LRC Services
236 Red Oak Lane
Defuniak Springs FL 32433
850-830-8656
Bridwell
2898 Tropicana Lane
Crystal Beach Texas
View of 2898 Tropicana Lane on May 12, 2009
(Please note the steel bar and piling in background oriented East to West)
This is a post-storm report on the effects of Hurricane Ike on 2898 Tropicana Lane,
Crystal Beach Texas for the period of September 12 through September 13, 2008.
The sources of data are as follows:
a.
b.
c.
d.
e.
National Weather Service
National Hurricane Center
National Climatic Data Center
Internet from various websites (i.e. Texas Tech University)
Photographs taken during my site visit
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2898 Tropicana Lane prior to Hurricane Ike
It is my professional opinion the initial and primary cause of damage at 2898 Tropicana
Lane, Crystal Beach Texas was caused by the following:
a.
b.
c.
d.
Extremely high wind speeds several hours prior to the storm surge
Microbursts and associated turbulence
Tornadic activity
Flying debris
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High level view of 2898 Tropicana Lane
The site visit was conducted on May 12, 2009. The site has been partially cleared and
bulldozed.
The National Hurricane Center has established the Bolivar peninsula near the landfall
point for Hurricane Ike with winds of 110 miles per hour at landfall at 2:00AM on the
morning of September 13, 2008. The Bridwell property was is in the right-front
quadrant of the hurricane.
Another source of wind data comes from a commercial firm called “Weatherflow”. This
company maintains a network of wind measuring equipment throughout the Houston
area. Based on the data collected by Weatherflow, there were only 2 sites (Beaumont
and Port Arthur Texas) with complete data records for Hurricane Ike. All other reporting
stations filed incomplete reports, with maximum winds as high as 111 miles per hour (on
Bolivar peninsula) with Hurricane Ike. The Weatherflow data is contained in the CD
database.
Only one land based station reported sustained winds of hurricane strength, which was
Hobby Airport (75 miles per hour with gusts to 92 miles per hour). Hobby airport is 50
miles northwest of Bolivar peninsula at a higher ground elevation. The lack of reporting
stations with sustained hurricane force winds is primarily due to widespread power
outages as Hurricane Ike approached shore. A statement issued by the National
Weather Service post-storm report dated January 16, 2009 says:
“We can only speculate that if other observations did not fail during the hurricane that
there would have been more reports of hurricane force winds.”
With a reported sustained wind of 110 miles per hour at landfall and gusts as high as
135 miles per hour (Hurricane Research Division paper, authored by Chris Landsea,
dated April 21, 2006), there is no argument to the sustained winds at 2898 Tropicana
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Lane. It is my professional opinion that winds of this magnitude affected the Bridwell
property many hours prior to landfall of Hurricane Ike.
NOTE: The reported winds from Hobby Airport were not the highest winds experienced
at that location. The recorded sustained wind speed of 75 miles per hour was
measured after a 3.5 hour power outage while the station pressure was dropping
rapidly. The observation with the winds of 75 miles per hour occurred at 6:02AM,
September 13, 2008, then the power was lost a second time for another 3 hours. A
sentence from the National Weather Service post-storm report states:
While the wind speeds may be at a Category 1 level on the Saffir-Simpson Scale, these
winds persisted for a several hours which would contribute to more extensive wind
damage across the region than if Ike was moving faster or had a smaller wind field.
The statement above from the National Weather Service infers that it was the
continuous hurricane force winds that contributed to the extensive wind damage caused
by Hurricane Ike.
All sustained wind observations from land based stations must be used with caution.
For the past 10 years, the National Weather Service has defined sustained winds as the
“average wind over a 2 minute period”. This is different than the hurricane definition of
sustained winds as averaged over 1 minute.
Statistically, there is a small percentage change between a 1 minute average versus a 2
minute average, but these statistics are based on all observations over a period of
several years. Individual situations such as hurricanes can produce a wide variance of
wind speeds resulting in a skewed 2 minute average.
For example, I have listed several 1 minute wind speed averages below to show how a
2 minute wind speed can produce a false picture of wind speeds. When a surface
observation is recorded, the last 2 minutes of wind speeds are averaged and reported.
