Summary...
A series of upper air disturbances moving in from the west
and southwest...plus an excellent moisture tap from the
Pacific Ocean and Gulf of Mexico...helped to develop a very
heavy rain event over South Central Texas and the Texas
Hill Country...on Saturday October 17, 1998.
As a cool front
moved into the area late Saturday night and Sunday morning...
October 18th...more rain developed ahead of and along the
cool front.
On Sunday the 18th...the cool front drifted near the coast
and stalled. In the wake of the front...on Sunday the 18th
and also Monday the 19th...clouds...rain and showers
lingered. Winds aloft continued out of the southwest...
bringing a series of weak upper air disturbances...that helped
trigger periods of occasional rain. Just above the shallow
cool air at the surface...southerly winds pumped plenty of
gulf moisture over the area...while at higher levels...southwest
winds brought plenty of moisture from the Tropical Pacific.
On the 20th and 21st of October...cloudy skies and occasional
light to moderate rain was observed over the area.
The wettest month of climate record for San Antonio...since 1871...
was October 1998. The heavy rains caused many rivers
in the area to reach near or exceed record stage heights...causing
widespread flooding in the flood plains of streams...creeks and
rivers.
According to the Texas Department of Public Safety,
31 people drowned during the floods, and the total property damage
was estimated to be about 750 Million Dollars.
...History...
This heavy rain event was similiar not only to the October 1994
rain event that affected South and Southeast Texas...also other
heavy rain events that have cause floods and flash floods over
South Central Texas and the Texas Hill Country.
The heavy rain events in October of 1994 over South and Southeast Texas
was similiar to the 1998 pattern for South Central Texas.
During the October of 1994 rain events...winds aloft carried the rain making systems
faster through South Central Texas on October 7th and 8th...
producing 5 to 10 inches of rain.
Later in October
of 1994 over Southeast Texas, the rain making systems moved slower...producing
a large flood event over Southeast Texas, with rain amounts
between 10 and 30.50 inches over
parts of Southeast Texas.
In the October 16 to 19, 1994 Southeast Texas rain event, the remnants of Eastern Pacific
Hurricane Rosa came over Texas, with a plume of deep tropical moisture
streaming northward in wake of Rosa. Over Southeast Texas most of the
rain came Monday the 17th to Tuesday the 18th. General 10 to 20 inch
rain amounts were observed. The maximum rain was 30.50 inches at
Liberty.
Like the Southeast Texas heavy rain event in October 1994...
winds aloft in the 1998 South Central Texas and parts of
Central Texas heavy rain event
did not carry the rain making system away...helping to bring
the large rain amounts of near 10 to near 30 inches of
rain. See Rain Map for
October 1998 Rain Event The largest documented rain was
in southern Hays County just south of San Marcos, where near 30
inches of rain fell. According to the U.S. Geological Survey,
about 2,300 square miles in 12 counties got at least 12 inches
of rain and about 5,000 square miles in 19 counties got at least
8 inches of rain.
In some years floods in fall and winter do occur. When fall and winter floods
come...rainfall can be just as heavy as other times of the year.
Thinner vegetation and lower evaporation in the cool season can
add to the flooding. From 1856 to 1998 out of the 10 wettest
months for the Austin City location...2 occurred in the fall
and winter, excluding September. If the transition month of
September was added...4 out of the 10 wettest came in fall and
winter. For Austin/Bergstrom since October 1942...6 out
of the 10 wettest months occurred in the fall and winter,
excluding September. With September included there is no change.
For Del Rio, 1905 to 1998, and San Antonio, 1871 to 1998,
out of the 10 wettest months of record...2 occurred in the
fall and winter, excluding September. If the transition month
of September was added the figures rise to 6 out of 10
for Del Rio and 5 out of 10 for San Antonio. September,
on average one of the wettest months, takes into account
late summer, tropcial storm, and very early fall events...
therefore it is not a true in the fall rain month all the
time.
Some of the heavy fall/winter precipitation events
in the past nearly 30 years include January of 1968,
September of 1973, January of 1985, December of 1986,
January of 1991, December of 1991,
January to March of 1992, October of 1994 and
October of 1998
over Central and South Central Texas.
The December 1991 event came around Christmas,
when widespread flooding affected not only South Central Texas,
also parts of Central Texas and Southeast Texas.
The heavy snow event over South Central Texas in January 1985,
associated with an arctic airmass, could have been a heavy rain
event if temperatures had been
much warmer. In this event 13.5 inches of snow fell in San Antonio,
8.6 inches at Del Rio and 7.5 inches at Austin.
...For San Antonio...
Rainfall records established for San Antonio in October 1998 follow.
The most rain recorded
on any calendar day occurred Saturday, Oct. 17th, 1998...when 11.26 inches of rain fell
at the San Antonio International Airport. The
previous record was 6.83 inches on September 9...1921. The 11.26
inches of rain on October 17th...1998 even shattered the greatest
24 hour amount of 7.28 inches...recorded on September 26 to 27...1973.
It also easily exceeded the record for October 17th...2.13 inches
October 17...1948.
The most rainfall in a 24 hour period of 13.35 inches occurred
from the 17th to the 18th. Previous record was 7.28 inches from
Sep. 26th to 27th, 1973.
A new 30 day rainfall record for San Antonio of 19.09 inches
from October 2...1998 to November 1...1998 has been established.
The previous record was 18.45 inches...from May 13 to June 12...1987.
Wettest Month and October of record...with 18.07 inches of rain.
Previous record wettest month 15.78 inches in Sep. 1946,
and previous wettest October of 9.74 inches in 1994.
