Voluntary Observing Ship (VOS) Program

John WassermanVOS Operations ManagerStennis Space Center, MS

The VOS ProgramThe mission of the VOS is two-fold:

(1) to collect and disseminate critical real-time maritime weather observations through the recruitment and support of ships to fulfill National needs and International agreements supporting commerce, forecasts and warning programs, and the Safety Of Life At Sea (SOLAS) worldwide, and

(2) to define the global climate and help measure extreme weather events, climate variability, and long-term climate changes.

Port Meteorological Officers (PMO)

Recruit, support and provide training for crewmembers of ships that participate in VOS program as part of the U.S. commitment to SOLAS

Check and calibrate barometers Provide equipment to selected vessels on a case by case basis Perform Quality Control of observations

PMO Locations

Oceanic Weather Data Sources

Strengths and Weaknesses

VOS Observations: Strengths and WeaknessesVOS Observations: Strengths and Weaknesses

• Quantity of observations (~ 3000 ships worldwide).• Provide information over the open oceans.• Accuracy (calibration and reporting errors).• Timeliness.• Sea heights estimated but not directly measured.• Ships tend to avoid high wind/wave areas. • Data void areas (Data gaps).

• Quantity of observations (~ 3000 ships worldwide).• Provide information over the open oceans.• Accuracy (calibration and reporting errors).• Timeliness.• Sea heights estimated but not directly measured.• Ships tend to avoid high wind/wave areas. • Data void areas (Data gaps).

Data gapsData gapsLife Without VOS DataLife Without VOS Data

Buoy/C-Man Observations: Strengths and Weaknesses

Buoy/C-Man Observations: Strengths and Weaknesses

• Provide information for heavily traveled coastal areas.• Accuracy.• Timeliness (update every half hour).• Sea heights directly measured.• Sea heights/temp not available on all platforms.• Sensitive instrument packages susceptible to failure in harsh marine environment. • Mooring failures.

• Provide information for heavily traveled coastal areas.• Accuracy.• Timeliness (update every half hour).• Sea heights directly measured.• Sea heights/temp not available on all platforms.• Sensitive instrument packages susceptible to failure in harsh marine environment. • Mooring failures.

Quikscat: Strengths and Weaknesses

Quikscat: Strengths and Weaknesses

• Estimation of both wind speed and wind direction.• Wind estimation at night and in cloudy regions.• Near global wind coverage (~ 90% daily coverage).

• Timeliness (~2-3 hr data lag).• Data available at most 2 times/day at any given location.• Limitations (directional ambiguity, rain contamination,

swath edge, noise at low wind speed, near land). • Gaps between swaths (largest over the tropical regions).• Satellite can repeatedly miss a system of interest.

• Estimation of both wind speed and wind direction.• Wind estimation at night and in cloudy regions.• Near global wind coverage (~ 90% daily coverage).

• Timeliness (~2-3 hr data lag).• Data available at most 2 times/day at any given location.• Limitations (directional ambiguity, rain contamination,

swath edge, noise at low wind speed, near land). • Gaps between swaths (largest over the tropical regions).• Satellite can repeatedly miss a system of interest.

Data gaps between swaths largest over the tropics

Satellite-Derived Winds: Strengths and Weaknesses

Satellite-Derived Winds: Strengths and Weaknesses

• Continuous global coverage. • No swath edge issues.• Estimates wind speed and direction.• Winds must be adjusted to surface. • Cannot see through areas of high clouds.• Limited data in areas void of low clouds

(tracking elements).• Has limited application for evaluating

small-scale features.

• Continuous global coverage. • No swath edge issues.• Estimates wind speed and direction.• Winds must be adjusted to surface. • Cannot see through areas of high clouds.• Limited data in areas void of low clouds

(tracking elements).• Has limited application for evaluating

small-scale features.

Satellite Data

C-Man/BuoysModel Data

Ship Data

Bringing It Altogether! Making a Forecast

Bringing It Altogether! Making a Forecast

Marine Forecasting

Marine Forecasting

How the Mariner can help?– Take and transmit weather

observations

How does the forecaster use the observation?

