Cool Wet Pattern Begins This Weekend

6/15/22 Wednesday 5:45 am
Models continue to show a major pattern change for this time of year, beginning late Friday. In my last post, I said that I was not ready to commit to this being the early start of the monsoon. Non-purists would say, if it looks like the monsoon, and acts like the monsoon, it is the monsoon. For the most part, that is true. There is definitely a monsoonal signature to this sub-tropical moisture. Officially, the monsoon season begins today. Dewpoints will reflect monsoonal conditions. Precipitable water values (PWAT) will reflect monsoonal conditions.
So why split hairs? The answer is because of the way it all happens. High-pressure will set up to our east. Low-pressure will set up to our west. Clockwise flow from the high pressure and counter-clockwise flow from the west will combine to draw in sub-tropical moisture over the area. I guess the best example I can give for why this event is not the start of the monsoon season is to compare it to a low elevation early to mid-November snow storm. Would that mean winter arrived for the season? Maybe, but highly unlikely. So I am going to hold off on my theory that this is not the start of our (SW Colorado) monsoon season for now. A week from now, that may change.
The purist in me which tortures my soul trying to overanalyze everything has been trying to come up with a name for this type of setup due to its unusual nature. So my first thought was to call this type of flow Pattern Induced Sub-Tropical (flow). I thought that was clever until I realized that these days you need to be able to apply an acronym to everything. This particular acronym in front of the word “flow” will probably not gain traction…
The biggest challenge at the moment is timing the beginning and the end of the event. Light showers will probably begin late Friday. It will take a while to saturate the atmosphere before the rain makes it to the ground in the lower elevations. The good news is the heaviest rain in all of the models is not supposed to fall until late Saturday into Monday. The GFS is extending the event through Tuesday but is outputting the same amount of precipitation as the Euro through Monday. Obviously, there are still some things to work out.
Here are the latest forecasted precipitation totals from the GFS and Euro from first drop to last.
There is a considerable difference between the two models. The GFS is showing a much deeper flow, forcing the precipitation into the northern San Juans. The Euro shows the precipitation trapped from the lower valleys to the southern San Juans.
The forecast amounts are still extraordinary. Half of these amounts would be extraordinary as well. To put this in perspective, especially if you just moved here from a wet climate, in the last 30 years the highest rainfall “officially” recorded in Durango in June is 1.55 inches. Looking at the longer term, There were only 8 times between 1894 and 1991 that total rainfall in June exceeded 2 inches. Some of you may remember Tropical Storm/Depression Bud that showed up during the 416 fire in June 2018. It seemed like a miracle at the time. tropical Storm Bud “dumped” 0.80 inches over the fire.
My next update will be on Thursday. Thanks for following and supporting the site!

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