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.




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


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.


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.

I’ll do another post tomorrow morning.
– Shawn
3 Responses
“Advected” – wow, now that’s a new word!
Got one heavy shower for about 10 minutes ….0.11 inches at 3 pm…..
That’s heavy rain! Thanks for the report Frank!