It had its origin in Tucson then progressed northward to Phoenix.  The “haboob” arrived in Phoenix late afternoon with winds in excess of 50 mph and a vertical height of 5,000 to 6,000 ft.    The picture to the left was taken at the National Weather Service Phoenix office.  The storm even shut down Phoenix SkyHarbor Airport for 45 minutes with visibility near zero.  While this haboob was one of the largest in history, Phoenix averages about 3 per year during June through September.

The Monsoon brings extreme weather to Phoenix

The monsoon brings a drastic change of weather to the valley.  The start of the monsoon is technically defined as the third consecutive day when the dew point is over 55 degrees which historically occurs July 7th.  However, in 2008, the National Weather Service decided to make it simplier and set the start of the monsoon as June 15 and the official end is September 30th. The monsoon is actually defined as a season, humidity levels increase, and is characterized by wind storms, heavy localized desert rains, microbursts, and dust storms or haboobs.  The above picture is courtesy of Mike Olbinski.

The typical Phoenix forecast is clear and sunny.   The monsoon provides some real change with a wide variation of weather patterns including the haboob we saw on July 5th.

It  is almost pointless to talk to someone in July when the temperature is 110 degrees about what happens in Phoenix when it rains. You want to point out how planned communities have drainage plans and retention basins, etc.   The situation in the summer  may be that no precipitation has been seen for months, so they wonder why you’re even bringing it up. Well, the last couple of day we’ve been drenched and now those plans and preparation are very much needed and appreciated.  Meteorologists are even saying that we may see as much rainfall in this 5 day period as we saw all of last year!  Yesterday there was even a tornado warning,  and many roads have been closed because of  flooding.  The picture above is not a lake water feature for a subdivision.  It may be for the time being, but actually it is a retention basin with grass in the community common area that accumualtes the runoff from storms such as the one we are having that has dumped over 3″ inches of rain in a 24 hour period in some parts of they valley.

Drainage Plans, Dry Wells and Retention Basins

This is not the most flashy or sexy subject,  but very few residents know about the planning that goes into a subdivision before the houses go up. Each city has engineering standards for drainage that the developer much follow.  I called and spoke to a Town of Gilbert planning engineer to get the details.  The standards and guidelines can also be found on line. 

How much water needs to be retained?  For the Town of Gilbert subdivisions must provide retention for the run-off generated from a fifty year, 24 hour storm which equals three inches.  House main level floors must be built higher than the water level that would be produced by a 100 year, 24 hour flood.  Many of the retention basins are also used as play areas or grassy parks within the subdivision.  However, the maximum allowable dept of a retention area is 2.5 feet as measured from the top of the side walk next to the basin.

How fast must the retained water drain from the basin? A retention area must drain within 36 hours to prevent “ponding”.  Dry wells can be used to assist with the draining of the area and must penetrate at least 10′ into highly permeable soil.

Because of the drainage plans that must be in place for a subdivision, it is highly unlikely that homes would require flood insurance.  However, it is best to consult a flood plain map.

This planning for the most part goes unnoticed until you have a significant rainfall that shows how important it is to manage run-off from a storm even in Arizona.

 It’s not a question I’m asked very often, but it is the start of the discussion regarding natural disasters and weather concerns from those considering relocating to the Phoenix area.

Our biggest climate concern? THE HEAT, followed by monsoon storms that can generate occasional high winds, dust storms and intense localized rainfall. The closest we get to a tornado are microbursts which accompany the monsoon storms.  The monsoon season runs from July through August.

I dislike comparing our weather to other cities and states during the summer when it’s 115 degrees in Phoenix. And throwing out the cliche, “but it’s a dry heat” just doesn’t quite convince them.  But the tables are turned when I have the conversation with someone in Minnesota in early January. At the end of the day it comes down to the phrase I heard years ago, ” You have to pick your poison.”

If you can tolerate the heat for 4 months and don’t mind giving up the below zero temperatures in Minnesota or Wisconsin or the humidity in the mid-west and south, or the earthquakes in California, hurricanes in Florida, or never seeing the sun in Washington state, then Arizona just might work for you!

How safe is Phoenix from natural disasters?

For years, AIR Worldwide Corp., a Boson based catastrophe modeling firm, has been researching cities and ranking them based on models evaluating the risk of hurricane, earthquake, severe thunderstorm, winter storm, and terrorism. Phoenix and the surrounding cities consistently place in the top 10 as the safest.  In 2006, Phoenix ranked number two.

If someone really misses the snow and freezing temperatures, a quick 2 hour drive from Phoenix past Payson to the Mogollon Rim will satisfy that craving. My son’s scout troop went snow camping in January this year.  We knew it was cold when we needed a gallon of gasoline to start the fire, not very scout-like! Everyone retired to their tents around 8 p.m. in an attempt to keep warm in our sleeping bags which were sandwiches in between layers of blankets.  We woke up to 24 degrees and a wind chill of below zero.  An accelerated exercise in packing and we were on the road to Payson to find a McDonald’s for breakfast, and then back to the 65 degree weather back home.  The snow camping event has become an annual tradition and serves as a reminder of why I really like Phoenix.