1. TROPICAL CYCLONES 1 1

2. REFERENCES
* These are just of few of the references available covering Tropical Cyclones, their effects on the Marine Industry and Marine Safety. *
Mariner’s Guide for Hurricane Awareness in the North Atlantic Basin (NOAA)
American Practical Navigator (Bowditch)
Port Heavy Weather Guide
Hurricane Havens Handbook for the North Atlantic (U.S. Navy)

3. TROPICAL CYCLONE DEFINED!
A warm core, non-frontal, synoptic scale system with cyclonically rotating winds characterized by a rapid decrease in pressure and increase in winds toward the center of the storm. Cyclones develop over tropical or subtropical waters and have a definite organized circulation.

4. How do they develop?
Favorable environmental conditions that must be in place before a tropical cyclone can form:
Warm ocean waters (at least 80°F / 27°C).
An atmosphere which cools fast with height (potentially unstable).
Moist air near the mid-level of the
troposphere (16,000 ft / 4,900 m).
Generally a minimum distance of at least 300
miles (480 km) from the equator.
A pre-existing near-surface disturbance.
Little vertical wind shear between the surface and
the upper troposphere. (Vertical wind shear is the change in wind speed with height.)
Outflow aloft/exhaust

5. STAGES OF DEVELOPMENT
Tropical Depression(TD): A tropical cyclone with wind speeds up to 33 knots. Identified by the letters “TD” and suffixed by a number (TD-01: the first tropical depression of the current calendar year.....TD-02, the second, etc...)
Tropical Storm (TS): A tropical cyclone with wind speeds 34 to 63 knots. Identified by names in alphabetical order consistent with formation date/time. (TS Arthur, Bertha...).
Hurricane: A tropical cyclone with wind speeds greater than 63 knots. Identified by the same name it had as a TS.

6. TROPICAL (EASTERLY) WAVE
No significant winds or seas
No defined near surface
circulation
Identified by areas of
Convergence (thunderstorms)

7. TROPICAL DEPRESSION (Formative Stage)
Winds < 34 kts
Tropical wave develops a
weak cyclonic circulation
Identified by thickening
clusters of thunderstorms
on satellite
Central pressure falls
rapidly below 1002mb if
system intensifies

8. TROPICAL STORM (Immature to Mature Stage)
Winds kts
Closed formation expands with spiral
bands becoming better organized
Increasing sea state makes navigation near the center increasingly
difficult and dangerous

9. HURRICANE / TYPHOON / WILLY-WILLY (Mature Stage)
Winds > 63 kts
DANGEROUSLY HIGH
SEAS navigation severely impaired
Radius of strong winds may exceed 350 NM
Gale Force Winds extend out further in right front quadrant (typically 120 NM)

10. TROPICAL CYCLONE Stages of Development
1. Tropical Easterly Wave 3. Tropical Storm
2. Tropical Depression Hurricane

11. Most damaging aspects of a hurricane:
INPORT:
STORM SURGE
TORNADO/SVR TSTMS
HIGH WINDS
AT SEA:
HIGH SEAS
HIGH WINDS

12. HURRICANE CATEGORIES Saffir- Simpson Scale
Category 1 (Minimal) - Winds 64 to 82 knots, storm surge 4 to 5 ft above normal. No real damage to building Structures. Low lying coastal areas flooded, minor damage to piers. Examples Irene 1999 and Allison 1995
Category 2 (Moderate) - Winds 83 to 95 knots, storm surge 6 to 8 ft above normal. Minor damage to structures, poorly constructed buildings major damage. Coastal and low lying escape routes flooded over, considerable pier damage. Examples: Bonnie 1998, Georges (FL & LA) 1998 and Gloria 1985
Category 3 (Extensive) - Winds 96 to 113 knots, storm surge 9 to 12 ft above normal. Major damage to structures, poorly constructed building destroyed. Serious flooding along the coast, extensive flooding may extend inland 8 miles. Examples: Keith 2000, Fran 1996, Opal 1995, Alicia 1983 and Betsy 1965