Once the observation is taken, those previous wind speeds are no longer considered for
the next observation.
Time
1 minute average wind speed
Observation time
Reported wind speed
0123L
0124L
83 mph
63 mph
0125L
73 mph
0254L
0255L
92 mph
71 mph
0256L
82 mph
In both cases above, the higher 1 minute wind speed average would never be reported.
Not only does this system cause misleading information, but when gusts are estimated
the result is based upon a lower number than what actually occurred.
Knowing this information, there had to be a higher 1 minute average than 75 miles per
hour.
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The Hurricane Research Division of the Atlantic Oceanographic and Meteorological
Laboratory produces a post-storm analysis of winds using a variety of data sources.
This product is called the H Wind and is an analysis for a snapshot in time of sustained
winds associated with hurricanes.
When the Hurricane Research Division (HRD) releases its’ H Wind product, it is a
compilation of data from a variety of sources. It is assumed that all sources report
reliable, accurate and calibrated wind speed measurements. Some of the data sources
are:
1. Weatherflow – a commercial company that maintains a mesonet of wind
measuring equipment across southeast Texas. There are no records
available that provide any calibration records or accuracy requirements for
this equipment. There is no explanation of how Weatherflow computes
sustained wind speeds.
2. Florida Coastal Monitoring Program – managed by the University of Florida.
As with Weatherflow, there are no records available to insure accuracy of
data and proper measurement of wind speed. I queried FCMP in the past on
how they compute sustained wind speeds and I never received an answer.
3. Moored buoys – this data comes from the National Oceanic Service using a 6
minute wind speed average.
4. ASOS – this is the automated network used by the National Weaher Service
that only reports a 2 minute sustained wind speed average.
5. METAR – these are manual surface observations that also must report a 2
minute wind speed average.
6. GPS SONDE – this is an instantaneous wind speed measurement recorded
as the sonde falls through the atmosphere.
All of these sources of wind speed use different times to ascertain sustained wind
speeds. Since the sustained wind speeds are not manipulated to reflect one minute
averages, the result is a mixture of different time intervals. This is one reason why the
product is considered “experimental”.
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H wind analysis for 2:30AM, September 13, 2008
All of these listed data sources are part of the HRD H Wind product. The HRD website
clearly states that the H Wind product is “experimental”. The H Wind output should only
be used as a “tool” of any analysis, not as an objective result.
This H Wind product has been used extensively to depict sustained winds surrounding
Hurricane Ike. Users of this product must understand how it is composed and the
weaknesses associated with this analysis.
All H Wind products relevant to this case are listed in the CD database.
All this information means is that the sustained wind speeds reported for Hurricane Ike
are not “true” one minute averages, but a mixed combination of different reporting
procedures and averaging times. Therefore, this data must be used with caution and
knowing it is lower than a real-time number.
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Using the Federal Meteorological Handbook Number 1 (the “bible” of weather
observations), (FMH-1) it states:
The National Weather Service has a published table on what the NWS considers
representative of expected results from wind speeds. It is below:
As it can be seen, the National Weather Service “expects” widespread damage with
winds greater than 56 knots (65 miles per hour). These are the official expectations of
the National Weather Service for wind speeds.
There are no instructions in the FMH-1 to utilize the Saffir-Simpson Scale as a tool to
estimate wind speeds based upon observed damages. There are numerous reports
each year where wind speeds of 50 miles per hour and greater cause serious damage
across the United States. As examples of how reliable this scale is, I placed some
photos of damages caused by wind speeds of 50 and 55 miles per hour. These photos
fit exactly into the 48-55 category of Table 5-1 above.
A noted Midwest tornado chaser, Mr. Tim Marshall, apparently agrees that the SaffirSimpson Scale and even the Fujita Scale are misleading when engineers assess
damages after-the-fact. Mr. Marshall was answering questions submitted to him
concerning tornadoes that struck La Plata Maryland in April 2002.
In one of his responses, Mr. Marshall made the following comment:
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Marshall: To me there was nothing tornado-resistant about the houses in La Plata. You're dealing
with conventional building construction, and that's done by a building code. Well, a building code is a
minimum, and if the goal is to get to the minimum, the chances are they're barely going to get there
or they're not going to get there. What is the minimum? A wind of 80 to 100 miles an hour. We're
finding that if you have winds greater than that, houses get into some serious trouble. And I mean
catastrophic-type trouble.
