Thursday, September 13, 2012

New Fall Pattern Setting Up; New LRC Pattern Evolving?

The latest model and ensemble forecasts for North America are showing a new fall pattern appears to be setting up.

As you can see above, this is the latest GFS forecast of 500mb height anomalies from the University at Albany. We can see two sets of high pressure ridging setting up across the area to the south of Greenland, as well as a strong ridge over eastern Alaska and western Canada. This ridging enables a strong low pressure system to sit in place and strengthen over the northern Plains and Midwest. We have not seen a pattern like this in the past 2 months. The lack of such a pattern's recognizance may suggest that the Lezak Recurring Cycle is changing. Here's a few pointers on the LRC.

*An annual pattern that starts in Fall and dissipates in summer.
*The pattern runs in cycles that vary between 40 and 60 days for each cycle.

Looking back 40 days, we are not seeing anything close to what is being projected here, indicating that the new LRC pattern for 2012-2013 could be setting up for the nation. That said, this same storm system and ridging may happen again in the next 40-60 days.

Also, the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) look to be heading negative in the future, indicating cold weather is on the horizon for the nation.