GEMPAK Manual

GEMPAK PARAMETERS This appendix contains a list of the GEMPAK parameters. Algorithms used in computing these parameters are also included. The following constants are used in the computations: KAPPA = Poisson's constant = 2 / 7 G = Gravitational constant = 9.80616 m/sec/sec GAMUSD = Standard atmospheric lapse rate = 6.5 K/km RDGAS = Gas constant for dry air = 287.04 J/K/kg PI = Circumference / diameter = 3.14159265 References for some of the algorithms: Bolton, D., 1980: The computation of equivalent potential temperature., Monthly Weather Review, 108, pp 1046-1053. Miller, R.C., 1972: Notes on Severe Storm Forecasting Procedures of the Air Force Global Weather Central, AWS Tech. Report 200. Wallace, J.M., P.V. Hobbs, 1977: Atmospheric Science, Academic Press, 467 pp. TEMPERATURE PARAMETERS TMPC - Temperature in Celsius TMPF - Temperature in Fahrenheit TMPK - Temperature in Kelvin STHA - Surface potential temperature in Kelvin STHK - Surface potential temperature in Kelvin STHC - Surface potential temperature in Celsius STHE - Surface equivalent potential temperature in Kelvin STHS - Surface saturation equivalent pot. temperature in Kelvin THTA - Potential temperature in Kelvin THTK - Potential temperature in Kelvin THTC - Potential temperature in Celsius THTE - Equivalent potential temperature in Kelvin THTS - Saturation equivalent pot. temperature in Kelvin TVRK - Virtual temperature in Kelvin TVRC - Virtual temperature in Celsius TVRF - Virtual temperature in Fahrenheit THTV - Virtual potential temperature in Kelvin TDXC - Maximum 24 hour temperature in Celsius TDNC - Minimum 24 hour temperature in Celsius TDXF - Maximum 24 hour temperature in Fahrenheit TDNF - Minimum 24 hour temperature in Fahrenheit T6XC - Maximum 6 hour temperature in Celsius T6NC - Minimum 6 hour temperature in Celsius T6XF - Maximum 6 hour temperature in Fahrenheit T6NF - Minimum 6 hour temperature in Fahrenheit DMAX - Daily weather map maximum temperature in Fahrenheit DMIN - Daily weather map minimum temperature in Fahrenheit SSTC - Sea surface temperature in Celsius SSTF - Sea surface temperature in Fahrenheit LTMP - Temp. in Celsius of surface air lifted to 500 or !x mb TMPC = ( TMPF - 32 ) * 5 / 9 TMPC = TMPK - 273.16 THTA = TMPK * ( 1000 / PRES ) ** KAPPA STHA = TMPK * ( 1000 / PALT ) ** KAPPA TVRK = TMPK * ( 1 + ( .001 * MIXR ) / .62197) ) / ( 1 + ( .001 * MIXR ) ) THTV = TVRK * ( 1000 / PRES ) ** KAPPA THTE = THTM * EXP [ ( 3.376 / TLCL - .00254 ) * ( MIXR * ( 1 + .81 * .001 * MIXR ) ) ] THTM = potential temperature for moist air = TMPK * ( 1000 / PRES ) ** E E = 2. / 7. * ( 1 - ( .28 * .001 * MIXR ) ) TLCL = temperature at the LCL in Kelvin MOISTURE PARAMETERS DWPC - Dewpoint in Celsius DWPF - Dewpoint in Fahrenheit DWPK - Dewpoint in Kelvin DPDC - Dewpoint depression in Celsius DPDF - Dewpoint depression in Fahrenheit DPDK - Dewpoint depression in Kelvin MIXR - Mixing ratio in g/kg MIXS - Saturated mixing ratio in g/kg SMXR - Surface mixing ratio in g/kg SMXS - Surface saturated mixing ratio in g/kg RELH - Relative humidity in percent TMWK - Wet bulb temperature in Kelvin TMWC - Wet bulb temperature in Celsius TMWF - Wet bulb temperature in Fahrenheit VAPR - Vapor pressure in millibars VAPS - Saturation vapor pressure in millibars LHVP - Latent heat of vaporization in J/kg PWTR - Precipitable water (mm) at any given level DPDx = TMPx - DWPx MIXR = .62197 * ( E / ( PRES - E ) ) * 1000 E = VAPR * [ 1.001 + ( PRES - 100) / 900 * .0034 ] VAPR = 6.112 * EXP ( ( 17.67 * DWPC ) / ( DWPC + 243.5 ) ) MIXS = .62197 * ( Es / ( PRES - Es ) ) * 1000 Es = VAPS * [ 1.001 + ( PRES - 100 ) / 900 * .0034 ] VAPS = 6.112 * EXP ( ( 17.67 * TMPC ) / ( TMPC + 243.5 ) ) SMXR = .62197 * ( E / ( PALT - E ) ) * 1000 E = VAPR * [ 1.001 + ( PALT - 100 ) / 900 * .0034 ] VAPR = 6.112 * EXP ( ( 