Journal of Natural Disaster Science, Volume 25, Number 2, 2003, pp47-56

An Analysis of Typhoon 9807 (Vicki) Based on Surface Meteorological Records
Obtained from Fire Stations
Yasuo OKUDA
Building Research Institute
Hirohiko ISHIKAWA
DPRI, Kyoto University
Takeshi FUJII
Kyoto Sangyo University(Received for 3. Mar., 2003 and in revised form 5 Jan., 2003)

ABSTRACT
Based on weather observation data collected at fire stations in the Kinki and Chubu districts of Japan, the surface structures of typhoon Vicki were investigated. There were four local, high wind areas in the Kinki district,the instantaneous wind velocity exceeding 50m/s. High winds occurred in two cases; almost simultaneously
when minimum atmospheric pressures were reached and about one hour after they were recorded. A comparisonof the local high wind areas and combined radar echo charts showed that the latter local high winds occurred
around a rain band that formed to the rear of the center of the typhoon. Detailed surface structures of the typhoon
concerned with temperature, humidity, precipitation, and atmospheric pressure were obtained. Weather observation data recorded at fire stations were shown to be very useful for analyzing the surface meteorological structures
within a typhoon.

1. INTRODUCTION
Typhoon Vicki made landfall on the coastline north of Gobo
City, Wakayama Prefecture at about 13:00JST on September 22nd
1998, just after typhoon Waldo which had made landfall at
Wakayama Prefecture the previous day. Typhoon Vicki coursed
through the Kinki district producing severe damage in many
places, especially Nara Prefecture. Because this typhoon passed
the central part of the Kinki district, surface weather data was

Table 1

recorded not only at official meteorological stations but at many
fire stations, schools, power stations, and other facilities.
In recent years, local governments in Japan have installed
weather data acquisition systems for fire fighting. Many fire fighting headquarters have been equipped with automatic weather
observation systems to help the prevention of disasters in local
areas. There are tens of fire fighting headquarters in each prefecture in the Kinki and Chubu districts, and surface weather data arecollected by data acquisition systems in most of them. The weath-Fire station responses

KEY WORDS: typhoon Vicki, fire station, weather situation, combined radar echo

48

Y. OKUDA, H. ISHIKAWA AND T. FUJII

er observation network that includes these fire fighting headquarters has a denser distribution than that of the JMA (Japan
Meteorological Agency) which has only one or two stations perprefecture. The average distance between the AMeDAS(Automated Meteorological Data Acquisition System) observationsites is about 20km whereas the average distance between the fire

Table 2

Total observation points

fighting headquarters is a few kilometers in urban areas.
Moreover, indispensable weather elements for the typhoon analysis which are not measured in the AMeDAS, the instantaneouswind velocity, atmospheric pressure, and humidity, are recorded intime series at the fire fighting headquarters. This weather observation network based on fire fighting headquarters has importancefor more detailed analyses of surface meteorological structures
within a typhoon.
Uematsu et al. (1999, 2002) published a database for theweather observation network covering Aomori, Akita, Miyagi,
Yamagata, and Fukushima prefectures in the Tohoku district.
There has been no report, however, that verifies the utility of aweather observation network that collects weather data recorded
by weather data acquisition systems that cover an extensive area,
because the purpose of these systems seems to be to provide
weather information only for local areas.

50 N

Typhoon 9807（Vicki）
40 N

Sept.23 (09h)Extra-tropical cyclone
Sept.22 (13h)Landfall

30 N

Sept.22 (03h)Central pressure 960hPa1
Maximum wind speed 40m/s

20 N

Sept.17 (15h)Tropical depression formation
10 N

Sept.17 (21h)
TS Vicki formation

0N
100 E

110 E

Fig. 1 (a)

120 E

130 E

140 E

Path of Typhoon Vicki

150 E

160 E

170 E

180 E

The times are JST.

Fig. 2 Locations of fire stations, meteorological observatories,
AMeDAS, and power stations

Fig. 1 (b)Weather chart at 9:00JST on September 22nd 1998.

Fig. 3 Path of Typhoon Vicki in the Kinki District
The change in wind direction at observation sites is clockwise
at the closed circles, anticlockwise at the open circles.

