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Tuesday, October 30, 2012

Hurricane Sandy: Highly Unusual Weather Patterns

10:30 AM EDT Monday - Eye 300 miles off-shore
A number of remarkable weather events happened between the time I wrote my blog entry yesterday morning and this morning.

Yesterday about 10:30 AM hurricane Sandy was about 300 miles off the coast of Delaware/Maryland.  Less than six hours later it was on-shore at Atlantic City, NJ.

What's interesting is that the eye moved so rapidly.   A "low pressure" trough which I have only seen one video about (unfortunately I have no images) showed how the trough extended out into the ocean.

As Sandy moved up the Atlantic coast of the US it literally was shuttled west when it encountered this trough.

By about 4:00 PM yesterday in western Pennsylvania we had the the first of two significant rain bands pass through the area.  Normally in hurricanes that survive to reach our area the bands are very distinct just like in someplace like Virginia or North Caroline in a more traditional hurricane.

Soon after, I believe around 6:00 PM or so the eye, visible in the image above as a small bright-green dot in the lower right, touched Atlantic City.

After that point something I have never seen happened.

What appeared to be almost a shock wave started to move inland from Atlantic City toward western Pennsylvania.  The shock wave looked like a "stalling" of the classic hurricane rain bands.  Almost as if their moisture supply had been shut down.

By about 8:00 PM or so in western PA the second rain band was dumping a lot of rain and wind on the area.

Over the course of the next three or so hours the "shock wave" moved toward the Ohio/PA border.

Here it is (edited in at 1:16 EDT):

The "shock wave" appears as a red bow in the middle of the state.

As it moved it "pushed" the the classic hurricane rain bands west and replaced them with a light wind and drizzle.  By midnight or so the rain band was gone for the western PA area.

The "eye" of the storm - the low pressure point - was only near Philadelphia at this point.

So my first question is what was this "shock wave?"

It moved across the state of PA at about 50 miles per hour literally pushing the hurricane bands out of the way as it moved.

The counter-clockwise motion of the storm, mean while, has brought cold arctic air down from Canada to dump more than three feet of snow on West Virginia and western North Carolina.

The small "pin" at the center of the image is the current rotational center (11:00 AM Tuesday October 30) of Sandy.

I have marked how the cold is being drawn in from Michigan and deposited as a blizzard in WV and western NC.

Meanwhile warmer air is still being drawn in on the back-side of Sandy contributing to the flooding of Manhattan, Long Island and New Jersey.

We can expect Sandy's rotational center to move north and, most likely, draw the colder air into western Pennsylvania.  So I expect some level of snow as this occurs.

I have been carefully following the predictions for this storm.

In general the gross movements appear to match what was predicted.  But beyond that I think things behaved in a unique way - particularly the "shock wave."  The blizzard and snow areas are much larger than predicted as well.

In terms of rain we received far less than the predictions showed.

In general I think that the "hurricane" Sandy lost much of its moisture as it touched land.

The rotation continued but the hurricane was literally starved of moisture.  So the winds kept rotating from inertia but there was no moisture to full the traditional rain bands.  The relatively dry winds created the "shock wave" pushing the traditional bands, created while moisture was still available, out of the way.

Unfortunately these traditional rain bands and their moisture are now being drawn into the cold arctic air being pulled down from Canada further compounding the blizzards.

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