~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

Hurricanes cont.

HURRICANES CONTINUED...

The final stage is the hurricane stage!

Stage 4: Hurricane

Hurricanes have sustained one-minute winds of at least 74 mph, at an elevation of 10 meters. Winds in most hurricanes can become much stronger.

Hurricanes are categorized on a scale of 1 to 5 based on their wind speed, a scale known as the Saffir-Simpson hurricane wind scale, named after its originators, Herbert Saffir and Dr. Robert Simpson.

In developing tropical cyclones, strong thunderstorms occur. Air pressure drops at the surface of these storms. This low pressure attracts warm moist air from the ocean's surface. The Coriolis force causes the resulting low-level winds to spiral in a counterclockwise direction around the center of the low in the Northern Hemisphere, whereas winds swirl clockwise in the Southern Hemisphere.

Typically, an "eye" forms when the tropical cyclone reaches hurricane strength, but an eye is not necessary for a tropical cyclone to become a hurricane.

Another way to think of a hurricane is as a large heat engine. The fuel is moisture from warm ocean water. The moisture is converted to heat in the thunderstorms that form. Spiral rain bands that surround the tropical cyclone's core help feed the circulation more heat energy.

As air nears the center, it rises rapidly and condenses into clouds and rain. The condensation releases tremendous amounts of heat into the atmosphere. The result is lower surface pressure and strengthening winds.

In this way, the tropical cyclone's engine refuels itself, concentrating its power in a donut-shaped area, called the eye wall, surrounding the center. The eye wall typically contains the strongest surface winds.

Sinking air at the center clears the tropical cyclone of clouds and forms the "eye." Falling surface pressure can occur only if air mass is removed from the circulation center. This is accomplished by wind flowing away from the circulation in the upper atmosphere.

Thankfully with technology today, we have learned so much about hurricanes!

http://www.weather.com/

Hurricanes

HURRICANES

I have never witnessed a hurricane and I hope it stays that way! Hurricane comes from the Spanish word "huracan" which was inspired by Hunraken, the name for the ancient Mayan storm god or Hurakan, the Quiche god of thunder or any number of Caribbean terms for evil spirits or big winds. The word "hurricane" was first used to describe any localized tropical cyclone in the West Indies.

What is a hurricane?

A hurricane is defined as a tropical cyclone with sustained winds that have reached speeds of 74 mph or higher. These storms reach the status of "hurricane" only after strengthening over a period of days or even weeks.

Where do hurricanes form?

The process begins in the warm, moist air over the waters of the region known as the tropics, which includes the Gulf of Mexico, the Caribbean Sea, the eastern North Pacific Ocean and the North Atlantic Ocean. Tropical depressions, tropical storms, hurricanes, and typhoons are all tropical cyclones, and all may develop in this region.



Hurricane Katrina



What are the stages?

Before it can become a hurricane, a tropical cyclone must pass through four distinct stages:

Stage 1: TROPICAL DISTURBANCE

A tropical disturbance is a discrete system of clouds, showers, and thunderstorms that originates in the tropics and goes on for 24 hours or more.

Tropical waves are a type of tropical disturbance that develops about every four to five days, and some of these waves eventually strengthen to become tropical storms and hurricanes. Sometimes called easterly waves, they are areas of low pressure that move generally from east to west, embedded in the tropical easterly winds.

Stage 2: Tropical depression

When a tropical disturbance develops a closed circulation (counter-clockwise winds blowing around a center of low pressure in the Northern Hemisphere), it is designated as a tropical depression. Tropical depressions contain maximum sustained one-minute winds of 38 mph or less, at an elevation of 10 meters.

Stage 3: Tropical storm

A tropical cyclone is given a name by the National Hurricane Center once it reaches tropical storm status. Tropical storms have maximum sustained one-minute winds of 39-73 mph, at an elevation of 10 meters.