– Looks for observations that tell the Meteorologist his current forecast is inaccurate.

– Looks for observations containing information about the location of fronts, dense fog or other hazards important to the Marine community.

WEATHER WEATHER BASICSBASICS

Pressure System Circulation

Pressure System Circulation

*Note: Wind flow opposite in Southern Hemisphere*

LOW PRESSURE:

COUNTER-CLOCKWISE

WINDS

HIGH PRESSURE:

CLOCKWISE

WINDS

Pressure Gradient = Wind!Pressure Gradient = Wind!

• The dominant cause of movement of air (in near horizontal conditions) is the pressure gradient. – When a high is next to a low

and the spacing of isobars (lines of equal pressure) of different values is fairly wide, the pressure gradient is small, and the corresponding winds speeds are slow.

– When the isobars are close-spaced you will have higher pressure gradient and faster wind flow.

SYSTEMS MOVE FROM WEST TOEAST IN BOTH HEMISPHERES

Isobars & Wind Flow

(isobars)

InteractingAir Masses

COOLCOLD

WARM

Pressure Systems & FrontsPressure Systems & Fronts

H LOCCLUDED

FRONT

WARMFRONT

COLDFRONT

FrontalTerminology

10

“Low”“High”

(Speed &Direction)

(CentralPressure)

1015

SHIP OBSERVATIONSFor every 1000 land observations, there is 1 marine observation. On a good day at 1200Z there are 500 to 800 marine observations world wide, including buoys. However the majority of ship observations are within established sea routes, leaving large gaps.

THE IMPORTANCE OF SHIP OBSERVATIONS CAN NOT BE

OVERSTATED!!!

Data gapsData gapsLife Without VOS

Data

Life Without VOS Data

SHIP OBSERVATIONS

NOAA and WMO request ships to take and transmit observations every 6 hours at 0000Z, 0600Z, 1200Z and 1800Z. These are the main synoptic times upon which most forecasts are based.

The 0000Z and 1200Z observations are the most important. These times correspond to the main global numerical weather models runs.

Intermediate observations are taken at 0300Z, 0900Z, 1500Z and 2100Z. These obs are used to run regional scale models and to aid with the initialization for the main global runs.

SHIP OBSERVATIONS

Intermediate observations are requested when a ship is:

- within 300 NM of a named tropical system- experiencing storm force winds (48 – 63 kts)- experiencing seas 12 ft or greater

You can take and transmit an observation whenever you feel conditions warrant.

- Alert Forecaster- Alert other ships in the vicinity- Safety consideration

ALL OBSERVATIONS ARE USED!

EQUIPMENT1. Precision aneroid barometer or marine

mercury barometer

2. Dry and Wet-bulb thermometers (sling psychrometer or housed in an outdoor vented shelter)

3. Sea water temperature thermometers. Intake or hull mounted sensor, or sea water bucket type thermometer.

4. Wind anemometer. (Alternative is to estimate wind speed using the beaufort scale.)

For “selected ships” participating in the VOS program, PMOs may supply a marine aneroid barometer, marine barograph, thermometers and vented shelter. * All VOS ships will have their barometer frequently calibrated by a PMO.*

ELEMENTS TO BE OBSERVED!

1. Atmospheric pressure, tendency and characteristic2. Wind speed and direction (True) 3. Air and wet-bulb temperature and dew point4. Visibility5. Cloud heights, amounts and type6. Past and present weather7. Ship course and speed8. Sea surface temperature9. Sea waves and swell – period, direction and height10. Ice conditions, including icing on board ship.

