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Advanced Navigation
Weather / Storm Avoidance
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Objectives
1. Be able to describe the major differences
between warm, cold, and occluded fronts. 2. Be
able to briefly describe the different heavy
weather terms. 3. Understand when a ship is
required to submit weather synoptics and with
what periodicity.
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Objectives
4. Be able to list the basic information
included in a hourly observation. 5. Be able to
define the different weather services available
to the ships nav team. 6. Be able to determine
the most dangerous and least dangerous
(navigable) semicircles associated with a
tropical storm.
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Objectives
7. Be able to draw the different safe
maneuvering techniques in relation to a tropical
storm.
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Warm Fronts
Active Warm Fronts are generally located in
pressure troughs. Other identifiers 1.
Pressure - Pressure usually falls for an
appreciable length of time before the front
passes. 2. Wind - Wind, usually from the
southeast in the northern hemisphere, increases
as the front approaches.
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Warm Fronts
3. Clouds - Nearly always well defined by
stratified clouds, generally cirrus, cirro-
stratus, altostratus, nimbostratus, and
stratus, with cirrus appearing as much as 1000
miles before the surface passage. 4.
Precipitation - Extends about 300 miles in front
of the surface front in the form of
intermittent rain, snow, drizzle.
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Warm Fronts
5. Temps Dew Point - Temp change is gradual.
Dew Point normally observed to rise as the
front approaches, and to further increase as the
frontal passage if the air in the warm sector is
of maritime origin. 6. Visibility Ceiling -
Visibility ceiling are normally good until the
precipitation begins, then they decrease rapidly.
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WARM FRONT STABLE CONDITIONS
30,000
CI
Stable warm air
CS
20,000
AS
AS
NS
10,000
ST
SC
FOG RAIN AND LOW NIMBUSTRATUS
400
500
200
100
0
300
200
100
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CB
30,000
CI
CS
Unstable warm air
20,000
WARM FRONT UNSTABLE CONDITIONS
AS
AS
NS
10,000
ST
SHOWERS
LIGTH RAIN AND SHOWERS
400
500
200
100
0
300
200
100
600
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CB
30,000
CI
CS
Unstable warm air
20,000
WARM FRONT UNSTABLE CONDITIONS
AS
AS
NS
10,000
ST
SHOWERS
LIGTH RAIN AND SHOWERS
400
500
200
100
0
300
200
100
600
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Cold Fronts
Cold Fronts are generally located in well-defined
pressure troughs whenever there is a marked
contrast between two air masses. Other
identifiers 1. Pressure - The pressure
characteristic is usually indicated by steady
or unsteady fall. 2. Wind - Usually from the
south or southwest in the northern hemisphere,
veering to parallel the front.
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Cold Fronts
3. Clouds - Typical of warm air towering
cumulus, cumulonimbus, stratocumulus, and
nimbostratus. 4. Precipitation - Showers and
thunderstorms occur as the cold front passes.
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Cold Fronts
5. Temps Dew Point - Temp is relatively high
before passage, dropping as the front passes.
Dew Point is observed to drop, especially in
mountainous regions. 6. Visibility Ceiling -
Visibility ceiling decrease and remain low
after the passage until well within the cold air.
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CIRRUS
CIRROSTRATUS
POSIBLE CUMULONIMBUS
15,000
ALTOCUMULUS
10,000
0º
NIMBOSTRATUS
5,000
CUMULUS
STRATOS
STRATOCUMULUS
200
MILES
100
0
100
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CIRRUS
FAST MOVING COLD FRONT
CIRROSTRATUS
15,000
ALTOCUMULUS
NIMBOSTRATUS
10,000
CUMULONIMBUS
0º
5,000
STRATOCUMULUS
200
MILES
100
0
100
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CIRRUS
FAST MOVING COLD FRONT
CIRROSTRATUS
15,000
ALTOCUMULUS
NIMBOSTRATUS
10,000
CUMULONIMBUS
0º
5,000
STRATOCUMULUS
200
MILES
100
0
100
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Occluded Fronts
1. Cold Occlusion - Warm air is lifted, all
clouds associated with a warm front are found
producing typical prefrontal precipitation with
cold front weather in the vicinity of the
surface. 2. Warm Occlusion - similar weather to
Cold Occluded with high level thunderstorms and
a wider weather band.
