In our last episode, it was foreseen that a confidently predicted, “Joe Trough” , was going to bash the West Coast on the last day of this month with a strong storm, little doubt about it. He had been tracked nicely by the computer. Looked the same, “buff”, potent, day after day 4-5, ten days away as he crossed the Pacific Ocean. But after entering the USA at the end of March, “Joe” lost control of himself, it was unpredictable about what he would do next. At that time, displayed here on this blog, one computer guess was that he was going to break up into pieces, one piece over Arizona for days, sitting around, dawdling really, producing scattered showers in the first week of April thoughout Arizona. It was an unusual pattern, but there it was on the model outputs.
Sadly, from the spaghetti factory at our NOAA Super Weather Computer weather center, and the wild fluctuations it showed, indicated “Joe T” might do a lot of different things after he entered the USA. We could see that this rainy Arizona forecast was just one of many possibilities for “JT”, he was “unreliable” after approaching the West Coast no matter how badly we wanted that forecast that came out to come true; we just couldn’t count on it.
Now “JT” is only a few days away from crashing into the West Coast, still well predicted. But how about after he enters the West Coast? What will happen now? Will Joe break up into pieces and dawdle over AZ? Will there be rain? Or will we have just a dust storm and a dry cold front?
Let’s look in on the spaghetti factory and see what happens to Joe on the way in now, only few days from possibly affecting our weather.
From last evening’s spaghetti plots (“ensembles” in weather higher ordered weatherspeak) this 96 h forecast showing “Joe Trough” as it is about to hit the West Coast. As you can PLAINLY see, the entire earth’s weather north of the equator is well predicted as far out as 96 h, valid the evening of March 30th, 5 PM AST. In case you’ve forgotten, when all of the lines run almost on top of each other, things are well predicted, little chance of a busted forecast. The southward bulge in the turquoise and red lines just off the West Coast is our incoming “Joe Trough.”
The next panel, for later, valid for 5 PM AST, March 31st, shows that “Joe” is now in the Great Basin doing his thing, and the southern part of “Joe” is over us! Yay! Or not.
Remember the Red Zone, not in fubball, but in these plots? The red lines represent pretty much the southern edge of the jet stream at this level, 500 millibars pressure, around 18,000 feet above sea level. The turquoise lines represent pretty much the northern side of the jet stream at this level.
So, what’s wrong with this pretty picture (2nd panel)? Joe’s Jet (sounds like a singer I’ve heard of), doesn’t pass south of us by all reasonable expectations. Those little “perturbations” they put into the model at the beginning of the run to see how they might change the prediction, and thus get a handle on its reliability in case of errors, missing data, chaos in general, have the Red Zone (where the red lines are grouped) north of us. Jet north of us, as these red lines indicate, means no precip no where ’round here.
Well, unless you count dust as precip, and it certainly will pile up some.
“Joe” is strong and cold, but passes too far to the north. But as he does, a huge, intense low forms in the Great Basin, drawing dusty southwest winds across southern Arizona before the dry cold front goes through with quite a chill.
Now, for a little humor to end this blurb, a real laugher spaghetti plot, that for 15 days from now. You’ll go into conniptions, burst out laughing, like I did I am quite sure with your knowledge of spaghetti plots when you see this one and what virtually “unforecastable” weather looks like in a spaghetti plot. They should put these in the newspaper as kind of weather cartoon.
Actually, after 15 days, they mostly look like this.
Ending on humor, The End.