Arizona monsoon begins early

  • Published
  • 56th OSS Weather Flight
LUKE AIR FORCE BASE, Ariz. --  Today is the average start date for Arizona monsoon, although this year it began Sunday. The few storms that blew into the Valley in the last two weeks were just teasers. Despite a two-month-long season, not every thunderstorm that blows into the Valley will be a monsoon.

From July through September, Arizona lies on the northern periphery of the Mexican monsoon. As Arizona temperatures climb through May and June, high pressure aloft moves northward out of Mexico and centers near the Four Corners region. Clockwise circulation around this high picks up moisture from the Gulf of Mexico and Gulf of California. The moist air then encounters the extreme heat and mountainous terrain of Arizona and rises as a result, until the moisture cools, condenses and forms thunderstorms over the mountains. These thunderstorms, which create outflows of cool air and dust storms called "haboobs," create the world-famous lightning displays and uncomfortable humidity levels that characterize the Arizona monsoon.

The National Weather Service in Phoenix declared the arrival of monsoon season after the average dew point at Sky Harbor reached 55 degrees Fahrenheit for three consecutive days.

The typical monsoon day starts out hot and a little muggy. Flag conditions will be close, if not already black, the thermal stress index will be nearing the danger point by the first takeoff and long clouds with thin vertical turrets may be seen overhead.

By noon, towering clouds will be seen from the north through the southeast. Increasing heat and a daily wind feeding moisture into the mountains fuel these thunderstorms. Through the afternoon, thunderstorms will spread into the 56th Fighter Wing operating areas and training ranges and thunderstorm advisories for the impacted areas will be issued by the weather flight.

By evening, these thunderstorms will begin to weaken and fall off the mountain toward Luke, giving us the first glimpse of what may come. The most frequent impact from these storms are outflow boundaries of strong wind driven by cool air rushing out from a collapsing storm and the walls of dust created along the leading edge of this cool air. They may come from any direction, but most commonly impact from the north through the southeast.

Intense lightning and heavy rain are also possibile if the storm maintains itself overhead. Forecasted wind warnings, lightning watches and crosswind advisories will all be issued by the weather flight and disseminated by the command post as these criteria materialize. By midnight, most of the activity is complete and the atmosphere will begin to organize itself for another round the next day.

The monsoon is unlike the severe weather season in the Midwest or hurricane season along the coasts, but it does present its own dangerous scenarios.

Flash flooding is the leading cause of thunderstorm deaths in the U.S. Never cross a flooded wash, and be sure you know about Arizona's Stupid Motorist Law. Dust storms can decrease visibility to zero in a matter of seconds. If caught in one while driving, pull onto the side of the road, turn off all lights and avoid pressing the brake pedal. Most dust storms last less than 30 minutes and arriving late for dinner is better than having dinner in the hospital.

Lightning can be beautiful to watch, but observe it from a shelter. Most injuries occur before and after the thunderstorm is overhead, so wait about 30 minutes before venturing out.

Summertime at Luke lasts more than four months and the monsoon is a nice break to the otherwise dog days of summer. Take a few minutes over the next few months to watch a haboob role in, go outside to feel the cool air as it passes and enjoy the many varieties of lightning on display.

Keep an eye to the sky, be safe and vigilant. The dedicated forecasters of the 56th Operations Support Squadron Weather Flight will be.