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WARM AIR
WARM FRONT SURFACE
COLDER AIR
COLD AIR
COLD TYPE OCCLUSION
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WARM AIR
WARM FRONT SURFACE
COLD AIR
COLDER AIR
WARM TYPE OCCLUSION
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Heavy Weather
1. Closed Cyclonic - Rotary circulation
storms. 2. Noncyclonic - Storms produced by
prevailing winds are identified by their
accompanying winds - predictable.
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Closed Cyclonic
1. Tornadoes - Violent, whirling storm of small
diameter that travels across land. Appear as
funnel shaped cloud, with a vortex that may or
may not touch the earth. Winds blow spirally
upwards from 150 - 300 mph. 2. Waterspouts -
Similar to tornadoes, occuring over oceans or
inland waters. Usually less destructive than
tornadoes.
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Closed Cyclonic
3. Squall - A wind of considerable intensity
caused by atmospheric instability. Comes up
dies quickly, sometimes accompanied by thunder,
lightning and precipitation. 4. Monsoons -
Steady winds somewhat similar to trade winds.
Can reach moderate gale proportions and are
accompanied by heavy squalls and thunderstorms
during the summer.
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Closed Cyclonic
5. Hurricanes - Tropical storm with continuous
winds greater than 63 mph. 6. Tropical Storms
- Categorized based on wind speed
- Tropical
Depression lt 34 kts -
Tropical Storm 34 - 63 kts
- Hurricane gt 63 kts
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Noncyclonic
ie gale - with winds from 34 - 47 mph
storm - with winds of 48 mph or greater.
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Northern Hemisphere
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Direction of travel - Hurricane Bonnie
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Ship Observation Reporting
Weather Observations - Ships are required to
take regular weather observations -
Observations taken hourly iaw
NAVOCEANINST. - Ships in company, OTC may
designate one ship to report
observations - In port with no manned weather
facility within 50NM
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Ship Observation Reporting
Synoptic - Formatted weather message - Every
6 hours PRIORITY if surface wind speeds lt
33 kts, seas lt 12 feet. - Every 3 hours
IMMEDIATE if surface winds gt 33 kts
sustained, seas gt 12 feet. - Via plain voice
first indications of a tropical cyclone,
unusual or hazardous weather.
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Ship Observation Reporting
Weather Observations - prepared by OOD - Type
of observation - Cloud Cover - Prevailing
visibility - Weather obstructions to
visibility - Sea level pressure in millibars
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Ship Observation Reporting
Weather Observations - prepared by OOD
(cont.) - Dry bulb temp in degrees
fahrenheit - Dew point temp in degrees
fahrenheit - True wind direction speed -
Altimeter setting (if aircraft embarked) -
Remarks
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Ship Observation Reporting
Weather Observations - prepared by OOD
(cont.) - Station pressure in inches of
mercury - Sea water temp (at sea water
injection) - Sea height, direction and
period - Ice (if applicable) - Clouds by
type, quantity, height
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Services Available
1. Wind Warnings 2. High-Sea Warning 3. Local
Severe-Storm Warning 4. WEAX 5. OTSR - Optimum
Track Ships Routing
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Storm Avoidance
1. Hurricane Season - June through November 2.
Procedure - Safest with respect to tropical
cyclones is avoidance. 3. Key Elements to
Determine - Position relative to storm center
axis - Path velocity of storms travel
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Storm Avoidance
4. Cyclonic Storms - Deflected by the
corriolis effect travel in a clockwise
direction. 5. Storm Division - Storm is
divided into 2 parts - Most Dangerous
Semi-circle - side that is right of storm
center and direction of path - Least Dangerous
Semi-circle - side that is left of storm center
and direction of path
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Storm Avoidance
6. Safe Passage - in the Northern Hemisphere -
Avoid crossing the T avoid passing in front
of a storm going from Most to Least Dangerous
semi-circle - Most Dangerous Semi-Circle
Bring the wind on STBD bow, hold course
make best speed.
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Storm Avoidance
6. Safe Passage - in the Northern Hemisphere -
Least Dangerous Semi-Circle Bring the wind on
STBD qtr, hold course make best speed. -
On Storm Track (ahead) Bring the wind to 160
deg R until a backing is noted in the wind
(indicating you are in the Least Dangerous
Semi-circle), then bring the wind on STBD
quarter, hold course make best speed.
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Storm Avoidance
6. Safe Passage - in the Northern Hemisphere -
On Storm Track (behind) Avoid the center by
best practical course (southerly).
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Questions?
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Compliments of Curtis Senior High School NJROTC