Here is a noted specialist (Mr. Marshall) that assisted in the development of the
Enhanced Fujita Scale saying that when winds get above 80 to 100 miles per hour,
there will be catastrophic-type trouble.
Damage to storage facility 80 mph winds Wisconsin 1998
Note how winds blew building away but barely disturbed contents
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Roof torn off – 55 mph winds (St. Mary’s Ohio September 2008)
Based on what the National Weather Services mandates for use to estimate wind speed
by observable damage, winds of this magnitude began on the night of September 12,
2008, many hours before the storm surge arrived between 1:00AM and 2:00AM,
September 13, 2008. Wind speeds of 50 miles per hour and higher were reported at
Hobby Airport as early as 6:00PM, September 12, 2008
There were a number of other weather elements within Hurricane Ike that affected this
specific property hours before landfall and at least 6 hours before the storm surge came
ashore on Bolivar peninsula.
Beginning on the evening of September 12, 2008 the Bolivar peninsula and 2898
Tropicana Lane experienced severe thunderstorms, microbursts and the first
mesocyclone that moved across the peninsula.
Before analyzing NEXRAD radar data for mesocyclones and tornadoes, you have to be
aware of the limitations of NEXRAD for these elements. The NEXRAD experts at the
NWS offices in Melbourne, Tampa and Jacksonville Florida stated : (this statement is
pertinent to this case because of the NEXRAD analysis technique used for hurricanes)
The shallow depth and weaker detectable rotation of the TC (tornadic) mesocyclones greatly reduced
the detection capability of the current WSR-88D mesocyclone algorithm when compared to
identification of traditional supercells. Even with an increased recognition of favorable synoptic scale
TC-tornado environments, many of these tornadoes still occur without official (NWS) warnings or with
little (or negative) lead time.
There many other publications authored by research groups that talk specifically of
NEXRAD limitations for tornadic mesocyclones associated with landfalling hurricanes.
Some publications state that NEXRAD may miss as many mesocyclones as it detects.
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There are two main reasons for this:
a. Mesocyclones and tornadoes associated with hurricanes are much smaller
than land based elements and are not detected by NEXRAD.
b. The algorithms placed in NEXRAD are designed for the Midwest and must be
changed at individual NEXRAD sites.
Based on the information I could find on the National Weather Service website, the
Houston NEXRAD still maintains the original default algorithms for both mesocyclones
and tornadoes. This means that the Houston radar would only detect these elements
as found in the Midwestern United States and Great Plains area. This places the
Houston NEXRAD at a huge and distinct disadvantage.
The image below is from the NWS Houston NEXRAD radar depicting the initial
mesocyclone affecting Bolivar peninsula. The NEXRAD image shows the mesocyclone
immediately offshore from Crystal Beach and moving in a northwesterly manner
coinciding with the track of Hurricane Ike.
A mesocyclone is a large rotating disturbance in the lower atmosphere that can spawn
tornadoes on the ground. Various research states that 30% to 50% of all mesocyclones
develop tornadoes. These percentages indicate that Bolivar peninsula was hit by
numerous tornadoes before the storm surge arrived and the eye made landfall.
Initial mesocyclone moving towards Bolivar peninsula.
This initial mesocyclone occurred at 10:31PM on September 12, 2008. Mesocyclones
continued to move directly over Bolivar peninsula and the Bridwell property for several
more hours.
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Mesocyclones moving on Bolivar peninsula September 13, 2008 12:21 AM
Mesocyclones on Bolivar peninsula September 13, 2008 12:30AM
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September 13, 2008 12:49AM
Using the collected NEXRAD data and knowing the limitations of NEXRAD to detect
these phenomena, I estimate that there were over 60 mesocyclones that moved over
the Bolivar peninsula. Based on this estimate and using the percentages from previous
studies, this would place between 18 to 30 tornadoes on Bolivar peninsula as early as
10:43PM, September 2008.
There are several pictures I took during the site visit that show distinct rotation based
upon how remaining structures and poles were oriented. This indicates tornadic
activity.
