Saturday, December 15, 2012

The Million Dollar Question

7:25 PM EST 12/15   (Forecasters Mike, Nic and the Long Range Team) - Winter has been quiet so far, but could exciting times be coming ahead? For several years, and especially so far this fall, our team has been closely following and experimenting with a scientific theory known as Lezak’s Recurring Cycle or the LRC. While the science behind it has not yet been proven, we do believe that there is a lot truth behind this theory and are using it to base our forecast for the next few weeks. 

OUR LONG RANGE IDEAS, IN ONE SENTENCE: Conditions in the Eastern U.S. could get much colder around Christmas time, with a possible warm up in the middle of January, then another shot of colder air by February.

A QUICK EXPLANATION – This theory has rarely been used in the past, but the idea behind it was first discovered by Gary Lezak, a meteorologist in the Midwest. 

  • The basic idea is that from the late summer through the fall each year, a unique weather pattern lasting about 40-60 days establishes itself. 
  • Around late fall, starts to repeat itself through the following winter and to early summer. 
  • This means that weather patterns that we see in October and November may come back again multiple times. 

THIS YEAR’S CYCLE – We believe that this years cycle averages about 58-60 days, but there are some variations. Right now on December 15th, we think we are seeing a similar pattern to the one around the 17th – 18th of October. Being later into the winter, the set-up is slightly different, but the overall pattern is very similar. For example, we have discussed the “teleconnections” such as the North Atlantic Oscillation. It appears that these oscillations are not affected by the LRC, but in turn can actually affect the LRC. 

The upper-level air pattern on December 11th (left) vs October 14th (right) - Credit: HPC

THE MILLION DOLLAR QUESTION – Now with the pattern corresponding currently to mid to late October, many people will remember Sandy. Is it possible that the pattern that produced Sandy will be back again? In short, the answer is both yes and no. 
  • No, because we are no longer in hurricane season, thus there will not be any tropical storm or hurricane interacting with the long range pattern. 
  • However, we DO expect the overall pattern of a strong Arctic cold front arriving at the east coast, and possibly forming a strong storm. 

SO, WHAT WILL THIS BRING? – We are expecting that the long range pattern that produced Sandy will be back again around December 21st- 23rd. You may be wondering how that adds up with the cycle though. 
  1. In late October, a very rare combination of events came together to form that strong Greenland Block that forced Hurricane Sandy back westward into the coast. 
  2. During the week prior to Sandy, we think that the Greenland Block slowed the progression of that strong trough across the country, and without the block now, that pattern will be allowed to move faster. 
  3. So therefore, this time around, the cycle may be several days shorter, allowing that pattern to return next weekend. Three major computer models are currently showing a strong storm bringing heavy rain and snow to the Great Lakes, Midwest, and East Coast. 
European Model "ECMWF" projection for Friday morning, December 21st (left)
from PSU E-wall vs the upper air pattern from October 30th, 2012 (right)
AFTER THAT? – After Hurricane Sandy hit, the east coast was very cold for a period of several days. As we head into this next phase of the cycle, it is possible that the length shortens from 58-60 days to more like 53-55 days, as a result of an accelerated progression of troughs and ridges in the jet stream without the Greenland Block. If this does pan out, it could get rather cold around Christmas time, with a possible warm up in the middle, then another shot of cool air close to the New Year. 

Beyond that, we have been tracking the possibility for a warm up to return by mid-late January. This would correspond to the upper air pattern from early-mid October and late November-early December returning for a third cycle around. We will certainly be watching this closely for the next several weeks as it could have more implications down the road for later in the winter!


SailorMitch said...

You guys/gls make my head hurt trying to figure this out. it will take some time for it to ink in. So keep explaining way!

Jack said...

Sandy was such a powerful storm, that it perturbed the jet stream way to the south. This caused a longer cold period for the east coast that lasted most of November. The next deep trough on the east coast will be shorter lived than in November and the cycle considerably shorter.

Mike Natoli said...

Exactly Jack. Sandy's tropical influence really distorted the cycle that time around. We think we already lost 5 or so days off of the cycle due to the lack of the negative phase of the North Atlantic Oscillation and Greenland Block this time around.

The storm next weekend will disturb the jet stream in a very similar way to what happened in late October, but the trough is not expected to last as long. Thanks for your comment!

lynmac said...

In other words...not much in the way of winter in Maryland. Again!