17.67 * DWPC ) / ( DWPC + 243.5 ) ) SMXS = .62197 * ( Es / ( PALT - Es ) ) * 1000 Es = VAPS * [ 1.001 + ( PALT - 100 ) / 900 * .0034 ] VAPS = 6.112 * EXP ( ( 17.67 * TMPC ) / ( TMPC + 243.5 ) ) RELH = VAPR / VAPS * 100 ( TMPK - TMWK ) * Cp - ( Rsat (TMWK) - RMIX ) * LVAP = 0 Implicit equation solved by Newton's method for TMWK. Cp - Specific heat at constant pressure Rsat - Saturation mixing ratio at TMWK RMIX - Mixing ratio LVAP - Latent heat of vaporization VAPR = 6.112 * EXP [ ( 17.67 * DWPC ) / ( DWPC + 243.5 ) ] VAPS = 6.112 * EXP [ ( 17.67 * TMPC ) / ( TMPC + 243.5 ) ] LHVP = ( 2.501 - .00237 * TMPC ) * 10E6 HEIGHT PARAMETERS HGHT - Height in meters HGTM - Height in meters HGTK - Height in kilometers HGTD - Height in decameters HGFT - Height in feet (3.28084 * HGHT) HGFH - Height in hundreds of feet HGFK - Height in thousands of feet HGML - Height in miles (6.2137E-04 * HGHT) DHGT - Dry hydrostatic height in meters MHGT - Moist hydrostatic height in meters STDZ - Character standard height convention used on u.-a. charts RSTZ - Numeric standard height convention used on u.-a. charts For data below 500 mb, the standard height is the last three digits of the height. For data at and above 500 mb, the height is the last three digits of the height in decameters. ZMSL, Z000, Z900, Z850, Z800 - Estimated height at a pressure level DHGT and MHGT are computed using the hypsometric equation and integrating from the surface pressure to the desired level. DHGT (MHGT) is computed without (with) the influence of moisture. DHGT = HB + ( RDGAS / G ) * LN ( PBOT / PTOP ) * TAVE HB = height of the bottom of a layer PBOT = pressure at bottom of a layer PTOP = pressure at the top of a layer TAVE = average temperature of a layer MHGT = HB + ( RDGAS / G ) * LN ( PBOT / PTOP ) * TVAVE HB = height of the bottom of a layer PBOT = pressure at bottom of a layer PTOP = pressure at the top of a layer TVAVE = average virtual temperature of a layer Zxxx = [ To * ( 1 - ( PRES / ALTM ) ** ( RDGAS * GAMUSD / G ) ] / GAMUSD Zxxx = height at the pressure level ZMSL : 1013.25 mb Z000 : 1000 mb Z900 : 900 mb Z850 : 850 mb Z800 : 800 mb To = sea level temperature in U.S. Std. Atmos. = 288 K PRESSURE AND ALTIMETER PARAMETERS PRES - Station pressure in millibars PRES is the actual pressure at a level as reported with upper air data. PMSL - Mean sea level pressure PMSL is reported with surface data. PALT - Surface pressure in millibars from ALTI ALTI - Altimeter setting in inches of mercury ALTI is reported with surface data. ALTM - Altimeter setting converted to millibars SALT - Abbreviated standard altimeter setting SMSL - Abbreviated mean sea level pressure in millibars SALI - Abbreviated altimeter setting in inches of mercury RMSL - First 3 digits left of decimal of PMSL * 10 RSLI - First 3 digits left of decimal of ALTI * 100 RSLT - First 3 digits left of decimal of ALTM * 10 PTND - Pressure tendency: graphics symbol with numeric change PTSY - Graphics symbol for pressure tendency P03C - 3-h numeric pressure change P03D - Pressure tendency and change group, appp P24C - 24-h numeric pressure change PMSL = PRES * EXP ( ( G * SELV ) / ( RDGAS * TVAVE ) ) SELV = station elevation TVAVE = average virtual temperature between station and sea level = TVRK + ( DELTV / 2 ) DELTV = GAMUSD * SELV / 1000 PALT = ALTM * ( 1 - ( ( SELV / 1000 ) * GAMUSD / To ) ) ** ( G / ( GAMUSD * RDGAS ) * 1000 ) SELV = station elevation in meters To = sea level temperature in U.S. Std. Atmos. = 288 K ALTM = ALTI * ( 1013.25 / 29.921 ) SALT = MOD ( ALTM * 10, 1000 ) PANY - Returns PMSL, if avaliable, if not, returns ALTM RANY - Computes the 3 digit display of pressure SANY - Creates a 3 character string from integral part of PMSL or ALTM WINDS UWND - U-component of the wind in meters/second VWND - V-component of the wind in