Lesson 15B:Lesson 15B: Storm Avoidance Storm Avoidance

Lesson 15B: Storm Lesson 15B: Storm AvoidanceAvoidance

AGENDA:– Storm Avoidance– Weather Reporting– Weather Prediction

Applicable reading: Hobbs WB, App A

Storm AvoidanceStorm Avoidance1. 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 storm’s travel

Storm AvoidanceStorm Avoidance4. Cyclonic Storms - Deflected by the

corriolis effect travel in a clockwise direction (Northern Hemisphere).

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 (Navigable) Semi-circle - side that is left of storm center and

direction of path

Least DangerousSemi-circle

Most DangerousQuadrant

More DangerousSemi-circle

Northern Hemisphere

Storm AvoidanceStorm Avoidance6. Safe Passage - in the Northern Hemisphere

- Avoid crossing the “T”: avoid passing in front of a storm going from Most toLeast Dangerous semi-circle

- Most Dangerous Semi-Circle: Bring the

wind on STBD bow, hold course &make best speed.

Storm AvoidanceStorm Avoidance6. 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.

Storm AvoidanceStorm Avoidance6. Safe Passage - in the Northern Hemisphere

- On Storm Track (behind): Avoid the center by best practical course (southerly).

Ship Observation & ReportingShip Observation & ReportingWeather 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

Ship Observation & ReportingShip Observation & ReportingSynoptic - Formatted weather message:

- Every 6 hours PRIORITY if: surface wind speeds < 33 kts, seas < 12 feet.

- Every 3 hours IMMEDIATE if: surface winds > 33 kts sustained, seas > 12 feet.

- Via plain voice: first indications of a tropical cyclone, unusual or hazardous weather.

Ship Observation & ReportingShip Observation & ReportingWeather Observations - prepared by OOD:

- Type of observation

- Cloud Cover

- Prevailing visibility

- Weather & obstructions to visibility

- Sea level pressure in millibars

Ship Observation & ReportingShip Observation & ReportingWeather 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

Ship Observation & ReportingShip Observation & ReportingWeather 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

Services AvailableServices Available1. Tropical Cyclone Alert

2. High Wind and Sea Warning

3. Local Severe-Storm Warning

4. WEAX

5. OTSR - Optimum Track Ships Routing

Weather PredictionWeather Prediction

Broadcast WEAX Messages– High Seas Warnings – Offshore Marine Forecasts– Coastal Marine Forecasts– OPAREA Forecasts

OTSR (Optimum Track Ship Routing)– Tailored track recommendations

National Data Buoy Collection Center– Provides real-time conditions throughout coastal U.S.

Weather PredictionWeather Prediction

42039 PENSACOLA– 56 NM South of

Panama City, FL

Measures:– Wind direction, speed

– Wave height, period

– Atmos. Pressure

– Air/Water Temperature

– Dew Point

Weather PredictionWeather PredictionHeuristicsHeuristics

Look for changes in wind direction– Veering: clockwise movement– Backing: counter-clockwise movement

Watch 3 hour trend of barometer Note cloud type and direction Monitor dew point spread

Weather PredictionWeather PredictionHeuristicsHeuristics

Buys Ballot Law– To locate High or Low use:

Stand with your back to the wind Turn 15º to the right The LOW is on your left, the HIGH on your right

Red sky at night … sailor’s delight Red sky at morning ... sailors take warning

Review/SummaryReview/Summary

Describe the difference between the dangerous semi-circle and the navigable semi-circle.

What is OTSR used for?

Questions?Questions?