drive weather patterns, which in turn drives events like the build-up or reduction of ice in polar regions.  But who knows, the aforementioned theory about the large high pressure systems in the west may have validity.  I say may  because while humans have gained some understanding of the causes of long-term climate and weather patterns and cycles, there is so much more to understand - and making long-term predictions is dicey at best.  

[raindancewx]

Winter precipitation kind of looks like a La Nina modified version of the +AMO / drought composites overall - since the PDO is only neutral / weakly positive.

[finnster]

Raindance - thanks for posting those PDO/AMO composite diagrams.  Would sure like to things evolve into the +PDO/-AMO pattern again.  Overall that was a great pattern for the Colorado front range throughout the later part of the '70's, 80's and early '90's.  It seems the PDO has been more positive than negative the last several years but the AMO has been positive for many years.  I read occasionally about the north Atlantic turning cooler for the last several years, but it has not spread to the rest of the basin.  Too bad - it would be sweet for our whole region to get back into the +PDO/-AMO pattern again

[finnster]

I noted in another post previously the Weatherwest.com site, which is mainly California-based.  I go there once in a while just to get a sense of what is happening in the Pacific. 

The guy who runs the site, Daniel Swain, seems pretty savvy. It is interesting to read not only the articles that are posted there periodically, but the readers comments as well.  After 5 years of mostly drought, a lot of those readers are pretty sure the end of the world (as we know it) is near.  Who  knows - they may be right.  We in the mountain west are having a terrible winter for snow as well.  Although it may be in the back of some of our minds (that better weather will not return), I do not sense folks on this site are giving up hope for the future - and I appreciate that perspective.  Large scale weather patterns are very cyclical, and we happen to be in one that is not good.

 

In any event here is a link to the Weatherwest site for anyone interested in getting a glimpse of the west coast gloom and doom .  I've learned not to go there very often - it will start to affect your outlook on things....

http://weatherwest.com/

[raindancewx]

I've never really bought the whole "California is a Mediterranean Climate" thing. It was 100F in LA for the World Series in late October, which is more like Arizona or Iraq than Spain or Italy, and its been 100F in LA in November on multiple occasions if you look through their records. Phoenix has a record high of 96F in November. In Europe, the Mediterranean climates are much less subject to extremes, with less interference from ENSO, and water sources in multiple directions relatively unblocked by mountains. Italy and Spain both have water N/S/E/W of them to some extent, with California East is completely blocked, as is North. South is partially blocked by the Baja, SE is blocked by the mountains of Mexico.

With New Mexico, we aren't near water, but waters are roughly equidistant southwest and southeast at relatively short distances compared to other directions, so you get the one reliable period: July-Aug when 90%+ of years will be 2.8", give or take up to two inches, and its pretty ENSO proof.

 

[Chinook]

It was 65 degrees in Fort Collins briefly yesterday (Jan 30). Today, we had a high of 40. So why not have some snow? And that's happening. There's a dusting of snow.

[Chinook]

We had another surprise storm. This may be about 3.5"

[finnster]

A pleasant surprise of snow in Fort Collins - indeed!  Seems to be good moisture content as well

[Chinook]

Drought is expanding over many areas of the country, including here. Fortunately, my place is not doing too badly in total precipitation, but mild temperatures have certainly been typical.

[mayjawintastawm]

7 hours ago, Chinook said:

We had another surprise storm. This may be about 3.5"

 

Good for you! I saw a bunch of cars in the parking lot in Aurora with snow and ice on them this morning, wondered where the heck they came from when we had broken clouds all night and partly sunny this morning.

[raindancewx]

Snowpack still looks below average for the entirety of the West except for Washington/Montana on a state-by-state basis. Oregon really stands out as way below average for a La Nina year.

The La Nina is running out of cold water below the surface, with the MJO looking likely to get to phase eight, and then maybe 1-2-3. Might help kill the Nina by forcing some of the warm waters West, at the surface and below, into the Nina. CPC really inspires a lot of confidence by spelling "equtorial" like its a real word...

