Monsoon in the Valley

Monsoon in the Valley
MGN Online
Weather Talk
Sunday, June 15, 2014 - 6:39pm

Many people think when the monsoon begins it means we will automatically see severe weather and endless rain come our way.

But that is completely false. In fact here in the Valley, you have a great example of how dry a monsoon can start.

Although we are still seeing a bit of isolated showers, we aren't seeing a whole lot of moisture for the beginning of the monsoon.

This year, the season began on June 15th and will end Sept. 30th for the entire Southwest U.S.

Monsoon basically means the seasonal shift in prevailing wind direction.

It doesn't mean we will automatically see storms in our region, but it helps to increase moisture which leads to storms.

So how do we know when the monsoon takes place?

We first need to understand that the engine of the monsoon is the sun.

As summer progresses, solar radiation warms the land and Pacific Ocean at different rates, causing a tug-of-war with the winds.

Once the land sufficiently warms, the westerly air flow does an about-face and the monsoon begins.

Did you know: monsoon season is a redundant phrase? Monsoon means season of rain. Therefore, saying "monsoon season" is technically saying "season of rain season."

Therefore, saying "monsoon season" is technically saying "season of rain season."

Until this year, the National Weather Service (NWS) declared that the monsoon season began on the first of three consecutive days when the average dew point temperature was greater than 54 degrees Fahrenheit in Tucson and 55 F degrees in Phoenix.

The dew point temperature, however, is just one of several indicators of the monsoon and it is typically the last index to suggest that the monsoon has arrived, said Eric Pytlak, science and operations manager at the NWS in Tucson.

In June, for example, numerous monsoon storms occurred around Tucson while the dew point remained below 54 degrees F.

For this reason, and to allow the media to more effectively communicate to the public when the monsoon storms are likely to form, the NWS in Arizona has designated June 15 as the official monsoon start date, starting this year.

It is too early to judge the monsoon season, and predicting it is difficult.

It is too early to judge the monsoon season, and predicting it is difficult.

For us in the Southwest, the long-term forecasts are calling for a chance of above-normal rainfall for the months of June through September.

This chance of precipitation being above average even carries into the winter months, and El Nino is still forecast to develop.
 

The official forecast from NOAA has eight to 13 named storms developing during the season from June 1 through Nov. 30, with a named storm being any tropical system in the Atlantic basin that has winds 35 miles per hour or greater, according to azcentral.com.

Of those storms, three to six are forecast to develop further into hurricanes, meaning they will have a wind speed of 74 miles per hour or greater.

And finally, from the three to six hurricanes during the season, one to two are forecast to strengthen into major hurricanes with winds at or about 111 miles per hour.

In an average season there are 12 named storms, six hurricanes and three develop into major hurricanes. So the upcoming season is expected to be right at or just below average.

During El Nino years, the storm track takes a more southerly route over the southwestern United States, generally leading to additional rainfall for Arizona and much of the southern United States.

It's exciting to see what mother nature has in store for us, and hopefully we see good rainfall coming into the Valley this year.

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