13. HURRICANE CATEGORIES cont.
Category 4 (Extreme)
Winds 114 to 135 knots, storm
surge 13 to 18 ft above normal.
Extensive roofing and window
damage, complete destruction of
mobile homes. Areas above 10 ft
flooded inland up to 6 miles, major
erosion of beaches, massive
evacuation of coastal areas.
(ANDREW 1992)

14. HURRICANE ANDREW DAMAGE MAP

15. HURRICANE CATEGORIES cont.
Category 5 (Catastrophic)
Winds above 135 knots, storm
surge greater than 18ft above
normal. Complete failure of roof
structures and very severe window
and door damage, some complete
buildings fail. Major damage to
structures lower than 15 ft above
sea level, massive evacuations of
residential units within 10 miles of
the coast.
(CAMILLE 1969)
AUG 16, 1969

16. The Power of a Category 5 “Hurricane Camille”
BEFORE!
AFTER!
Richelieu Apartments
The Mansion

17. TROPICAL CYCLONE FORMATION, LOCATION
The map below shows where the seven basins noted for TC development are located and typical tracks for each. It also has the average number of tropical storms, and hurricanes, created in each basin.

18. 2005 ATLANTIC TROPICAL CYCLONE NAMES
FORMATION CONT.
2005 ATLANTIC TROPICAL CYCLONE NAMES
Hurricane Season Atlantic
01 June November
Eastern Pacific
15 May November
Western Pacific
Year round
Arlene
Bret
Cindy
Dennis
Emily
Franklin
Gert
Harvey
Irene
Jose
Katrina
Lee
Maria
Nate
Ophelia
Philippe
Rita
Stan
Tammy
Vince
Wilma

20. Distribution of Surface Winds
Winds are very light in the eye, and increase rapidly in the eyewall.
Fastest winds are found in the eyewall.
Gale-force winds can extend nm from the center of the storm.
Hurricane Andrew Strong CAT 4

21. TROPICAL CYCLONE CHARACTERISTICS
Feeder Bands (curved lines of convection) spiral inward to the Eye Wall. Some of the most violent weather (tornadoes/severe thunderstorms) occur in these areas
“Pumping Action” announces the approach of, and passing of the Tropical Cyclone 23 26 39 35

22. TROPICAL CYCLONE CHARACTERISTICS, CLOUDS
Most significant clouds are heavy Cumulus and Cumulonimbus
Spiral bands of CU/CB inward toward outer edge of eye
Cirrus changing to Cirrostratus and lowering, good indicator of approaching TC for the mariner
Cloud sequence similar to approaching warm front

23. BAROGRAPH TRACE Hurricane Bob 1991 Newport, RI
TROPICAL CYCLONE CHARACTERISTICS, ISOBARS/PRESSURE
18AUG 15Z
19AUG 12Z
20AUG 12Z
970
975
990
985
980
995
1005
1000
1020
1015
1010
18Z
15Z
21Z
00Z
03Z
06Z
09Z
MILLIBARS
BAROGRAPH TRACE Hurricane Bob 1991 Newport, RI
Isobars nearly symmetrical or elliptical in shape
Tightest isobaric gradient to right of storms line of movement
Central pressures well below average (890 – 940 mb not uncommon)
Barograph trace often shows “V” as eye passes (not something a ship wishes to see). 24 27 40 36

24. TPC/NHC Six-hour forecast cycle
Time (UTC)
Task / Event
00:00
Synoptic time, cycle begins, receive aircraft fix (generally within +/- 00:30)
00:45
Receive satellite fix data (TAFB, SAB, AFWA)
01:00
Initialize models
01:20
Receive model guidance, begin preparing forecast
02:00
NWS/DOD hotline coordination call (international coordination, if necessary)
03:00
Advisory package deadline
03:15
FEMA conference call
06:00
Next cycle begins

25. Hurricane Isabel Track Guidance
1800 UTC 10 Sep 2003

27. NOT-SO EXCELLENT! “HURRICANE KATE”
29 SEP 2003

28. BIG IMPROVEMENTS IN TC TRACK FORECASTS OVER RECENT DECADE, ESPECIALLY BEYOND 2 DAYS

29. UNDERWAY
A wise mariner needs to know what to do if warnings are in error (or plotted incorrectly), or they get caught unaware, and end up in the vicinity of a tropical cyclone at sea!

