Thursday, February 9, 2012

February 14-18 Possible Snowstorm (Issued 2/9/12)

I am in awe at the consistency of the storm strength that the ECMWF has been trending with, so let's get down to it.

12z ECMWF Hour 216
For the past at least 6 model runs, the ECMWF has been consistently showing a strong storm system impacting the Great Lakes and Midwest. In case you did not know, the ECMWF is a very reliable model in these times of model instability (which have moderated recently, for some models). Seeing this trend of a strong storm in the Ohio Valley only increases my confidence in this actually occurring.
Not seeing much of a change from yesterday's 12z runs, as the ECMWF portrays two storm systems phasing into one massive storm system in the Plains that moves north.

12z ECMWF ENS Hour 192
 Today's 12z ECMWF Ensembles show there is still room for change, with the ensembles showing the storm being a more progressive one than the ECMWF model itself is showing. It also does not phase the two systems, which essentially takes power out of every aspect of the storm- warm air advection north, cold air following the storm, precipitation, etc. I do feel that the presence of the storm on the ensembles is a reassuring one, however, and believe that there is a good amount of confidence right now of having this system happen.

12z ECMWF ENS Hour 216 500mb Height Anomalies
I found this image of 500mb height anomalies at the time of the storm. What I am seeing is a big ridge in the Pacific that could very much be a key player here. The reason it is disrupted is due to a low pressure system moving along, but I am paying attention to the main ridge and imagining it without the low pressure disruption in the Pacific Ridge, as the low pressure system really doesn't make a difference- it's the big ridge that counts.
Analyzing the ridge leads me to see that the ridge favors possibly going into the Western US. This would lead into a +PNA-like storm track, which would happen if we didn't have a monster ridge just south of Greenland. What this ridge will do is essentially lift the jet stream north and slice through the Northeast. This slice would bring the jet stream from North Texas through Tennessee and dashing north into Pennsylvania/Ohio. This is indeed the solution that the operational ECMWF is showing.

Model Tips & Caveats
•This is still long range, so the models are subject to major changes.
•The ECMWF has been trending very long, adding a lot of support to forecasting.
•The GFS has been flip-flopping, so I do not want to use it.

Looking through the latest PNA and NAO forecasts from the ESRL/PSD and NCEP agencies on the left and right sides respectively, I'm not seeing anything major. The PNA is forecasted by the NCEP (basically the GFS) to be positive, which could lead to a little ridge over the west US. At the same time, the ESRL/PSD is showing the PNA to be negative. Due to the inconsistency, I do prefer to not comment on it right now.
The NAO forecasts are having slightly better agreements at this point, showing a strong negative NAO around mid month going back neutral around the storm. Seeing as the storm will be arriving when a strong -NAO is just leaving, I would think that some effects of the -NAO would still be lingering. This is agreed by some characteristics of the ECMWF ENS/ECMWF OP models and ensembles. (ECMWF ENS are the ECMWF Ensembles, while the ECMWF OP is the ECMWF model itself.) While both ECMWF ENS/ECMWF OP do not show a -NAO in their calculations, look back to that strong ridge just south of Greenland in the 500mb height anomalies image I showed earlier. A +NAO is characteristic of a trough of low pressure south of Greenland. The height anomalies show a ridge south of Greenland. I believe that this inadvertently shows a -NAO still lingering but not shown in the model forecasts. This would still keep parts of the Northeast in the game.

I am opting to not show the PSD ESRL Ensembles as I cannot confirm that the storm is in the right timeframe or if it even exists in those ensembles.

My Preliminary Thoughts
I'm liking the way the ECMWF has been handling this. While the ECMWF ENS may still be a tad shaky, I am really liking the way the ECMWF has been trending the storm, while keeping the same general placement and strength of this storm through the past several runs. Trending is always a good sign, especially on such a reliable model like the ECMWF. If I had to put a VERY PRELIMINARY guess % chance on if this storm will occur, I would put it at 35% due to model uncertainty in other models and the long range-ness of it, but increased by the ECMWF's trending.

Side Notes:
Tom Skilling, reputed meteorologist in Chicago, IL and a personal favorite meteorologist of mine, has been talking up this storm for the past couple days. He is not one to hype storms at all, so him talking about it this far out is grabbing my attention.

If you have any questions you may ask them below. They will most likely be answered tomorrow morning.

Update on February 14-18 Possible Snowstorm at 4:00 PM CST

An update on the possible February 14-18 snowstorm will be published at 4:00 PM CST Today (2-9-12)