BBXX D.....D YYGGiw 99LaLaLa QcLoLoLoLo iRixhVV Nddff00fff 1snTTT 2snTdTdTd 4PPPP 5appp 7wwW1W2 8NhCLCMCH222Dsvs 0ssTwTwTw 2PwPwHwHw 3dw1dw1dw2dw2 4Pw1Pw1Hw1Hw15Pw2Pw2Hw2Hw2 6IsEsEsRs 8swTbTbTb ICE ciSibiDizi

SHIP SYNOPTIC CODEWorld Meteorological Organization Code FM 13-X

Section 0 “Identification Data” BBXX D.....D YYGGiw 99LaLaLa QcLoLoLoLoSection 1 “Meteorological Data” iRixhVV Nddff 00fff 1snTTT 2snTdTdTd 4PPPP 5appp 7wwW1W2 8NhCLCMCH Section 2 “Supplementary Data” 222Dsvs 0ssTwTwTw 2PwPwHwHw 3dw1dw1dw2dw2 4Pw1Pw1Hw1Hw1 5Pw2Pw2Hw2Hw2 6IsEsEsRs 8swTbTbTb ICE ciSibiDizi

Within NOAA there are two different means to take and record marine observations:

1. WS Form B-81 SHIP’S WEATHER OBSERVATIONS Paper form

2. AMVER/SEAS Software

VISIBILITY

Report Prevailing visibility – The greatest distance that objects can been seen throughout at least ½ of the horizon circle. If visibility is uniform in all directions, use maximum distance.

If visibility is not uniform, determine prevailing visibility by choosing the two highest sectors ( 5 & 2 ½). Then choose the lower of the two values for prevailing visibility ( 2 ½). Four Sectors Visibility (NM) Approx Degrees 5 90 2 ½ 90 --------------------- 180 2 90 1 ½ 90

5 2

1 ½ 2 ½

WIND SPEED & DIRECTION

Report only “TRUE” wind

Average mean speed and direction over a ten minute period.

dd Direction in tens of degrees enter 36 for 360 degrees (North) enter 00 for calm winds enter 99 for variable winds

ff Speed in knots, measured or estimated as indicated by iw (98 knots or less). To determine use only (1) Estimated - appearance of the sea state (Beaufort Scale) (2) Measured - ships anemometer

For winds over 99 kts, code as 99 and report wind speed using the group 00fff.

AIR TEMPERATURE

Sn Sign of Air Temperature indicator

positive or negative

0 - Temperature is positive or zero 1 - Temperature is negative

TTT Dry Bulb temperature. Enter degrees and tenths in Celsius Examples: 12.1o C = 121 Sign is 0 4.20 C = 042 Sign is 0 0.80 C = 008 Sign is 0 -0.80 C = 008 Sign is 1 -6.20 C = 062 Sign is 1

Take reading from windward side of the ship.

DEW POINT TEMPERATURE

SN Sign of dew point temperature indicator

positive or negative

0 - Temperature is positive or zero 1 - Temperature is negative

TdTd/ Dew Point temperature. Enter whole degrees in

Celsius followed by a slash ( / ) Examples: 12oC = 12/ Sign is 0 40C = 04/ Sign is 0 -80C = 08/ Sign is 1

-180C = 18/ Sign is 1

Take wet bulb reading immediately after reading the dry bulb temperature. The wet bulb temperature will ALWAYS be lower than the dry bulb temperature.

DEW POINT CALCULATION

- Subtract wet-bulb temperature from dry-bulb temperature to get “wet-bulb depression.”

- Locate depression across top of table and nearest wet-bulb temperature down the side.

- Read encoded dew point at intersection of wet-bulb temperature row and depression column.

The dew point temperature, TdTd, should always be less than the air temperature TTT.

Example: Dry Bulb reading 25.5 Wet Bulb reading 19.5 Wet Bulb depression 4.0

Dew Point is 17 encode as 17/

SEA LEVEL PRESSURE

PPPP Atmospheric pressure at mean sea level, in tenths of a hectopascal (millibar), omitting the thousands digit. It represents the weight or force exerted by the air above a given point.

Enter millibars in tenths. When the pressure is 1000.0 mbs or greater, 1 is omitted.

Pressure is the last element you should take before encoding the observation.

Marine Aneroid barometers should be checked and calibrated every three months.

Example: 1012.5 mbs encode as 0125 997.5 mbs encode as 9975

3-HOUR PRESSURE CHANGE (Tendency)

a the characteristic of pressure tendency during the 3 hours preceding the time of observation. It describes how pressure has varied, e.g. increasing then decreasing, decreasing then increasing, decreasing then steady, etc.

