|
Arizona's Monsoons are almost legendary, but what are they and why can they be so dangerous?
Basically, it is a major rain storm that is caused due to the wind shift. Arizona winds (during the winter) flow from the west or northwest from California and Nevada. During Monsoon season (summer) Arizona winds flow to a southerly or southeasterly direction bringing moisture northward from the Gulf of Mexico and the Pacific Ocean. Add the shift of winds with the arid dry of Arizona's daytime heat, and it can cause a monsoon.
The monsoon season is determined more on the flow of winds, moisture in the air, and the temperatures. Officially the "Monsoon Season" starts on June 21st and lasts thru (roughly) September 30th.
Without getting technical, Monsoon Thunderstorms are powered by intense surface heating with strong moisture. During the season, monsoon thunderstorms do not occur everyday, but in "bursts". A "burst" is a condition that creates intense atmospheric destabilization and leads to strong widespread thunderstorm outbreaks.
During the stages of a thunderstorm (storm cell), the downdraft of air (due to precipitation) is found at the leading edge of the thunderstorm cell. This downdraft hits the ground and is forced out ahead of the cell which creates a gust front, this gust front will pick up large quantities of dust and sand creating a dust wall (this is called a "haboob").
Dust storms or haboobs created by monsoon winds are particually dangerous while driving (see Dust Storms in our Tips Section). They average a maximum wind velocity over 30 mph and can send dust as high as 3000 feet.
A "downburst" is a strong localized pocket of intense downdraft that induces an outward burst of winds on or near the ground. If they have an outflow diameter of 2.5 miles, then they are called a "macroburst which usually last 5 - 20 minutes of damaging winds. If they have an outflow diameter of less than 2.3 miles, then they are called a "microburst" which usually last only 2.5 minutes of damaging winds.
Welcome to Arizona! Let's discuss high severe winds during the monsoon season. High severe winds refer to powerful gusts that occur during thunderstorms and dust storms, predominantly in the summer monsoon season. These winds can exceed 50 miles per hour and are capable of causing significant damage to structures, trees, and power lines. They often accompany intense thunderstorms or haboobs (dust storms) and can pose dangers to outdoor activities and transportation.
The following is a simple wind chart to help you understand wind speeds. It is adaped from Beaufort Wind Scale for Land Wind Observations, Smithsonian meteorological Tables.
Wind Speed |
|
Description |
| Less than 1(mph) |
|
Calm, smoke rises vertically |
| 1 - 3 (mph) |
|
Light air, direction of the wind shown by smoke but not by wind vanes |
| 4 - 7 (mph) |
|
Light breeze, wind felt on the face, leaves rustle, wind vanes move |
| 8 - 12 (mph) |
|
Gentle breeze, leaves and small twigs in constant motion, light flags extended |
| 13 - 18 (mph) | |
Moderate breeze, raises dust and loose paper, small branches move |
| 19 - 24 (mph) |
|
Fresh breeze, small trees in leaf begin to sway, crested wavelets form on inland waters |
| 25 - 31 (mph) |
|
Strong breeze, large branches in motion, whistling heard in overhead wires |
| 32 - 38 (mph) |
|
Moderate gale, whole trees in motion, inconvenience felt when walking against the wind |
| 39 - 46 (mph) |
|
Fresh gale, twigs break off trees, generally impedes progress |
| 47 - 54 (mph) |
|
Strong gale, slight structural damage occurs (chimney pots and slates removed) |
| 55 - 63 (mph) |
|
Whole gale, trees uprooted, considerable structural damage occurs |
| 64 - 72 (mph) |
|
Storm, widespread damage occurs, exceptionally high waves |
This chart can assist you in understanding the severity of winds you might encounter during Arizona's monsoon season, enabling you to take necessary precautions and stay safe.
A Gustnado is a short-lived, ground-based rotating wind that forms along the gust front of a thunderstorm. Unlike tornadoes, which form from rotating updrafts within a storm, Gustnadoes are not connected to the storm's mesocyclone and are generally weaker. They often appear as small whirlwinds or dust devils, spinning up debris and dust along their path. While Gustnadoes can be visually striking, they typically do not cause significant damage compared to tornadoes. However, they can still pose hazards to outdoor activities and can be a sign of approaching severe weather.
A tornado is a violently rotating column of air that extends from a thunderstorm to the ground. They can appear as a funnel-shaped cloud or a swirling mass of debris, often accompanied by a loud roaring noise. Tornadoes are capable of causing immense destruction, with winds reaching incredible speeds that can surpass 200 miles per hour. They can uproot trees, demolish buildings, and toss vehicles like toys. Tornadoes are classified based on the Enhanced Fujita (EF) scale, which measures their intensity and the damage they cause. In Arizona, tornadoes are less common compared to other regions in the United States, but they can still occur, especially during the monsoon season. It's crucial to stay informed about tornado warnings and have a plan in place to seek shelter if one approaches.
|
