A What Kind of Cloud?

A big shout out to Amie Montes who captured an interesting cloud photo taken today near Willcox.

Here is the photo, and at first glance it certainly looks like it could be a funnel cloud.

Beaver Tail Cloud

What do you see?

Okay here’s the scoop. Without seeing video we don’t know if the cloud is rotating.

Looking back at our Doppler radar from earlier today, there was no indication of rotation in any of our afternoon storms.

So the question is, what kind of cloud is this? The answer: a Beaver Tail Cloud.

Beaver Tail Clouds form in the boundaries between a thunderstorm’s updraft and downdraft.

In the storms downdraft, the heavier rain-cooled air descends and spreads out laterally.

At the same time, warm, moist air is being lifted.

As this warmer air becomes saturated it undergoes condensation and becomes visible in the shape of the ‘Beaver Tail’.

According to the American Meteorological Society, ‘the Beaver Tail shows that a supercell thunderstorm is getting its act together’

The Beaver Tail Cloud can become a much larger Shelf Cloud if there is enough low-level moisture.


Monsoon Madness ‘A Tale of Two Cities’

Have you been a bit disappointed lately with the lack of rain in midtown Tucson?

Would you belive me if I told you that this monsoon has been epic so far? Well it has, and I’ve got the proof.

As of today, Tucson (at the airport where records are kept) is way above average for July rain. Monsoon City Column

In fact we are at double in the rain department.





Monsoon City Column 2And if this wasn’t enough to wash away any doubt – check out the July rain in Douglas:

Nearly 700% of average for July.

So despite what you may consider a slow start to the monsoon, we are actually faring quite well.




I expect a bit of a downturn in rain chances from Friday through the weekend, but some signs are indicating another uptick as we head into the middle of next week.

Hopefully the daily round of storms works its way a bit farther to the north.

Matt’s Monsoon Update

Here’s my Monday monsoon update.

We’re off to a good start this year when it comes to our monsoon rain. Nearly 1″ of rain fell at TIA on Friday, and way more out toward Vail.

We have two positive factors for the potential of heavy rain this week and one potentially negative.

I’ll address the ‘good’ first, good  if you were hoping for rain.temp1

1) Tropical Storm Erick

A very favorable factor is on our side if you like rain. Tropical Storm Erick is churning to the West off  Baja  in Mexico. Often times we get what’s called a ‘gulf surge’ from tropical storms – even when they’re well to our south. Essentially, mid level moisture travels up the Sea of Cortez and helps us in the rain category. We still need a ‘trigger” or a mechanism to lift this tropical moisture to create rain. Enter factor #2.

2) A disturbance moving from East to West.

Remember the definition of monsoon? A seasonal shift of the wind. While most of the year we look to the West for our weather, disturbances this time of year come from the East and can help lift our moist air to create the rain. A disturbance is moving our way and should help lift our moist air for good rain chances. In the following picture you can see an area of lower pressure to our Southeast- this would be our trigger. wave

The Bad

I’ve seen this too many times during the summer months. Often times despite a ‘trigger’ and good moisture, we do NOT get good rain in the Desert. This can be a function of too much of a good thing.

Ample storms may fire-up, many miles away from Tucson, but they can weaken sending us only clouds. If we are left with leftover clouds, we do not get warm enough at the surface to destabilize the atmosphere for convection (aka storms).

So as of now, I think the two ‘good’ factors outweigh the one ‘bad’ one and parts of Southern Arizona get abundant rain this week. But keep in mind, as contrary as it may sound, waking up with sunshine is a good thing if you are hoping for rain!

From the Heat to the Rain

It’s now in the record books: for the first time ever, all 30 days in June were greater than 100 degrees in Tucson. 

So if you thought it was unusually hot, you were correct.

Chapter II: The monsoon 

Thanks to the position of high pressure, which also brought us the heat, moisture has already begun moving into the region.

Dew point’s at TIA are now near 50 degrees and forecasted to increase over the next few days.

You may recall that the dew point is the absolute measurement of how much moisture is in the lower levels of the atmosphere.

The following images are high-resolution depictions of projected rainfall across the region for the next 72 hours.


This image is our 72 hour RPM model indicating a noticeable uptick in our monsoon.

We like to look at other model runs to make sure that there is consistency among our forecasting tools.


This image is from the WRF Hi-Res Model from the UA

Bottom line: The first week of July looks to be at least the beginning of what I hope is a great monsoon.

It’s Hard to Hold a Candle in the Cold November Rain

A warm September rain is exactly what folks in the desert southwest are likely to face.


It’s even hard to hold a candle in the warm September rain. A warm September rain is exactly what peeps in the desert southwest are likely to face.

While the Mexican Monsoon typically winds down at the end of September, folks in Tucson begin to whine about the return of the heat. “The monsoon wasn’t like it used to be” “We had non-soons” Such laments founded in fact or fable needn’t matter. The Sonoran Desert is called a desert for a reason. It just doesn’t get that much rain!

Not so fast: 

Another fact many people in the southwest are soon to forget, is that despite the infrequency, late September through late October can be relentless months when it comes to rain. Why? Well let’s not forget, my friends, that we are smack-dab in the middle of peak hurricane season. Remember Octave in 1983? Remember Olivia in 2000? Well for a place that receives just under 12.00″ of rain annually, both October’s (1983 and 2000) yielded 5.00″ of rain.

Georgette 2010:

As weak tropical storm Georgette moves into the Gulf of California, moisture will surge into the region. A trough of low-pressure off the coast of California will help capture this moisture and act as a trigger to get things kicked-up. So is it time to build an ark? No, I’ve seen plenty of similar situations where diurnal dynamics, warming aloft etc. have capped flooding rains, but I would certainly keep an eye to the sky on this one.

Click here to learn more about the 1983 Tucson floods