Frances was a tropical storm that brought
more than 15 inches of rainfall to portions of east Texas, about ten inches in southern Louisiana,
and lesser amounts were spread northward across Oklahoma, Arkansas, Kansas, Missouri, and Iowa.
a. Synoptic History
Frances formed within a broad area of low pressure which first showed signs of
organization of its associated convective cloudiness on 4 September. The convection
was widespread over the western Caribbean and southern Gulf of Mexico, but there
was no well-defined low-level center of circulation.
This situation persisted for several days as the system moved slowly west-northwestward and during this
time three poorly-defined closely-spaced tropical waves moved into the area,
perhaps contributing to the development of this system. By the 8th, the system developed a
1000-mb central surface pressure and considerable organized deep convection over a
large area of the western Gulf of Mexico. The best track
is listed in Table 1 and plotted in Fig. 1
(11K GIF) and begins as a tropical depression at this time at a
position about 140 nautical miles east of Brownsville, Texas.
The tropical cyclone formation described above,
with its large size, loosely organized convection and lack of a distinct center, is known as a
"monsoon depression" in the western North Pacific basin.
The tropical depression drifted southward for about a day. By 1800 UTC on the 10th,
wind observations from a data buoy, reconnaissance aircraft, and several oil rigs
indicated that Frances had strengthened to a 35-knot tropical storm. It
began moving north to northwestward at 10 to 15 knots. The center moved inland across the Texas coast
just north of Corpus Christi at 0600 UTC on the 11th. By this time, Frances had strengthened to
55 knots under a large anticyclone aloft, weak vertical shear and
SST's near 30 degrees Centigrade.
After moving inland, the center moved in a small cyclonic loop for 12 hours
between Corpus Christi and Victoria and then moved northward across eastern Texas as a
weakening tropical depression. The best track ends at 1800 UTC on the 13th, when
the center was near the Texas/Oklahoma border north of Dallas, but the remnant low
pressure and rainfall were tracked northward to Iowa during the next 24 hours.
b. Meteorological statistics
Figs. 2 (6K GIF) and
3 (11K GIF) show plots of
U.S. Air Force reconnaissance
aircraft wind
and pressure data and satellite Dvorak intensity estimates,
as well as the best-track pressure and wind curves. Dvorak estimates were provided by the U.S.
Air Force Weather Agency (AFGWC), the
Tropical Analysis and Forecast Branch (TAFB) of the NWS Tropical
Prediction Center, and the
Synoptic Analysis Branch (SAB) of NESDIS.
Table 2(a) lists selected surface observations and
Table 2(b) lists additional selected
rainfall totals. Tropical storm force wind speeds were observed at several data buoy
and oil rig locations in the western Gulf of Mexico. The CMAN station at Sabine
Texas reported a maximum 2-minute wind speed of 44 knots; this is the highest
sustained surface wind speed in Table 2(a). Tropical storm force sustained winds
were observed over land at Galveston, Victoria, and Jefferson County Airport, Texas.
Frances was a large storm and the 34-knot wind speed radius
extended approximately 300 nautical miles north and east of the center.
Storm surge flooding of up to six to eight feet
occurred along the middle and upper Texas coast and up to 5 feet along the Louisiana coast. This
flooding persisted for about 48 hours.
Freshwater flooding from rainfall was the most significant weather effect. Frances
dropped copious amounts of rain over east Texas and southern Louisiana. The
highest total reported in Texas was over 16 inches in Brazoria County and the highest
total from Louisiana was over 11 inches. Undoubtedly, even higher amounts are likely
to have accumulated in these areas.
c. Casualty and damage statistics
The only known fatality directly attributable to Frances was in Lafourche Parish,
Louisiana, where a man was killed when his trailer home was destroyed by a tornado
spawned by the tropical storm. Six others were injured by this tornado. An indirect
death occurred in the New Orleans area where a woman died in an automobile accident.
Moderate beach erosion occurred along much of the upper Texas and western
Louisiana coastlines.
Three Texas counties and four Louisiana parishes have been declared as federal
disaster areas, primarily due to the rainfall flooding in the wake of Tropical Storm
Frances. These include including Brazoria, Galveston, and Harris Counties and the
parishes of Cameron, Jefferson, Lafourche and Terrebonne.
The American Insurance Association reports that a total of 110 million dollars in
insured property damage has been claimed in Texas, Louisiana and Mississippi. The
Houston Chronicle reported that 256 million dollars in damage was inflicted in
Galveston County. The total NHC damage estimate for Frances is 500 million dollars.
d. Forecast and warning critique.
Table 3 lists the various watches and warnings that were issued.
Tropical storm warnings were issued along the Gulf of Mexico coast
from Tampico, Mexico northward and eastward including all of Texas and Louisiana. The warnings for
the central Texas coast were issued at 2100 UTC on the 9th, some 33 hours before landfall and
almost 24 hours prior to tropical storm force winds reaching the coast. There were
only eight forecasts issued while Frances was a tropical storm and none verified at 48
or 72 hours. This number of cases is too small to make any meaningful conclusions
about forecast accuracy.
![[NCEP Logo]](graphics/ncep.gif)
![[1998 Atlantic Hurricane Season]](graphics/smalllogo.gif){kind=small}
