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From: "Mike Reddin" <mreddin{at}nii.net>
To: <casilist{at}weatherwatchers.org>
Subject: Bomb Formation Alert
Date: Sun, 28 Sep 1997 14:34:22 -0400
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The following is an alert covering the mid-atlantic and New England: This
advisory is in no way
associated with the National Weather Service or any Government Agency.
9/29/97 1:30pm 35.5N 76.0W 1005mb Max sustained wind: 40kts
Peak Wind Gusts: 50kts
A narrow area of sustained 35kt to 42kt winds are being reported just off
the NC/SC Coastline
between ~ 33N/76W to 36N/74W. This is the eastern side of the storm center,
in and near
the region of developing convection. Good spiral banding around the storm
center near 35/75
appears on radar.
Buoy data, satellite images and METARS indicate the process of 'Explosive
Cyclogensis' has commenced along the mid-atlantic coastline of the United
States. This development is not tropical in nature, however is taking on
some semi-tropical characterisitics which is not uncommon for these cases
[especially given the time of year and location].
Most cases of east coast 'Bombs' hinge upon the formation of 'convective
feedback mechanisms' similar to Tropical Storms or Hurricanes. In other
words, when strong convection with significant areal coverage becomes
involved near or within the storm center, the rate of deepening (and
subsequent increase is winds and surface convergence) cause the formation
of additional convection.. and hence a loop which leads to explosive
pressure drops and strong winds (in some cases reaching Cat-2 hurricane
force in gusts).
This is not to say that all 'bombs' must be coastal, while fewer in nature,
there are cases of explosive storm development over the midwest and Plains.
Again convection can be involved although without the aid of the Gulf
Stream, inland storms typically are not as intense.
In order to be classified as a 'bomb' [Explosive Cyclogensis] the deepening
rate must meet or
exceed 12mb in 12 hours of 24mb in 24 hours. It appears the low now near
Cape Hatteras
will deepen from 1005 at 2pm to 992mb by 2am using the current trend of 1 ~
1.5mb per hour through early morning. It will be a close call but the
center is currently mostly over water featuring a temperature range of
Keep in mind this is not a tropical system so the 'magic' 26C line often
mentioned by the TPC in their hurricane forecasts is not as critical. As
long as the water is warm enough to support and sustain convection with the
aid of upper atmospheric dynamics is the critical element. Obviously having
the very warm waters is a major boost [especially in terms of potential
energy].
Visit my website [CASI Mirror] @
For the pictures and data as I gather it. Unfortunatly I lack the real
workstation capabilities
required to documenting such storms at this point, but I am using some
interest mix of data
from NOAA, WeatherNet, Intellicast and such.
The website will be activated by 5pm [or sooner].
Mike Reddin
mreddin{at}nii.net
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