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Vessel shelter conditions ascertained byNILAM-AIS at the time of Typhoon No. 18of 2009

Course of Typhoon
No. 18-Centrair
Ship movement
ToyohashiEntering the bay

25 m/s or higher(high-wind zone)
Locations of measurement:
Centrair Toyohashi
Wind direction: ENE
E

Irago Suido Traffic
Route
Exiting the bay

Wind speed

Figure 1: Shelter conditions
Landfall at Chita Peninsula→Tue, Oct, 6Wed, Oct, 7Thu, Oct, 7

6:00～8:00

4:00～6:00

8:00～10:002:00～4:00

0:00～2:00

22:00～24:00

20:00～22:00

18:00～20:00

16:00～18:00

12:00～14:00

6:00～8:00

10:00～12:00

4:00～6:00

2:00～4:00

0:00～2:00

22:00～24:00

20:00～22:00

18:00～20:00

16:00～18:00

14:00～16:00

12:00～14:00

6:00～8:00

10:00～12:00

4:00～6:00

8:00～10:00

2:00～4:00

5

8:00～10:00

100Power outage

No measurement

Entering the bay
Exiting the bay

15

14:00～16:00

20

0:00～2:00

2. Actual conditions of vessel shelter
Figure 1 shows conditions immediately before thetyphoon made landfall at the Chita Peninsula at 4:00 A.M on
October 8. The wind speed at Central Japan International
Airport (Centrair) was 22.1 meters/second. Each of theships taking shelter is pointed into the wind direction thatwas observed in its vicinity.
The ship movement shown in the center of the figure
pertains to an ordinary cargo ship of approximately 9,000
tons that was anchored in Mikawa Bay. Until the typhoon
made landfall at around 5:00 A.M. on October 8, the ship isswinging around in a circle with little change in the central
anchor point.
NILIM-AIS also ascertained the number of ships passing
through the Irago Suido Traffic Route in two-hour units.
The results are shown in Figure 2. From this figure, it ispossible to confirm the following trends:
1) During the roughly 20-hour period centered on the time of
maximum measured wind speed, no ships entered or exitedthe bay. Peaks are observed before and after this period.
2) The number of ships entering the bay peaked prior to thetyphoon’s approach, and the number exiting the bay peaked
after the typhoon passed.
It should be noted that no measurements were made during
the period between 4:00 A.M. and noon on October 8 due toa typhoon-caused power outage.

22:00～24:00

1. Outline
The “Technical Standards for Port and Harbor Facilities
and their Interpretation” that were revised in 2007 make noquantitative statements regarding anchorage size during
times of stormy weather. Although, in the past, theStandards/Interpretation did provide a quantitative formulafor calculating anchorage size, this formula was removed at
the time of the 1999 revision because the grounds for it wereunclear.
A real-world problem here is difficulty inascertaining actual shelter conditions of vessels duringstormy weather, and particularly the area of water needed for
shelter, and as a result no calculation formula has been
proposed.
In 2008, a regulation requiring both ocean-going anddomestic vessels that meet or exceed a certain size to carry
the Automatic Identification System (AIS) was implemented.
Against this backdrop, the Port Planning Division isconstructing an NILIM-AIS system by setting up AIS land
stations in Japan’s major sea areas. This system functions
to observe ship movement in real time and conduct dataanalyses. The data analysis function was used to ascertain
actual conditions surrounding vessel shelter, anchoring bylarge ships, and movement into/out of ports during thepassage of Typhoon No. 18, which struck Japan in October
2009.

No. of ships

Research trends and results

TAKEMURA Shinji, Researcher
Port Planning Division, Port and Harbor Department(Keywords) NILIM-AIS, anchorage size, shelter conditions

Fri, Oct, 8Observation times

Figure 2: Time-series analysis of numbers of passing ships
The author intends to conduct a more detailed analysis ofthese results and to reconsider the formula for calculatinganchorage size during stormy weather in the TechnicalStandards/Interpretation.
[References]
Technical Note of NILIM Nos. 431, 500, 529, 561