[wxqc] Check out the pressures in the N.E.!

[Gary Ferdinand]

As a teenager in the late 50s early 60s (yeah, I'm an old goat!) I was an
avid weather student, living on Long Island, NY.  I remember seeing lots of
barometric readings in the same range as what we just saw in the NE this
past weekend.  Apparently, the makers of living room barometers and sea
barometers agreed.  If you look at the older instruments you'll see the
"storm" designation quite low on the scale - 29" and below.   Then over the
years I recall wondering to myself why they were labeled that way, since the
storms d'jour always seemed to bring lots of rain and wind, but with
pressures more like the mid-29s at worst.

This forces me to wonder whether these are just memories of a kid, entranced
by the weather engine, or whether instead the climate was more prone to
pressure extremes "back then" then it has been over the past decade or two.

BTW the low pressure recorded here, near Albany, NY in the past storm was a
mere 28.762 (VP2/WxLink).  Pretty much in line with many others.

Gary W2CS (AR975)
North Chatham, NY

  -----Original Message-----
  From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net]On Behalf Of Evan Bookbinder
  Sent: Tuesday, April 17, 2007 8:23 AM
  To: Discussion of weather data quality issues
  Subject: Re: [wxqc] Check out the pressures in the N.E.!


  Eleanor,

  While these pressures are low, they're likely not even in the top 30 of
storms (extratropical or tropical) to affect the Northeast. Indeed a 974mb
pressure might be the equivalent of a cat 1 hurricane, but we'd be comparing
apples and oranges. If we think about it, absolute pressure it of little
inherent value, as it's the pressure gradient (the change of pressure over
some distance) that drives the wind speed and direction. A hurricane's
internal structure causes that gradient to be focused tightly around the
storm's center. An extratropical cyclone's gradient is spread out over a
great distance (controlled by surrounding high pressure systems), and light
winds can be found in a much larger area around the low pressure center than
a hurricane's eye. As a result, the wind speeds associated with the same
absolute low pressure might be half those found in a similar hurricane.

  I doubt you'll see pressures posted from the event, because while
certainly VERY low, they're by no means a historic or shocking value for the
Northeast. The shock value really comes from the fact that the Northeast was
spared any major storms this winter so you didn't see these sporadic 28.xx"
pressure values.

  As for where the lowest pressure occurred, this could be found by doing
surface analyses of each hours during the peak portion of the storm event. I
wasn't watching closely enough, but it's possible this value may have
occurred just offshore as well leaving you with interpolation between inland
observations, ships (anyone daring enough) and buoy observations.

  Hope this helps!
  Evan
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