Jan 30, 2015
In
case you haven't noticed the weather oriented web sites are going crazy
with rain predictions for Mazatlan. You could get whiplash watching
them shrink and balloon the number of days they're calling for
rain. For
example one popular site started with one day of rain, increased that to
three,
dropped it back to one again, only to go back up to a ludicrous FIVE day
forecast of wet stuff.
We've had folks legitimately
worried their plans will be ruined if they schedule an outside venue like Surf's
Up. Or they're coming in for a short
stay and think their entire vacation will be rained out. Several people aren't sure what to do for
Super Bowl viewing, and one visitor even considered paying fees to re-book for
Cancun.
All in all it's been quite a
comedy. So what is causing all this
angst and concern? First let's review a couple
things for context.
1. We've talked before about Mazatlan
not having a dedicated weather service.
These weather sites use computer modeling, and in the end a prediction
is only as good as the data used to make it.
Most weather predictions for Maz are based on readings taken at the airport,
so their forecast is fatally flawed.
2. Everybody NOB has heard of
the Alberta Express, and many seasoned travelers know the Pineapple Express carries
rain from Hawaii to California. Maz has
what I've dubbed the Mango Express. It originates
near the equator and spins off clouds and rain through Mexico into Texas.
So we end up with a 1-2 combo of
bad data fed into computers, which are currently spitting out nonsense
predictions on a weather condition they don't understand. So what's really going on? Two things:
Those who've been in Maz this
winter are aware we've had an unusual amount of overcast, as opposed to our
typical clear skies. This is because the
Mango Express train has been very active.
In fact an unusually large dose of it is poised to move in shortly.
This front has combined with a
rare lined up double pressure system. We
have a stable high sitting over northern Nevada and pushing clockwise winds
southward toward Mexico. In the meantime
we also have a slowly moving low system in the waters off southern Mexico. Of course low systems push out counter
clockwise winds.
So the net result is a northerly
flow from the US, which holds the cloud cover and moisture from Mango in longer
over Mexico. Then opposing southerly flow
off southern Mexico is fueling Mango, and sending new moisture right toward
Maz. Hence the overcast and rain
predictions.
You can see what we're talking
about in the following links. The first
one is a world view that will show the massive size of this particular front:
The next is a little different
angle from a infrared source that allows for a better detail:
Lastly here's a view from a
camera designed to show water vapor in the air.
The brighter the white color, the more moisture:
So after that long prelude
(sorry, but my Weather Updates are meant to be tutorials), let's take a shot at
determining what's in store for the next few days. We'll use a question and answer format to
dispel some of the misinformation flying around out there.
Weather Underground called for five straight days of rain
starting on Thursday, and Intellicast predicted rain from Thursday thorough
Tuesday! Is that actually possible? The chances for that are even less than not
having a drop, in fact I don't think that's ever happened this time of year.
Since Maz has had quite a bit of overcast lately, aren't we due
for some clear weather? Yes,
but unfortunately it's temporarily going to get a little worse before it gets
better. The good news is the condition
causing this Mango Express train is deteriorating. The chances Maz gets back to Fun, Fun, Sun
for February are improving rapidly.
A weather site named timeanddate is predicting rain from
Saturday through Monday. Is that a
little more accurate? That's
still overly strong on the rain, but at least they're not off the reservation
with five and six days of it. However
timeanddate is a computer modeling system based on readings from the
airport. You'll certainly want to take their
temperature and wind predictions with a grain of salt.
Is it going to rain on Super Bowl Sunday? I think Sunday looks like a day
when the overcast would be comparatively light and not carrying enough moisture
to actually rain. In fact it wouldn't
surprise me at all if the this front were to mover easterly by then, and things
were relatively clear.
Some people are saying if it does ease off for Sunday, rain will
come back in for Monday...what do you think?
Rain predicted for Maz in the winter, often fails to
materialize. Last year I forecast rain
for both Christmas and New Year's Eve, but that was the only time I predicted
rain. All the other times it was called
for by web sites never happened. A
second push of rainfall would require this Mango to both keep generating AND
stay in position. That's expecting too
much in my opinion.
Is there a silver lining in these clouds? Yes there's a couple of them I think you can
take to the bank, and one other you'll really like. Firstly because this is a front from the
south and not the Northern Pacific, we're talking very mild temps in spite of
any rainfall. Secondly due to the
canceling out affect of the opposing wind flow, it looks to be a period of calm
or mild breezes.
Lastly as I've alluded to above,
extended rain would require both of two independent, and unusual factors. I'm not buying this double down forecast for
a second wave. While there might be some
remaining periods of cloud cover for Monday or Tuesday, I'm don't think we'll
see rain then. Furthermore I think the
chances this moves though and it's relatively clear for that period are better
than 50/50.
So how do Friday and Saturday look? If we're going to have actual
rain during the day (and not just at night with some drizzle during daylight
hours), it's likely Saturday would be the day.
I expect Friday to be quite overcast and moist, but don't look for any
rain until near or after nightfall.
Can you see a light at the end of the tunnel? February is a time when there
can be a few windy days, and a little chill at night. However it looks like this February will be warmer
than usual, and with much less in the way of blustery weather. In fact I'll go out on a limb and predict
many people will end up saying next month had the best weather of the entire
winter.
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