STAGE 4: THE HURRICANE STAGE IS CONTINUED IN MY NEXT BLOG...

http://www.weather.com/

*Hail*

Have you ever been in a hail storm?

Growing up in Montana I witnessed many hail storms. As kids we always thought they were fun! Sometime they weren't so fun. I remember one day we had to stay in the house because the hail came down so hard. The next day we came outside and a couple car windshields were cracked!

What is hail?

Hail is precipitation in the form of a chunk of ice that can fall from a cumulonimbus cloud. They are usually associated with thunderstorms and most hail falls from the central region of a cloud in a severe storm. 

How does hail form? 

Hail begins as tiny ice pellets that collide with water droplets.
The optimum freezing level for the formation of hail is from 8,000 to 10,000 feet.
The water droplets attach themselves to the ice pellets and begin to freeze as strong updraft winds toss the pellets and droplets back up into the colder regions of the upper levels of the cloud.
As the attached droplets freeze, the pellets become larger.
Both gravity and downdraft thunderstorm winds pull the pellets back down, where they encounter more droplets that attach and freeze as the pellets are thrown, once again, back up through the cloud.

Hailstones

The more times a hailstone is tossed up and down through the cloud, the larger the hailstone will be. Hailstones the size of softballs had many more trips up and down through the cloud than pea-sized hailstones.
Large hailstones are an indication of powerful updraft and downdraft winds within a thunderstorm. This is why large hail is associated with severe thunderstorms.
To create pea-size hail (about 1/2 inch in diameter) winds within the thunderstorm updraft will generally be around 20 miles per hour. Quarter size hail (3/4 of an inch in diameter) requires updrafts of about 40 miles per hour.
Golf ball size hail (1 3/4 inches in diameter) needs updrafts of around 55 miles per hour and softball size hail, approximately 100 miles per hour!
The largest hailstone ever measured in the United States fell at Coffeyville, Kansas, on September 3, 1970. It weighed 1.67 pounds and measured 17.5 inches in circumference.

Hail Alley
The Great Plains states, especially northeastern Colorado and southeastern Wyoming, receive more hail yearly than any other part of the United States. Hail in this area of the country is most likely to fall late in the afternoon during the months of May and June and is often responsible for extensive crop loss, property damage and livestock deaths.

http://www.weather.com/

Tornadoes

Have you ever witnessed a tornado?

While being stationed in Oklahoma, I witnessed a tornado! It was very scary! I remember we were woken up from sleeping outside and we were being yelled at to run to the bus! Seeing that tornado was unbelievable, the sky looked so unreal. We raced away to safety and thankfully no one was harmed. I never want to witness a tornado again. I will never live where there are tornadoes!

Tornado heart

What is a tornado?

A tornado is a violent rotating column of air extending between a cloud and the surface of the earth.
Tornadoes are usually formed by thunderstorms. Even though, they have been known to occur without the presence of lightning.
 

 

Tornado Facts

 
Tornado wind speeds are estimated on the damage they cause. Tornadoes are categorized on a scale of 0 (weakest) to 5 (strongest).
 
The United States has the highest incidence of tornadoes worldwide, with more than 1,000 occurring every year. This is due to the unique geography that brings together polar air from Canada, tropical air from the Gulf of Mexico, and dry air from the Southwest to clash in the middle of the country, producing thunderstorms and the tornadoes they spawn.
 
Tornadoes can come one at a time, or in clusters, and they can vary greatly in length, width, direction of travel, and speed. They can leave a path 50 yards wide or over a mile wide. They may touch down for only a matter of seconds, or remain in contact with the ground for over an hour.

When & Where are Tornadoes?

In the United States, "tornado season" is generally in the spring. Tornadoes usually occur April through July. May and June are the peak months. But like thunderstorms, tornadoes can form any time of the year.

The area in which tornadoes are most common is known as "tornado alley," typically defined the region from Texas north to Nebraska. Even though, tornadoes can and do occur in every state in the country.

http://www.weather.com/