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SURFACE DATA AND WEATHER FEATURES

SURFACE DATA AND WEATHER FEATURES. MSC 243 Lecture #2 09/03/09. Recap from last week. MOS is a combination of computer model output (run on supercomputers) and bias corrections. Models: GFS (AVN), NAM (ETA).

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SURFACE DATA AND WEATHER FEATURES

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  1. SURFACE DATA AND WEATHER FEATURES MSC 243 Lecture #2 09/03/09

  2. Recap from last week • MOS is a combination of computer model output (run on supercomputers) and bias corrections. Models: GFS (AVN), NAM (ETA). • While MOS is a good “first guess” at point forecasts for cities, it is not the only thing we should examine. • Over the next few lectures, we look at the main weather observations used to find current conditions and to make short-term forecasts.

  3. This Lecture • AWOS / METAR Observations • Decoding METAR • Surface Station Models • Pressure-Wind Relationship

  4. Surface Weather Analysis http://www.hpc.ncep.noaa.gov

  5. Surface Observations • Automated Weather Observing System (AWOS)

  6. AWOS: http://www.nws.noaa.gov/asos/ • Instruments: • Tipping bucket (rain gauge) • Hygrothermometer (temp/dewpoint sensor) • Present Weather Identifier (precip/fog/haze) • Wind speed and direction sensors • Ceilometer (cloud height) • Freezing rain and thunderstorm sensors • Visibility sensor • Data collection, processing and transfer in METAR format

  7. Time and Temperature • Observations across the globe taken and recorded using Universal time (UTC) • UTC = Greenwich Mean Time • Eastern Daylight Time = UTC – 4 Hours • Temperatures reported using Celsius scale • F = (9/5)*C + 32 • C = (5/9)*(F-32)

  8. METAR Observations Website with key on decoding METAR observations http://weather.cod.edu/notes/metar.html

  9. METAR Observations Example METAR Report METAR KABC121755ZAUTO 21016G24KT 180V240 1SM R11/P6000FT -RA BR BKN015 0VC025 06/04 A2990 RMK A02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T00640036 10066 21012 58033 TSNO $ KABC- ICAO STATION (location) IDENTIFIER Four character ICAO location identifier. 121755Z - DATE/TIME All dates and times in UTC using a 24-hour clock; two-digit date and four-digit time; always appended with Z to indicate UTC. AUTOREPORT MODIFIER AUTO: Indicates a fully automated report with no human intervention. It is removed when an observer logs on to the system. COR: Indicates a corrected observation. No modifier indicates human observer or automated system with human logged on for oversight functions.

  10. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT180V2401SM R11/P6000FT -RA BR BKN015 0VC025 06/04 A2990 RMK A02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T00640036 10066 21012 58033 TSNO $ 21016G24KT - WIND DIRECTION AND SPEED Direction in tens of degrees from true north (first three digits); next two digits: speed in whole knots; if needed, include character as: Gusts (character) followed by maximum observed speed; always appended with KT to indicate knots; 00000KT for calm 180V240- if direction varies by 60o or more and speed greater than 6 knots, a Variable wind direction group is reported, otherwise omitted. If wind direction is variable and speed 6 knots or less, replace wind direction with VRB followed by wind speed in knots. 1SM VISIBILITY Prevailing visibility in statute miles and fractions with space between whole miles and fractions; always appended with SM to indicate statute miles; values <1/4SM reported as M1/4SM.

  11. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT –RA BR BKN015 0VC025 06/04 A2990 RMK A02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T00640036 10066 21012 58033 TSNO $ -RA BR - WEATHER PHENOMENA - Intensity or Proximity “-” Light, “no sign” Moderate, “+” Heavy, VC Vicinity - Precipitation: DZ Drizzle, IC Ice Crystals, UP Unknown in automated observations, RA Rain, PL Ice pellets, SN Snow, GR Hail, SG Snow grains GS Small hail/snow pellets • Obscuration: BR Mist (< or = 5/8SM), SA Sand, FU Smoke, HZ Haze, VA Volcanic Ash, PY Spray, DU Widespread Dust • Other: SQ Squall, FC Funnel Cloud, SS Sandstorm, +FC Tornado/ Waterspout, DS Duststorm, PO Well developed dust/sand whirls.

