Hurricane Sandy To Morph Into Landfalling Perfect Storm

It has been 21 years almost to the day of the Perfect Storm, and 58 years since Hurricane Hazel came roaring into the Mid-Atlantic.  Now, the Northeastern United States is looking at a possible landfall from one of the more rare and powerful storms to make a left turn into the region in recorded history.   Hurricane Sandy first developed in the Caribbean on Monday as the 18th named storm of the 2012 Atlantic Hurricane Season.  Since that time, the storm has grown to near major hurricane strength.

Sandy significantly strengthened on Wednesday from a strong tropical storm to high end Category Two Hurricane with winds of 110 miles per hour as it approached the southeastern coast of Cuba.  The storm has weakened a bit since crossing Cuba and moving into the Bahamas, but the storm is going through changes that could make it even more devastating.  The environment around Sandy has a cold front to the west, and a dip in the jet stream that will allow this hurricane to morph into a hybrid storm combining elements of a nor’easter and a tropical cyclone.

Hurricanes are much different than the usual storms we see here in the Northeast.   They are warm core and barotropic systems, which means that they have warm air around the center of circulation, or the eye, and have a cloud structure profile that is completely vertical.  The upper level and surface low pressures in a hurricane are stacked on top of each other, which is not the case for nor’easters, or what meteorologists define as a Mid-Latitude Cyclone.  Storms that usually effect the Northeast are cold core lows and baroclinic.  

Mid-Latitude Cyclones have cold air around the area of low pressure, and the cloud structure is sloped or slanted because the upper level low and surface low are not on top of each other.  Nor’easters tend to like wind shear, or wind going in different directions at different heights of the atmosphere, involved because of this while hurricanes do not like shear at all.  Another difference between hurricanes and nor’easters is the wind field.  Hurricanes tend to have the strongest winds near its core while nor’easters have winds cover more larger area.

With all of this in mind, we return to Sandy, a storm that is about to undergo a radical transformation from a storm system that has a warm core and is baroptric in nature to one that has more of a cold core and is more baroclinic in nature.  To what degree this transformation goes remains to be seen, but already Sandy’s wind field is expanding.  As of 8:00 PM this evening, hurricane force winds extend some 35 miles from the center while tropical storm force winds reach out some 205 miles.  Pressure is already low at 965 millibars, or 28.50 inches of Hg.

So, we have significantly low pressure with Sandy, a cold front approaching from the west, a significant dip in the jet stream, and a lot of warm moist air ahead of the front over the Northeast and Mid-Atlantic.  It was been a fairly mild and humid autumn so far in New Jersey.  True, there have been some days of chilly weather with the first frost  happening a couple weeks or so ago, but overall, temperatures have been quite mild.   Put all of these ingredients together, and mother nature has quite a storm to cook up.  

Currently, Sandy is moving through the Bahamas.  The most recent advisory on Thursday evening had the storm centered  between Cat and Eleuthera island in the Bahamas.  Winds have decreased since late last night from 110 miles per hour to 100 miles per hour, and the pressure has risen a bit, but don’t be fooled by this.  As Sandy approaches the Mid-Atlantic and Northeast early next week, it will still be quite a potent storm, maintaining much of its strength as it moves over the warm water of the Gulf Stream, and generating energy as a result of its transformation into a hybrid storm.

Changing to more of a cold core or baroclinic storm will require some transfer of energy.  This transfer of energy will make what is left of Sandy more powerful and dangerous.  The storm will also grow in size thanks to its larger wind field so a large area of strong winds will be felt in the Northeast and Mid-Atlantic.   Have we seen such a circumstance where this has happened before?  The answer is yes.  Back in late October 1991, the Perfect Storm developed from the combination of a cold front, a strong jet stream, and Hurricane Grace, a Category One storm that formed near Bermuda.  However, that storm never made landfall.  This one has a very strong likelihood of landfall somewhere from Delaware Bay to Maine.

The latest forecast models are coming closer together on a track for this  potentially powerful and dangerous storm.  Earlier in the week, the GFS (American model) and ECMWF (European Model) were a bit apart on a forecast track.  The GFS had the storm coming ashore somewhere in Maine while the ECMWF had it moving into Delaware Bay.  Now, they are much closer together with the European still moving through the Mid-Atlantic near Delaware Bay while the GFS is further south with an impact along the Jersey Shore.  Both of these scenarios do not bode well for the Northeast.  

After dodging a bullet with Irene back in August 2011, the Northeast and Mid-Atlantic States could be staring down at a monster of a storm early next week.  A region that has been long overdue for a powerful storm may be making up for lost time come Monday or Tuesday.