Tuesday, August 7, 2012

What does the term Bombogenesis mean?

Hi Rebecca here again with another blog installment,  I meant to write this last week. However with the severe weather I had to postpone it until now. Anyway, let's get into today's subject. Most of us have seen it, been a bit of worried by it, and even had to do quite a bit of work because of it. I'm talking about  a storm coming up the coast that rapidly intensifies. The result is a huge mess, we have feet of snow, hurricane force winds, downed trees, and widespread power outages that can last for days.  Meteorologist call a storm where the pressure drops very rapidly a bombogenesis. This post will cover what a bombogenesis is, what ingredients are needed to form one, and a brief history of a few of the noteworthy ones of the past.

                                                                                   The October 26 2010 storm

Fronts and pressure systems:

When two different air masses meet, a front is formed. The boundary between these masses is called a stationary front. The air between the two masses never really combines. The stationary front may only last for a few days. One of the air masses, usually the colder and drier mass, pushes to the south, while a warmer and moister air mass moves up from the south.  In the northern hemisphere air masses will to move to the right of the direction that they were originally moving. High and low pressure systems are defined by their direction of rotation, counterclockwise  is a low pressure system, clockwise is a high pressure system. The low pressure center forms along the stationary front. As the system spins, a cold front and a warm front are created. The cold front is the leading edge of the cold air. This cold air pushes under the air in the warm sector. As the warmer air rises clouds are formed.

Fronts are associated with larger storm systems known as mid-latitude cyclones. A mid-latitude cyclone is a weather system that includes a well-defined surface low-pressure area and associated warm, cold, and occluded fronts.  An occluded front is when  a cold front overtakes a warm front and joins with it.

Cyclogenesis is a term that refers to the development of mid-latitude cyclones.

The ingredients:

The timeframe for bombogenesis is normally from October to March. The perfect setting involves a large temperature difference between the high and mid latitudes.  This make the Northeast a prime canadate for these type of storms. We have cold arctic air spilling out of Canada's cold dome and have the Gulf Stream running along the East Coast. Also the strength and placement of upper level winds is key.  Storms need energy and winds equal energy. The wind draw in cold air on the northern side and warm air from the southern side. The winds will increase the temperature difference, increase the upwards motion, and decrease the central pressure. This will keep going until the temperature difference is erased.  The end result is when the mid-latitude cyclone reaches rock bottom and the central pressure drops at least 24 mb in a 24 hour period, when this happens a bombogenesis is born.  

A bombogenesis is nothing more than an extreme cyclogenesis of a mid-latitude cyclone.

The East Coast of the United States during the colder months of the year, is the perfect breeding ground for storms to intensify rapidly due to the warmer waters of the Gulf Stream and the positioning of the low between two very different air masses. The Nor'easter's we see in the Northeast are usually the result of a bombogenesis. Now while most often bombogenesis are seen on the East Coast the Midwestern states and the Great Lakes have seen them as well.  

Notable Nor'easters

The Great Blizzard of 1888 March 11 - March 14). This storm has been called the granddaddy of all Nor'easters. We can only imagine the impact of four feet of snow when the main means of snow removal consisted of horse and buggy. The storm was very intense, snow amounts of 40 - 50 inches along with winds of 45 to 50 mph, caused snowdrifts  in excess of 50 feet. The storm caused more than 200 ships to be grounded or to be sunk. The great white hurricane paralyzed the east coast from the Chesapeake Bay all the way to Maine. Railroads were shut down and people were confined to their houses for up to a week.  All the coastal cities in the region were hard hit. However, New York City was given a killer blow. The storm left New York with a paralyzed transit system, non-existent communications, two hundred people died  in New York City from an estimate of four hundred casualties (most likely more) across the East.

The Ash Wednesday Storm of March 6–8, 1962. It has been called one of the most destructive storms ever to affect the Mid Atlantic states.  The storm ended up killing 40 people, injuring over 1,000, and causing hundreds of millions in property damage in six states.

The 1991 Perfect Storm, also known as the Halloween Nor'easter of 1991. This storm started when a area of low pressure moved out of Canada. This storm  absorbed Hurricane Grace and near it's end it  evolved into a small hurricane with winds of 75 mph on the 1st of November. This storm sunk the Andrea Gail with all hands lost. This Nor'easter is also the same storm that was featured in the movie  "The Perfect Storm" with George Clooney.

The Storm of the Century, also known as the ’93 Super-storm, or the Great Blizzard of 1993.  The storm dropped snow as far south as the Florida Panhandle and snowfall amounts were measured as deep as 16 inches in parts of Alabama.  In the northeast, the nor'easter left behind two feet of snow in Hartford Connecticut, 43 inches fell in Syracuse, New York, even New York City saw over 12 inches of snow.

I'm sure most of us can remember the  Halloween nor'easter in 2011. The storm broke snowfall records in over 20 cities and left millions in the dark for over a week.

When the skies of October turn gloomy:

I've been on the waters of Lake Ontario numerous times...I've also been on and around the other four Great lakes as well......I can tell you, I've seen the Witch of November.  Those who live around the big lakes or venture on them...pay very close attention to the sky in the Fall.... I'm not talking about leftover Halloween witches....I talking about bombogenesis. A November Witch is what those around the Great Lakes call a late fall violent storm.  The Great Lakes are home to weather systems that  are like nowhere else in the world. The waters of Lake Ontario and the other Great Lakes are still very warm in the late fall. When cold arctic air rushes over them and meets the warm moist air intense storms are created . These storms bring sustained winds of 50 to 80 miles per hour with gusts of 90 to a 120 miles per hour and waves of 20 to 40 feet. The greatest witch I've seen was the November 2003 storm that moved over Lake Ontario. I had just got back home from a storm chase in Wooster, OH. So I spent the day down by the shore.  The witch had waves  of 10 to 18 feet high with huge breakers coming ashore. I had rain mixed with snow and ice pounding me. The winds were so strong it was almost impossible to stand... to me this was fun..... . I know I'm strange....The witches are the major reason the Great Lakes are called the graveyard of ships and sailors.

Undoubtedly the most infamous November Witch was the one that sunk the Edmund Fizgerald in 1975 on Lake Superior.

The November Witch of 1913 has been dubbed the White Hurricane because snow produced blizzard conditions. The storm sunk19 ships and 250 people lost their lives.

The November Witch of October 26, 2010 was one of the most powerful storms to ever move across the Midwest and Great Lakes. Meteorologists called it the biggest non-tropical cyclone ever recorded.

The five most intense Great Lake bombogenesis on record.

1. The Great Ohio Blizzard - January 26, 1978 (958mb/28.05 inches).

2. The October 26-27, 2010 (at 955mb/28.20 inches).

3. Armistice Day Storm - November 11, 1940 (967mb/28.55 inches) and Anniversary Storm - November 10, 1988 (967mb/28.55 inches)

4. Cyclone of 1913 - November 7-9, 1913 (968mb/28.60 inches)

5. Edmund Fitzgerald Storm - November 10, 1975 (980mb/28.95 inches)

Well that's about it. You should now have a good understanding of what a bombogenesis is. Hope you enjoyed the post.


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