What is a ‘bomb cyclone’ and what will happen when it arrives?


What is a ‘bomb cyclone’ and what will happen when it arrives?

A winter storm set to hit the East Coast beginning Wednesday could break all-time record cold temperatures by the end of the week.

The term “bomb cyclone” has been trending on social media as the storm threatens to push frigid temperatures as far south as northern Florida.

The ominous name “bomb cyclone” comes from a process called explosive cyclogenesis, or bombogenesis, in which a weather system undergoes a rapid drop in pressure. 

Bombogenesis occurs “when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours, according to the National Oceanic and Atmospheric Administration (NOAA).

A millibar measures atmospheric pressure. A drop in pressure in a system equals strengthening of the system. 

Such weather systems in the northern hemisphere are centers of low pressure. When the pressure drops, the storms get stronger. When they drop in such a dramatic fashion over a short period of time, the results are equally dramatic.

Think of it as a winter hurricane.

Some forecast models put the potential pressure reading of the storm around 950 millibars at its peak. A category 3 hurricane has a minimum surface pressure of 964-945 millibars

What will happen when it hits?

The extreme weather will come in two parts. First, the winter storm will bring rain, sleet and snow to the eastern coast of the United States from northern Florida to Maine. Then a “polar vortex” will sweep south across the region dropping temperatures to record low levels, according to forecasters.

With the approaching weather system, a warning has been issued for winds up to 55 mph, near blizzard conditions in some areas and record-breaking low temperatures. The National Weather Service said areas in northern Florida and southeastern Georgia could see up to an inch of snow and ice on the roadways early Wednesday. The NWS said wind chills of minus 50 degrees could be seen in northern New York by Saturday morning.


The NWS national forecast Wednesday said:

  1. This winter storm is forecast to bring the potential for a mix of freezing rain/sleet/snow from portions of northern Florida to North Carolina, and snowfall northward along portions of the Mid-Atlantic into New England. Blizzard conditions are possible across portions of eastern New England late Thursday.
  2. If this winter storm tracks closer to the coast, it could mean more snow while a track farther east could mean less snow.
  3. This system has the potential to produce strong, damaging winds possibly resulting in downed trees and/or power outages.
  4. Minor to moderate coastal flooding/erosion is possible due to a combination of high tides and wave action, especially Thursday afternoon, Jan. 4.
  5. Winter storm watches and warnings are in effect from north central Florida northward through eastern New England.
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