The barograph provides the best indication of the pressure tendency characteristic. Look at the barograph trace in the three hour period preceding the time of observation. The shape of the trace determines which code figure to use.

If the ship does not have a barograph, encode 2 if pressure is higher over the past three hours, encode 7 if lower, and 4 if it is the same.

3-HOUR PRESSUE CHANGE

(Amount)

ppp the amount of pressure change in tenths of millibars

Example: 1500Z 1800Z Change Encode

1025.5 1022.0 3.5 mbs 035

998.0 989.0 9.0 mbs 090

PRESENT WEATHER

ww present weather refers to atmospheric phenomenaoccurring at the time of observation, or which has occurred during the hour preceding the time of observation.

Precipitation, obstructions to visibility, thunder, squalls, haze, dust, smoke, and cloud development.

Report the most severe weather condition that you observe, reading down the list from 99 (most severe) to 00 (least severe).

59 - 99 PRECIPITATION AT SHIP AT TIME OF OBSERVATION

00 - 49 NO PRECIPITATION AT SHIP AT TIME OF OBSERVATION

Present weather is broken down into two categories

PAST WEATHER

Mean synoptic times 00Z 06Z 12Z 18Z use past 6 hours

Intermediate synoptic times 03Z 09Z 15Z 21Z use past 3 hours If the past weather has been continuous and unchanging since the last main synoptic hour, W1 and W2 are coded the same. W1 is always greater than or equal to W2.

W1 Highest priority W2 Second highest priority

CLOUDS

Nh Amount of all the CL cloud present or, if no low

clouds present, the amount of all the mid cloud present. Encode amount in eights Encode 9 when sky is obscured

CL Type of low cloud present ST, NS, SC, CU, TCU, CB

CM Type of mid cloud present AS, AC

Ch Type of high cloud present CI, CS, CC

Use the NOAA cloud poster, cloud brochure, or other suitable cloud atlas which relate cloud photographs to cloud definitions and descriptions

Encode each individual layer. Codes are in priority order.

---------------------------------------------------------------------------------------------------------Range Polar Temperate Tropical------------------------------------------------------------------------------------------------High 10,000 to 25,000 ft 16,500 to 45,000 ft 20,000 to 60,000 ft

Middle 6,500 to 13,000 ft 6,500 to 23,000 ft 6,500 to 25,000 ft

Low Surface to 6,500 ft Surface to 6,500 ft Surface to 6,500 ft

APPROXIMATE CLOUD HEIGHTS

LOW CLOUDS If more than one type of CL is present, the order of priority for reporting (from highest to lowest priority) is CL = 9, 3, 4, 8, 2.

These are followed in priority by CL = 1, 5, 6, 7, all of equal priority. If two or more of this second category are present, report the type which covers the greatest part of the sky.

MID CLOUDS If more than one code figure for CM is applicable at the same time, the priority order is CM = 9,8,7,6,5,4,3,2,1,/

HIGH CLOUDS If more than one code figure for CH is applicable at the same time, the priority order is CH = 9,7,8,6,5,4,3,1,2,/

Hints for cumulus-type clouds

• Low cumulus cloud cells (the individual puffs of cloud) are about the size of your fist or larger, when you hold up your hand at arms' length.

• When cumulus clouds are just forming or evaporating, they can look considerably different from those that are fully-formed. Do not be fooled! Sometimes you can tell that the clouds are forming or evaporating if there is strong wind and both new and fully-formed clouds are moving along in the same layer. Other times you may have to look for other clues.

• Mid-level cumulus cloud cells (altocumulus) are about the size of your thumbnail when you hold your hand at arm's length. (Note that in the picture the clouds look larger then a thumb. This is because the photo was taken from behind, considerably more than an arm's length from the thumb.)

• High-level cumulus cloud cells (cirrocumulus) are about the size of the nail on your littlest finger - again, at arm's length.

Unless you live next to a tall skyscraper or a mountain, it is not possible to figure out the height of a cloud just by looking. This is because there are no points of reference in the sky. That's why our determination of height relies on identifying the cloud type.

