Rejected! (that 06 Z mod run from last night with no rain here for 15 days)

I had to laugh when I saw the very latest WRF-GFS model run, the run from last night’s 11 PM AST (06 Zulu) that had not ONE green pixel of rain over Catalina in the next 15 days!  You can see that really bad run here, from IPS MeteoStar.  You’ll get quite a guffaw out of it, as I did.  Quite bogus, really, or, as Wallace Shawn’s character repeats several times in the movie classic, “Princess Bride”, “Its inconceivable.”  (Of course, he was wrong, but we’ll ignore that.)

Completely dry cannot happen here over this 15-day period, period.

I was really afraid you had looked at this model run right off the bat this morning and had gotten down because of it, so I thought I’d better take it on right from the get go to get you going; so you wouldn’t be sad at work thinking about it all day.

What would be the reasons for firmly rejecting this latest model run, as a defender might a potential layup in a basketball game, this model run send up, the result of billions of calculations on our best, fastest computers?  They’d better be pretty good ones, we know.

1.  Its based on data at 06 Z when there are not so many observations, lots of gaps in the data, filled in by what the prior model run thought would be in those gaps (possible “fantasy” weather in those).

2.  Wildly different from the model run just 6 h earlier (00 Z) 5 PM AST, one that was based on oodles of global data.

3.  Is inconsistent with a steady depiction of several rains here over the next two weeks in prior model runs. The big storms during the last week of December into early January, written about here for some days now, are only close calls for us in this latest 06 Z run.

4.  It doesn’t agree with the superior Environment Canada model run, either, on the first of these coming rains.   For example, the Enviro Can mod has rain here late on Christmas Eve into Christmas Day, as it has steadily of late, while the 06 Z run has zip.

5.  Principal reason designate last night’s 11 PM (06 Z) run as a “laugher”, an “outlier”, completely bogus piece of computer trash?

The NOAA-NCEP (National Centers for Environmental Prediction) “Ensembles of Spaghetti“, which we often discuss here.  Let’s look at one of these, one valid for 5 PM AST, December 28th.  Looks like rain here to me.

Here’s where both nascent CMJs (cloud-maven juniors) can really shine because they know about “spaghetti” and when to reject “outlier” model runs.  And they can also impress others with their black, really great-looking,   “I ‘heart’ spaghetti” tee-shirts with the colorful example on the front.  Shows your in with the “in” weather crowd, always a great thing.

Note the positions of all the red lines (570 decameter heights of the 500 millybar surface) in the above example.  They bulge down toward the equator magnificently in the eastern Pacific and to the south of the SW.  These red lines virtually guarantee a big trough in the lower (southern) portions of the jet stream on this day and the days around it.

While ordinary folk, and maybe some of the weather practitioners on TEEVEE making huge amounts of money might be chagrined, taken aback by that latest, 06 Z model run and back off big claims and dreams of strong storms ahead, the CMJ will stand tall against this model run and continue to proclaim significant rains in the last week of December into January, ones that will juice up our water year precip totals significantly.

Well, at least I will.

One final note….  The exact day of the major storms in late December are unknown; those will wobble around until the smaller elements/waves in the global picture come more into focus over the coming days.  Significant rains might occur on the 28th-29th of December and/or the 30th and 31st, with still another possibility in early January (a bit more dicey, of course.)

In the meantime, before Christmas, a glorious Arizona winter storm break.

The End.



By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.