December Snowstorm Only a Cat 3 on NESIS Scale

NOAA Ranks December Snowstorm a Category 3 on the Northeast Snowfall Impact 5-tier Scale

Snowfall accumulation from the Dec. 18-21, 2009 storm. (Credit: NOAA). [Click image for High Resolution]

NOAA says the Dec. 18-20, 2009 system that dumped heavy snow from the mid-Atlantic to southern New England, was only a Category 3 or “Major” winter storm on its Northeast Snowfall Impact Scale,  NESIS.

NESIS ranking uses data provided by NOAA’s National Climatic Data Center, which are based on

• How much snow falls in the area (must deposit at least 10 inches)
• Scale of the area impacte
• Population of the impacted area

NESIS ranks these storms on a five-tier scale ranging from Category 1 “Notable” to Category 5 “Extreme.”

“While snowfall from the December storm ranked in the top ten for Washington, Baltimore and Philadelphia, the storm only provided a glancing blow to the New York City and Boston metropolitan areas and overall affected a relatively small area. This led to it being classified as a Category 3,” said Louis Uccellini, director of the National Centers for Environmental Prediction – a division of NOAA’s National Weather Service – and co-developer of NESIS with Paul Kocin also with NCEP in Camp Springs, Md. Both Uccellini and Kocin are published winter weather experts.

“Last month’s storm was one of only five in the past decade that ranked Category 3 or higher,” added Kocin. The others being: December, 2002 (Category 3); February, 2003 (Category 4); January, 2005 (Category 4); February, 2006 (Category 3) and February, 2007 (Category 3).

Category 5 storms or  the  ‘Superstorm’ top the NESIS scale the only two storms rated Cat 5 occurred on March, 1993 followed by the ‘Blizzard of ’96‘ in January, 1996. The scale was devised in 2004 and it catalogs storms since 1888, NOAA said.