The greening of July

Update at 7:17 AM:  while mods had a dry day today (e.g., U of A yesterday), NWS has a much higher chance at 30% for our area today, and it sure looks like a higher chance.  (U of A Beowulf Cluster mod not available this morning for hi res check.)

While trying to get through the next couple of predicted days with lesser chance of rain though it doesn’t feel like it right now at 7:17 AM, and after a disappointing  0.02 inches yesterday afternoon, I wanted to check the Arizona rain futures in two models, the N-viro Can U-ro (as we would write it today) and the USA WRF-“Goofus”, both spoken with affection, to see how much “green” they have for us.  “Green1” has been the chosen color for rain by meteorologists, a particularly colorful people, who as children had an extra wide assortment of Crayolas and colored pencils.

Both models have a LOT of green in Arizona during the next 6-15 days except, as noted, for today and tomorrow where rain is marginal.

Below, as example from the Environ Can mod result for the evening of July 22nd.  Note green splotches in AZ, lower right hand corner (blue is very light rain; yellows and reds are heavier rains).

Along with the positions of rain here, in the upper left hand corner, is the forecast for where “our” big fat summer anticyclone is going to be on that day: centered way over the state where Dorothy used to live.  The air circulating around that high, clockwise, is circulating moist air into Arizona (while baking Dorothy and a lot of other people in the nation’s mid-section).  I love these maps and what they portend for AZ over the next week!

Below a sample chart for even farther out into the future from a rendering of WRF_GFS from IPS Meteostar for the evening of August 1st.   There is still “green” in Arizona, this time around Yuma, and there has been green in Arizona every day!  With our great start, it could mean that we will experience one of the wettest July’s ever in SE AZ!  The droughty weather pendulum may have swung back to make things up to us.

How do we know such medium range forecasts are have a better chance than usual of verifying?

Of course, if you are a regular part of this blogpire, you will know the answer.

It comes from the NOAA Spaghetti factory.  We meteorologists, not satisfied with one model run, like to mess them up at the start, and then look at the various “perturbed” model runs fro the 500 millibar level, and see if there is one “answer” that remains “strong”, still visible in the output amongst all the many contours of the wrecked ones. The middle of the troposphere, that domain where all weather occurs, is at about 500 millibars of pressure; sea level pressure averages around 1000 millibars (1013.6 millibars is the bottom of the “standard” atmosphere.  We like to see what the pressure patterns are like in the middle because things clarify up there, that’s where you can find jet streams, those steering currents for storms at the ground.

OK, now the punch line, don’t laugh too hard.

Below is the (humorous) plot from NOAA based on last evening’s global data for the 500 mb level due to combining:

1) the model run using the actual measurements made around the world at 5 PM AST,

2) and along with that one run, many model runs due to inputing slightly erroneous data at the beginning of the run.

Many of you will see this as a “knee-slapper”, and it really is because its a faulty production with too many contours.

But, in spite of a faulty NOAA run, there is still some information about our “big fat anticyclone” and where the most likely position will be on the evening of August 1st, some two weeks from now.  Believe or not, it is a powerful tool.

That likeliest of positions of our big fat anticyclone is that little dark spot over the Four Corners area mostly devoid of lines in this humorous output.  On this map, the Four Corners area is straight above the yellow legend line segment. At left,  a close-up of that Four Corners area with the fewest lines.

In the summer, Arizonans “need” to have a high in the middle of the troposphere to the north or east.  And that’s where the signal is strongest, represented by a center of that high situated over the Four Corners area even when the model has been degraded by bad measurements.

So, in sum, look for lots of rain in Arizona overall during the rest of July.  How nice, except when telephone poles are blown over, as happened on Sunday.


PS:  I took a lot of great cloud scenes yesterday afternoon and evening, but you need to have an SD card installed in your camera before a photograph is recorded. So no photos.  I hope this is a useful hint for photographers out there.


1“Green” in the meteorological color scheme of things, means rain, an area where the models think it will have rained is colored green as a rule.  Green has been the choice of meteorologists for liquid precip ever since weather began, back in the early 20th Century at the Bergen School of Meteorology in Norway.  Why did those Norwegian meteorologists with names like Bjerknes, Palmén, Holmboe, Godske, Petterssen, Rossby, Bergeron, choose green for rain?  Just because.