  12. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT –RA BR BKN015 0VC02506/04 A2990 RMK A02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T00640036 10066 21012 58033 TSNO $ BKN015 OVC025-SKY CONDITION. Cloud amount and height: CLR (In automated METAR reports only, no clouds detected above 12000 feet.); Sky CLeaR 0/8; FEW 1/8-2/8; SCattered 3/8-4/8; BroKeN 5/8-7/8; OVerCast 8/8; 3-digit height of base in hundreds of feet; followed by Towering CUmulus or CumulonimBus if present. More than 1 layer may be reported. 06/04 - TEMPERATURE/DEW POINT. Each is reported in whole degrees Celsius using two digits; values are separated by a slash; sub-zero values are prefixed with an M (minus). Dew Point is the temperature which air must be cooled to in order to be saturated.

  13. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT –RA BR BKN015 0VC025 06/04 A2990RMKA02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T00640036 10066 21012 58033 TSNO $ A2990ALTIMETER. Altimeter setting (in U.S. reports) is always prefixed with an A indicating inches of mercury; reported using four digits: tens, units, tenths, and hundredths. RMKREMARKS IDENTIFIER. Remarks includes clarifying or augmenting data concerning elements in the body of the METAR, additive coded data and maintenance data. AO2 TYPE OF AUTOMATED STATION. AO1; automated station without a precipitation discriminator. AO2; automated station with precipitation discriminator.

  14. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT –RA BR BKN015 0VC025 06/04 A2990 RMK A02 PK WND 20032/25WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T00640036 10066 21012 58033 TSNO $ PK WND 20032/25 - PEAK WIND. PK WND dddff(F)/(hh)mm; direction in tens of degrees, speed in whole knots, time in minutes after the hour. Only minutes after the hour is included if the hour can be inferred from the report. WSHFT 1715 - WIND SHIFT. WSHFT followed by hours and minutes of occurrence. The term FROPA may be entered after the time if it is reasonably certain that the wind shift was a result of a frontal passage.

  15. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT –RA BR BKN015 0VC025 06/04 A2990 RMK A02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO36OOO9 T00640036 10066 21012 58033 TSNO $ P0003 - HOURLY PRECIPITATION AMOUNTPrrrr; in tens, units, tenths and hundredths of an inch since last regular hourly METAR. A trace is reported as P0000. 60009 - 3- AND 6-HOUR PRECIPITATION AMOUNT. 6RRRR; precipitation amount, including water equivalent, to nearest 0.01 inches for past 6 hours reported in 00, 06, 12, and 18 UTC observations and for past 3 hours in 03, 09, 15, and 21 UTC observations. A trace is 60000. 7**** Not on this report - 24-HOUR PRECIPITATION AMOUNT. 7****; precipitation amount to nearest 0.01 inches for past 24 hours reported in 12 UTC observation; e.g., 70015 indicates 0.15 inches of precipitation for past 24 hours.

  16. METAR Observations Example METAR Report METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT –RA BR BKN015 0VC025 06/04 A2990 RMK A02 PK WND 20032/25 WSHFT 1715 VIS 3/4V1 1/2 VIS 3/4 RWY11 RAB07 CIG 013V017 CIG 017 RWY11 PRESFR SLP125 POOO3 6OOO9 T006400361006621012 58033 TSNO $ T00640036- HOURLY TEMPERATURE AND DEW POINT. TsnTaTaTa snT'aT'aT'a; reported to nearest tenth of oC; sn: 1 if temperature or dew point below 0oC and 0 if temperature/dew point 0oC or higher. 10066 - 6-HOUR MAXIMUM TEMPERATURE. 1snTxTxTx; maximum temperature for past 6 hours reported to nearest tenth of degree Celsius; reported on 00, 06, 12, 18 UTC reports; sn = 1 if temperature below 0oC and 0 if temperature 0oC or higher 21012 - 6-HOUR MINIMUM TEMPERATURE. 2snTnTnTn; minimum temperature for past 6 hours reported to nearest tenth of degree Celsius; reported on 00, 06, 12, 18 UTC reports; sn = 1 if temperature below 0oC and 0 if temperature 0oC or higher.

