HURRICANE
COMMENTARY
Hurricane Sandy
Date / Time:
Location:
Windspeed / Pressure:
Speed / Direction:
2300EDT 10/28/12
34.5N, 70.5W East of N. Carolina.
75mph, 950mb (Cat 1 Hurricane)
14mph NE
Executive Summary
Hurricane SANDY is on course to create widespread damage along
the US East Coast with effects felt well inland. SANDY has one of the
largest areas of tropical storm force winds ever recorded in the North
Atlantic. Models have come into agreement for a New Jersey landfall
though the immense size means impacts will be widespread.
Communities in the Mid-Atlantic States should pay close attention to
storm development and warnings.
Satellite Image of Hurricane Sandy
(image from NOAA/NESDIS)
Over the past couple of days SANDY has taken on a variety of guises, unwilling to fit our usual definitions of a tropical or
non-tropical storm. The environment SANDY is in is very different from that in which it formed. Moisture-rich and calm
conditions of the Caribbean were favorable for SANDY’s early formation but over the past two days SANDY has had to
contend with very strong wind shear and dry air in between shorter, more favorable periods. What has emerged is a battlescarred yet powerful storm.
The US East coast has begun to feel the impacts of SANDY, with strong winds and heavy rain currently extending from North
Carolina in the south to New Jersey in the North. This despite the hurricane center being more than 500 km offshore.
SANDY is one of the largest hurricanes ever recorded in the North Atlantic, as measured by the extent of tropical storm force
winds. Remarkably, reliable records of storm size only go back about three decades so we have much to learn about the
importance of storm size for hurricane impacts. However, we know that size is one of the main drivers of storm surge, and
major coastal cities are located in the path of a significant storm surge event.
Maximum rainfall totals of 10 inches are predicted, centered on New Jersey and Delaware with significant totals extending
inland as far as the Great Lakes region. Had SANDY been slower moving, these rainfall totals could have been much higher.
Something we don’t normally think about in terms of Hurricane impacts is snow. This late in the season, there is sufficiently
cold air on the continent that, when wrapped up in SANDY’s large circulation, has the potential to dump feet of snow, likely
centered on West Virginia.
A number of competing factors will affect SANDY’s intensity before it makes landfall. Passage over the warm waters of the
Gulf Stream will allow for some modest strengthening, yet the waters quickly cool to less favorable temperatures just prior to
landfall. However, SANDY will benefit from a source of energy usually reserved for winter storms that arises at the
boundaries between air-masses of different temperature. These competing factors are expected to cancel out with SANDY to
remain at Hurricane Category 1 strength for the next 24 hours before landfall. The major models are in agreement that
Willis Hurricane Commentary  08/27/2012  1
SANDY will soon make a left turn towards the US and a New Jersey landfall (Fig. 1). Note that the forecast tracks that remain
on a northward heading are from models generally considered far less reliable than those that forecast tracks towards the US
and are only shown in Fig.1 for completeness.
Storm size is a major component of the Cyclone Damage
Potential (CDP) Index and the immense size of SANDY
is contributing to the high values of CDP for a category 1
hurricane. The previous commentary forecast SANDY’s
CDP at 2.1 (on a scale between 0 and 10) whereas the
forecast CDP has since risen to 3.7 owing to the increase
in forecast storm size. Again, we note that non-tropical
storm characteristics are not explicitly included in this
index and may increase the damage potential
significantly.
Values of CDP provide an indication of how the damage
potential of the storm changes along the forecast track
and between forecasts, and the actual damage will
depend on the specific portfolio. The CDP is
undergoing ongoing research and development at the
National Center for Atmospheric Research and more
information can be found at
http://www.mmm.ucar.edu/people/done/files/CDP.pdf
Figure 1: Model forecast tracks for Hurricane SANDY as at 0000UTC
10/29/12 (NCAR/TCGP). Note that the best performing models all take
Sandy to US landfall at New Jersey.
FOR FURTHER INFORMATION PLEASE CONTACT:
Dr James Done
Project Scientist and Willis Research Fellow
National Center for Atmospheric Research
Earth System Laboratory
P.O. Box 3000, Boulder, CO 80307
Tel: +1 (303) 497-8209
Email: [email protected]
Website:
http://www.mmm.ucar.edu/people/done/
Roy Cloutier
Catastrophe Management Services
Willis Re Inc.
7760France Avenue South Suite 450
Mineapolis, MN
55435
Tel: +1 (952) 841-6652
Email: [email protected]
Website: http://www.willisresearchnetwork.com/
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2  Willis Hurricane Commentary  08/27/12 2012