Monday, December 10, 2012

December 18-21 Potential Major Winter Storm

There is growing potential for a winter storm during the timeframe of December 18-21. Let's see what the models are saying.

This is the European's ECMWF model, and here we see a storm system coming out of the South Plains with a central minimum pressure of 996 millibars. Looking at the atmospheric set-up surrounding this system, we see a strong high pressure system in south central Canada, so that makes my enthusiasm for an Ohio Valley hit go down slightly. However, watch that extended dark orange color, as we could see a high pressure try to form in that region, which could provoke this storm slightly to the north.

Advancing 24 hours to the morning of December 19, we see that this system has moved north and actually into the Ohio Valley, thanks in part to a developing high pressure system in the Gulf Coast and what appears to be another high pressure system to the east of this system. The storm system in question is now predicted by the ECMWF to be 991 millibars, a pretty strong storm. Notice how it is more elongated than compressed, with those 991mb values trying to push east into the Mid Atlantic. This could be a sign that the system wants to split, but that's too far out for me to be confident in deciphering.

I can't say I'm sure what the GFS forecast for the afternoon of December 18th is showing. It does have a low pressure system in the picture, but the GFS has the system just offshore Florida in a bizarre set-up that could turn into a nasty Nor'easter. I have no idea what the GFS is doing, but to entertain those in a snow drought, let's move on.

Wow. The GFS bombs out a storm just off the Mid-Atlantic coast on the afternoon of December 19th. Again, this is pretty bizarre. I'm just not even sure what to say about this forecast other than... wow.

(Originally posted Dec. 9, edited slightly) The Lezak Recurring Cycle, or LRC is involved in this situation. Using the 53 day LRC timetable, I traced back December 18th to October 28th, and here is the 500mb pattern observed that day.

Look at that! We see a strong system in the Ohio Valley on this day, as well as a weak high pressure system in the Southwest indicating a possible positive PNA. There is a negative NAO in place, though we can't tell whether it is west or east based. Does this look familiar to the first image shown? You bet. It looks like our 53 day cycle is working.

The models are having some trouble, so let's go a day ahead to October 29th and see what happened.

Our storm system has now moved to the east, wobbling a bit as it did so, and combined with Sandy. Notice we still had our positive PNA showing itself with high pressure in the West US. If we were to follow this system and discount Sandy, I still believe an eastward movement would have prevailed, likely not as fast if Sandy were not present. The lack of Sandy in this potential storm system, combined with a positive PNA and east-based negative NAO leads me to believe that this forecast system should go a little more to the north and east than it did in October.

Looking at this 53 day timetable, I think I know why the GFS is acting so weird. It is trying to imitate Sandy in its forecast, with a strong storm system sliding up the coast. However, I highly doubt such an event will happen- the GFS is likely playing its games.

Preferred Forecast: ECMWF
Confidence: 35%



Anonymous said...

Thenks so much andrew! If a system DOES make it's way through the northeast whether it be the european model or hthe north american one, do you think it would be a snow/mix event or is there to much warm air?

Keep up the great work!

Andrew said...

Anonymous: The European is showing a rain event at the moment, but we're still quite a while away. Nothing is set in stone.

Anonymous said...

What does that mean for the chicago northwest indiana area?It does mention a lot of snow falling in my area along with michigan. They update the forecast every morning and based off of these models they still say snow.

Anonymous said...

More rain. I think we should be discussing systems more in the 72 hour range rather than the 240-192 hour range. Hope the cold air dives south and east but don't see that happening until mid-January.

Ray T. said...

For the Chicago area... this could mean anywhere from a huge dumping of snow to no precipiation at all, it just depends on the exact storm track which is critical in determining who gets the heavy snow and who gets nothing, and possibly even an outbreak of severe weather for the Gulf coast states. Nothing it set-in-stone and there are no models in good agreement at this time. You are urged to stay tuned, this could be a really nasty one for a large part of the country if all works out just right.

Andrew said...

Anonymous #2: See Ray T.'s response. Thanks to him by the way for responding.

Anonymous #3: Not so fast- just because last year as bad and this month isn't the best doesn't mean it's all doom and gloom.