  17. Lab 1: Jacksonville FL • Based on GFS MOS Guidance • Your WXChallenge-style forecasts for 06 UTC Sep 2nd – 06 UTC Sep 3rd Max Temp 82F Min Temp 70F Max Wind Speed 10kt Precipitation amount: anything between 0.62 and 1.41 inches is OK

  18. http://www.hpc.ncep.noaa.gov/html/sfc_archive.shtml 1800 UTC Tuesday 1st (During Lab)

  19. 0000 UTC Wednesday 2nd (8pm Tues our time)

  20. 0600 UTC Wednesday 2nd

  21. 1200 UTC Wednesday 2nd

  22. 1800 UTC Wednesday 2nd

  23. 0000 UTC Thursday 3rd

  24. 0600 UTC Thursday 3rd

  25. Jacksonville: decoding METAR for forecast verification • Look for 6-hourly high and low temperatures via 5-digit codes that begin with “1” and “2”. • Look for the highest wind speed value every hour (verification can be different) • Look for the precipitation accumulated every 6 hours (purple, in bold)

  26. Start of period: METAR KJAX 020556Z 00000KT 10SM FEW040 OVC150 23/22 A3002 RMK AO2 SLP165 60111 T02280222 10250 20217 58012 -- none of these values used in verification METAR KJAX 020656Z 00000KT 10SM FEW020 SCT070 OVC150 23/22 A3000 RMK AO2 SLP158 T02280222 METAR KJAX 020756Z 02005KT 5SM +RA BR SCT012 BKN018 OVC032 24/23 A3000 RMK AO2 RAB22 SLP157 P0024 T02390233 METAR KJAX 020856Z 30005KT 8SM SCT012 BKN018 OVC060 23/23 A3000 RMK AO2 RAE11 SLP160 P000560029 T02330228 55005 METAR KJAX 020956Z 35005KT 7SM OVC080 23/23 A2999 RMK AO2 RAB10E40 SLP156 P0001 T02330228 METAR KJAX 021056Z 33003KT 9SM SCT017 BKN100 OVC150 23/23 A3000 RMK AO2 SLP160 T02330228 METAR KJAX 021156Z 02007KT 7SM FEW004 BKN014 BKN030 OVC150 23/23 A3002 RMK AO2 RAB19E50 SLP165 P000360033 70151 T02330228 1023920228 53005 METAR KJAX 021256Z 35005KT 6SM BR FEW014 SCT039 BKN080 BKN150 23/23 A3002 RMK AO2 SLP164 T02330228 METAR KJAX 021356Z 33008KT 5SM BR BKN004 BKN016 OVC023 23/22 A3003 RMK AO2 RAB04E52 SLP168 P0000 T02330222 METAR KJAX 021456Z 03011KT 3/4SM +RA BR BKN005 BKN015 OVC026 22/22 A3005 RMK AO2 TWR VIS 1 1/2 RAB23 SLP176 P005560055 T02220222 53011 METAR KJAX 021556Z 36007KT 1 1/2SM +TSRA BR BKN008 OVC020CB 23/22 A3004 RMK AO2 PK WND 03026/1506 TSB09E30B54 SLP171 OCNL LTGIC E TS E MOV SW P0305 T02280222 METAR KJAX 021656Z 03008KT 4SM RA BR BKN006 BKN013 OVC026 23/23 A3002 RMK AO2 TSE45 SLP165 P0009 T02330228 METAR KJAX 021756Z 04012KT 2SM -RA BR BKN008 BKN011 OVC025 24/23 A3000 RMK AO2 SFC VIS 5 SLP160 P000860377 T02440233 1024420211 58015

