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October 2009
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It's time to re-define the Arizona monsoon, our summer thunderstorm season. It's time to set specific dates, on the calendar, which indicates the monsoon "season" has arrived and ended. It's time to forget about dew points and the endless debate over whether a storm "is or isn't" part of the monsoon. It's time for the definition to apply to the entire state. It's time to simplify. First, a bit of history: the term "monsoon" as it applies to the desert Southwest is generally accepted by most meteorologists and climatologists, and is sometimes referred to as the North American monsoon because the monsoon is actually more noticeable in Mexico. It represents the seasonal shift of wind in the upper atmosphere from westerlies (most of the year) to a southerly or easterly flow. Before the 1960s, no one had identified the Arizona summer thunderstorm season as a regional monsoon. We just had summer thunderstorms. Over the years, researchers noted, using upper-air data, that there were several conditions that make thunderstorms more likely during the summer months. Those conditions, they also found, roughly translated to a dew point at the surface in Phoenix of 55 degrees. One presumes they were looking for a surface "translation" of their upper-air data because before the 1960s, regular upper-air soundings were non-existent. Dew points, however, have been around for hundreds of years. What they found was a climatological way of comparing past summer thunderstorm seasons using dew points. The use of the term outside of the meteorological community doesn't seem to be clearly understood. Though it is a season, many still incorrectly refer to individual thunderstorms as "monsoons," as in, "Another monsoon is rolling into town." What is clear is that people liked the word monsoon. It was more interesting, one supposes, to call our summer thunderstorms something instead of just thunderstorms. The late 1970s into the 1980s were years when the term started to take off. By the time we moved here in 1981, (We drove into town during an August dust storm.) the term was in use. And as all newcomers, I remember asking: How can Arizona have a monsoon? To many, the monsoon has become a monster. When is the monsoon coming? Was that a monsoon storm? When will it end? What does it all mean anyway? One of the problems with the current definitions of the monsoon is that it relies on dew points, the very thing that gave it some legs. That's because a monsoon is officially declared "started" only after we have three consecutive days in Phoenix with average dew points of 55 degrees or more. Obviously, the folks who developed the system weren't intending it to be used as we do today because they didn't care if we had to wait three days to decide whether the monsoon had begun. But just ask the folks at the Weather Service exaclty how many calls they get when Mother Nature is working on starting the monsoon. I bet they get hundreds of calls a day asking if, indeed, it's started. We, in the media, eagerly count "monsoon days" and tabulate the "monsoon breaks." It's as if we don't have enough to describe in our summer thunderstorm without doing this weird, "yes it is, no it isn't" game all summer long. And when it ends, it's also the poor dew points that come in to play. But to end it, a study of the upper air wind is also used before the Weather Service will declare the monsoon over. One local climatologist said he used to just "eyeball it" to figure out when it ended. That isn't very satisfying, is it? And did you know Weather Service at Tucson uses a dew point of 54 degrees to determine its monsoon? Did you know the Weather Service office in Flagstaff makes no effort to define the monsoon? I say if it's a season, which it is, and if it impacts the entire state and region, which it does to differing extents, it's time to treat it like a season and give it dates. One of the ideas is to begin the monsoon "officially" on June 15, and end it on Sept. 30, each year. It would be our monsoon, our summer thunderstorm season. It's simple. It says what it is. And it works. And we have a great example already in use: the Hurricane Season. The Atlantic Hurricane Season runs from June 1, through Nov. 30. What does that mean? It means that's the most likely time for hurricanes to form in this region. During that time there are more likely and less likely times. And hurricanes can form before and after the season ends. But it's a way of telling a region of the U.S. that it is time that a certain type of weather could, at some point, some into play. You don't have to have a hurricane to start the hurricane season. You could have none. Or you could have too many, as we saw a couple of years ago. It doesn't mean my city will get hit. There are no guarantees. It's a season. And with that season comes the potential for hurricanes. But hurricanes are neither exclusive nor inclusive to this season. So if we go to a system that just calls a season a season, we know it's time for summer thunderstorms. It doesn't mean it has to storm. It doesn't mean it will storm. It doesn't mean a thing except that there's an increased chance for thunderstorms in the region. (And, yes, New Mexico, northern Mexico and west Texas are part of the same deal.) This system is simple to understand and explain, makes sense meteorologically and in no way limits anyone who is in love with the current dew-point system. If you want to count days, count them. If you want to say dew points have reached the 55 dew point threshold for three straight days, do it. If you want to compare this year's monsoon to previous ones using that information, more power to you. This new definition does not in anyway hinder you. But you must remember when you're counting monsoon days, you're counting them for the Valley only, leaving out the rest of the state. Which is another argument for the dates: It will include a state, several states, or even a region. Can you imagine how confusing things would be in the southeast if, say, Miami's hurricane season started on July 23, while New Orleans started Aug. 12, and Wilmington, W. Va., started their hurricane season on June 12? And let's face it. When it comes right down to it, the monsoon isn't about dew points at Sky Harbor Airport. It's about rainfall, lightning, and the potential for severe weather statewide. The folks at the local Weather Service offices are discussing this idea. And while I'll let them voice their opinions over the coming months, I think most of them like the idea. It just makes sense. I'd like to hear your opinion. You can respond to this blog and we'll post the responses. I'll also forward your opinions to folks at the Weather Service offices in our state. 14 CommentsLeave a comment |
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I think it is a great ideal to set a date.
