Cbus Weather Nerd

What is a 'bomb cyclone,' and when should we expect it?

COLUMBUS (WCMH) -- So if you have spent any time on social media, or the web in the past day or two, you probably have come across the trending weather topic "bomb cyclone."

Well, it is a real thing, and I can tell you it is not a new thing. It is also something that will not have a direct impact on Central Ohio.

What is a bomb cyclone?

All cyclones in the northern hemisphere are centers of low pressure.  They can be a simple low on a map bringing the typical changing weather, a tropical storm, a hurricane for example.  Hurricanes and tropical storms are tropical because of their characteristic of having a warm core.

This system is an area of low pressure that will become massive, deep (low pressure), and will cause some major weather changes over a vast area of the planet.  The 'bomb' part comes from the fact that this low will intensify rapidly, so much so that it will have what is considered explosive intensification.

For example, right now here in Central Ohio, we have cold high pressure in command for the moment, and our surface pressure is roughly 1030 millibars.  Well this system will develop tomorrow morning with pressure at about 1005 millibars, so lower pressure for sure.  But within 24-30 hours, some forecast models have this pressure dropping 30-40 or more millibars, which is incredible.  It would be an alarming drop in pressure for a hurricane as well.

For the record, Hurricane Wilma in 2005 had a 24 hour record pressure drop of 97 millibars.

How does the forecast pressure minimum compare to a hurricane?

Well according to some of the forecast models, this storm could drop its central pressure into the 950 millibar range.  If it were to get that low, it would be a deeper low than many of our hurricanes and tropical storms in the Atlantic in 2017.  Tropical Storm Don, Bret, Emily, Philippe, Rina, Cindy, Arlene, and Hurricanes Nate, Franklin, Katia, Gert, Lee, and Ophelia all had higher central pressure minimums than this storm may have.  Lee and Ophelia were cat. 3 storms too!

So what are we going to see happen on Wednesday and Thursday?

First, there are winter weather advisories to winter storm warnings from Florida to Maine.  Let that sink in, WINTER STORM WARNINGS IN FLORIDA!!!

The bulk of what falls in northern Florida could fall as mainly icy mix, which we all know is worse than getting some snow.  This will be a threat up the east coast, and with stronger and gustier winds expected as the storm builds north, this could risk power outages and many other hazards from ice.

Below is the morning look at the American (GFS) forecast model.  Notice we are watching that system forming over Florida and the northern Bahamas.

Fast forward 12 hours to Wednesday night and notice the low getting deeper well off the Carolina coasts.  Yes they will see several inches of snow in South Carolina through North Carolina tomorrow/tomorrow night.

By Thursday morning, this storm will explode (like a bomb) in intensity as it moves up the east coast.  It is a very vigorous and pronounced storm, producing the worst weather off in the Atlantic, but still dropping snow along the east coast, and bringing increasingly gustier winds.

By Thursday night, this storm is enormous and covering most of the east coast of the US and up into Canada.  The problem is when a storm gets this big, it start to impact and drive other weather events.  Remember that Wednesday night we are going to have a cold front roll through our area.

By Friday morning this storm is up into Canada, moving away from the United States, but also displacing the much colder Canadian air southbound.  Remember the circulation around lows in the Northern Hemisphere drives counter-clockwise.  This means the colder air is going to be driven southbound on the backside of this system.

While this all appears not good for the east coast, the worst of this system should continue to stay out at sea.  That is where the worst of the winds, waves, and precipitation will fall.  If this system jogs a bit to the left (west) this will worsen the forecast for the east coast, and the more to the right (east) this goes, the better off the east coast may be overall.

What are the biggest threats with this system for the east coast, and for us in Ohio too?

Clearly for the east coast, wintry precipitation, ice near the coasts, and blowing snow.  The tighter the pressure field in a storm the stronger those winds are going to be.  As you saw from the above images by Thursday, the red lines on the map (isobars) are lines of equal pressure.  Notice how many of them there are around the center of the storm.  Now look at the image below of the wind field with the precipitation.  Yes, it does almost look like a winter hurricane!

Here is the other problem I see, and more of a problem for Ohio.... temperature, and to some extent the winds as well on Thursday and early Friday.  Notice by Thursday night, the model already had temperatures on the backside of this system falling into the single digits to below zero in parts of Ohio.  Also, we are going to keep a bit of a breeze due to proximity to this system.  This should produce additional wind chill advisories for Friday morning.

The treat will come Saturday morning, when the system pulls far enough away that clouds and winds should relax, and that lobe of much colder polar air dives south for Saturday morning.  This model shows most of Ohio in subzero temperatures to start the day on Saturday.  But it could be a lot worse.  Look at areas in upstate New York which could be at -20 to -25 for the air temperature Saturday morning!  Highs on Saturday may stay in those spots as cold at -10!

Hang in there though, because here in Ohio, this will be a short lived event as warmer air will briefly look for a return early next work week ahead of another cold front.

If you ever have questions about cold weather, bomb cyclones, or any other weather or science questions, email me, dmazza@wcmh.com

-Dave


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