  27. METAR KJAX 021856Z 02010KT 2SM BKN009 OVC019 24/23 A2999 RMK AO2 SFC VIS 8 RAE08 SLP157 P0001 T02440228 METAR KJAX 021956Z 02009KT 7SM SCT005 BKN009 OVC025 24/23 A2999 RMK AO2 SLP154 T02390228 METAR KJAX 022056Z 01006KT 7SM SCT009 BKN014 OVC031 24/23 A2997 RMK AO2 RAB06E22 SLP150 P000160002 T02440228 58010 METAR KJAX 022156Z 02006KT 7SM SCT009 BKN014 OVC025 24/23 A2998 RMK AO2 SLP151 T02440228 METAR KJAX 022256Z 01006KT 8SM BKN014 BKN028 BKN130 24/22 A2998 RMK AO2 SLP152 T02390222 METAR KJAX 022356Z 01010KT 7SM -RA FEW005 BKN017 BKN036 OVC130 23/22 A2997 RMK AO2 RAB51 SLP149 P000060002 T02330217 1024420233 58002 METAR KJAX 030056Z 36006KT 7SM BKN017 BKN034 OVC130 23/22 A2998 RMK AO2 RAE24 SLP151 P0001 T02280217 METAR KJAX 030156Z 35007KT 10SM BKN017 BKN130 23/21 A2999 RMK AO2 SLP157 T02280211 METAR KJAX 030256Z 35004KT 7SM -RA BKN019 BKN050 23/22 A3000 RMK AO2 RAB21 SLP158 P000060001 T02280217 51009 METAR KJAX 030356Z 01008KT 10SM BKN016 OVC050 23/21 A2998 RMK AO2 RAE15 SLP153 P0000 METAR KJAX 030456Z 01006KT 10SM FEW022 SCT030 BKN038 OVC130 23/21 A2997 RMK AO2 SLP149 T02280211 402440211 METAR KJAX 030556Z 35005KT 10SM FEW020 SCT026 OVC033 22/21 A2996 RMK AO2 SLP147 60001 T02220206 1023320222 56012 VERIFICATION: High 24.4C (76F), Low 21.1C (70F), Max Wind 12 kt, Total Precip 4.13 in !!!

  28. Forecast Verification: Jacksonville From METAR: 76-70-12-4.13 Recall GFS MOS prediction: 82-70-10- (<1.41) Was the GFS MOS a good forecast? The thunderstorm was impossible to predict one day in advance (or even hours in advance). Also, the high temperature was lower than predicted because of the cloud cover and rain.

  29. Plotting METAR data: Station Modelshttp://www.rap.ucar.edu/weather/surface/ Mean sea level pressure in mb/10, with first “9” or “10” removed. 1000.5 mb here http://www.rap.ucar.edu/weather/info/index.php?referrer=surface

  30. Map of Station Models

  31. Surface analysis based on Station Models How is wind related to pressure?

  32. LOW HIGH Winds: No Friction • Winds, in the absence of any frictional forces, are the result of a balance of forces acting on a parcel of air: • Pressure Gradient Force • -(1/r)*(dP/dx) • Coriolis Force • 2*W*sin(latitude)*(velocity) • Net wind blows parallel to lines of constant height or pressure, with lower values on to the left of the wind direction PGF WIND CORIOLIS

  33. Upper tropospheric Winds Winds blow parallel to lines of constant height or pressure The tighter the gradient of pressure, the stronger the wind The balance of the pressure gradient force and the Coriolis force is called GEOSTROPHIC BALANCE

  34. Surface Winds LOW • Winds are the net result of forces acting on a parcel of air: • Pressure Gradient Force • Coriolis Force • Friction – Caused by the surface roughness 996 mb PGF 1000 mb WIND 1004 mb FRICTION 1008 mb CORIOLIS 1012 mb HIGH

  35. Surface Winds Surface winds spiral into and counter clockwise around a low pressure center Surface winds spiral out from and clockwise around a high pressure center http://www.rap.ucar.edu/weather/model/

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