For Weather Geeks 1/30/13

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Learn To Love Corn As It May Be That Way A While

by Mark

I am not a meteorologist, I just play one on the internet.

Actually, I have learned a lot from studying Bryan Allegretto’s forecasts (formerly Tahoe Weather Discussion) for a couple of years. The tools are definitely out there for making some reasonable guesses at what might happen in the medium range. Right now, things are not quite coming together for the powder days we are all craving.

Last week, we posted hope for the February 4th time frame, but hope is fading there as well, with just a minor refresh in the forecast. There are several different factors that affect our winter weather, but two of them seem to have the greatest impact: the phase of the MJO or Madden-Julian Oscillation and the PNA or Pacific-North American Index.

A quick lesson on the MJO

The MJO basically tracks tropical moisture as it cycles in a predictable pattern in the western hemisphere. The pattern normally completes an oscillation every 30-60 days. The pattern is divided into 8 different phases. The magic phases for us, according to Bryan, are phases 1, 2 and 3. They seem to coincide with our largest storm cycles. We are currently in Phase 8. The Euro models have us transitioning to Phase 1 and 2 in the next two weeks while the GFS keep us in Phase 8 the next two weeks.

Euro Model

The Euro forecast for MJO


GFS model for MJO

GFS forecast for MJO

We sure hope the Euros are correct.

A quick look at the PNA

The PNA Index tracks sea level air pressure anomalies.  If you know your basic weather, from a snow enthusiast perspective, low pressure is good, high pressure is bad. So we want the PNA to trend negative.  In the picture below, the black line is where we have been. You can see the long storm cycle in early December was all negative PNA. The red lines are the various model forecasts for the PNA Index. Most of them are not going  negative any time soon.

PNA Trend

PNA Trend

So learn to love the corn. Snow will return at some point…but probably not as soon as some of us would like.

PS I would love to be wrong..and the models can change quickly. Wash your car, remove your snow tires, flush some ice cubes….

Mark | January 29, 2013 at 5:17 pm | Tags: Bryan AllegretoGFSMadden Julian Oscillation,MJOPNAsnowTahoe Weather Discussionweather | Categories: Mark’s Reports | URL:


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