AN ANALYSIS OF TYPHOON 9807 (VICKI) BASED ON SURFACE METEOROLOGICAL RECORDS OBTAINED FROM FIRE STATIONS

Okuda et al. (2000a) asked for weather data after typhoon
Vicki s attack in order to analyze in detail the surface weather situation during that typhoon. Many responses were received asshown in Table 1. The response rates for Nara and Aichi prefectures, in particular, exceeded 80%. In addition, weather records
were obtained from government weather service stations (Japan
Meteorological Agency, 1998a) and from power stations in the
Kinki district. Totally, data was received from 253 observationsites (Table 2). Okuda et al. (2000a) determined the meteorological characteristics of typhoon Vicki from these observation data.
Okuda et al. (2000b) also discussed the high wind generated
behind the center of typhoon Vicki. Here, findings on time serieschanges in the weather elements seen in the typhoon passage
charts are discussed and compared with rainfall strength figuresfrom combined radar echo charts. The utility of weather observation networks at the fire stations is verified from the findings.
2. GENERAL FEATURES OF TYPHOON VICKI
The course of typhoon Vicki and weather chart at 9:00JST on
September 22nd (Japan Meteorological Agency, 1998b) are shownin Fig.1 (a) and (b), before landfall on the Kii Peninsula. A weaktropical depression, in the western sea off of the Philippines
Luzon Island at 15:00JST on September 17th, developed into
typhoon Vicki at 21:00JST the same day. Development was gradual over the course shown in Fig.1 (a), and the typhoon struck theKii Peninsula of Japan about 13:00JST on September 22nd. The
atmospheric pressure at its center was recorded as 960hPa at landfall. Maximum wind velocity was 35m/s in the vicinity of the center. The radius of the severe wind area in which the wind velocity
was more than 25m/s was 190km on the southeast and 150km on
the northwest sides. The radius of the strong wind area in which
the wind velocity was more than 15m/s was 700km on the southeast and 220km on the northwest sides.
After landfall, typhoon Vicki moved northeast over the centerof the Kinki district weakening gradually as it approached ToyamaBay. Moreover, it made re-landfall in Yamagata Prefecture before
22:00JST the same day. The central atmospheric pressure at thesecond landfall was 990hPa, and the maximum wind velocity near
the center 25m/s. The radius of the strong wind area with a windvelocity of more than 15m/s was 460km on the southeast and
190km on the northwest sides. It passed through Honshu to the
Pacific Ocean, becoming an extra tropical cyclone at 9:00JST on
September 23rd. This was not an abnormal typhoon in size or
intensity, but it moved very fast and was accompanied by heavy
rainfall owing to the front to the rear of the typhoon s center. The
speed (Japan Meteorological Agency, 1998b) of this typhoon was
about 50-55 km/h immediately before landfall on the Kii
Peninsula, thereafter increasing to about 75-85 km/h.
3. SURFACE METEOROLOGICAL DATA
Locations of fire fighting headquarters, government weather service stations, and power stations from which the observation data
were obtained, are shown in Fig.2. AMeDAS stations are spatiallyarranged approximately 17km apart, and there are one or two
meteorological observatories per prefecture. In contrast, the firefighting headquarters observation sites are concentrated in urban

49

centers such as the large cities of Osaka and Nagoya. Few firefighting headquarter observation sites are located in ravine areas,
but there are many power station observation sites in those andcoastal areas of the Kinki district. They complement the observation network based on fire stations. In the northern region of Nara
Prefecture, where serious damage was caused by the severe windsof typhoon Vicki, there is only one meteorological observatory andthree AMeDAS stations, but as the number of fire fighting headquarters is 11, more detailed information on surface meteorologicalconditions could be obtained. This figure shows that the dense
weather observation network based on fire stations that mainly has
developed in urban or suburban areas is very useful for understanding severe storm disasters such as this typhoon, in urban
areas.
4. METEOROLOGICAL ANALYSIS
4.1 Course of Typhoon Vicki
Fig.3 shows the distributions of veering and backing of thechanges in wind direction. The thick lines represent the border
between them. This border divides the Kinki district into approximately east and west regions. The line is equivalent to the courseof the wind center of the typhoon. As the times when wind direction changed were recorded at some anemograms in some observation sites, the hourly position of the circulation center in thetyphoon is shown in Fig.3. The positions of the atmospheric pressure center of the typhoon, determined at 10-minute intervals by
objective pressure analysis (Fujii et al., 1999) are shown by double
circles. Fujii et al. used atmospheric pressure records from JMA
stations. Triangles mark the positions determined by the JMA forintervals of one hour. Each typhoon center course meanders. The
courses in the circulation and atmospheric pressure centers closely
resemble each other, but the course of the circulation center isabout 10 to 20km to the left of that of the atmospheric pressure
center.
4.2

