~MONSOONS~

~MONSOONS~

Those of us who live in Arizona, likely know what to expect when the Arizona monsoon arrives.
Probably the most debated weather event in Arizona is our so called "monsoon". Just the word conjures up visions of rains and widespread flooding followed by heat and drought. The drastic wet/dry combination is the example that most of us learned about in school. However, the monsoon actually occurs in varying degrees, and in Arizona it's marginal, just not as intense as those found in other parts of the world.

DID YOU KNOW?

The term "monsoon" comes from the Arabic "mausim" meaning "season" or "wind shift."

WHAT IS A MONSOON?

A monsoon is a seasonal shift in the prevailing wind direction, that usually brings with it a different kind of weather.

The persistent wind flow is driven by a warm air mass with low pressure at the surface that forms over the continent as it is warmed by the sun.

Air from the relatively higher pressure air mass over the ocean flows toward the low pressure over land.

The most famous monsoon is the Indian summer monsoon, as it affects such a large portion of Asia. In May and June of each year, the dry northerly wind flow over India changes direction, and warm humid air from the Indian Ocean flows from the south, gradually overspreading the Indian subcontinent. Widespread torrential rains, and even severe thunderstorms, accompany the "onset" of the monsoon.

The Indian Ocean version of the hurricane, called a "cyclone", can also occur and move ashore in association with the onset of the monsoon. These cyclones have at times killed thousands of people who live in the low-lying areas along the eastern coast of India and Bangladesh.

A weaker version of this monsoon occurs over the normally dry southwestern United States like Arizona in the later summer when more humid air, accompanied by thunderstorms, invades the region.

WHEN DOES A MONSOON OCCUR IN ARIZONA?

Prior to 2008 the Arizona area monsoon was considered to have started when there were three consecutive days when the dew point averaged 55 degrees or higher. In 2008 the National Weather Service decided to take the guesswork out of monsoon start and end dates. After all, monsoon is a season, and most people should not be concerned with whether or not a particular dust storm was defined as monsoon storm or not. Beginning in 2008, June 15 will be the first day of monsoon, and September 30 will be the last day. Now we can be more concerned with monsoon safety and less concerned with definitions!

WHAT HAPPENS DURING A MONSOON?

Monsoon storms range from minor dust storms to violent thunderstorms. They can even spawn tornadoes, though that is very rare. Typically, Arizona monsoon storms start with heavy winds sometimes resulting in a visible wall of dust hundreds of feet high moving across the Valley. These dust storms are normally accompanied by frequent thunder and lightning often leading to heavy downpours. Monsoon rains average about 2-1/2", about 1/3 of our yearly rainfall.

SAFETY TIPS

WHILE DRIVING

-First SLOW DOWN
-Leave plenty of room between you and the vehicle ahead of you
-Watch carefully for water pooling on the roadway surface as this could cause your vehicle to slide or hydroplane.
-Do not enter an area where the roadway has been closed due to flooding!
-Drive with your headlights on and slowly
-Watch for blowing dust and if possible avoid driving into a dust storm
-If you choose to stop in a dust storm, do not stop on the roadway
-Make sure your vehicle is in good condition
-If you suffer a mechanical breakdown or tire failure, remain calm, slow down, keep the steering straight, and drive the vehicle to a safe area as far from traffic as possible
-ALWAYS wear your safety restraints

IF YOU ARE AT HOME

-Turn off all unnecessary power equipment to reduce the draw on power companies
-Keep batteries, flashlights, and a battery operated radio or TV handy
-Stay off the phone. Even cordless phones can cause a shock when lighting strikes nearby. Use cell phones only if necessary.
-Stay away from plumbing fixtures as lightning can travel along metal pipes.
-Keep away from windows as high winds can blow heavy debris.

 IF THE POWER GOES OUT 

-Switch off high usage items such as air conditioners, computers and televisions so there is no danger of overloading your system or damaging these products with voltage fluctuations when power returns.
-Surge protectors for your computer and electronic equipment will provide extra protection.
-Turn on your battery powered radio or TV for information
-Limit how often you open doors so cool air stays inside
-Keep your freezer and refrigerator door closed

 LIGHTNING

Lighting is dangerous no matter where you are. If you find yourself outdoors when lightning strikes:

-Seek shelter immediately
-Stay away from open fields, high land, trees, poles and standing bodies of water
-Do not swim or hold metal objects, including golf clubs and lawn chairs
-Once again stay off your phones and away from plumbing