I am trying to find out some information about hurricane Ivan and its
impact on Grand Cayman. I wanted to know why the surge affecting the
island was so severe. I want to find out what causes surge and if the
storm had any unusual patterns or characteristics that may have
increased the surge's effect such as back-tracking or stalling or
hitting at high tide or slow movement etc.

Hi, 

2004 saw a huge display of atmospheric angst. Over 1500 tornadoes were
reported, and nine named tropical storms in the Atlantic coast area
from Texas to North Carolina. Four of these were hurricanes of the
large and damaging type. As you know, Ivan was one of the largest of
these.

Storm Surges

"Storm surges can come ashore up to five hours before the storm and
destroy low-elevation coastal areas. It is especially damaging when
the storm surge occurs during high tide and consequently is often
responsible for most hurricane-related deaths. Storm surge is a large
dome of water often 50 to 100 miles wide that sweeps across the
coastline near where a hurricane makes landfall. Storm surge can range
from 4 to 6 feet for a minimal hurricane to greater than 20 feet for
the stronger ones. The surge of high water topped by waves is
devastating. The stronger the hurricane and the shallower the offshore
water, the higher the surge will be. Along the immediate coast, storm
surge is the greatest threat to life and property, even more so than
the high winds."
(See referance links below)

Topography:
Terrain: low-lying limestone base surrounded by coral reefs 
Elevation extremes: 
lowest point: Caribbean Sea 0 m 
highest point: The Bluff 43 m 

Grand Cayman's tide table is based on that of Galveston, Texas, minus
8 hours 1 minute. Spring tides range from 10 to 12 inches and
autumn/fall tides from 15 to 20 inches.

According to the tide table I found (see link below), it was low tide
at the time Ivan hit the Caymans.

Ivane hit Grand Cayman on the 12th at 1345 EST, sustained wind speed
was 130 kts. with gusts to 149 kts. The surge that hit was 8-10 feet
high with a total rain downpour of 12.14 inches. Ivan was at Category
4 when it hit the Grand Cayman, coming down from Category 5.  The
coast line and water depth around Grand Cayman is certainly optimum
for a very devastating surge.

Something to keep in mind however is that if it had been high tide,
the expected surge would have been much higher (perhaps up to 20
feet), and more forceful. So, truth be told, they lucked out really.
It could have been much worse.

Even with the long history the Caymans have with tropical storms, Ivan
stood out simply because of its strength. Staying between Category 4
and 5 is not common, thankfully. So I would say that the "uncommon"
thing we are looking for is simply the strength of the storm itself,
rather than any particular anomaly of the event.


Reference Links

Western Caribbean Bathymetry Map
http://stormcarib.com/climatology/WCAR_map_bathy.htm

Grand Cayman Tide Table 2004-09-12
http://www.mobilegeographics.com:81/locations/2236.html?y=2004&m=9&d=12

Grand Cayman Fact Book
http://www.gesource.ac.uk/worldguide/html/848.html

Bathymetry/Topography 
http://www.gesource.ac.uk/worldguide/tectonics/11.html

Hurricane Summary 2004
http://www.maineharbors.com/weather/h2004sm.htm

Unisys Weather: Hurricane
http://weather.unisys.com/hurricane/

Tropical Cyclone
http://en.wikipedia.org/wiki/Hurricane

Storm Surge
http://hurricanes.noaa.gov/prepare/surge.htm

The Saffir-Simpson Hurricane Scale
http://www.nhc.noaa.gov/aboutsshs.shtml

Public Adisory Archive for Tropical Depression Ivan
http://www.hpc.ncep.noaa.gov/tropical2004/IVAN/IVAN_archive.shtml

Hurricane Ivan Advisory Archive
http://www.nhc.noaa.gov/archive/2004/IVAN.shtml?

Tropical Cyclone Report -- Hurricane Ivan
http://www.nhc.noaa.gov/2004ivan.shtml?
Hurricane Ivan (Sea pressure charts)
http://www.atmos.ucla.edu/~fovell/WRF/ivan/

Storm Track Hurricane Ivan
http://cimss.ssec.wisc.edu/tropic/archive/2004/storms/ivan/ivan.html

Stormy onslaught continues
http://www.geo.utexas.edu/courses/302p/Stormy%20onslaught%20continues.htm



Other links of interest

Comprehensive Atmospheric Modeling Program
http://camp.gmu.edu/significant_weather_prediction.html

UGM Experiments During Hurricane IVAN
http://www.met.utah.edu/jnpaegle/homepages/labyerle/hurr_ivan15sep.html

Hurricane Ivan Impact Studies
http://coastal.er.usgs.gov/hurricanes/ivan/discussion.html

FEMA Mapping and Analysis Center (Hurricane Ivan)
http://www.gismaps.fema.gov/2004pages/ivan.shtm

Caribbean Hurricane Network
http://www.stormcarib.com/

Hurricane Ivan - Wikipedia
http://en.wikipedia.org/wiki/Hurricane_Ivan

Reynolds SST Analysis
http://www.nhc.noaa.gov/archive/2004/pub/al092004.public.039.shtml

Hurricane Ivan Advisory Number 39 (24 hours from Cayman Islands)
http://www.nhc.noaa.gov/archive/2004/pub/al092004.public.039.shtml

What if Hurricane Ivane had not Missed New Orleans?
http://www.colorado.edu/hazards/o/nov04/nov04c.html

SSEC Images and Data
http://www.ssec.wisc.edu/data/

http://www.ssec.wisc.edu/~gumley/modis_gallery/index.html

CIMSS Tropical Cyclones
http://cimss.ssec.wisc.edu/tropic/


Searches used

+topography +map +"Cayman Islands"
+Bathymetry +"Cayman Islands"
+"Tide Table" +"Grand Cayman" +2004
+"Storm Surge" +Cause +Hurricane
Hurricane Ivan +"Cayman" +surge site:edu

many others...

If you have questions please feel free to use the Clarification Feature


thanks, 

webadept-ga

---

Request for Answer Clarification by sjoseph-ga on 02 May 2005 12:37 PDT

I was somewhat confused by your statement that the islands had a long
history with hurricanes. In the past 70-odd years there have only been
three major hurricanes having only minor impact on the islands. I live
on Grand Cayman and have asked several Caymanians about the hurricane
history and only one is generally mentioned - the 1932 storm. This was
only a Cat 4 and was not as close as Ivan. I also found several
documents that suggested that, due to the duration of the storm (36
hours effecting Grand Cayman)that high tide was experienced and
increased the surge effect. I could not load some of the referenced
web pages and was wondering if my information could be completely
off-base.

Tide tables are sometimes deceptive because they predict tides when
all other factor are normal.  The longer the winds are around before a
hurricane hits, the more water can pile up in bays and sounds.  This
is seen more on the mainland, however, as islands generally are able
to mitigate this type of water build-up.  Grand Cayman is a fairly
low-lying island, and keep in mind everyone wants to be on the coast
which is right at about sea level.