30. MONITOR THE STORM
National Hurricane Center issues warnings every 6 hours 0300Z, 0900Z, 1500Z, 2100Z
NAVTEX
SafetyNet
Annotated on weather facsimile charts
Private weather routing companies
List servers from the National Hurricane Center

31. 1-2-3 Rule

32. WARNING’S Upon Receipt of Warning:
1. Plot the current and forecast 24 hour storm positions and forecast radius of 35 kt winds.
2. Using a compass extend the radius of the forecast 24 hour 35 kt wind area by 100 NM.
100 NM
135 NM
24 HR FORECAST POSITION
CURRENT POSITION

33. WARNING’S, cont. DANGER AREA
3. Draw tangents relative to the direction of the storm from the 35 kt radius (current position) to the outermost radius at the 24 hr forecast position. Avoid the DANGER AREA
TANGENT
100 NM
DANGER AREA
100 NM
TANGENT
24 HR FORECAST POSITION
CURRENT POSITION

34. WARNING’S, cont.
4. Use the same procedure for the 48 and 72 hr forecast positions, however, use 200 and 300 NM radii/respectively.
Avoid the DANGER AREA.
300 NM
200 NM
DANGER AREA
100 NM
DANGER AREA
300 NM
200 NM
DANGER AREA
100 NM
72 Hr
48 Hr
24 Hr
Current 43 46 57 62

35. TROPICAL CYCLONE EVASION
Meteorological elements are not uniformly distributed throughout a tropical
Storm is divided into left/right semicircles and quadrants, relative to the direction of motion
Usually strongest winds are on right side in N.H. (added to motion)

36. TROPICAL CYCLONE EVASION cont.
Storm’s location relative
to own ship’s position:
Dangerous semi-circle:
Wind greater due to wind
augmented by the forward
motion of the storm.
“Less Dangerous” semi-circle:
Wind decreased by forward
Winds and seas force
vessel into path of storm.
Winds blow vessel away
from storm track.

37. TROPICAL CYCLONE EVASION cont.
Ship in the “Dangerous” (right) semi-circle:
1. Maneuver ship so relative wind is from 045 degrees to starboard.
2. Continually hold course with respect to relative wind, making best way possible.
045 DEG REL

38. TROPICAL CYCLONE EVASION cont.
Ship in the “Less Dangerous” (left) semi-circle:
1. Maneuver ship so that relative wind is from 135 degrees to starboard.
2. Hold course with respect to relative wind, and make best SOA.
135 DEG REL

39. TROPICAL CYCLONE EVASION cont.
157 DEG REL
BEHIND CENTER (ON STORM TRACK)
Avoid center by best practical course (storm may recurve).
AHEAD OF CENTER (ON STORM TRACK)
Maneuver ship so that relative wind is 157 degrees relative, hold course and speed.

40. TROPICAL CYCLONE EVASION cont.
DO NOT CROSS THE “T” unless the ship is > 300 NM ahead of the storm and crossing right to left.
300 NM +

41. TROPICAL CYCLONE EVASION cont.
Never cross the “T”: Do not plan to cross the track of a hurricane.
NEVER LEFT TO RIGHT! Respect the negative effects that heavy weather places on vessel speed/handling. Sudden accelerations in hurricane motion can ultimately place a vessel in conditions not originally expected, resulting in disaster!
Adjustments to course & speed in order to remain clear of the danger area in a hurricane are the most prudent navigation decisions a mariner can make in these instances.
If it becomes necessary to cross the “T” right to left, ensure you are at least 300NM from the center.
Follow the 1 – 2 – 3 Rule

