Post-Storm Report and Commentary
Issued by the Jamaica Beach Weather Observatory
10:57 AM CDT Wednesday, October 18, 2006
A large and unusually intense non-tropical surface low pressure area
in combination
with a warm front moving inland from the Gulf of Mexico produced
tropical storm-like
conditions with torrential rainfall...high tides...strong gusty
winds and several tornadoes
Sunday night and Monday along the Upper Texas Coast and Southeast
Texas.
In Tuesday's edition of the Galveston County Daily News,
several statistics attributed
to Jamaica Beach and other locations in the area were highly
inaccurate and/or
erroneous despite several e-mails and faxes sent to the newspaper by
the Jamaica
Beach Weather Observatory with the correct data. Strictly in the
interest of setting
the historical record straight, I would like to present the true
facts of what occurred
with this weather system at the local area's official weather and
tide stations:
I would like to emphasize that I am a loyal daily reader of the
Galveston County
Daily News and think they do a terrific job. However,
I also feel they have a
responsibility as the official newspaper of record for Galveston
County to check
and double check facts and figures before they go to print. I
feel that, in this case,
that may not have happened or they were given some really bad
information. One
thing that is really confusing here is that they cited their
source as the National
Weather Service. Since ALL of the statistics I will cite
below were reported to...and
later disseminated by...the National Weather Service, I don't
quite understand how
these numbers ended up so completely different.
TIDES:
The newspaper reported that "tides were 6 feet above normal" on the
front page. Had
this actually been the case, the tidal flooding experienced would
have been far worse
than what occurred. Tide level (i.e. the level of the water)
is referenced to feet above a
tidal datum known as Mean Lower Low Water (MLLW) which is the
average of the
lower of two daily low tides over a 19 year period known as the
National Tidal Datum
Epoch. In Jamaica Beach, the average daily tidal variation is about
one foot from low
tide to high tide and vice-versa. Therefore, MLLW is roughly a half
foot below Mean
Sea Level (MSL) which is the average of high and low tides.
On Monday, the Jamaica Beach Weather Observatory recorded a peak
tide level of
4.74 feet above MLLW at the time of high tide at 5:51 AM CDT. Since
the normal
astronomical tide should have been 1.20 feet above MLLW at that
time...this means
the tide was 3.54 feet above normal. At 7:00 AM CDT..the tide had
fallen slightly
to 4.62 feet above MLLW or 3.42 feet above normal and it was this
reading that was
distributed via e-mail and fax to the newspaper and the National
Weather Service.
Other tide gauges in the Galveston Bay complex and along the
immediate Gulf of
Mexico coastline reported similar tides and departures from
normal. The only tide
gauge that had a value even approaching 5 feet above normal was the
Manchester
Wharf tide gauge along the Houston Ship Channel at the IH 610 Loop
near the Port
of Houston. At this particular location, tidewater funnels up the
ship channel from
Galveston Bay. No tide gauge in Galveston County reported any tide
readings more
than 4 feet above normal. This includes: Galveston Pier 21,
Pleasure (Flagship) Pier,
Eagle Point, the North Jetty at the tip of Bolivar Peninsula, the
entrance to Clear
Lake near the Kemah/Seabrook bridge, and Rollover Pass.
One last point to consider: On September 11, 1998, during Tropical
Storm Frances,
the maximum tide at the Jamaica Beach Weather Observatory was 7.10
feet above
MLLW...or 6.00 feet above the normal astronomical tide of 1.1 feet.
This put over
3 feet of saltwater in the building and in roadways near the
station. By comparison,
only about 4 to 6 inches of water got in the same building on
Monday.
WIND SPEED:
The Galveston County Daily News reported that Jamaica Beach
had the "highest area
wind gusts at 55 mph." This did not occur at the weather station,
either. The peak
wind gust recorded at the Jamaica Beach Weather Observatory was 41
knots...which
is equal to 47 mph...from a South direction at 5:09 AM CDT
Monday morning.
In fairness to the newspaper, NWS Doppler Radar did indicated a
possible tornado
may have moved onshore just east of Jamaica Beach at Galveston
Island State Park
early Monday morning. Supporting this possibility, there were power
lines down at the
park that utility crews repaired at sunrise Monday. So, I will
concede that at least in
this localized area...winds could easily have been 55 mph...or even
greater.
At Scholes International Airport in Galveston, wind gusts actually
did peak at 48 knots
(55 mph) from a Southeast direction at 3:28 AM CDT Monday morning.
However, this
statistic was completely overlooked by the newspaper. Or, perhaps
they got the two
locations mixed up with each other.
RAINFALL:
This was the primary item the newspaper misreported. The Jamaica
Beach Weather
Observatory reports rainfall daily to the National Weather Service
at 7:00 AM CDT
each morning via computer. On Monday morning at 7:00 AM CDT, I
transmitted a
rainfall report of 6.26 inches during the preceding 24-hour period.
Somehow, the
newspaper inexplicably reduced this to "3.96 inches at Jamaica
Beach." During
the same period of time, Scholes International Airport in Galveston
reported a total of
4.72 inches of rainfall for the 24-hour period ending at 7:00 AM
CDT. Instead, the
newspaper reported that Galveston only received 3.57 inches of
rain. Texas City
reported 6.43 inches for the same 24-hour period...yet, the
newspaper cited only
3.20 inches. Why they drastically underreported these numbers
is unclear.
Keep in mind that several more inches of rain fell during the day
Monday which
would have bumped up these numbers EVEN MORE.
Again, my only interest here was to correct and clarify the
historical record. Since
some of this data was attributed to my weather station, I felt I had
an obligation to
the users of my web site and weather e-mail distribution list to
respond to these
inaccuracies. I hope the record now stands corrected.
Jim O'Donnel
Jamaica Beach Weather Observatory
