Monday, February 11, 2013

February 21-23 Potential Winter Storm

Two runs of the American GFS forecast model have predicted a major winter storm to hit the Midwest, Plains and Great Lakes from February 21 to the 23rd.

Synopsis... The upcoming period will be an interesting one. We will be seeing the Madden-Julian Oscillation shift to Phases 3-4, and the North Atlantic Oscillation going negative. A strong negative Pacific North American index could very well act to work against such a potential, however. In non-weather speak, there are some indices that bode well for a storm system taking a path through the Midwest and Ohio Valley. However, if persistant low pressure is able to hold its ground in the West Coast, I worry that it will either shoot north into the Plains and Canada or way down south in the Gulf. One thing that I will say in this mess of uncertainty is, this American model and the more reliable European ECMWF model have the center of low pressure in nearly the same spot on the 21st. The European model does not go out past 10 days, so we will have to wait a day or two more to see how it develops this system fully.

For now, I suggest not really caring about this system. It's great to see potential and at least some model agreement, but I'm not comfortable enough with the predicted atmospheric pattern that I will definitely go ahead with this potential storm.


February 18-20 Potential Winter Storm

There is potential for a winter storm to strike the Midwest and Plains from February 18th to 20th.

The GFS model has been forecasting a fairly strong storm hitting the Midwest for a few days now, off and on again every few runs. The track has varied from run to run, but more times than not it has had the storm go into the Midwest. And when it does go into the Midwest, more times than not it takes the track shown above. As is my favorite guideline to abide by when tracking storms, always look for the trends and not the individual runs. I post this individual run because it sums up what the GFS has been showing for multiple days now.

Even more significant is that the ECMWF model (top) and their prestigious ensemble system (bottom) have joined in the fun. The ECMWF does have the key difference of two low pressure systems in the Great Lakes during this time, while the GFS only has one. The presence of two storm systems would aid in warm air advection and cut down on snowfall for cities like Chicago and northern Indiana, who are slated to get snow from this system per the above GFS forecast. The ECMWF Ensemble system has a single low pressure system, but it is in southern Lake Michigan. This would still support an all snow solution for the aforementioned city and region, but the heaviest snow would certainly be north in northern Wisconsin into Michigan. I do want to watch that area in east Arkansas and to the northeast where the pressure contour lines jut out further south towards the Gulf Coast. That can either mean another low pressure system or the more-likely cold front.

Confidence in a fairly strong storm system hitting the region shown by the GFS: 15% confidence