At 7:00PM, September 12, 2008 there were measured winds of 115 knots (126 miles
per hour) only 2000 feet above the surface along the edge of the Bolivar peninsula.
This measurement was recorded by a rawinsonde observation. With the numerous
convective cells over the Bolivar peninsula, it is very plausible that winds from 2000 feet
above the surface were transported down to the surface causing gusts as high as 100
miles per hour. These winds would not be detected by NEXRAD because the radar
beam would be located above the 2000 foot level over Bolivar peninsula.
At 7:43PM, September 12, 2008 the first wave of severe thunderstorms moved over the
Bolivar peninsula. Though NEXRAD appears to show echoes between 35 to 45 dbz (an
indicator of intensity), by blowing up the NEXRAD image I found several cells that
moved directly over 2898 Tropicana Lanein the 45 to 49 DBZ range. Guidelines state
that cells of 50 dbz or higher must be present for severe weather, but this guideline only
states that individual situations must be looked at objectively and not with a broad brush
approach.
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925 millibar chart September 12, 2008 7:00PM
By correlating the Composite Reflectivity image and Vertically Integrated Liquid
NEXRAD product with the Echo Tops data, it is shown that the top of this specific cell
went from a height of 29,000 feet to less than 10,000 feet within 5 minutes, indicative of
a microburst. In my experience, storm cells that collapse that much within a short
period produce high gusty surface winds in the vicinity of 100 miles per hour. This
microburst gust of 100 miles per hour was at least 6 hours before the surge came
ashore between 1:00AM and 2:00AM, September 13, 2008.
Another microburst occurred at 8:28PM, September 12, 2008 with an estimated
downward speed between 100 and 105 miles per hour. This specific weather element
continued to occur throughout the evening of September 12, 2008 until the hurricane
made landfall at 2:00AM, September 13, 2008
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Depiction of microburst flow hitting the surface.
Using the VAD Wind Profile from NEXRAD, it shows that there were low level winds in
excess of 65 knots (74 miles per hour) as low as 1000 feet above the surface. The
strong convection of the individual cells within the spiral bands of Hurricane Ike would
result in these stronger winds at 1000 feet to be brought to the surface, mix with the
prevailing surface winds resulting in gusts as high as 50 miles per hour as early as
4:00PM, September 12, 2008.
Microburst schematic
A study by the famed research expert, Theodore Fujita, states that a microburst may be
created and fueled by a low level jet stream affecting the specific thunderstorm cells.
The VAD Wind Profile proves that a low level jet was present over Bolivar peninsula
from the afternoon of September 12, 2008. Dr. Fujita also noted that the potential wind
speed from a microburst is higher than 168 miles per hour.
I point this out because whenever the winds increase in speed, the associated wind
force increases exponentially. For example, if the wind speed doubles, the associated
wind force increases by a factor of 4, not 2 as one would think.
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VAD Wind Profile for Houston NEXRAD
The graphic on Page 13 depicting the outflow of a microburst also shows the resultant
turbulence as the downward winds hit the ground and spread out. People tend to forget
that not only does a microburst create very strong surface winds, but also extreme low
level turbulence capable of destroying large commercial airliners.
One commonly overlooked element of a microburst is that the resultant ground
turbulence (though short-lived) is a horizontal vortex, similar to a weak tornado.
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Tornado formation in hurricanes
Another indicator that the winds at 2898 Tropicana Lane were higher and fluctuating
rapidly is seen by comparing every day winds at the property to determine how narrow
and varied true wind fields are at all times.
There is a misunderstanding of how wind fields are constructed. A recorded wind of
110 miles an hour pertains only to that exact spot. By moving only a few feet from the
measuring instrument, different wind speeds will always be observed. This can be seen
by simply taking 2 or 3 hand anemometers to the site and measuring the wind speeds.
Over 85% of the time, though taken simultaneously, the recorded speeds will be close,
but not exactly the same.
Another deterrent to the storm surge was the prevailing winds from the northeast. For
the majority of the day on September 12, 2008, the wind direction was northeasterly
which would cause the water to move parallel to the coastline towards the southwest.
Based upon the recorded winds at Hobby Airport, the wind direction did not shift to a
southerly component until the late morning of September 13, 2008.
