Potent storm still in cards for SE AZ and Catalina!

First, lots of cirrus clouds overhead.  Get ready for a great sunrise photo.

AZ incoming storm update:  Yay! (overall impression)

Now that the US and Canadian models are “converging” a bit to a similar depiction of where the highs and lows and upper level features will be come this Saturday,  a good rain seems in the bag for at least SE AZ.  Both models were having quite a headache trying to figure out where this low off the West Coast now was going to end up, and still do, as shown below.  However, both have significant rain here in SE AZ, though when it happens Sunday or Monday, is still a conundrum.

But with that next rain, and there may be some strong winds again, our November rainfall should be substantially higher than normal.  Seems like another half inch will materialize over the weekend into Monday, as this system passes by.  That should bring us (here in Catalina Land) to around a 1.50 inches total.  Average over the past 33 years here (not in Tucson!) is just under an inch.  You can go here to see how Enviro Can (the Canadians) depict this storm situation, and here for the US version.

You will see that in the Canadian version, a trough from the Pac NW and our incoming storm off Cal now “mesh” into a single trough as both combine over the interior of the West Coast.   They do this in time for a major storm in AZ in that model with lots of wind.  In the US model, the Pac NW trough bypasses our incoming low, and so they don’t combine into a larger storm system;  rather the Cal system muddles across us a day later but still brings significant rain, though mostly to southern AZ and us.  No doubt, that in the next model run or so, these discrepancies between Enviro Can and the US model with be healed.  Still, it seems we are assured of a good rain no matter what happens at this point (he sez).  Yay#2.   Below a couple of snapshots from these runs, first the less-potent-AZ storm depicted in the US “GFS” run:

Note in the first panel that you have a trough over ID and one off San Diego.  If they combine, look out!  A much more potent storm results for us.   If they bypass one another, then things ain’t quite so good.  But see what happens?  In the US prediction, the low dawdles off Baja while the ID trough is, only a day later, over the the Corn Palace in Mitchell, SD!   Not so good for us, though that Baja low DOES dribble over us on Monday bringing some rain.

The next two panels are from the Environment Canada model run, a model based on the European Center for Medium Range Forecasting model.  Here’s what that model came up with for these same two times shown above for the US GFS one.

The difference between the US and Canadian runs are pretty subtle for Saturday morning (leftmost panels).  But look at the difference for Sunday morning; they’re gigantic!

The Canadians think that the Pac NW trough will inject itself southward into our Cal-Baja trough, meshing for a stronger storm over AZ as all that Pac moisture from the system off Baja is swept into Arizona.

The Canadian model is therefore the preferred solution to our storm dilemma.  In sum, though, rain appears in the bag for SE AZ, not so much confidence elsewhere in AZ unless these troughs combine rather than bypass one another.

Hope this is comprehensible (as usual).  Local advice:  clean out your rain gauges of dust and bugs.

The End