Without the size clues provided by individual cumulus clouds, determining the height of stratus-type clouds can be a challenge. Some hints for stratus-type clouds:

• If it rained recently or is about to rain, you are most likely dealing with a low level stratus cloud. While it is possible for rain to fall from mid-level clouds, it is quite rare. • If it is raining during your observation, you have nimbostratus (or cumulonimbus - but the difference should be obvious! The latter is a thunderstorm).

• The terms nimbo/nimbus are from a Latin word for rain. • If a stratus cloud is so thick you can't even figure out where the sun is, most likely it is a low level stratus.

• If you can see the sun but it looks diffused (like looking through a glass bottle), most likely you have altostratus.

• High-level cirrostratus will generally be thin enough that the sun is still quite distinct. If the cirrostratus is not between you and the sun, you may be able to distinguish cirrostratus as being so thin that parts of the cloud appear bluish (that is, you are seeing through to blue sky).

The most important thing is to pick a cloud type at the right level. Satellite instruments cannot distinguish cumulus from stratus from stratocumulus. All of them will be identified as low level water clouds.

When determining cloud fraction, consider the whole sky that you can see; not just the portion of sky right above you. If you are in an area where your view is partially blocked by masts or stacks, this is OK. Just find a safe area where you can see as much of the sky as possible, and then report from that spot.

Mentally divide the sky in half (4/8) and imagine all the low or middle clouds in the right half pushed together toward the horizon. Do the same for the left side. Add the halves together to get the best estimate of total coverage!

Cloud estimation tips courtesy of “Lin's Tips for S'COOL Observers” http://asd-www.larc.nasa.gov/SCOOL/lintips.html

Cl or Cm Sky Cover (in eighths)

SHIPS COURSE AND SPEED

Ds course made good during the past 3 hours.

Vs ships average speed made good during the

past 3 hours.

Code True Direction 0 Ship hove to 1 NE 2 E 3 SE 4 S 5 SW 6 W 7 NW 8 N 9 Unknown / Not reported

Code True Direction 0 0 knot 1 1 to 5 knots 2 6 to 10 knots 3 11 to 15 knots 4 16 to 20 knots 5 21 to 25 knots 6 26 to 30 knots 7 31 to 35 knots 8 36 to 40 knots 9 Over 40 knots / Not reported

SEA SURFACE TEMPERATURE

ss sign of the sea surface temperature (SST), and

indicates how the SST was measured.

TWTWTW enter degrees and tenths in Celsius

Methods: Engine room intake thermometer, hull mounted contact sensor thermometer, or bucket thermometer.

Example: Intake temp 23.5o C encode 0235 Bucket temp -0.7o C encode 3007

Code 0 positive or zero intake measurement 1 negative intake measurement 2 positive or zero bucket measurement 3 negative bucket measurement 4 positive or zero hull contact sensor 5 negative hull contact sensor 6 positive or zero neither intake, bucket or hull 7 negative neither intake, bucket or hull

SEA WAVES / Wind Waves

PwPw period of wind waves in seconds.

Wave period is the time between the passage of two successive wave crests (or successive troughs) past a fixed point.

Coded directly in seconds. If the sea wave period is 8 encode as 08.

SEA WAVES / Wind Waves

HWHW Height between trough and crest for

wind waves in units of 0.5 meter.

Consider only the larger well-formed waves nearthe center of the wave group. Estimate the average height of these larger waves, and disregard the lesser waves.

There is a tendency to underestimate wave height if you are fifty feet or more above the sea surface. Your visual estimate may be more accurate from a lower deck.

Code for Height of Waves (HWHW)

PREDOMINENT / PRIMARY “SWELL” DIRECTION

dw1dw1 True direction, in tens of degrees, from which

primary swell waves are coming.

Use swell wave height to distinguish primary from secondary swell. The primary swell system is the one having the larger swell waves.

Swells are waves that have been generated by wind in other areas. Some swell waves travel over 3000 nm.

