Key Terms

ALBERTA CLIPPER - a quick moving storm that typically originates in the vicinity of Alberta, Canada and drops down to the United States exiting off the East Coast. Often these storms bring with them cold air and strong winds. These storms sometimes redevelop and intensify when they near the coast.

AMERICAN MODEL (GFS) - The medium range model created by the United States to forecast the weather The American global model is consistently either the second or third most accurate of the global forecast models, trading places occasionally with the British model. The medium range American model goes out in time 16 days. This is the model that I typically refer to as the American model in my discussions. 

AMERICAN MODEL (NAM) -The short range model created by the United States to forecast the weather. The short range American model goes out to three and a half days. 

BACKDOOR COLD FRONT - A cold front that moves westward or southwestward into our area off the ocean, usually bringing cooler weather.

BLIZZARD WARNING - A blizzard warning is issued when a blizzard is imminent.

BRITISH MODEL (UKMET) -The model that Great Britain uses to forecast the weather. This model goes out to 6 days and is typically ranked second or third in terms of accuracy, sometimes trading places with the American model. 

CANADIAN MODEL (GEM-GLB) - The model that Canada uses to forecast the weather. This model goes out to 10 days and is typically the 5th most accurate of all the models.  

ENSEMBLE MEAN - The ensemble mean of a model is the average of all the various ensemble members.

ENSEMBLE MEMBER - An ensemble member of a model is a run of the model under slightly different parameters, to show various results under slightly different conditions. 

EUROPEAN MODEL (ECMWF) - The forecast model designed by the European Center for Medium Range Weather Forecasts on behalf of the European Union The European model is the most statistically accurate of all the forecast models.  The European model goes out to 10 days in high resolution and 15 days in low resolution. 

FREEZING RAIN - Rain that freezes when it hits a surface that is below 32 degrees Fahrenheit



HAIL - Occurs during thunderstorms when rain drops are blown upward by strong winds, so high into the clouds that they freeze, then they fall to the ground as balls of ice

HEAT WAVE - The official definition of a heat wave is three consecutive days of high temperatures exceeding 90 degrees.  

HIGHER RESOLUTION RUN OF THE MODEL - When the model is run with more detail.  This is also refereed to as the operational run of the model and is the normal run of the model. When I am talking about model runs, I am usually talking about the higher resolution run of the model.   


JANUARY THAW - A one week period which is much warmer than the month before or after, usually occurring near the end of January.

JAPANESE MODEL (JMA) - The Japanese model is the model that Japan uses to forecast the weather.  The Japanese model is typically the 4th most accurate model.

LAKE EFFECT SNOW SHOWER/SQUALL - Lake Effect snow showers occur when strong and very cold winds blow across the relatively warm water of the Great Lakes.  

LOWER RESOLUTION RUN OF THE MODEL - This is when the operational run of a model is run with slightly less detail or information. This can be useful as on some occasions having more information or detail can impact the accuracy of a model. Models are also often run in lower resolution to save time and money, as they can be run much faster and easier. Also, extended versions of models are often run in lower resolution, such as the European model, which is run in higher resolution through 10 days, then in lower resolution through 15 days. Typically lower resolution is not as good as higher resolution, but there are exceptions to this rule.

NAVY MODEL - The Navy model is the model that the United States Navy uses to forecast the weather. The Navy model is typically the 6th most accurate model.  

NORTHERN SECTIONS - areas north of about Rt. 78 in Eastern Pennsylvania and Northern NJ.

OPERATIONAL RUN OF THE MODEL - The operational run of a model is the main run of the model that is used to forecast the weather. 

POLAR VORTEX - a persistent area of cold-core low pressure where the coldest temperatures in the hemisphere are usually located.  And click here for an interesting video from the White House.

SEVERE THUNDERSTORM WARNING - The National Weather Service issues a Severe Thunderstorm Warning when severe thunderstorms are currently occurring or are imminent. 

SEVERE THUNDERSTORM WATCH - The National Weather Service issues a Severe Thunderstorm Watch when they believe there is a high likelihood of severe thunderstorms occurring. 

SLEET - Rain drops that freeze before reaching the ground, reaching the ground in the form of ice pellets

SOUTHERN SECTIONS - areas south of about Rt. 78 in Eastern Pennsylvania and Northern NJ.

VIRGA - Precipitation that falls from the clouds but evaporates before reaching the ground

WEATHER MODELS - Computer programs created by weather services around the world designed to forecast the weather Many countries around the world have their own computer models to forecast the weather. Most models are global models, meaning they forecast the weather around the entire globe, not just for that particular country.