A Little More Than A Forecast: St. Patrick's Day Storm

Weather information today is a result of computer models run constantly by super-computers. These models try to give a three dimensional picture into how the dynamic atmosphere will act and respond to changes in conditions through time. 

There are several different model runs that meteorologists can use to help assemble a forecast. There's the Euro (ECMWF) model, the North American (NAM) model, the Global Forecasting System (GFS) model and even a Canadian (CMC) model to help give insight on what the future brings.

These models are mentioned from time to time on the Weather Channel and even on the occasional news blurb. The question is, what really goes on and why are forecasters so dependent on these super-computers?

Starting out is the basic math and physical science that goes into the atmosphere. There are certain sets of physical rules that apply to all facets of the atmosphere. These governing equations are the set of instruction codes that the computers have at their disposal for computation. All that needs to be plugged in though is the initial conditions.

These initial conditions are observed conditions from weather balloons shot up into the sky and surface conditions at the many weather stations all around the United States. They are confirmed though through the thermo-sensing technology of the several satellites circling the Earth. 

Once the initial conditions are set and a set grid parameter and accuracy is set. The model is run. The output given is to be extrapolated and studied and in no way do the computers just spit out a number that the scientists transfer to their findings.

With the European model and other operational weather forecasting models, this output will be run several times to show trends and give a clearer outlook at the forecast.  Since the atmosphere is a dynamic system, no model run is the exact replica of another. Thus the forecast is just a fair presumption based off of the output given and along with historical analysis and instinct.

In this storm, the initial conditions are also set on the positioning of key ingredients including upper level airflow, the surface low pressure, and the cold and warm fronts. All of these will have major impacts into how warm or cold the air is and is the air conducive into producing snow. 

All that being said, the conditions last night will much more favorable for heavier snowfall, but now with new information being entered in as the system progresses, there is new output. This output shows snow totals to be around 3-6 inches for the area.  Thus the National Weather Service in Silver Spring, Maryland distributed this information to all local news stations and weather outlets to communicate that information to you. 

Want to know more about the science of snow totals? Please message me and ask!

-James