Is it the monsoon? July so far and July to come…

Clouds building and spotty showers over the mountains are typical this time of year. – Pic taken 7/17/2021

Sunday – 18 July 2021 – 4:00pm

There is a lot of gray area in meteorology. We use terms like “spotty” “isolated” “chance” “potential” and ranges for temps, precip, and winds because weather is not an exact science. If 20 meteorologists look at the same satellite loop, we’d probably agree on the general pattern and then vigorously debate the specifics.

So, is this the monsoon? In some aspects yes, and in others no.

To call it a monsoon we primarily look at flow and moisture. In a perfect world, we’d have lots of subtropical moisture being advected into the area from the south. Lately we’ve had the moisture but flow over Colorado has mostly been out of the north.

Instead of the subtropical high setting up to our east or southeast and giving us southerly flow, it has been to our west and north and giving us northerly flow. Subtropical moisture has been flowing into Arizona and New Mexico and then flowing around and under the high. This results in scraps for us. Thankfully the scraps have been pretty good, but precip amounts have not been distributed as the well as they would be with an actual monsoonal pattern.

Current 500mb pattern shows the low to our north and northeast flow into our area – not monsoonal flow for Colorado. — *Current 500mb pattern shows the high to our north and northeast flow into our area – not monsoonal flow for Colorado.*

*The GFS forecast 500mb for 26 July shows the high to our east over the southern plains and southerly flow into our area – ideal monsoonal flow for Colorado.*

Current water vapor. I circled the monsoonal moisture in green and the yellow arrows indicate flow around the high pressure. We are on the northern edge of the moisture plume. If north or northeast flow increases around that high pressure, it would push the plume to our south. Thankfully the plume is expected to stay with us.

The National Weather Service in Arizona and New Mexico track surface dew points for another indicator of the monsoon. Dew points are currently above average and indicate monsoon moisture is in place. — The National Weather Service in Arizona and New Mexico tracks surface dew points for another indicator of the monsoon. Dew points are currently above average and indicate monsoon moisture is in place.

National Weather Service Office	Yes	No
Grand Junction		X
Pueblo		X
Albuquerque	X
Flagstaff	X
Phoenix	X
Tucson	X

Who’s calling it a monsoon?

Does the National Weather Service call it a monsoon? They do for Arizona and New Mexico, but not for Colorado. Everyone agrees it’s monsoonal moisture, but a northerly flow over Colorado is not a monsoonal pattern. Thankfully the result has been decent rain so enjoy it no matter what we call it!

First half of July…

First off, the average precip for July is 1.88”. Roughly 2/3 of that usually falls the second half of the month when the monsoon sets up.

So far in July 2021, precip amounts vary considerably but are looking decent.

*CoCoRaHS precip totals so far in July range from 0.33” south of town to 1.41” northwest of town.*

The Quantitative Precipitation Estimates (QPE) so far in July shows most of the county and the mountains doing quite well. This product uses multiple sources to estimate precip. It’s not perfect, but it is a good tool, especially in data sparse regions like ours.

Second half of July…

Just about every forecast product I look at indicates we’ll get above average precip during the remainder of the month.

The Climate Prediction Center 6-10 day (top) and 8-14 day (bottom) forecasts indicate a chance for above average precip. — *The Climate Prediction Center 6-10 day (top) and 8-14 day (bottom) forecasts indicate a chance for above average precip*.

The Euro 15 day ensemble precip for Pagosa (top) and Wolf Creek (bottom) also indicate a strong finish to July. Long range forecast products are unreliable, but have been consistent which increases forecast confidence.

While some folks may detest the rainfall, keep in mind that we are experiencing significant drought conditions, rivers and lakes are low, and fire danger is high. We need all the rain we can get! The Four Corners region typically swings wildly between feast and famine. It’s great to see us swing towards feast! And if you don’t like the rain, it rarely lasts more than an hour.

Brief periods of rain rates of 2” per hour are common with monsoon storms, but it rarely rains that hard for that long. We ended up with 0.21” in about 45 minutes from that cell. We love it when our rain gauge says, “It’s raining cats and dogs”! Brief periods of rain rates of 2” per hour or more are common with monsoon storms, but it rarely rains that hard for that long. We ended up with 0.21” in about 45 minutes from that cell. We love it when our rain gauge says, “It’s raining cats and dogs”! — Brief periods of rain rates of 2” per hour or more are common with monsoon storms, but it rarely rains that hard for that long. We ended up with 0.21” in about 45 minutes from that cell. We love it when our rain gauge says, “It’s raining cats and dogs”!

I’ll do another post tomorrow morning.

– Shawn

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Shawn Pro

I’ve been a “weather geek” since I was young child. I joined the military out of high school and was lucky to get my dream job in weather. I have 20 years of military weather experience which includes forecasting the weather all over the world. Highlights were six years in Alaska and making life and death weather decisions during deployments. I love mountains, I love snow, and I love summertime thunderstorms. I spend a bunch of time playing outdoors and found my paradise in Pagosa Springs. I do Pagosa Weather as a community service. Hopefully you find us helpful!

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3 Responses

John Mosher says:

July 18, 2021 at 6:06 pm

“Advected” – wow, now that’s a new word!

Reply
Frank Snyder says:

July 18, 2021 at 4:20 pm

Got one heavy shower for about 10 minutes ….0.11 inches at 3 pm…..

Reply
1. Shawn Pro says:
  
  July 18, 2021 at 4:46 pm
  
  That’s heavy rain! Thanks for the report Frank!
  
  Reply

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