Local High Wind Events
Mean wind velocity distributions for 10 minutes (average 50
to 00 an hour) are shown for the time series from 13:00 to
16:00JST in Fig.4 (a)-(d). At 14:00JST, when the atmosphericpressure center of the typhoon reaches around the border between
Osaka and Nara prefectures, a local high wind area, in which themean wind velocity exceeds 20m/s, appears in the rear region as
well as on the right side of the typhoon. At a fire station in
Wakayama City, the maximum recorded wind velocity was
32.4m/s at 14:20JST. Thereafter the local high wind area passed
Osaka, Nara, and Mie prefectures and reached the western part of
Aichi Prefecture and the southwest part of Gifu Prefecture. Meanwind velocities exceeding 30m/s were recorded; maximum windvelocity 31.9m/s at 15:48JST in Kameyama City, Mie Prefectureand 32.7m/s at 15:57JST in Kaitsu Town, Gifu Prefecture. As thewind velocity vector of Fig.4 shows, wind direction mainly was
southeast to south in the local high wind area on the right side of
the typhoon, whereas it was mainly south to west in the local highwind area within the rear area of the typhoon.
Fig.5 shows the distribution of the daily maximum instantaneous wind velocity at each observation site. The local high windarea, in which the maximum instantaneous wind velocity exceeds

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Y. OKUDA, H. ISHIKAWA AND T. FUJII

40m/s, spreads from the southern part of the Kinki district to thewestern part of the Chubu district. The recorded daily maximum
instantaneous wind velocities were 51.0m/s at 13:13JST in Tanabe
City, 50.0m/s at 14:13JST in Wakayama City, 50.8m/s at 14:07JST
in Sumoto City, 59.5m/s at 14:59JST in Shinjo Town, and 56.4m/s

at 15:14JST in Ueno City.
Fig.6 shows the difference in the times of the maximum
instantaneous wind velocity and minimum atmospheric pressure ateach observation sites; Area A, little difference in occurrence
times, Area B, a time difference of more than one hour. In Tanabe
City the maximum instantaneous wind velocity and minimum
atmospheric pressure were recorded at the almost same time,

Fig. 5 Daily maximum instantaneous wind velocity distributions(m/s)
Circles show the position of the atmospheric pressure centerof the typhoon obtained from an objective pressure analysis(Fujii et al., 1999).

Fig. 4 Mean wind vector distribution (m/s)
Circles show the position of the atmospheric pressure centerof the typhoon at each time in an objective pressure analysis(Fujii et al., 1999).

Fig. 6 Difference in hours between the time of the daily maximum
instantaneous wind velocity and daily minimum atmosphericpressure
Area A: little difference, Area B: more than one hour
Circles show the position of the atmospheric pressure centerof the typhoon obtained from an objective pressure analysis(Fujii et al., 1999).

AN ANALYSIS OF TYPHOON 9807 (VICKI) BASED ON SURFACE METEOROLOGICAL RECORDS OBTAINED FROM FIRE STATIONS

Fig. 7 Distribution of the difference in temperature from the dailymean temperature (℃)
Small circles show the position of the atmospheric pressure
center of the typhoon obtained from an objective pressure
analysis (Fujii et al., 1999). The large circle in Fig.7 (c)denotes the large temperature gradient region.

Fig. 8 Distribution of hourly precipitation (mm/h)
The atmospheric pressure center position of the typhoon is
the same as in Fig.7.

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Y. OKUDA, H. ISHIKAWA AND T. FUJII

Fig. 9 Distribution of specific humidity (g/kg)
The atmospheric pressure center position of the typhoon is
the same as in Fig.7.
The large circle in Fig.9 (b) denotes the high specific humidity region.

Fig. 10 Distributions of differences from maximum atmospheric pressures before daily minimum atmospheric pressure (-hPa)
The atmospheric pressure center position of the typhoon is thesame as in Fig.7.

