Presentation on theme: "Voluntary Observing Ship (VOS) Program John Wasserman VOS Operations Manager Stennis Space Center, MS."— Presentation transcript:
Voluntary Observing Ship (VOS) Program John Wasserman VOS Operations Manager Stennis Space Center, MS
The VOS Program The 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
Oceanic Weather Data Sources Strengths and Weaknesses
VOS Observations: Strengths and Weaknesses VOS 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 gaps Life 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/Buoys Model Data Ship Data Bringing It Altogether! Making a Forecast Bringing It Altogether! Making a Forecast
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.
Pressure System Circulation *Note: Wind flow opposite in Southern Hemisphere* LOW PRESSURE: COUNTER-CLOCKWISE WINDS HIGH PRESSURE: CLOCKWISE WINDS
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 TO EAST IN BOTH HEMISPHERES Isobars & Wind Flow (isobars) Interacting Air Masses COOL COLD WARM Pressure Systems & Fronts H L OCCLUDED FRONT WARM FRONT COLD FRONT Frontal Terminology 10 “Low” “High” (Speed & Direction) (Central Pressure) 1015
SHIP OBSERVATIONS For 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 gaps 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!
EQUIPMENT 1.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 characteristic 2. Wind speed and direction (True) 3. Air and wet-bulb temperature and dew point 4. Visibility 5. Cloud heights, amounts and type 6. Past and present weather 7. Ship course and speed 8. Sea surface temperature 9. Sea waves and swell – period, direction and height 10. Ice conditions, including icing on board ship.
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 ½ ½ ½2 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 i w (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 S n 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: 12.1 o C = 121 Sign is C = 042 Sign is C = 008 Sign is C = 008 Sign is C = 062 Sign is 1 Take reading from windward side of the ship.
DEW POINT TEMPERATURE S N Sign of dew point temperature indicator positive or negative 0 - Temperature is positive or zero 1 - Temperature is negative T d T d / Dew Point temperature. Enter whole degrees in Celsius followed by a slash ( / ) Examples: 12 o C = 12/ Sign is C = 04/ Sign is C = 08/ Sign is C = 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, T d T d, 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 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: mbs encode as 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 mbs mbs 090
PRESENT WEATHER ww present weather refers to atmospheric phenomena occurring 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) PRECIPITATION AT SHIP AT TIME OF OBSERVATION 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, W 1 and W 2 are coded the same. W 1 is always greater than or equal to W 2. W 1 Highest priority W 2 Second highest priority
CLOUDS N h Amount of all the C L 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 C L Type of low cloud present ST, NS, SC, CU, TCU, CB C M Type of mid cloud present AS, AC C h 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 C L is present, the order of priority for reporting (from highest to lowest priority) is C L = 9, 3, 4, 8, 2. These are followed in priority by C L = 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 C M is applicable at the same time, the priority order is C M = 9,8,7,6,5,4,3,2,1,/ HIGH CLOUDS If more than one code figure for C H is applicable at the same time, the priority order is C H = 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” C l or C m Sky Cover (in eighths)
SHIPS COURSE AND SPEED D s course made good during the past 3 hours. V s 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 s s sign of the sea surface temperature (SST), and indicates how the SST was measured. T W T W T W enter degrees and tenths in Celsius Methods: Engine room intake thermometer, hull mounted contact sensor thermometer, or bucket thermometer. Example: Intake temp 23.5 o C encode 0235 Bucket temp -0.7 o 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 P w P w 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 H W H W Height between trough and crest for wind waves in units of 0.5 meter. Consider only the larger well-formed waves near the 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 (H W H W )
PREDOMINENT / PRIMARY “SWELL” DIRECTION d w1 d w1 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 (3d W1 d W1 d W2 d W2, 4P W1 P W1 H W1 H W1, 5P W2 P W2 H W2 H W2 ) or encode as 3//// 4//// 5////
SECONDARY SWELL DIRECTION d w2 d w2 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 P W1 P W1 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 H W1 H W1 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 P W2 P W2 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 H W2 H W2 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 ACCRETION I s 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 S W Indicates how the wet bulb temperature was determined, either a hand-held sling or an outdoor unit housed in a shelter. T b T b T b 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/Time19 May 1200Z Position25.5N 095.1W ShipKWVA Pressure mbs 3 Hr Pressure Change.05 mbs Rising True Winds250 at 20 kts Dry Bulb27.5 o C Wet Bulb20.0 o C Intake Temp26.0 o C Low CloudsStratocumulus 2 eights 2000 ft Mid CloudsAltocumulus 2 eights 9000 ft High CloudsCirrus 3 eights ft Visibility5 nm Present WeatherLight Rain Showers Past WeatherRain Showers Wind Wave5 ft 3 second period Primary Swell300 3 ft 5 second period Secondary Swell010 2 ft 10 second period Ship Course/Speed045 at 16 kts
Marine Observation #2 Date/Time20 June 2355Z Position50.6N 165.0E ShipKWVA Pressure998.5 mbs 3 Hr Pressure Change1.5 mbs Falling True Winds320 at 35 kts Dry Bulb15.5 o C Wet Bulb12.8o C Intake Temp19.0o C Low CloudsCumulonimbus 6 eights 1000 ft Mid CloudsAltocumulus 2 eights 8500 ft High CloudsCirrus 2 eights ft Visibility1 nm Present WeatherHeavy Rain Showers / Thunderstorm Past WeatherRain Showers Wind Wave10 ft 4 second period Primary Swell270 5 ft 6 second period Secondary SwellNone Ship Course/Speed230 at 15 kts