International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 6
Number 1
March 2012
119
1 INTRODUCTION
In areas where tropical cyclones occur navigators
must apply the procedure for obtaining information
and the identification of the danger on the expected
track of the vessel, the accuracy in determining the
sectors safe and unsafe, taking into account velocity
vectors of the ship (Vs) and the cyclone (Vc). As a
result, we decide how to most effectively avoid the
area threatened by a tropical cyclone [1-5].
The means for using the procedure include a
computer program developed by these authors, de-
scribed in previous publications [6]. Among others,
the software takes into account the procedure for
programming the route of the vessel at the time of
receiving the message about the cyclone for the fol-
lowing hours and days, with forecasts of expected
cyclone positions, and predicted by calculations fu-
ture positions of the ship.
2 PROCEDURES AND METHODOLOGY
One may find that being together with the cyclone
vessel is possible in three specific situations:
− vessel and cyclone move in opposite directions
(ahead or nearly ahead of the ship);
− vessel catches up with the cyclone on a similar
course;
− projected route of the ship crosses the projected
path of the cyclone (eye of the cyclone track) at
an angle of (30° ÷ 90°) and the moment when the
ship will enter the waters on tropical cyclone
threat.
For these three variants examples were tested,
based on real data on cyclones in the years 2008 -
2010 and for the actual and random positions of se-
lected ships owned by the Polish Steamship Compa-
ny (PSC). Typically, for one cyclone four vessels in
positions spaced symmetrically around the cyclone
were chosen, that is, from the point of dangerous
winds ≥ 34 kn. The moment of decision-making was
the situation when calculations showed the entry of
the vessel in a dangerous sector of the cyclone in
less than 48 hours (TCPA)
The test results will be illustrated by a situation,
where the cyclone Bill was being avoided from 20 to
23 August 2009. The cyclone moved along a para-
bolic trajectory across the North Atlantic. Part of the
first message of 20 Aug 2009 is shown in Table 1.
Elements of Tropical Cyclones Avoidance
Procedure
B. Wisniewski & P. Kaczmarek
Maritime University of Szczecin, Poland
ABSTRACT: The updated version of the Cyclone II program was used for analyzing hundreds of cases where
ships were facing dozens of developed cyclones. The program generates directions for navigators that are
recommended for consideration before making decisions on passing around or avoiding tropical cyclones.
Three specific situations were defined where a vessel may enter the area affected by a tropical cyclone, and its
commander must consider three recommendations for safe passing of the cyclone:
– vessel – cyclone encounter, where if on opposite course, the most effective is course alteration;
– when the ship overtakes the cyclone, speed reduction is the most effective action;
– when the vessel and the cyclone are on crossing routes (30 ÷ 90°), a slight decrease in speed or a slight
course alteration or both actions can be effective.
120
Table 1. Fragment of a message printout: cyclone BILL on
20/08//2009
___________________________________________________
ZCZC MIATCMAT3 ALL
TTAA00 KNHC DDHHMM CCA
HURRICANE BILL FORECAST/ADVISORY NUMBER
21...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
AL032009
1500 UTC THU AUG 20 2009
REPEAT...CENTER LOCATED NEAR 22.6N 61.7W AT
20/1500Z
AT 20/1200Z CENTER WAS LOCATED NEAR 22.1N
61.0W
FORECAST VALID 21/0000Z 24.2N 63.8W
MAX WIND 110 KT...GUSTS 135 KT.
64 KT... 90NE 45SE 30SW 75NW.
50 KT...120NE 90SE 60SW 100NW.
34 KT...225NE 200SE 100SW 200NW.
FORECAST VALID 21/1200Z 26.6N 66.0W
MAX WIND 115 KT...GUSTS 140 KT.
64 KT... 75NE 45SE 30SW 45NW.
50 KT...120NE 100SE 70SW 100NW.
34 KT...225NE 200SE 120SW 180NW.
FORECAST VALID 22/0000Z 29.5N 67.5W
MAX WIND 115 KT...GUSTS 140 KT.
64 KT... 75NE 45SE 30SW 45NW.
50 KT...120NE 100SE 70SW 100NW.
34 KT...225NE 200SE 120SW 180NW.
FORECAST VALID 22/1200Z 32.5N 69.0W
MAX WIND 110 KT...GUSTS 135 KT.
50 KT...120NE 100SE 70SW 100NW.
34 KT...225NE 200SE 120SW 180NW.
FORECAST VALID 23/1200Z 40.5N 66.5W
MAX WIND 100 KT...GUSTS 120 KT.
50 KT...120NE 120SE 70SW 100NW.
34 KT...225NE 225SE 120SW 180NW.
___________________________________________________
Four ship positions for 12.00 (20.08.2009)
− a ship at the port road of New York travelling to
Brazil,
− vessel B in the position φ = 15.07°N,
λ =059.9°W on the way to N. York,
− ship in the Mona Passage φ = 18.04°N,
λ =074.98°W on the way to Europe,
− ship in the actual position D φ = 40°N,
λ = 040°W on the way to N. York,
− and the position of the cyclone φc = 22.1°N,
λ = 061°W at the same time and day.
In connection with weather forecasts for the next
12, 24, 36, 48, and 72 hours, cyclone positions were
taken from messages and then future ship’s positions
were calculated.
3 RESULTS
For ship (A) departing from New York after receiv-
ing a message about the cyclone, data were entered
to the computing program "Cyclone II ":
− their position, intended course (course over
ground = 15°) to Brazil, and the estimated speed
of 13,
− data on the location of the cyclone, its course and
speed (vertical panel) - Fig.1.,
− data on forecasts of the cyclone 12, 24, 36, 48, 72
hours (horizontal panel) - Fig.1.
