tropical revolving strom
TRANSCRIPT
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* These are just of few of the references available
covering Tropical Cyclones, their effects on theMarine Industry and Marine Safety. *
Mariners Guide for Hurricane Awareness in the North AtlanticBasin (NOAA)
American Practical Navigator (Bowditch)
Port Heavy Weather Guide
Hurricane Havens Handbook for the North Atlantic (U.S. Navy)
REFERENCES
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TROPICAL CYCLONEDEFINED!
A warm core, non-frontal,synoptic scale system withcyclonically rotating windscharacterized by a rapiddecrease in pressure andincrease in winds toward thecenter of the storm.Cyclones develop over
tropical or subtropicalwaters and have a definiteorganized circulation.
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How do they develop?
Favorable environmental conditions that must be
in place before a tropical cyclone can form:
Warm ocean waters (at least 80F / 27C).
An atmosphere which cools fast with height (potentiallyunstable).
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 andthe upper troposphere. (Vertical wind shear is the changein wind speed with height.)
Outflow aloft/exhaust
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STAGES OF
DEVELOPMENTTropical Depression(TD): A tropical cyclone with wind speeds up to 33knots. Identified by the letters TD and suffixed by a number (TD-01:the first tropical depression of the current calendar year.....TD-02, thesecond, etc...)
Tropical Storm (TS): A tropical cyclone with wind speeds 34 to 63knots. Identified by names in alphabetical order consistent with formationdate/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.
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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
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TROPICAL STORM(Immature to Mature Stage)
Winds 34 - 63 kts
Closed formation expands with spiralbands becoming better organized
Increasing sea state makes navigation
near the center increasinglydifficult and dangerous
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HURRICANE / TYPHOON / WILLY-WILLY(Mature Stage)
Winds > 63 kts
DANGEROUSLY HIGH
SEAS navigation severely impaired
Radius of strong winds may exceed 350NM
Gale Force Winds extend out further inright front quadrant (typically 120 NM)
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TROPICAL CYCLONEStages of Development
1. Tropical Easterly Wave 3. Tropical Storm
2. Tropical Depression 4. Hurricane
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Most damagingaspects of a hurricane:
AT SEA:
HIGH SEAS
HIGH WINDS
INPORT:
STORM SURGE
TORNADO/SVR TSTMSHIGH WINDS
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HURRICANE CATEGORIES
Category 1 (Minimal) - Winds 64 to 82 knots, storm surge 4 to 5 ft abovenormal. No real damage to building Structures. Low lying coastal areasflooded, minor damage to piers. Examples Irene 1999 and Allison 1995
Category 2 (Moderate) - Winds 83 to 95 knots, storm surge 6 to 8 ft abovenormal. Minor damage to structures, poorly constructed buildings majordamage. Coastal and low lying escape routes flooded over, considerable pierdamage. Examples: Bonnie 1998, Georges (FL & LA) 1998 and Gloria 1985
Category 3 (Extensive) - Winds 96 to 112 knots, storm surge 9 to 12 ft abovenormal. Major damage to structures, poorly constructed building destroyed.Serious flooding along the coast, extensive flooding may extend inland 8miles. Examples: Keith 2000, Fran 1996, Opal 1995, Alicia 1983 and Betsy1965
Saffir- Simpson Scale
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HURRICANE CATEGORIEScont.
Category 4 (Extreme)
Winds 113 to 136 knots, storm
surge 13 to 18 ft above normal.
Extensive roofing and window
damage, complete destruction ofmobile homes. Areas above 10 ft
flooded inland up to 6 miles, major
erosion of beaches, massive
evacuation of coastal areas.
(ANDREW 1992)
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Category 5 (Catastrophic)
Winds above 137 knots, storm
surge greater than 18ft above
normal. Complete failure of roof
structures and very severe windowand 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 ofthe coast.
(CAMILLE 1969)
AUG 16, 1969
HURRICANE CATEGORIES
cont.
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Richelieu Apartments
The Power of a Category 5 Hurricane Camille
The Mansion
BEFORE!AFTER!
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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 oftropical storms, and hurricanes, created in each basin.
TROPICAL CYCLONE
FORMATION,LOCATION
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Hurricane Season Atlantic
01 June - 30 November
Eastern Pacific
15 May - 30 November
Western Pacific
Year round
TROPICAL CYCLONEFORMATION CONT.
2005 ATLANTICTROPICAL CYCLONENAMES
LeeMaria
NateOpheliaPhilippeRitaStan
TammyVinceWilma
ArleneBret
CindyDennisEmilyFranklinGert
HarveyIreneJoseKatrina
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TROPICAL CYCLONECHARACTERISTICS
Feeder Bands (curvedlines of convection)spiral inward to the EyeWall. Some of the mostviolent weather(tornadoes/severethunderstorms) occur inthese areas
Pumping Actionannounces the
approach of, andpassing of the TropicalCyclone
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Clouds
Most significant clouds areheavy Cumulus andCumulonimbus
Spiral bands of CU/CB
inward toward outer edge ofeye
Cirrus changing toCirrostratus and lowering,
good indicator of approachingTC for the mariner
Cloud sequence similar to
approaching warm front
TROPICAL CYCLONE
CHARACTERISTICS, CLOUDS
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18AUG 15Z 19AUG 12Z 20AUG 12Z
970
975
990
985
980
995
1005
1000
1020
1015
1010
18Z 15Z21Z 00Z 03Z 00Z 03Z06Z 06Z09Z 15Z 18Z 21Z 09Z
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).
