Wednesday, February 1, 2012

Pattern Change Update (2/1/12)

There are indications that winter weather may be on the horizon for good this time. Both the 12z ECMWF and GFS models are projecting the polar vortex to turn into a very small, pathetic, but still strong vortex that will drop into Canada. This vortex could easily moving towards the Northeast and wreck a massive wreck upon the region with a huge storm. Either way, the demise of the polar vortex may be at hand.
Other things we are seeing in these 8-10 day height anomalies are how there is a strong +PNA. This +PNA appears to be overwhelming the US weather. At the same time, the Alaskan Vortex looks to be shunted westward away from Alaska, where the +PNA ridge may be inclined to propagate towards Alaska. This remains to be seen but appears to be a valid possibility.
There is a -EPO spotted on the long range ECMWF but not really existent on the GFS.
While it is too late for stratospheric warming to have effects on us in the month of February, I am seeing a couple signs that another stratospheric warming event may be oncoming. An indicator of this is how both the height Waves 1 and 2 will be moving closer to each other in the 3rd image. The last time we saw them make contact, so to speak, was roughly around the time of the last sudden stratospheric warming (SSW). In the first image, it is the same 2 waves but this time with temperatures. We look to be seeing both waves 1 and 2 rocket to higher temperatures which is showing warming in the stratosphere. Again, February will not be impacted by this, but if a SSW does occur and this warming propagates down to the surface, March-April could be absolutely horrible for severe weather (abnormal severe weather).

Questions may be asked below.

February 2-6 Significant Snowstorm Discussion (2/1/12)

12z GFS 84 hour Snowfall Forecast

12z NAM 84 hour Snowfall Forecast
I am looking at a significant snowstorm to impact the Plains and Midwest in the next several days as a strong storm system makes its way across the region.

Discussion. . .
Seeing potential for a significant snowstorm rise across the Plains today as the NAM/GFS models begin to agree on placement of snowfall. Totals are a different matter. Currently have NAM ordering over 15 inches of snow in Iowa, with the GFS maxing out at 13 inches. 
Typically find NAM to be overdone with snowfall totals in winter storm scenarios. This does not rule out the NAM's idea, however. . .as the amount of Gulf moisture the storm pulls in will be crucial. Storm system is expected to rapidly strengthen and likely increase the amount of moisture it pulls in during the strengthening. The exact point of this strengthening will be key, as that area will receive the heaviest snows.
12z suite of weather models appears to be solid with a track up until the Great Lakes. . .when the ever-changing GEM makes a move north rather than offshore, like the other models are predicting. 
For the next 84 hours, the ECMWF looks to be rock solid. The ECMWF and GFS combined appear to look like the big ones to trust. I find the ECMWF to be unusually good in it's previous 0z verification- 12z verification data has yet to be seen. Here's the verification from the 0z suite. Models closest to the bottom of the image are theoretically better at forecasting for that forecast cycle.

I am expecting to see snowfall totals approaching 1 foot in Iowa and Nebraska, with isolated totals over 1 foot. I am taking a somewhat conservative route with this storm as the details are not nailed in. (Just saw the 18z NAM data, it is around the same as my forecast below)

If anyone has observations from the storm, I would appreciate a shout out on our Facebook page, which is accessible on our right-hand sidebar.
Any questions may be asked below.


Pattern Change Update coming out at 5:00 PM CST Today.


Have not looked at latest stratospheric diagnosis, so will not post much, but I have heard talk of the polar vortex dropping into Canada, which theoretically would unleash frigid air into the US.

Side note: February 2-6 Snowstorm
Update at 4:00 PM CST.

February 2-6 Major Snowstorm Update Will Be Published at 4:00 PM CST