Sunday, January 29, 2012

February 2-6 Potential Significant Snowfall

The latest 18z GFS is printing out a stunning 2 feet of snow for the Great Lakes regions, with widespread 1 foot+ totals across the Northeast and Ohio Valley. This storm has been watched very closely and with this run, the need to monitor this scenario only grows.
At this point it looks like the models are projecting a low pressure system to eject out of the Plains and into the Ohio Valley, where it phases with another strong storm system, thus introducing massive amounts of snow into the Northeast and Ohio Valley.

The PNA looks to be raging positive in this timeframe, leading me to think that this scenario up to the system appearing in the Plains will happen. From then on, it gets a little dicier.
The Arctic Oscillation looks to be moderately negative in this timeframe, enhancing the potential for snow. The NAO looks to me like it may stay positive through this timeframe. The CPC NAO chart, which takes in multiple models, shows that the NAO should be anywhere from neutral to moderately positive in this timeframe. That will have to be closely watched.
A big factor will also be the MJO, forecasted to go into Phase 6 into 7, however the storm should strike in Phase 6 if this verifies. Phase 6 favors the Midwest and Ohio Valley for Precipitation, but also includes parts of the Northeast. This somewhat goes along the MJO lines.
Here's where it gets confusing. The MJO will be strong, meaning its effects will be stronger than usual. At the same time, the PNA will be a strong positive, meaning its effects will also be noticeable. This means that it can come down to these two factors. A closer analysis of the MJO reveals that the heaviest precipitation in a transition of phases 6 to 7 typically occurs in the interior Midwest and lower Great Lakes into the Ohio Valley.
What this 18z GFS has done is combine the +PNA and Phase 6 MJO in an incredible fashion. I believe that if any solution is to work with the PNA and Phase 6 MJO being the main factors, the 18z GFS is the one.


The GFS Ensembles. As I have claimed this winter, the models are horrific in performance. Thus, I have advocated the use of ensembles throughout. This 18z run is a different story in some aspects for the storm.
Hour 144 18z GFS ENS.
Hour 156 18z GFS ENS.
Hour 180 18z GFS ENS.
The GFS Ensembles have the system bring in more precipitation into the interior Midwest and Ohio Valley than the 18z GFS itself.

My Thoughts
Looking at the MJO in Phase 6, I think that this could go either way. Both the 18z GFS and 18z GFS Ensembles print out very good solutions in my opinion. However, seeing as the MJO will be in a very strong phase, it may win out the PNA to push the storm track and precipitation a tad further west like the ensembles are showing above. On the other hand, a very strong PNA could also waver the MJO to take the storm to the Northeast and keep it away from the Midwest, like the 18z GFS itself is showing.

FOR NOW, i'm going to go with the ensembles, because I feel a consensus among a group is more powerful than a consensus among one person. I emphasize 'for now' because both parties I have shown here are putting up quite good arguments.

Any questions you have may be asked below in comments.