AN ANALYSIS OF TYPHOON 9807 (VICKI) BASED ON SURFACE METEOROLOGICAL RECORDS OBTAINED FROM FIRE STATIONS

whereas in Sumoto City, Wakayama City, Shinjo Town, and Ueno
City maximum instantaneous wind velocity was recorded about
one hour after minimum atmospheric pressure.
4.3

Temperature
The distributions of air temperature from 13:00 to 16:00JST
are shown in Fig.7 (a)-(d). The absolute temperature value cannot
be compared among the stations because it depends on the altitudeof each observation site. The distribution of the temperature difference from the daily mean value at each observation site therefore is shown.
The cold area spreads out on the western side close to the center of the typhoon. From 14:00 to 15:00JST, this cold area is distributed like a hook from west of the center, indicative that cold air
entered the center of the typhoon from the northwest. At this time,the isotherm interval became dense from southern Osaka
Prefecture to northern Nara Prefecture, and the temperature gradient in space became very large; 0.2℃/km. The cold air invadingfrom the northwest side of the typhoon therefore brought a rapid
decrease in temperature across the border of Osaka and Nara prefectures.
4.4

Precipitation and Specific Humidity
Hourly precipitation distributions from 13:00 to 16:00JST are
shown in Fig.8 (a)-(d). As typhoon Vicki approached, precipitation in the southern Kinki district rapidly increased. From 14:00 to
15:00JST, the precipitation distributions made a hook as therainfall area from the western side of the typhoon surrounded thecenter of the typhoon. In contrast, on the east side of the typhoon,
rainfall was less than several mm/h, and some sites had none.
Thereafter, the rainfall area moved northeast together with thetyphoon. The hook-shaped rainfall area became illegible, no rain
falling in the Kinki district, except in the north.
Specific humidity distributions from 13:00 to 16:00JST are
shown in Fig.9 (a)-(d). While typhoon Vicki was passing throughthe Kinki district, dry air entering the Kii Peninsula from thesoutheast met the damp air on of the typhoon s northwest side. As
a result, the damp air region was a swirl around the eye of thetyphoon from 14:00 to 15:00JST. The high specific humidity,
exceeding 20g/kg around the border between Wakayama andOsaka prefectures at 14:00JST seems to have been brought by therain band that developed on the west side of the typhoon. In contrast, the specific humidity on the east side of the typhoon was
reduced to 10-15g/kg by the dry air flowing in from the southwestof the Kinki district.
4.5

Atmospheric Pressure
Fig.10 (a)-(d) shows the atmospheric pressure distributions
from 13:00 to 16:00JST. Atmospheric pressure values observed atmost of the fire stations were not normalized to the sea level value.
Moreover, the accuracy of pressure values recorded at some firestations were not considered highly confident because they had notbeen officially approved by the JMA. The pressure difference
between the atmospheric pressure at each recording time and thepeak pressure before passage of the typhoon therefore are given.
The pressure differences are distributed in a rotating elliptical
form.

5.

53

THE COMBINED RADAR ECHO AND HIGH
WIND AREA RELATIONSHIP IN THE KINKI
DISTRICTThe combined radar echo charts together with observations at
Murotomisaki and Takayasuyama sites were used in the comparison with maximum wind distribution. Fig.11 (a)-(p) shows the
combined radar echo charts for every 7 minutes and 30 seconds
from 14:00 to 16:00JST and maximum instantaneous wind velocities are displayed as vectors based on the times when the maximum was recorded. The combined radar echo at 14:45JST lacks
an image. In Fig.6, the severe storm area mainly is divided into
two areas, in which the minimum atmospheric pressures and maximum instantaneous wind velocities were recorded at the almost
same time or maximum instantaneous wind velocities were recorded about one hour after the minimum atmospheric pressures. The
first area corresponds to the local high wind area present on theright side of the typhoon, whereas the second is the local high windarea that formed to the rear of the center of the typhoon.
Yamamoto et al. (1963) reported severe storms accompanied by acold front in their study of the 2nd Muroto typhoon. The highwind formed behind typhoon Vicki seems to have the same character as that in the 2nd Muroto typhoon.
The combined radar echo chart at 14:00JST shows a band ofstrong rainfall on the western side of the typhoon. High winds
were recorded mainly inside the rain band. The daily maximum
instantaneous west wind around the north of the rain band wasrecorded in Sumoto City, Hyogo Prefecture at 14:15JST. In the 6
minutes from 14:15 to 14:21JST, a southerly high wind wasrecorded at Matsuzaka City, Mie Prefecture, but on the right sideof the typhoon. A westerly high wind was recorded in Wakayama
City. These high winds at Sumoto and Wakayama cities were
inside the same rain band indicated as A in Fig.11. Thereafter, thelocal high wind area moved in the east-northeast direction together
with the movement of the rain band. At 14:37JST, the local highwind area had moved from the north of Wakayama Prefecture to
the west of Nara Prefecture.
Very high winds blew in the south of the Nara basin and thewest-southwest area along the Yoshino River. The inflow angle
across the isobars was large along the Yoshino River, whereas it
was small in the south of the Nara basin. There were high winds
from the south across Mt. Kongo on the border between Osaka andNara prefectures. The maximum wind velocity was 59.5m/s inShinjo Town, Nara Prefecture at 15:00JST. Only the wind direction recorded at Shinjo Town was south-southeast. At 15:07JST,
westerly high winds were recorded around the rain band from thesouthern Osaka Prefecture to northern Nara Prefecture. Withinjust 15 minutes, from 14:52 to 15:07JST, the wind direction across
Mt. Kongo had changed from west to south and again from south
to west. Our field study in Nara Prefecture turned up many firsthand testimonies: at first a southerly wind blew then it shifted to awesterly one, and there was much evidence of the damage done tohouses and trees by the westerly wind, as well as by the southerlyone. It therefore is believed that the rain band that had a rapidchange in the wind direction had passed through.
From an analysis of the Doppler radar echo obtained at KansaiInternational Airport at 15:30JST, Sakakibara et al. (1999) showedthat a converging shear line existed near the rain band over Nara

