Monsoons
Summer in the Southwest
Each year, a variety of weather related dangers affect the American Southwest, especially from late spring into early autumn. Through a collaborative effort between SW U.S. National Weather Service offices, the time period from June 15th through September 30th has been defined as “The Monsoon.” A period of extreme heat is typically ongoing at its onset, which in the coming days or weeks is followed by an influx of moisture leading to daily rounds of thunderstorms. The heat is deadly in its own right, causing more deaths than any other weather hazard in the region each year. In addition, thunderstorms present an array of hazards which often strike suddenly and with violent force.
Lightning strikes, high winds, dust storms, wildfires, tornadoes, flash flooding and extreme heat cause numerous deaths and injuries along with tens of millions of dollars of damage each year (see www.ncdc.noaa.gov/stormevents/). Road closures, as well as power and communication outages are additional consequences of monsoon weather hazards.
Flash Floods
Downburst Winds
Lightning
Thunderstorms and Dust Storms
Extreme Heat
Wildfires
Every June, SW U.S. NWS offices work with public safety partners and broadcast media to observe Monsoon Awareness Week with the goal of reducing the number of deaths, injuries and property damage caused by weather related dangers that occur during the monsoon. Through education about proper precautionary actions to be taken, lives can be saved and property losses can be minimized.
Warning Information for Monsoon Season
Armed with Doppler radars, powerful supercomputers, advanced weather satellites, automated weather and stream gages, and an advanced lightning detection network, forecasters at the National Weather Service are able to provide highly accurate severe weather warnings.
Advanced National Weather Service computer systems now allow warnings to be generated in seconds for highly detailed areas. Those warnings are then transmitted to the public, the media and emergency management officials via NOAA Weather Radio, the Emergency Alert System, and the Internet.
Television meteorologists play critical roles in the warning process. They relay National Weather Service warnings to the public and provide additional detail about the storms, what they are doing and where they are going.
Weather Terminology — Understanding Watches, Warnings, and Advisories
*A watch means that potentially life threatening weather or flooding is possible, or may occur in a matter of hours. Pay close attention to the weather, and tune into TV, radio, or NOAA Weather Radio broadcasts frequently.
*Warnings (Severe Thunderstorm, Flash Flood, Dust Storm, or in rare cases, Tornado) mean that life-threatening weather is about to occur, or has been reported. Take action immediately.
*Flood Advisories mean heavy rains will cause minor flooding of washes, streams, and typical flood-prone areas. Flooding in this situation is usually not serious. If the flooding does become life threatening, then the flood advisory is upgraded to a Flash Flood Warning.
Warnings are not issued for lightning, mainly because most thunderstorms, no matter how weak, produce deadly cloud-to-ground lightning.
Here is a summary of the severe weather watches, warnings and advisories the National Weather Service issues during the monsoon:
Severe Thunderstorm Watch: Conditions are favorable for widespread thunderstorms with damaging winds and even large hail to develop. These are usually issued only when an especially active day is expected. Watch weather reports and conditions closely.
Severe Thunderstorm Warning: A thunderstorm with damaging winds of 60 mph or greater is about to occur, or is already underway. These winds could also produce a dust storm with visibilities below ¼ mile. Hail over 1″ in diameter or larger is also possible. Take cover now! Note that heavy rain doesn’t always accompany a severe thunderstorm.
Dust Storm Warning: A dust storm, with visibilities of ¼ mile or less, is about to strike, or has already developed. Pull off the road now! Wind gusts between 40 and 60 mph are also likely. If winds associated with a dust storm are 60 mph or greater, then a Severe Thunderstorm Warning is also issued.
Tornado Warning: A tornado has been sited and is still on the ground, or is about to develop based on radar information. Take cover now!
Flash Flood Watch: Conditions are favorable for flash flooding over large or multiple areas of the region. These are usually issued only when an especially active day is expected. Monitor weather reports and conditions closely.
Flash Flood Warning: Life-threatening, rapid flooding is about to occur, or is already underway. Move to higher ground now! It is particularly dangerous to be in a low lying area or near a wash.
Weather Statistics
*Tucson, Phoenix, Albuquerque, and El Paso average 5.69, 2.43, 4.48, and 5.27 inches of precipitation respectively during the Monsoon. A plethora of rainfall statistics can be found at the NWS Monsoon Tracker page.
*On average, over 1.5 million lightning strikes occur in Arizona and New Mexico each year. This accounts for over 15% of all lightning strikes in the lower 48 states. See the National Weather Service lightning safety page for additional lightning statistics.
*The highest risk of tornadoes is in eastern New Mexico during April through July, but tornadoes have been verified in most New Mexico counties. New Mexico averages about 10 tornadoes in a year. Even though Arizona rarely experiences a tornado, they do occur (an average of four every year). However, thunderstorm-generated winds can exceed 100 mph over a fairly large area, with the damage looking very much like tornado damage.
Monsoons
Arizona’s monsoon season begins in June and continues through September. With it comes higher humidity, which can lead to thunderstorms, heavy rain, lightning, hail, high winds, flash flooding, dust storms and extreme heat.
ADOT urges drivers to be prepared for summer storms.
Monsoon safety driving tips
• Expect the unexpected. Have extra supplies, including a fully charged cell phone, drinking water and an emergency kit in case you experience an extended highway closure.
• When in doubt, wait it out! If you see a dust storm or heavy rain ahead, it’s best to exit and wait for the storm to move through the area. Get to a safe area as far off the roadway as possible.
• When faced with low- or zero-visibility conditions, pull your vehicle off the road as far to the right as possible. Turn off your lights, set the parking brake, and take your foot off the brake pedal. These steps reduce the chances that other drivers mistake your vehicle as the one to follow.
• Don’t risk crossing a flooded wash, even if it doesn’t look deep. Water is a powerful force that should not be underestimated. Even a few inches of running water poses a serious risk.
• Do not drive around “Road Closed” signs. You risk your life and face being cited under the state’s Stupid Motorist law.
• If traffic lights are out, treat an intersection just like a four-way stop.
• Storm runoff can loosen boulders and rocks on slopes above highways. Stay alert in areas prone to falling rocks.
Heavy rain and hydroplaning
Although much of Arizona is known for having an arid climate, the monsoon season can produce thunderstorms with sudden, heavy rainfall. Keep these tips in mind:
• Before you drive, inspect your windshield wipers, and replace them if necessary.
• Turn on your headlights while driving.
• Reduce your speed and maintain a safe distance between your vehicle and the one in front of you; create a “space cushion.”
• Avoid sudden braking, which can cause you to slide on the wet pavement. To slow down, take your foot off the gas pedal and brake slowly.
• Avoid areas where water is pooling in travel lanes; if possible, use center lanes and drive in the tracks of the vehicle ahead of you.
• The tires of larger vehicles, like trucks and buses, create spray that can lessen visibility so don’t follow them too closely.
• Be cautious of hydroplaning. This occurs when a thin layer of water accumulates between your tires and the asphalt and your vehicle loses contact with the roadway. You might suddenly feel your vehicle sliding or drifting because you’ve lost traction. If you feel you are hydroplaning, ease your foot off the gas pedal until you regain traction. Do not brake suddenly. If you are sliding or drifting, gently turn your steering wheel in the direction of your slide.