With a forward speed of only 12 miles per hour, I believe a northerly wind component
affected Bolivar peninsula until mid-morning of September 13, 2008.
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With high wind speeds and the parallel flow, the surge is pushed towards the hurricane
eye creating a larger surge wall around the eye wall. Once the winds swing around to a
southerly component, this water comes ashore usually at a higher than expected height.
This helps to explain why the actual surge heights were higher than forecasted by the
National Weather Service.
This parallel flow is responsible for the higher surge height readings at Rollover Pass at
a much earlier time than what actually occurred at the client’s property.
This same situation occurred with Hurricane Katrina in 2005. Parallel flow along the
Mississippi coastline kept the surge at a minimum until the winds gained a southerly
component.
Another factor that must be considered in all hurricane damage is flying debris. With
many buildings along the coastline made with wood, wind speeds over 65 miles per
hour would create swaths of flying debris all over Bolivar peninsula.
In a study by John Hopkins University, it was noted that flying debris is a major cause of
damage to structures during a hurricane. Once a structure is breached, the high speed
winds enter the structure and destroy the interior of the building, thereby weakening the
entire structure.
Although hurricane winds can exert tremendous pressure against homes, a large fraction of
hurricane damage is not from the wind itself, but from airborne missiles such as tree limbs and
branches, signs and sign posts, roof tiles, metal siding and other pieces of buildings, including
entire roofs in major storms. This wind-borne debris penetrates doors and windows, and allows
the force of the wind to act against interior walls and ceilings not designed to withstand such
forces.
Once the envelope of the building has been breached through loss of windows or doors, or
because of roof damage, wind pressure on internal surfaces and structures becomes a factor.
Openings may cause pressurization or depressurization of a building. Pressurization pushes wall
panels and sheathing out, while depressurization can pull ceilings down. Internal pressure
coupled with external suction adds to the withdrawal force on sheathing fasteners. When the
openings are on the leeward side of the building, the result is a pressure drop in the interior,
which can pull ceiling materials away from the framing. (Wolfe et al., 1994).
An uncontrolled buildup of internal air pressure occurs once the envelope of a building is
breached. This can result in a wide range of damage (Oliver and Hanson, 1994; Mitrani et al.,
1995). Damage can range from the blowout of windows and doors to total building collapse due
to structural failure. Structural failure of exterior wall components because of internal pressure is
most common in wood-frame construction, but has also been seen in concrete block/stucco
construction (Oliver and Hanson, 1994).
Wind-borne projectiles are a major factor in home damage and destruction during a hurricane.
Penetration of the building envelope by wind-borne debris was directly responsible for many
catastrophic failures of roof systems during Andrew because such penetration allowed the
uncontrolled buildup of internal air pressure (Minor and Behr, 1994; Mitrani et al., 1995). An
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opening on the windward wall of a building of only 5% is enough to allow full internal
pressurization and effectively doubles the pressures acting to lift the roof and push the side walls
outward (Minor and Behr, 1994).
Three poles going in 3 different directions
The pool of potential projectiles that can be picked up by hurricane-force winds and turned into
wind-borne debris includes roofing materials such as shingles, tiles, and gravel; inadequately
attached cladding components such as sheathing and siding; and rocks and tree limbs (HUD,
1993). Smith (1994) reported that wind-borne debris from Andrew included tree limbs, fences,
dislodged rooftop antennas and HVAC equipment, and components from failed buildings.
FEMA (1992) observed that the failure of metal-clad buildings and mobile homes generated
considerable wind-borne debris during Andrew.
Again I refer to Mr. Tim Marshall who commented on flying debris within a hurricane:
Mr. Marshall stated: “I've often said your house is only as strong as your neighbor's house. If your
neighbor builds a house that's not very wind resistant, and you do, when your neighbor's house falls
apart and hits your house, you have more debris. And it's really the flying debris that abrades or breaks
down a house.”
The closest gauge used to measure the surge height is located on the western end of
Bolivar peninsula designated SSS-TX-GAL-002. At the highest point of surge height,
this gauge registered below 14 feet MSL. I have some concerns with how this height
was measured and the true accuracy of the equipment.