54

Y. OKUDA, H. ISHIKAWA AND T. FUJII

20m/sec
40
60

AA(a)14:00(e)14:30

AA(b)14:07(f)14:37

Sumoto City

A

A(c)14:15(g)14:52

Matsuzaka City
Wakayama City

A(d)14:22

Mr. KongoA

Shinjo Town

Yoshino River(h)15:00
Fig. 11 Combined radar echo and daily maximum instantaneous wind vectors
The rain band formed behind the typhoon center is shown as a boxed A.

AN ANALYSIS OF TYPHOON 9807 (VICKI) BASED ON SURFACE METEOROLOGICAL RECORDS OBTAINED FROM FIRE STATIONSAA(i)15:07(m)15:37

Ritto Town
Shigaraki Town

A(j)15:15

A(n)15:45

AA(k)15:22(o)15:52

A
A
Rain [mm/h]

0 1 4 16 32 64(l)15:30(p)16:00
Fig. 11 (continued)

55

56

Y. OKUDA, H. ISHIKAWA AND T. FUJII

City. They reported that this converging shear line caused the highwind on the ground. Kawano et al. (1999) observed 3 componentsof wind velocity in typhoon Vicki based on MU radar system datafrom Shigaraki Town, Shiga Prefecture. At 15:53JST, observation
was stopped by a blackout, but they recorded a strong down draftof 4-5m/s, at height of 2-3 km above Shigaraki Town. At thattime, the rain band seen on the combined radar echo charts
approached Shigaraki Town. Maximum instantaneous wind velocities were 36.4m/s at 15:45JST in Ritto Town and 41.6m/s at
16:16JST in Yokaichi City, both in Shiga Prefecture. The converging shear line, down draft, and local high wind on the groundare considered to have been related.
6. CONCLUSIONS
Based mainly on weather observation data obtained at fire stations, we analyzed the surface structures of typhoon Vicki:
1) The weather observation networks of fire stations were
extremely useful for the analysis because they were muchdenser than the observation networks of the JMA.
2) Three courses shown for this typhoon in the Kinki district
were meandering ones. The meanderings of the wind circulation and atmospheric pressure centers, in particular, were wellcorrelated.
3) The local high wind area in the typhoon was divided into twoparts, one formed on the right side of the typhoon, the other in
its rear area as shown by the typhoon tracking. The first local
high wind area occurred in Wakayama and Aichi prefectures,the second, in the central of Kinki district, causing widespread
damage.
4) The temperature distribution showed that cold air intruded thecenter from the typhoons northwest side. The temperature
gradient became very large across the border between Osakaand Nara prefectures at 15:00JST.
5) The hourly precipitation distribution of showed a hook-shaped
rainfall area within the typhoon.
6) The specific humidity distribution showed that dry air fromthe southwest and damp air from the northeast flew in the center of the typhoon at 15:00JST.
7) The isobar distribution in the typhoon often had a rotating
elliptical form.
ACKNOWLEDGEMENTS
A part of this study was supported by Grants-in-Aid for
Scientific Research from the Ministry of Education, Science,Sports and Culture (Research Representative; Prof. Masaru
Matsumoto). In our collection of the various weather data, we
received much cooperation from stuff members of the Japan

Meteorological Agency (JMA), Japan Weather Association(JWA), Japan Meteorological Business Support Center (JMBSC)
as well as the fire fighting headquarters of the local governments,
Kansai Electric Power Co. Inc. and Nihon Electric Instruments Co.
Inc.
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