42. TROPICAL CYCLONE EVASION cont.
Monitor warnings and advisories to prevent an encounter.
Forecast Track Tendencies: Comparison of the most recent NHC forecast track with forecast tracks from the past 24 hours can be useful for determining a trend in the forecast motion of a hurricane.
For instance, a comparison of forecast tracks issued every 6 hours over the last 24 hours, may show a noticeable shift right or left (with respect to storm motion) in the forecast track of a hurricane. This information may provide some indication as to how the forecast & actual hurricane track are trending and provide more guidance in navigation planning for avoidance, particularly in the 2-3 day forecast range & beyond.

43. TROPICAL CYCLONE EVASION cont.
Assess your options: Plan Ahead. Never leave yourself with only a
single navigation option when attempting to avoid a hurricane.
Sea room to maneuver is not a significant factor when operating in the
open waters of the North Atlantic, but becomes extremely important in the
confined waters of the Western Caribbean Sea/Gulf of Mexico.
More often than not, early decisions to leave restricted maneuver areas
are the most sensible choice.

45. IN PORT

46. MONITORING THE STORM Local Radio / TV stations
NHC Warnings/Bulletins
Local Radio / TV stations
Port Authority / Coast Guard
Internet

47. CONDITIONS OF READINESS
CONDITION 5 - Destructive force winds (35 kts or as specified ) are possible
within 96 hours.
CONDITION 4 - Destructive force winds are possible within 72 hours.
Whiskey
CONDITION 3 - Destructive force winds are possible within 48 hours.
X-Ray
CONDITION 2 - Destructive force winds are anticipated within 24 hours.
Yankee
CONDITION 1 - Destructive force winds are anticipated within 12 hours.
Zulu
These are the most common conditions of readiness.

48. Stay Inport or Ride it out at Sea?
Factors to consider!
The decision to leave port for hurricane avoidance must be made very early, and must be balanced with a number of other factors
- Storm Intensity, Size, Strength, and Speed.
- Port Facilities, Berthing & Shelter Requirements
- 24 hours prior to onset of gale force winds.
- Probability of Hit (angle of approach)
- Vessel, size, speed, engineering status
- Time window to clear last vessel
- Vessel Route (safe, heavy seas, etc...)
* Early decisions to leave port in an attempt to avoid hurricanes are crucial.*

49. Ports Evaluated in Hurricane Havens Handbook for the North Atlantic (U
Ports Evaluated in Hurricane Havens Handbook for the North Atlantic (U.S. Navy)
1 - BOSTON
2 - NEWPORT
3 - NEW LONDON
4 - NEW YORK CITY
5 - PHILADELPHIA
6 - NORFOLK
7 - MOREHEAD CITY
8 - CHARLESTON
9 - SAVANNAH
10 - KINGS BAY
11 - MAYPORT
12 - PORT EVERGLADES
13 - KEY WEST
14 - TAMPA
15 - PENSACOLA
16 - GULFPORT
17 - NEW ORLEANS
18 - PORT ARTHUR
19 - GUANTANAMO BAY
20 - ROOSEVELT ROADS
21 - BERMUDA 1 4 1 2 16 3 8 5 10 6 7 9 21 11 12 14 18 15 17 13 19 20

50. TROPICAL CYCLONE DISSIPATION
Recurvature:
Tropical storm curves towards the NNE-E. Usually accelerating and decreasing in strength, often increasing in size. Speed is difficult to forecast.
Frictional forces of land:
Often becoming extra-tropical as storm merges with frontal zone.
Unfavorable atmospheric/oceanographic
influences:
Includes, but not limited to, upper level shearing, dry air intrusion in mid levels, cooler sea surface temperatures, upwelling behind other tropical systems, etc…
“Floyd”
“Charley”