BAROGRAPH TRACE
Hurricane Bob 1991 Newport, RI
TROPICAL CYCLONECHARACTERISTICS, ISOBARS/PRESSURE
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Time (UTC) Task / Event
00:00Synoptic 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 preparingforecast
02:00NWS/DOD hotline coordination call
(international coordination, if necessary)
03:00 Advisory package deadline
03:15 FEMA conference call
06:00 Next cycle begins
TPC/NHC Six-hour forecast cycle
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Hurricane Isabel Track Guidance
1800 UTC 10 Sep 2003
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0
100
200
300
400
500
600
700
1954
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
2002
year
errorinn.mi
Tropical Prediction Center Performance Measuresyearly-average official track forecast errors and trend lines, Atlantic basin
120-hour
96-hour
72-hour
48-hour 24-hour
BIG IMPROVEMENTS IN TC TRACK FORECASTS OVER RECENT DECADE,ESPECIALLY BEYOND 2 DAYS
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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!
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MONITOR THE STORM
National Hurricane Center issues warnings every 6hours 0300Z, 0900Z, 1500Z, 2100Z
NAVTEX
SafetyNet
Annotated on weather facsimile charts
Private weather routing companies
E-mail List servers from the National Hurricane Center
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1-2-3 Rule
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WARNINGS
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.
24 HR FORECAST POSITION CURRENT POSITION
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WARNINGS, cont.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
24 HR FORECAST POSITION CURRENT POSITION
DANGER
AREA
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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.
Current24 Hr48 Hr72 Hr
200 NM
200 NM
300 NM
300 NMDANGERAREA
DANGER
AREA
DANGERAREA
WARNINGS, cont.
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Meteorological elements are
not uniformly distributedthroughout a tropical
Storm is divided intoleft/right semicircles and
quadrants, relative to the
direction of motion
Usually strongest winds are
on right side in N.H. (added
to motion)
TROPICAL CYCLONE
EVASION
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TROPICAL CYCLONE
EVASION cont.
Storms location relative
to own ships position:
Dangerous semi-circle:Wind greater due to wind
augmented by the forward
motion of the storm.
Less Dangerous semi-circle:
Wind decreased by forwardmotion of the storm.
Winds and seas forcevessel into path of storm.
Winds blow vessel awayfrom storm track.
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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
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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
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AHEAD OF CENTER (ON STORM TRACK)
Maneuver ship so that relative wind is 157
degrees relative, hold course and speed.
157 DEG REL
BEHIND CENTER (ON STORM TRACK)
Avoid center by best practical course (storm
may recurve).
TROPICAL CYCLONE
EVASION cont.
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DO NOT CROSS THE T unless the ship is > 300 NM ahead of thestorm and crossing right to left.
300 NM +
TROPICAL CYCLONE
EVASION cont.
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Never cross the T: Do not plan to cross the track of ahurricane.
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 youare at least 300NM from the center.
Follow the 1 2 3 Rule
TROPICAL CYCLONE
EVASION cont.
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Monitor warnings and advisories to prevent an encounter.
Forecast Track Tendencies: Comparison of the most recent NHC forecast track withforecast 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 foravoidance, particularly in the 2-3 day forecast range & beyond.
TROPICAL CYCLONE
EVASION cont.
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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.
TROPICAL CYCLONE
EVASION cont.
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IN PORT
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MONITORING THE STORM
NHC Warnings/Bulletins
Local Radio / TV stations
Port Authority / Coast Guard
Internet
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CONDITIONS OF READINESSCONDITION 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 areanticipatedwithin 24 hours.
Yankee
CONDITION 1 - Destructive force winds areanticipatedwithin 12 hours.
Zulu
These are the most common conditions of readiness.
St I t
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Stay Inport
orRide it out at Sea?
Factors to consider!The decision to leave port for hurricane avoidance must be made veryearly, 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.*
Ports Evaluated in Hurricane Havens Handbook
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11
6
2
3
4
5
7
8
21
19
20
12
119
10
14
13
17
16
1815
1 - BOSTON2 - 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 EVERGLADES13 - KEY WEST
14 - TAMPA
15 - PENSACOLA
16 - GULFPORT
17 - NEW ORLEANS
18 - PORT ARTHUR19 - GUANTANAMO BAY
20 - ROOSEVELT ROADS
21 - BERMUDA
for the North Atlantic (U.S. Navy)
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TROPICAL CYCLONEDISSIPATION
Recurvature:Tropical storm curves towards the NNE-E.
Usually accelerating and decreasing instrength, often increasing in size. Speed isdifficult to forecast.
Frictional forces of land:Often becoming extra-tropical as stormmerges with frontal zone.
Unfavorable atmospheric/oceanographicinfluences:
Includes, but not limited to, upper levelshearing, dry air intrusion in mid levels,cooler sea surface temperatures, upwelling
behind other tropical systems, etc
Floyd
Charley
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