Royal,
I totally concur with you. It should be defined as a season, starts June 15th and ends September 30th. I have been in the valley since 1974. I have seen dewpoints in the 60's and nothing, dewpoints in the 40's and it just pours. It makes no sense at all. This is such a much better way than looking at the dewpoints and kinda guessing when it will begin. I have found myself checking dewpoints in southern arizona this time of year, trying to get an idea when it will begin. No longer will I fall into this trap. Phewy! If i am asked, my reply will be, it is a sesaon which begins June 15th and ends September 30th, just like a Hurricane season does.
Actually you could make the start of the monsoon today. Today marks the one year anniversary of my house being hit by lightening by one of those "monsoon storms". It actually wasn't a monsoon storm, just a storm. I think you could just date the start and stop of the season. The "Royal Monsoon" would be appropiate.
I think your monsoon "season" is a great idea.
Howdy! Yes it is time to SIMPLIFY! As a native born Arizona'n I was just fine with Thunder Storm! Monsoon, bull-oney! There ain't any set start and stop. This cool weather is not the start I'll tell you whut! A a cowpuncher, (3rd. Generation)I have been outside enough to know and do not need the "weather guy\gal" to tell me as I can see "em a comin" and usally better'n they do!!!!
I'd like to respond to the online article about redefining the dates for the monsoon season.
Even though the article makes some valid points, I personally am opposed to setting official beginning & ending dates for the summer monsoon. I especially find that starting the season on June 15th is ridiculous. In
Arizona, June is usually an extremely dry month. In fact, on average, it is
the driest month of the year. The chances of having thunderstorms in June is slim, unless you count dry thunderstorms over the higher terrain.
Having official start & ending dates wouldn't make sense anyway because
there are certain rare occasions in the spring & fall when monsoon-like
activity happens. Remember the April 28th dust storm in the Valley this
year? It looked & felt a lot like a summer storm (same ingredients & wind
flow that happens during July August). So with that in mind, why not have the official monsoon starting date as April 15th? Of course, that wouldn't make much sense. Nor does it make sense to start the offical season in June.
The article also mentions that if the season impacts the region, it's time
to give it dates. That would be silly. Did you know that monsoon type of activty in New Mexico often begins in MAY? So using the article's logic,
the Southwest monsoon season should start in May. But wait! Those
thunderstorms in NM very seldom affect AZ in May & June. On the other hand,
Nevada & the southern CA deserts usually don't see monsoon activty until the last half of July, or later! So the June starting date wouldn't mean anything in that part of region, would it?
I say keep using the dew point criteria to measure the starting date of the monsoon, and forget about making changes that are unnecessary & incorrect. The current system works just fine. If it's not broken, don't try to fix it!
Royal, I completely agree with the idea of defining the monsoon with a set start and end date. The comparison to the hurricane season is perfect. I'm amazed the national weather service hasnt already given the monsoon set start and end dates. Every year we have a few storms that roll into the valley well before the monsoon is considered official with 3 consecutive dew points. They are storms directly related to the wind shifts in mexico and the southwest. Good article.
Amen Royal... I don't ever remember the weather forcasters using "monsoon" in the late '60's when I was growing up in Phoenix. Then again, I don't remember them using "haboob" to define what we use to call a big rolling dust storm. (Gee that brings back memories of running in and shutting all the windows because most of us had swamp coolers then) I realize that science has changed how we see and learn about weather, but monsoon - thunderstorm season, massive rolling dust storm - haboob, isn't it all the same? Why does everything need to revolve around a magic number?
All of Arizona has a thunderstorm season, but not all of Arizona has the same EXACT criteria for the start and end of the Monsoons. Typically, in the White Mountains, we will start receving afternoon thunderstorms days before the valley will start reaching that magic "55" number. So let's call it what it is - it's the Thunderstorm Season. Expect hot temperatures, with a chance of thunderstorms and blowing dust from Mid-June until the end of September! Sure makes your job easier... same weather predictions for weeks ;o)
"Good idea, Ollie."
That's an interesting idea. I'm for keeping the name "monsoon" to denote the seasonal shift, but defining it by dates rather than dewpoint. July 1 thru Sept 15?
A good point you bring up also about the comparison to hurricane season defined by dates. Sometimes it will be stormy, and sometimes there will be clear days. Visiting storm chasers who come out for monsoon should also expect a burst/break on/off pattern, and should prepare to drive some miles (nothing new about that :)
Well, however we define it, I'm looking forward to it as always.
-Susan Strom, Lightning Photographer Lightninglady.com
Royal - this is an excellent idea. The one suggestion I have is to make the start date of the season July 1 versus a June 1 or June 15. As you're well aware, rainfall in June is about as rare as a white Christmas in the Valley. The monsoon as we have known has started on July 7 in most years so a July 1 kick off date makes the most sense to me.
The dew point method is antiquated and ambiguous as you point out. Most of the storms form in the mountains to the NE or from the SE which have totally varying climate. Even in the Valley the dews can vary from downtown (or Sky Harbor as you referenced) to the outlying areas which are still ag land.
Either way, great idea and keep up the good work!
We live in the Sonoran desert, not the Sarahan desert. What did the native americans call this Sonoran event.
Not one to be politically correct - I think changing the monsoon is a dumb idea - the monsoon is an important meterological phenomenon - one that does not deserve "dumbing down" so certain people can understand it. We don't have a summer thunderstorm "season" - like many deserts - our monsoon is marked by a change in airflow to bring in moisture from the ocean and that does not happen in a fixed pattern or on a fixed date. I think, personally that it is yet one more useless goverment trick to be politically correct. Some Darwin award recipient probably got struck by lighting in the high country and his family sued the government because there were no warnings... gotta love this country.. DR
I completely agree with this, it is a very good idea. Don't they have tornado season in the midwest?