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Lab 2: METAR Decoding and Station Observations

Lab 2: METAR Decoding and Station Observations. Weather Forecasting Handbook Ch . 3. Station Plot Format. PPP = sea-level pressure pp = pressure tendency over the past 3 hours a = overall pressure tendency RR = precipitation TdTd = dewpoint temperature VV = visibility in miles

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Lab 2: METAR Decoding and Station Observations

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  1. Lab 2: METAR Decoding and Station Observations Weather Forecasting Handbook Ch. 3

  2. Station Plot Format • PPP = sea-level pressure • pp = pressure tendency over the past 3 hours • a = overall pressure tendency • RR = precipitation • TdTd = dewpoint temperature • VV = visibility in miles • ww = current weather • TT = temperature • dd = wind direction • ff = wind speed • N = cloud cover

  3. Station Plot – Temperature and Dewpoint Temperature • The temperature (measured in degrees Fahrenheit) is at the upper left side of the station’s circle. • Dewpointtemperature (measured in degrees Fahrenheit) is on the bottom left side of the station. • Temperature is 27°F and the dewpoint temperature is 25°F.

  4. Station Plot – Current Weather • Located directly below the temperature • Weather symbol is not included in the station plot if nothing interesting is happening. • Here, there is light rain

  5. Station Plot – Precipitation • Precipitation during the past 24 hours is given on the bottom right side. • This is measured in inches • Here, it has rained 0.31 inches over the past 24 hours

  6. Common Weather Symbols:

  7. Station Plot – Cloud Cover • Cloud cover is indicated by the amount of shading in the station’s circle • no shading = clear • ¼th shaded = few clouds • half shaded = scattered clouds • ¾th shaded = broken clouds • fully shaded = overcast conditions

  8. Station Plot – Wind Speed and Direction • Wind barb indicates wind direction and speed • The barb points in the direction FROM where the wind is blowing. • Wind speed is measured (in knots) by the number and type of flags on the barb. • Short flag=5kts, Long flag=10kts, Triangle=50kts • Here, we have a northwesterly wind at 30 kts http://www.meteor.wisc.edu/~hopkins/aos100/wndcod2.gif

  9. Station Plot – Sea Level Pressure • Sea level pressure is on the top right side • Need to add a 9 or a 10 in front of numbers on map and a decimal goes between the last two numbers • Typical values between 970mb and 1030mb • Here, the SLP is 999.7 mb

  10. Station Plot – Pressure Tendency • The pressure tendency is given to the right of the cloud cover symbol • The pressure tendency is given over the past 3 hours and the units are tenths of millibars • The pressure tendency trend provides a graphic illustration of how the change of pressure has occurred. • Here, the pressure has decreased 1.1 millibars continuously over the past 3 hours

  11. Station Plot – Pressure Tendency Trend

  12. Examples http://cimss.ssec.wisc.edu/wxwise/station/page5.html

  13. METAR • METAR is a format for reporting weather information. • Raw METAR is the most popular format in the world for the transmission of weather data. • This METAR example is from Trenton-Mercer Airport near Trenton, New Jersey, and was taken on 5 December 2003 at 18:53 UTC. METAR KTTN 051853Z 04011KT 1/2SM VCTS SN FZFG BKN003 OVC010 M02/M02 A3006 RMK AO2 TSB40 SLP176 P0002 T10171017=

  14. METAR – Type and Station ID TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Type - METAR • METAR is the scheduled observation taken at the end of each hour. • SPECI is an observation taken at an unscheduled time due to certain criteria that is met such as low visibility, low clouds, frozen precipitation, or thunderstorms. • Station ID - KORD • In this example, K refers to a North American Station and ORD is the three letter ID for O’Hare. • Other example: KDEN (Denver, CO)

  15. METAR – Time & Date TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Time and Date – 041656Z • The 04 represents the day of the month • The 1656 represents the time at which the observation went out • The Z represents that the time is in ZULU or UTC (Universal Time Code).

  16. METAR - Winds TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Winds – 19020G26KT • The 190 (the first three numbers) is the direction of the winds in degrees from 0 to 360 degrees. • The 20 (next two numbers) is the speed of the winds in knots. • The G26 represents the wind gusts of 26 knots. • The KT simply means knots. It will always be at the end

  17. METAR - Visibility TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Visibility – 6SM • The 6SM simply means 6 statute miles. • Occasionally you might see visibility up to 20 or 30 SM but for the most part it will go from < ¼ (visibility below ¼ SM) up to 10 SM.

  18. METAR – Present Weather and Obscurations TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Present weather and obscurations –SHRA • (-) is the designator for light. Precipitation will be light (-), moderate (), or heavy (+) based on certain criteria must be met. • SH means showers and RA means rain. • The following is from the FMW-1 Handbook

  19. METAR – Cloud Cover TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Sky Condition – BKN070 • BKN represents a broken sky. (The clouds cover 5/8 to 7/8 of the sky) • The 070 represents the clouds are at 7,000 feet (simply add 2 zeros to get the height) • The cloud cover will be either be FEW (1/8 to 2/8 cloud coverage), SCT (SCATTERED, 3/8 to 4/8 cloud coverage), BKN (5/8-7/8 coverage), and OVC (OVERCAST, 8/8 Coverage). • There will often be more than 1 designator (i.e. SCT035 BKN090 OVC140) • An indefinite ceiling caused by fog, rain, snow, etc., will require a designator as VV (Vertical Visibility). VV is how high you can see vertically into the indefinite ceiling. • Significant clouds such as TCU (towering cumulus), CB (cumulonimbus), or ACC (altocumulus castellanus) will be found on the end of a category (i.e. SCT035TCU)

