Tuesday, January 31, 2012

February 2-6 Major Snowstorm Discussion **UPDATED TODAY**

We have a lot to discuss, so let's get down to it.

12z GFS ENS. Hour 120
12z GFS ENS. Hour 132
12z GFS ENS. Hour 144
I think we are close enough to the storm's occurrence to stop using the ensembles and start using the models themselves. We will post on them, anyways. The GFS ENS are projecting the snow to fall in the Plains into the Midwest and Ohio Valley. I'm thinking that the Plains snowfall looks to be a good bet, with a strip of snow into the Midwest. The Ohio Valley has yet to be worked out. Right now, looking at the 12z GFS, it shows snow hitting the Plains and midwest, but not the Ohio Valley. See below.
I'm thinking that this snowfall forecast looks like a good solution. It shows a snowstorm for the Plains and a strip of 6-12 inches of snow into the Midwest. But there are things that have to be looked at to confirm this.

The PNA forecasts indicate a strong PNA developing as the storm is starting to form. This could be a problem, as it is possible the ridge forms when the storm is already past the area where the PNA ridge forms. In that scenario, a Northeast storm scenario would look to be unlikely, as a +PNA directs the jet stream to the Northeast, but cannot bring this storm there if it is already in the Plains after the PNA forms.

Precipitation Patterns with MJO phases
The MJO is projected to move into a strong period of Phases 6 and 7. Phase 6 strongly favors above normal precipitation in the Great Lakes and Midwest into parts of the Ohio Valley and South Central US, leading me to think that a Phase 6 MJO develops a Southeast Ridge to divert the storm towards the upper Northeast and Ohio Valley, therefore giving precipitation to the Midwest. Phase 7 eases off the ridge and precipitation, but still shows above normal precip anomalies in the Midwest and Plains.

Model Diagnosis
Will not be using UKMET/ECMWF/GEM in my forecast as they have been inconsistent and are not finding a solution. Prefer GFS out of the most consistency I have seen. Eventually, a SREF blend may be preferred, especially today as verification at hour 72 forecasts can be actually very good.

In my opinion, the +PNA should come too late for the storm system to be diverted into the Northeast. That said, an increasingly strong MJO Phase 6 would favor the storm to move into the Plains if it cannot travel along the +PNA jet stream that goes through the South. As of now, I see the storm moving into the Plains and subsequently being pushed east into the nation's Midsection, much like the ECMWF Ensembles have been showing. Checking out the HPC, I'm finding drastically increased precipitation forecasts in the Plains, leading me to think that confidence in a Plains solution has grown. The CMC model is further north than the GFS and will have to be watched.

Over 6 inches of snow is very well possible in the Plains into the Midwest, with the west central Plains in the big target zone. We outlined a lower confidence area in the event that the storm ends up farther south than anticipated. The low pressure system is going to be moving through Oklahoma and kentucky before speeding offshore.

Side notes:
*Several upcoming model runs will be equipped with observation data from specialized airplane flights that drop items recording data in the storm-to-be that is then ingested into a certain model run (typically the 0z or 12z suites).

Any questions may be asked below.
And for the record, I do not expect this solution to change dramatically.

UPDATED February 2-6 Snowstorm Discussion TODAY at 4:00 PM CST