If there is no swell, or if the swell cannot be distinguished, you can either:

omit the swell groups (3dW1dW1dW2dW2, 4PW1PW1HW1HW1, 5PW2PW2HW2HW2)

or encode as 3//// 4//// 5////

SECONDARY SWELL DIRECTION

dw2dw2 True direction, in tens of degrees,

from which the secondary swell waves are coming.

The secondary swell system has smaller waves than the primary swell, and usually comes from a different direction.

If only one swell system is observed, use slants (//) for the secondary swell.

Example: 327//

PRIMARY SWELL PERIOD

PW1PW1 Period of primary swell waves, in seconds.

Coded directly in seconds.

Period is the time it takes two successive swell wave crests to pass a fixed point. Same as for wind wave period.

Record the average period for several of the larger, well formed swell waves.

PRIMARY SWELL HEIGHT

HW1HW1 Height of primary swell wave.

Coded in half-meters.

Swell wave height is the vertical distance between trough and crest.

The primary swell system will have larger waves than the secondary swell.

When determining swell wave characteristics, direction, period and height, always select the larger, well formed swell waves of the wave system being observed. These are referred to as the “significant” swell waves.

SECONDARY SWELL PERIOD

PW2PW2 Period of primary swell waves,

in seconds. Coded directly in seconds.

Period is the time it takes two successive swell wave crests to pass a fixed point. Same as wind wave period.

Record the average period for several of the larger, well formed swell waves.

Usually the secondary swell period will be longer than the primary swell period.

SECONDARY SWELL HEIGHT

HW2HW2 Height of secondary swell wave.

Coded in half-meters.

Swell wave height is the vertical distance between trough and crest.

The secondary swell system has lower waves than the primary swell.

When determining swell wave characteristics, direction, period and height, always select the larger, well formed swell waves of the wave system being observed. These are referred to as the “significant” swell waves.

ICE ACCRETIONIs Cause of ice accretion on ship.

Ice accretion refers to a deposition of a coating of ice on the ships superstructure or exposed surfaces, from freezing precipitation, ocean spray, super cooled fog, or cloud droplets.

An accumulation of ice can cause radio or radar failures, due to the icing of aerials. Ice can also cause difficulty in unloading cargo in port if containers and their lashings are frozen to the deck.

Significant ice accretion can adversely affect the weight and stability of a vessel.

By reporting this information, you alert the forecasters to this condition, enabling them to broadcast reliable warnings when a danger is foreseen.

Ice Accretion Code 1 Icing from ocean spray 2 Icing from fog 3 Icing from spray and fog 4 Icing from rain 5 Icing from spray and rain

WET BULB

SW Indicates how the wet bulb temperature was

determined, either a hand-held sling or an outdoor unit housed in a shelter.

TbTbTb Wet bulb temperature in degrees and

tenths Celsius.

Code 0 Positive or zero measured 1 Negative measured 2 Iced bulb measured 3-4 Not used 5 Positive or zero computed 6 Negative computed 7 Iced bulb computed

ICE

Choose the coding which describes the condition which is of the most navigational significance.

THE END

“except”

Marine Observation #1

Date/Time 19 May 1200ZPosition 25.5N 095.1WShip KWVAPressure 1024.5 mbs3 Hr Pressure Change .05 mbs RisingTrue Winds 250 at 20 ktsDry Bulb 27.5o CWet Bulb 20.0o CIntake Temp 26.0o CLow Clouds Stratocumulus 2 eights 2000 ftMid Clouds Altocumulus 2 eights 9000 ftHigh Clouds Cirrus 3 eights 18000 ftVisibility 5 nmPresent Weather Light Rain ShowersPast Weather Rain ShowersWind Wave 5 ft 3 second periodPrimary Swell 300 3 ft 5 second periodSecondary Swell 010 2 ft 10 second periodShip Course/Speed 045 at 16 kts

BBXX KWVA 19124 99255 70950 41597 72520 10275 20161 40245 52000 78088 82563 22214 00260 20303 33001 40502 51001 6//// 80200 ICE /////=

1200Z 19 May

Marine Observation # 1