Thread by @NWSPueblo

Hey Everyone! Have you ever wondered why places in and around Pueblo County don't get precipitation, but places immediately around it do?

Then join us on this journey of a thread as we take a dive into the reasoning behind the "Pueblo Precipitation Doughnut Hole"!(🧵1/12) #cowx

So, what is the "Pueblo Precipitation Doughnut Hole" (PPDH)? This is an area in southern Colorado that tends to get less precipitation than areas immediately around it.

The PPDH is clearly visible on satellite imagery and even the drought monitor.

But why does it exist?(2/12)

First, let's take a look at some basic meteorology.

Stated simply... Precipitation likes rising air, and inversely of that, precipitation doesn't like sinking air.

How do we get these conditions in southern Colorado? (3/12)

Ways we get rising air are:

Strong low pressure systems, air forced to rise along a boundary, and/or air forced up along terrain (upslope winds).

Ways we get sinking air are:

Strong high pressure systems and/or air forced down terrain (downslope winds). (4/12)

Now these upslope and downslope winds will be important to understanding this phenomenon, so remember those!

With some simplified meteorology under our belt, let's take a look at the terrain for this area. (5/12)

Looking at a cross section of terrain from south to north (standing out east across the plains and looking west), there are notable terrain features that play a role in the PPDH.

These are the Palmer Divide, Arkansas River Valley, Raton Mesa, and the mountains. (6/12)

Now remember how we said winds along terrain have a role in precipitation?

Well the aforementioned terrain features have major impacts in how winds, and therefore precipitation, materialize for southern Colorado and the PPDH. (7/12)

Most of the time, winds will be northerly, southerly, or westerly for southern Colorado.

These winds will upslope along the Palmer Divide and Raton Mesa areas (precipitation) and downslope into the Arkansas River Valley (no precipitation). (8/12)

Guess what's right in the center of the Arkansas River Valley?

Yep! Pueblo and the surrounding areas. These downsloping winds give us the PPDH! These winds cause drying and warming for this region! (9/12)

So if the majority of the time there are downsloping winds, how does the PPDH get precipitation then?

They need to get easterly winds! Easterly winds upslope along the rising terrain from east to west. The upsloping winds then help precipitation develop. (10/12)

Now with all of that said there are exceptions to this...

Such as when a strong and dynamic storm system passes over, it can overcome the mitigating downslope winds and either push precipitation off the terrain over the PPDH or just develop it over the PPDH. (11/12)

So this brings us to the end of this thread.

Hopefully you've enjoyed this little in depth look into the "Pueblo Precipitation Doughnut Hole" and why it exists. Thanks for reading! (12/12) #cowx