Topic: NWS redefines the Start of the Monsoon in Ariz

[AZmonsooncats]

Hello all,

I know this has been out at least 10 days in the local media here, but it is Big news Here in Arizona and I want to share it fellow weather buffs. 

The NWS office here in Phoenix and all the other NWS offices across the state of Arizona have change the way the they define the start of the Arizona Monsoon Season.

They have decided to use the firm dates method like the Hurricane Season has been define by for years. "The Arizona Monsoon Season" will now be from Jun 15th to September 30th and not defined by the "Dewpoint method" of three days in row with a dewpoint average at 55 degrees or above.

Here's the official press release.

"We're going to simplify the start and end of the monsoon.  June 15th, 2008, will be the first day of the monsoon season.  September 30th, 2008 will be the last day of the monsoon season," said Tony Haffer, Meteorologist in Charge of the National Weather Service in Phoenix.   

The new strategy to make the monsoon a season with an official start and end date will include 99 percent of all of our severe summer thunderstorms. 

"Somewhere between those calendar dates, the wind shift is going to occur, we're going to have easterly winds, we're going to see things come off the rim, we're going to see things come up from Tucson," said Haffer.

The decision to switch to the calendar system was based on the idea that scientists will be able to study and analyze the monsoon consistently throughout all of Arizona. 

"What we hope to do is give [the National Weather Service] a better understanding of what's going on on a day to day basis," he said.

In the past, our monsoon was made official when Sky Harbor Airport saw three consecutive days when our dew point reached 55 degrees or higher. 

"We feel like we've got to come along and modernize the starting date and ending dates of the monsoon.  So instead of focusing on whether the monsoon has started or ended, let's focus on the thunderstorms that actually cause the violent weather we see every summer," said Haffer.

Our average start date for the monsoon was July 6th, and would last through mid-September. 

Now, with the added weeks in June, we can expect to pick up a higher amount of rainfall during our monsoon months.

Haffer said that he expects some flack from people who have lived in Arizona for years. 

However, he thinks the new system will uncomplicate things. 

"For people who are still use to the old way, we will still have that information available...to the newcomers and to the people who have always been confused by it and hopefully we're getting everyone to think about the thunderstorms and the violence they bring with them."

Source: http://www.abc15.com/content/weather/news/story.aspx?content_id=99c34620-3f24-4e4d-afba-044179f37ba0

I personally think this change is a mistake as the old method was much better and by  definition a "Monsoon" is a seasonal wind shift not always clearly defined and definately not arriving by fixed dates.

 I think the old method by dewpoint even with it flaws was a better indicator of the start of the season as you would always have a record of when the dramatic rise of dewpoints occured and the winds shift from the dominant westerly direction to the Southernly and Southeasterly direction and you can clearly see the change of seasons as Sunny Hot dry days on June and Early July lead into the more humid days as the clouds and storms begin to build.

I have always felt the dewpoint was a true measure of the start of the season, but since Phoenix, is really on the outer fringes the monsoon the dewpoint has not always worked out as well as a reliable measure as it did in Tucson.

The dates they pick are interesting as those dates June 15th to Sept 30th have been used unoffically,( at least in Tucson), for monsoon rainfall statistics already for several years,  I have been using this measure for the rainfall data why still using the dewpoint as the actual measure of monsoon days, in most years this scenario of the June 15th to Sept 30th dates for rainfall , has worked out well as little rainfall has fallen outside the "monsoon days"  days with 55 degree or higher dewpoint averages. 

see: http://www.pepperridgenorthvalley.com/monsonrn.html

I also have in depth infomation on the monsoon at:

http://www.pepperridgenorthvalley.com/monsoon.php and details on the storms and summer weather patterns over Arizona at http://www.pepperridgenorthvalley.com/monsoon_basics.php

Please note these pages still mention the Dewpoint Method I will have to update them to reflect the firm dates of June 15th to September 30th.

It will be interesting to watch how things play out this year 

Jeanette

[ocala]

While we generally don't have a start date for rainy season in Florida, it's usually about June through September, the NWS defines our rainy season when the dewpoint goes above 70 and stays there.
Jeanette, as you said Phoenix being on the fringe probably prompted move.
Guess things are kind of slow out there and they decided shake things up.
Is your yearly rainfall still Jan-Dec?

[AZmonsooncats]

Ocala wrote....

Jeanette, as you said Phoenix being on the fringe probably prompted move.
Guess things are kind of slow out there and they decided shake things up.

Well they felt some people were (confused) and because of variability of start dates and dewpoint thresholds in different cites..

Phoenix was 55 degrees avg, Tucson was 54 degree avg and I think Flagstaff didn't use a average and for Example my start date last year was the same as Tucson's July 8th but Phoenix offically didn't start to July 19th!! Also the storms tend to be quite isolated it my be high and dry where you are but only 1 mile away an 1 1/2 of rain falls in 30 minutes

As for your question

Is your yearly rainfall still Jan-Dec?

Yes we still use the calendar year for rainfall totals, but they also track what they call the water year which in from Oct 1st to Sept 30th.  The water year is use more for hydrology and tracking Snow Pack in the mountains and spring runoff into the resevoirs as the winter rains provide the bulk of the widespead beneficial rainfall for the State.

Jeanette