  20. METAR – Temperature, Dewpoint, Altimeter/Pressure TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Temperature and Dewpoint – 12/08 • 12 represents the temperature in Celsius • 08 represents the dewpoint in Celsius • If the temperature or dewpoint falls below 0, then there will be an “M” before it (i.e. 03/M02). “M” means minus • Altimeter/Pressure – 3016 • A simply stands for Altimeter • 3016 means 30.16 inches of mercury for the pressure

  21. METAR – Remarks TYPE ID TIME WIND VIS WX SKY T/TD ALT REMARK METARKORD041656Z19020G26KT6SM-SHRABKN07012/08A3016RMK AO2 • Remarks – RMK A02 • RMK simply mean remarks and marks the end of the standard METAR observation and the beginning of the remarks that are put in as necessary. • A02 means that the site is automated and has a precipitation sensor. If it were A01, there would be no precip sensor. • There are many remarks and the FMH-1 gives a full listing

  22. Remarks • Lightning: frequency, type, and direction of lightning • occasional, OCNL; frequent, FRQ; or continuous, CONS; cloud-to-ground, CG; in-cloud, IC; cloud-to-cloud, CC; cloud-to-air, CA • e.g., OCNL LTGICCG NW for occasional lightning in-cloud and cloud-to-ground northwest

  23. Remarks • Beginning and ending times of weather phenomena: expressed in minutes past the hour • e.g., TSB05E40 for thunderstorm began 5 minutes past the hour and ended 40 minutes past the hour • Sea-level pressure: station pressure (mb) reduced to sea level • e.g. SLP122 for sea-level pressure of 1012.2 mb

  24. Remarks • Hourly precipitation:preceded by P and expressed in hundredths of an inch • e.g. P0022 = 0.22 inches of precipitation • 3- and 6-hour precipitation: preceded by 6 and expressed in hundredths of an inch • e.g. 60061 = 0.61 inches of precipitation in the last 6 hours • 24-hour precipitation: preceded by 7 and expressed in hundredths of an inch • e.g. 70063 = 0.63 inches of precipitation in the last 24 hours

  25. Remarks • Hourly temperature and dew point: preceded by T and followed with 0 if the temperature is 0°C or higher, or 1 if the temperature is less than 0°C and followed by the temperature in tenths of a °C, then 0 or 1 again followed by the dew point in tenths of a °C. • e.g. T00940079 = temperature of 9.4°C and dew point of 7.9°C • 6-hour maximum temperature: preceded by 1 and followed by 0 or 1 to denote temperatures above or below 0°C, respectively, and expressed in tenths of a degree • e.g. 10167 = maximum temperature of 16.7°C • 6-hour minimum temperature: preceded by 2 and followed by 0 or 1 to denote temperatures above or below 0°C, respectively, and expressed in tenths of a degree • e.g. 20094 = minimum temperature of 9.4°C

  26. Remarks • 3-hour pressure tendency: preceded by 5 and followed by 0 though 9 to indicate trend, followed by the amount in tenths of millibars • e.g. 51007 Interpretation: increased then steady with a change of 0.7 mb

  27. Examples 1. KMLU 171153Z AUTO 03007KT 6SM RA BR BKN009 BKN014 OVC025 09/08 A3001 RMK AO2 SLP163 P0013 60033 70033 T00940079 10167 20094 51007 TSNO= • Location: KMLU (Monroe) • Day of month: 17, Time: 11:53 UTC • Report is fully automated, with no human intervention or oversight • Wind: True direction = 30°, Speed: 7 knots • Visibility: 6 Statute Miles • Weather: Rain and Mist • Clouds: broken at 900 ft, broken at 1400 ft, and overcast at 2500 ft • Temperature: 9°C • Dewpoint: 8°C • Altimeter: 30.01 in Hg

  28. Examples 1. KMLU 171153Z AUTO 03007KT 6SM RA BR BKN009 BKN014 OVC025 09/08 A3001 RMK AO2 SLP163 P0013 60033 70033 T00940079 10167 20094 51007 TSNO= • SLP163 = Sea level pressure of 1016.3 mb • P0013 = 0.13 inches of rain in the last hour • 60033 = 0.33 inches of rain in the last 3 hours • 70033 = 0.33 inches of rain in the last 24 hours • T009440079 = Temperature of 9.4°C and dew point of 7.9°C • 10167 = Maximum temperature of 16.7°C • 20094 = Minimum temperature of 9.4°C • 51007 = Increased then steady with a change of 0.7 mb • TSNO = lightning information not available

  29. Examples 2. KINL 181155Z 04006KT 10SM CLR M18/M22 A3012 RMK AO2 SLP234 T11831222 11122 21189 53012 • Location: KINL (International Falls, MN) • Day of month: 18, Time: 11:55 UTC • Wind: True direction = 40°, Speed: 6 knots • Visibility: 10 Statute Miles • Weather: Clear • Temperature: -18°C • Dewpoint: -22°C • Altimeter: 30.12 in Hg

  30. Examples 2. KINL 181155Z 04006KT 10SM CLR M18/M22 A3012 RMK AO2 SLP234 T11831222 11122 21189 53012 • SLP234 = Sea level pressure of 1023.4 mb • T11831222 = Temperature of -18.3°C and dew point of -22.2°C • 11122 = Maximum temperature of -12.2°C • 21189 = Minimum temperature of -18.9°C • 53012 = Decreased then increasing with a change of 1.2 mb

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