The calculation results indicate that the ship pro-
ceeds to a dangerous course sector 149° - 197°,
1254.7 Nm from the eye of the cyclone, and after
43.7 hours (TCPA) it will reach the closest point ap-
proach 234Nm (CPA). By obtaining the cyclone po-
sition from 72 hour forecast illustrating the predicted
cyclone movement path, the captain chooses a new
ship’s course (COG = 180°) and decides to check
what the vessel and cyclone positions will be in 12,
24, 36, 48 and 72 hours. Figure 2 illustrates the re-
sults of calculations and relative ship – cyclone posi-
tions after 24 hours. The ship passes the cyclone af-
ter 48 hours and alters the new COG = 130° to
return on route to Brazil, being safe on this course at
a distance of 328.4 Nm from cyclone eye (Fig. 3).
Finally, the ship extends its distance covered by
210Nm, maintaining a speed of 13.2 kn, i.e. and
will prolong the voyage by 16 hours to pass by the
cyclone.
For ship (B) in position: 51.07°N, 059.9°W on
the way to New York (COG = 230°, Vs = 23kn) it is
estimated that it is on a dangerous course (308 ÷
343°) and after 37.8 hours will be at the closest point
approach, i.e. 129.2 Nm from the cyclone influence,
affected by winds ≥ 34 knots (Fig. 4). The ship has
to reduce its speed below 19.1 kn.
To avoid entry into the cyclone-affected area, the
vessel loses 72Nm (3 x 24), which means proceed-
ing at a speed of 19.1kn. This prolongs the expected
time of voyage by about 3 hrs 40 min.
Ship (C), sailing in the Mona Passage on its way
to Europe, performs testing to pass by the cyclone
Bill for the same times on 20.08.2009. The infor-
mation obtained is that it is on the boundary of dan-
gerous sector (331° to 55°) remaining on course
COG = 055° and sailing at a speed of 13 knots (re-
sults in the vertical panel - Figure 5). By introducing
cyclone data forecast to the program Cyclone II for
up to 72 hours, the ship commander finds out that
continuing the trip at a speed Vs = 13.0kn, after 12
hours (Fig. 6) its COG = 055°, while the ship will
get into a safe sector reaching the closest point of
approach 333.4 Nm from the cyclone eye. For this
situation no changes of speed and course relative to
121
the cyclone Bill are needed, therefore neither dis-
tance not voyage time will be extended.
On 20.08.2009. at 12.00UTC ship (D) is very far
from the cyclone, in position φ = 40°N, λ =
039.15°W and on course COG = 270° on the way to
New York. From entered forecast data and expected
vessel positions (Vs = 13.0kn), only simulation (test-
ing) for 48 hours shows that ship’s course will ap-
proach the dangerous sector (272°-358°), then sail-
ing at a distance of 907.16 Nm from the cyclone eye
(Fig. 7). A simulated situation for passing the cy-
clone Bill is shown in Figure 7, 8 and 9 for August
22
nd
2009. The ship, sailing one day on course COG
= 230° and then returning to the course COG = 288°
leading to New York, extended the original rhum-
bline route by about 104 Nm only, corresponding to
a prolonged travel time of 8 hours. The ship made a
successful maneuver, passing the cyclone at a dis-
tance of 338Nm from the outer cyclone dangerous
area, where wave heights were 4.0m ≥ m. Perform-
ing simulations of the cyclone and ship position pro-
jections for the next 72 hours, we get a positive re-
sult confirming cyclone avoidance.
4 CONCLUSIONS
1 For the vessel and the cyclone collision situation
on opposite courses (ship A) the course altera-
tion is the most effective. The reduction of speed
only did not give a positive result for a speed of
cyclone movement Vc ≥ 10kn.
2 For the situation when the ship overtakes the cy-
clone, the most effective is ship’s speed reduction
relative to cyclone movement, because the track
will not be prolonged, and is fuel consumption is
likely to be lower (ship B).
3 A special case is where a vessel expects that its
planned route will cross the cyclone path, but
without the entry of the vessel into the cyclone af-
fected area, and it does not alter change speed or
course (vessel C).
Figure 1 Graphic illustration of the cyclone path, based on
weather report and calculations for ship A, heading for Brazil
(20-08-2009, 12.00UTC).
Figure 2 Graphic picture of cyclone and ship A positions, after
24 hour travelling time, and calculation results.
4 With the projected route of the vessel and the cy-
clone path are likely to cross each other (30 ÷
90°), and when the probability of vessel entry in-
to the area of cyclone influence, slight ship’s
speed decrease or small course alteration (∆COG
≤ 40°) can be effective, as illustrated by the case
of ship D, or both changes mentioned above may
be made.
Figure 3 Graphic picture of ship A and cyclone positions after
48 hours in relation to course alteration to 130 degrees.
Figure 4 Graphic picture of cyclone track according to received
data and calculations for ship B, heading for New York (20-
08-2009, 1200 UTC).
122
Figure 5 Graphic picture of cyclone track according to re-
ceived data and calculation results for ship C, Mona Passage,
ship proceeding to Europe (20-08-2009, 1200 UTC).
Figure 6 Graphic picture of cyclone and ship C positions dur-
ing the voyage and calculation results.
Figure 7 Graphic results of cyclone track according to message
and calculation results for ship D after 48 travel hours from
20-08-2009, at. 1200 UTC.
Figure 8 Graphic picture of cyclone and ship D positions ac-
cording to the message on 22-08-2009, after altering course.
Figure 9 Graphic picture of cyclone and ship D positions after
12 hours after altering course to 288 degrees, voyage to to New
York.
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[3] Wiśniewski B. Radio fax Charts in sea navigation (in
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