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt

Equtorial Upper 300m temperature Average anomaly based on 1981-2010 Climatology (deg C)
YR    MON   130E-80W   160E-80W   180W-100W 
2017    9    -0.45     -0.57      -0.79
2017   10    -0.54     -0.77      -0.97
2017   11    -0.41     -0.65      -0.84
2017   12    -0.31     -0.54      -0.75
2018    1     0.01     -0.17      -0.16

 

[Chinook]

Unfortunately, the upper ridge looks pretty strong near the West Coast on most frames of the GEFS. It would be nice to have a changing MJO to get pattern changes from time to time.  

The GFS/Canadian have taken away the snow for northern CO low elevations in the short term, although there will be areas of 6-18" for mountains north of I-70 in the short term. So that's positive for the mountain snowpack. Possible storm threat for most of Colorado on Feb 9/10. 

NWS/WPC is going for pretty big snow totals in populated areas of Montana. (This seems to be happening a lot this winter.)

[raindancewx]

Here is some fun math from my Spring outlook. March has been drier than average each year from 2008-2017 in Albuquerque.

Based on 1932-2017 averages, 143/228 streaks where the same month is drier than average continue into the next year, if the streak is 5-9 years. This means 37.2% of all dry-streaks end once a streak is 5-9 years, compared with 39.6% odds of a wet month overall. Long-term dryness in the same month has no effect on when a wet month will come in that month if the streak is under 10 years.

Based on 1932-2017 averages, 6/14 streaks where the same month is drier than average continue into the next year, if the streak is 10-12 years. This means 57.1% of all dry-streaks end once a streak is 10-12 years, compared to 37.2% of all dry-streaks that are 5-9 year in length. The frequency of a wet month increases by 20 percentage points after the same month has been drier than average 10-years in a row or more. This is a nearly statistically significant (p=0.069) increase compared to dry streaks of 5-9 years, even though the number of streaks when the same month is drier than average for 10 or more years are tiny.

Visually, it looks like this -

 

 

[Chinook]

Today, I think we have a Hudson Bay vs. Everybody Else oscillation

[raindancewx]

If this SOI crash / MJO propagation doesn't change the pattern somewhat I don't know what will. We're going to be in 7/8 for 2+ weeks. The SOI was +8.9 in January, and its currently -20.3 for February. Would have to get to +3.4 for the rest of the month just to get back to 0. That's got to have some kind of effect on the pattern. A lot of the wind depictions over the tropics for the next ten days imply it stays pretty negative. Shame the MJO crash was not in January. The correlations for the Feb SOI / March, and also Feb SOI to Mar-May are irrelevant here. January is a much better indicator for Feb, and Feb-Apr.

Amarillo, TX is at 114 days without measurable precipitation. This is the type of nonsense I was afraid of when I kept mentioning 1932 earlier, this is a Dust Bowl winter for a lot of the country, in terms of dryness. Some of the Dust Bowl winters were actually pretty cold regionally.

[Chinook]

This might be one of those days when you get 3 or 4" of snow over a long time period and it's just pretty darn cold.

[raindancewx]

Looks like we have a non-trivial (~20%) chance of a 20 point SOI drop from January to February, which has happened in ~1.3% of months since 1931? SOI was +8.9 in January. For February 1-6, its -21.4. If it stays below -8.3 for Feb 7-28 its a 20-point crash or more. The GFS, when I looked yesterday, was showing relative high pressure over Darwin and storminess near Tahiti, they are both around 15S through 2/15? 

Historically, there is about a 64% chance of a wet month here the month AFTER the 20 point SOI crash takes places, which would be March. All other months have only a 39% chance of being wet (p=0.028). SOI 3 is the month after the big crash, i.e. Sept 1934, January 1941. So SOI 1 is July 1934, SOI 2 is August 1934, SOI 3 is September 1934. SOI3/Avg gets the SOI 3 month precipitation and divides it by the long-term mean precipitation in that month. So the long-term signal is around 1.6x normal precipitation after a 20 point SOI drop, but it obviously varies tremendously. The SOI crashes that finished in Jan/Feb/Mar (SOI2) lead to a Feb/Mar/Apr of 0.89 inches of precipitation on average.

Not sure how the math would change for a -15, or -10 drop. Suspect its just a weaker signal. Odds of a 10-point drop are 2:1 at this point, as the SOI can be +4.4 for Feb 7-28 and still be -1.1 for the month.