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There is an oddity concerning the raw data from SSS-TX-GAL-002, located on Bolivar
peninsula. Based upon information from the US Geological Survey agency, the height
of the storm surge is based upon calculations from a barometric sensor and a surge
sensor. The surge data from Bolivar peninsula is predicated on data from 2 sensors at
different locations. This is the only method used by the USGS to determine surge
heights, yet the data is not measured at the same location. The distance between these
2 sensors is over 1 mile apart.
With Hurricane Ike, the surface winds that initially affected the Bridwell property at 2898
Tropicana Lane came from the north-northeast, moved more northward and finally
swung around to the southwest on the morning of September 13, 2008.
Beginning on September 12, 2008 the wind direction was from the northeast (040 to
060 degrees) resulting in parallel flow with the coastline of the Bolivar peninsula.
For the majority of the morning of September 13, 2008, the wind direction on Bolivar
peninsula was from the north-north-east and was actually an off-shore wind, thereby
preventing any high water levels from reaching the peninsula. When the wind direction
was parallel to the Bolivar coastline, this also acted as a barrier to water levels
increasing near the Bridwell property. The same principle was evident with Hurricane
Katrina in 2005.
Track of Hurricane Ike
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Parallel flow along Bolivar peninsula due to winds from the northeast
In both illustrated cases, there was plenty of opportunity for a push of high water levels
on the bay side of the peninsula and towards Galveston, but there was no high water
levels affecting the Bridwell property at 2898 Tropicana Lane at these times. (Even with
the northerly flow, the fetch across Galveston Bay was not sufficient to create a high
surge).
Once the wind direction rotated from the southwest, then the high surge levels moved
onshore and washed over the Bridwell property, but this did not occur until the early
morning hours of September 13, 2008. By that time, the strongest winds associated
with Hurricane Ike and several other weather elements had already caused the initial
and primary damage to 2898 Tropicana Lane.
Northerly flow until mid-morning September 13, 2008
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With high wind speeds and the parallel flow, the surge is pushed towards the hurricane
eye creating a larger surge wall around the eye wall. Once the winds swing around to a
southerly component, this water comes ashore usually at a higher than expected height.
This helps to explain why the actual surge heights were higher than forecasted by the
National Weather Service.
The storm surge hit Bolivar peninsula between 1:00AM and 2:00AM, September 13,
2008. A simple explanation shows why this happens. As wind flows over the water, the
lowest layer of wind is adjacent to the water surface and experiences friction with the
water. This friction causes the lowest level of wind to move slower than higher heights.
As you move up in height, the friction between the wind and water lessens until you
reach approximately 33 feet above the water. This is the established standard height
used by the World Meteorological Organization (WMO) and the National Weather
Service (NWS) to measure wind speed with minimal surface friction.
Winds with
height
Water surface
Using the drawing above, the lowest level of wind has to be slower than higher heights
because of the drag of surface friction on the water. This results in higher wind speeds
with an increase in height. If this principle wasn’t true, there would be no reason to
measure wind speeds at the WMO and NWS standard of 33 feet above the ground.
The speed of the surge is actually slower than the lowest level of wind speed due to the
tremendous amount of water mass being moved with the hurricane. Other factor that
affects the surge movement is the directional wind vectors associated with the right front
quadrant of the hurricane.
As the hurricane moves forward, surface wind direction “backs” due to surface friction.
This means that the wind direction is rotates counter-clockwise. This rotation of the
surface wind can be anywhere from 30 degrees to 120 degrees counter-clockwise from
the movement of the hurricane.
With Hurricane Ike, the surface winds that initially affected the Bridwell properties came
from the north-northeast, moved more northward and finally swung around to the
southwest on the morning of September 13, 2008.
To summarize; the Bridwell property was affected by a number of factors that were part
of the initial and primary cause of damage at 2898 Tropicana Lane, Crystal Beach
Texas:
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1. High wind speeds that began as early 6:00PM, September 12, 2008. These
wind speeds also created other wind associated elements such as wind shear
and ground turbulence.
2. Tornadoes, mesocyclones and severe thunderstorms.
3. Microbursts and associated turbulence
4. Flying debris
Though high water levels moved over this property, it did more to mask the true cause
of damage at this location.
Rocco Calaci
LRC Services
May 24, 2009
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