For San Antonio - 10 wettest Octobers...
*1. 1998 - 18.07 inches 6. 1981 - 8.61 inches
2. 1994 - 9.74 " 7. 1976 - 8.48 "
3. 1942 - 9.56 " 8. 1960 - 7.84 "
4. 1913 - 8.86 " 9. 1949 - 7.58 "
5. 1919 - 8.66 " 10. 1871 - 6.65 "
For San Antonio - 10 wettest months...
*1. 18.07 inches - October 1998
2. 15.78 " - September 1946
3. 14.07 " - May 1935
4. 13.96 " - December 1991
5. 13.09 " - September 1973
6. 12.85 " - May 1987
7. 12.47 " - May 1993
8. 11.95 " - June 1986
9. 11.71 " - September 1874
10. 11.64 " - April 1915
The 10 greatest calendar day rainfall totals for San Antonio are:
*1. 11.26 inches - October 17 1998
2. 6.83 " - September 9 1921
3. 6.82 " - May 31 1937
4. 6.78 " - April 18 1915
5. 6.54 " - September 26 1973
6. 6.26 " - May 5 1993
7. 6.18 " - June 3 1951
8. 5.97 " - December 19 1991
9. 5.96 " - October 1 1913
10. 5.84 " - May 9 1935
|
...For Austin...
For October 1998 Austin received 12.39
inches of rain making October 1998 the 3rd wettest October and
15th wettest month for the Austin City climate location
since the mid 19th century...when
climate records began. On October 17...6.24 inches of rain
fell at the Robert Mueller Airport in Austin. This is a new
daily record for October 17. The old record for October 17th
was 2.48 inches set back in 1937. Rainfall records for the
Austin City location date back to 1856.
Austin/Bergstrom Airport received 6.89 inches of rain on Saturday
October 17 1998. For the Austin/Bergstrom location...the
12.73 inches in October 1998 was the 2nd wettest October
and 5th wettest month since October 1942.
The 10 wettest Octobers for the Austin/City Location are...
1. 1925 - 12.63 inches 6. 1919 - 10.92 inches
2. 1870 - 12.54 " 7. 1984 - 10.34 "
*3. 1998 - 12.39 " 8. 1923 - 9.25 "
4. 1960 - 12.30 " 9. 1913 - 8.92 "
5. 1973 - 11.11 " 10. 1957 - 8.79 "
The 10 wettest Octobers for Austin/Bergstrom are...
1. 1960 - 13.08 inches 6. 1957 - 9.00 inches
*2. 1998 - 12.73 " 7. 1994 - 7.79 "
3. 1973 - 10.40 " 8. 1976 - 6.99 "
4. 1984 - 9.30 " 9. 1959 - 6.94 "
5. 1986 - 9.11 " 10. 1981 - 6.39 "
The 10 wettest months for Austin/Bergstrom are...
1. June 1981 - 15.59 inches 6. November 1974 - 12.49 inches
2. May 1965 - 13.69 " 7. April 1957 - 12.18 "
3. October 1960 - 13.08 " 8. January 1991 - 10.53 "
4. December 1991 12.88 " 9. May 1974 - 10.48 "
*5. October 1998 - 12.73 " 10. October 1973 - 10.40 "
The 10 wettest months for the Austin/City Location are...
1. September 1921 - 20.78 inches 6. May 1895 - 14.10 inches
2. April 1915 - 19.82 " 7. July 1919 - 12.80 "
3. December 1913 - 16.14 " 8. September 1874 - 12.78 "
4. June 1981 - 14.96 " 9. May 1929 - 12.75 "
5. December 1991 - 14.16 " 10. July 1903 - 12.65 "
October 1998 was the 15th wettest overall month of record for
the Austin/City Location.
The 6.24 inches of rain on October 17 1998 is the 8th greatest
calendar day precipitation total ever for the Austin City climate
location. The 6.85 inches at Austin/Bergstrom was the 3rd
wettest day of record.
For Austin/City - 10 greatest calendar day precipitation totals...
1. 15.00 inches - September 9 1921
2. 10.00 " - April 23 1915
3. 8.56 " - July 21 1919
4. 7.39 " - October 14 1923
5. 6.95 " - October 13 1925
6. 6.50 " - April 6 1900
7. 6.34 " - December 3 1913
*8. 6.24 " - October 17 1998
9. 6.16 " - May 28 1929
10. 6.00 " - December 11 1891
For Austin/Bergstrom - 10 greatest calendar day precipitation totals...
1. 8.70 inches - November 23 1974
2. 8.53 " - May 9 1974
*3. 6.85 " - October 17 1998
4. 5.97 " - September 6 1986
5. 5.93 " - August 3 1966
6. 5.73 " - June 11 1981
7. 5.04 " - May 30 1995
8. 5.01 " - January 9 1991
9. 5.00 " - August 9 1994
10. 4.95 " - June 3 1951
|
Rainfall amounts from northern Bexar county to southeast Kendall
county...parts of Comal county...including the New Braunfels
metro area...and parts of Hays county on October 17 and 18th...were
near 15 to near 30 inches.
Del Rio was west of the heaviest rains. From October 16th to
1 pm October 21st Del Rio has had 0.41 inches of rain. For October
1998 Del Rio had 1.46 inches of rain. The wettest
October of record for Del Rio was 11.69 inches in October of 1930.
GO TO 146 pm cdt Satellite picture of the rain event
on Saturday, October 17, 1998.
GO TO 245 pm cdt Satellite picture of the rain event
on Saturday, October 17, 1998.
October 1998 Daily Data...
weather.gov
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