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T.S. Alberto Remembered: Ten Year Anniversary
by James Noel, Hydrologist WFO Preachtree City
7/1/04
Radar Image from Tropical Storm Alberto - click to enlarge
![[Radar estimate of rainfall during Tropical Storm Alberto]](../images/albertosm.gif)
The first week of July will mark the ten-year anniversary of Tropical Storm
Alberto’s devastating floods in Georgia. Areas of west Georgia were
particularly hard hit, with three-day rainfall amounts in excess of 21
inches producing over $750 million in damage and contributing to 33 deaths.
Tropical Storm Alberto originated in Senegal, near the west coast of Africa,
on June 18, 1994 as a tropical wave. The system became Tropical Depression
One on June 30, 1994. On July 2, 1994 the depression strengthened in the
Gulf of Mexico near the Yucatan Peninsula to become Tropical Storm Alberto.
When the center made landfall near Destin, Florida, on July 3, Alberto was
at its peak intensity with 65 mph winds. Alberto quickly weakened to a
tropical depression again. After landfall, the motion of the storm slowed
and precipitation increased. The storm moved slowly through Alabama into Georgia,
stalling just south of Atlanta. Over the next few days it reversed its course
and then looped back on its previous course before ultimately dissipating.
During the period of July 3-6 of 1994, Alberto dumped copious amounts of
rain across the area. The heaviest rainfall was south of a Carrollton to
Atlanta line and west of an Atlanta to Macon to Cordele line. The greatest
rainfall in Middle Georgia fell in a band from Peachtree City south to Americus.
Rainfall amounts of 12 to 24 inches were common in this stretch. Rainfall
amounts as high as 21.1 inches in 24 hours were observed at Americus, Georgia
with storm totals at Americus of 27.61 inches.
This rainfall produced record and near-record flooding along the Flint,
Ocmulgee and Chattahoochee Rivers. In Middle Georgia, the worst-hit
cities were Macon and Montezuma. In Macon, parts of downtown were
flooded and the water supply was lost for many days as flooding inundated
the water plant. In Montezuma, flood waters topped the levee and flooded
much of downtown. Overall, flash flooding and flooding caused by the
rainfall from Alberto took 33 lives, destroyed thousands of homes,
including entire communities, forced approximately 50,000 people to be
evacuated, and caused property damage estimated at $750 million.
Approximately two-thirds of the deaths were related to vehicular incidents.
The Weather Forecast Offices and the Southeast River Forecast Center of
the National Weather Service (NWS) played critical roles in getting the
word out to the record crests that were expected. Peak flood stages from
Alberto in the NWS Peachtree City's area of responsibility were:
River Location Alberto Record (feet) Old Record (feet)
Flint Culloden 45.73 38.40 (3/5/1929)
Flint Montezuma 34.11 27.40 (3/17/1929)
Ocmulgee Macon 35.30 29.83 (3/19/1990)
Ocmulgee Hawkinsville 40.91 36.50 (1/21/1925)
Ocmulgee Abbeville 23.10 20.30 (1/23/1925)
Ocmulgee Lumber City 24.59 26.30 (1/21/1925)
There have been significant advances in NWS hydrologic programs in the last
ten years. New technologies which have improved flood warnings and forecast
operations in Georgia include the Advanced Hydrologic Prediction Service (AHPS),
the Site Specific Hydrologic Model, multi-sensor rainfall estimates, Flash Flood
Monitoring Program (FFMP), and NWS Hydrologic Forecasting System (WHFS).
The Advance Hydrologic Prediction Service is the NWS’s frontline solution to
provide improved river and flood forecasting and water information across the
United States. AHPS builds upon the NWS’s long history of around-the-clock
forecasting excellence by bridging to new sciences and technologies. AHPS
includes state-of-the-science forecasting tools covering flash floods on small
streams to long-range forecasts for floods in larger rivers. AHPS can be seen
on our website by going to weather.gov and clicking on Georgia. Select
“Lakes&Rivers – AHPS” on the left menu.
The Site Specific Model is a hydrologic model run at local NWS offices.
This model allows local NWS offices to improve forecasts on smaller streams
and creeks mainly associated with flash floods or shorter-duration floods.
The NWS office in Peachtree City is leading the way with over a dozen specific
forecast points now provided. New sites are being added when needed by local
communities. Recently, for example, a new forecast point was added to the
Etowah River near Dawsonville, Georgia at the request of Forsyth County
emergency management officials.
Multi-sensor rainfall is now being used to produce many of the hydrologic
forecasts in Georgia. In the past, the NWS either rainfall from rain gauges
alone or from radar estimates. Today, we combine rainfall estimates from the
NWS WSR-88D radar with rainfall gauge data provided by NWS observers and automated
NWS and USGS sites. This high-quality rainfall estimate from multiple sources is
being used by our Site Specific Model in Georgia.
Another tool added to our flood detection arsenal is called the Flash Flood
Monitoring Program. This tool allows local NWS meteorologists and hydrologists
to get a better handle on flash floods. This tool combines high resolution
rainfall estimates from the WSR-88D Doppler radar with small hydrologic basins
in Georgia. The result is the ability to issue flash flood warnings for counties,
and naming specific creeks that will be affected. In addition, this tool allows
for earlier and better detection of floods by keeping forecasters alert to fast
changes within individual creeks. The benefits of this were seen during the 2003
floods in Georgia. Prior to 2003, the NWS in Peachtree City detected 70% of flash
floods with a false alarm rate around 50%. In 2003, our detection of flash floods
improved to about 80% while our false alarm rate dropped to 20% due, in large part,
to the new technologies.
The last tool for NWS meteorologists and hydrologists to use is called the
hydrologic forecast system. This tool allows forecasters to be alerted whenever
a river or stream is approaching flood stage. In the past, flood warnings were
issued by doing a lot of typing. Now, we can issue these warnings quickly because
most of the work is done by our high technology computer systems.
Finally, the National Weather Service has launched a campaign called,
"Turn Around Don't Drown (TADD)". This is to discourage citizens who see
flooded roadways or bridges from crossing them. It is better to turn around
and take a different and safer route.
Since flooding is the number one storm-related killer, the NWS is committed to
continued improvements to detection of floods and flash floods.
For additional hydrologic questions, call Jim Noel, Senior Hydrologist with
the NWS in Peachtree City at 770-486-1133.
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