meters/second UKNT - U-component of the wind in knots VKNT - V-component of the wind in knots DRCT - Wind direction in degrees SPED - Wind speed in meters/second SKNT - Wind speed in knots SMPH - Wind speed in miles/hour PSPD - Packed direction and speed in meters/second (ddfff) PKNT - Packed direction and speed in knots (ddfff) GUST - Wind gusts in knots GUMS - Wind gusts meters/second PWDR - Peak 5-second wind direction in degrees PWSP - Peak 5-second wind speed in meters/sec PWHR - Hour of 5-second peak wind PWMN - Minutes of 5-second peak wind WNML - Wind component toward a direction 90 degrees counter- clockwise from a specified direction. WCMP - Wind component toward a specified direction BARB - Barb feathered in m/s BRBM - Barb feathered in m/s BRBK - Barb feathered in knots BRBS - Barb feathered in mi/hr ARRW - Arrows scaled in m/s ARRM - Arrows scaled in m/s ARRK - Arrows scaled in knots DARR - Wind direction arrows of uniform length UWND = - SIN ( DRCT ) * SPED VWND = - COS ( DRCT ) * SPED DRCT = ATAN2 ( -UWND, -VWND ) * 180 / PI SPED = SQRT ( UWND ** 2 + VWND ** 2 ) SPED = SKNT / 1.9438 PSPD = JDRCT * 100 + JSPED JDRCT = NINT ( DRCT / 5 ) JSPED = NINT ( SPED ) PKNT = JDRCT * 100 + JSKNT JDRCT = NINT ( DRCT / 5 ) JSKNT = NINT ( SKNT ) WCMP = - COS ( DRCT - SPCD ) * SPED SPCD is the specified direction WNML = - COS ( DRCT - ( SPCD - PI/2 ) ) * SPED SPCD is the specified direction LIFTED CONDENSATION LEVEL (LCL) TLCL - Temperature in Kelvin at the LCL from the given level PLCL - Pressure in millibars at the LCL from the given level TLCL = [1 / ( 1 / ( DWPK - 56 ) + LN ( TMPK / DWPK ) / 800 )] + 56 PLCL = PRES * ( TLCL / ( TMPC + 273.15 ) ) ** ( 1 / KAPPA ) Poisson's equation STABILITY INDICES Note: Default depths given in the definitions below are preceded by an ! and may be changed using the in-line depth specification. Negative depths reset to the default values. Zero depth will yield missing values for layer parameters. dz in the definitions below defaults to the layer thickness in the sounding. BRCH - Bulk Richardson number BRCH = CAPE / ( 0.5 * U**2 ) CAPE = Convective Available Potential Energy U = magnitude of shear ( u2 - u1, v2 - v1 ) u1,v1 = average u,v in the lowest !500 m u2,v2 = average u,v in the lowest !6000 m BRCV - BRCH computed by using CAPV BRCH = CAPV / ( 0.5 * U**2 ) CAPV = CAPE computed by using virtual temperature U = magnitude of shear ( u2 - u1, v2 - v1 ) u1,v1 = average u,v in the lowest !500 m u2,v2 = average u,v in the lowest !6000 m BVFQ - Brunt-Vaisala frequency in a layer BVFQ = SQRT ( ( G / THTA ) * STAB ) BVPD - Brunt-Vaisala period in a layer BVPD = 2. * PI / BVFQ BVSQ - Brunt-Vaisala frequency squared in a layer BVSQ = BVFQ ** 2 CAPE - Convective Available Potential Energy CAPE = GRAVTY * SUMP ( DELZ * ( TP - TE ) / TE ) SUMP = sum over sounding layers from LFCT to EQLV for which ( TP - TE ) is greater than zero DELZ = incremental depth TP = temperature of a parcel from the lowest !500 m of the atmosphere, raised dry adiabatically to the LCL and moist adiabatically thereafter TE = temperature of the environment CAPV - CAPE computed by using virtual temperature CAPV = GRAVTY * SUMP ( DELZ * ( TVP - TVE ) / TVE ) SUMP = sum over sounding layers from LFCV to EQTV for which ( TVP - TVE ) is greater than zero DELZ = incremental depth TVP = virtual temperature of a parcel from the lowest !500 m of the atmosphere, raised dry adiabatically to the LCL and moist adiabatically thereafter TVE = virtual temperature of the environment CINS - Convective Inhibition CINS = GRAVTY * SUMN ( DELZ * ( TP - TE ) / TE ) SUMN = sum over sounding layers from top of the mixed layer to LFCT for which ( TP - TE ) is less than zero. DELZ = incremental depth TP = temperature of a parcel from the lowest !500 m of the atmosphere, raised dry adiabatically to the LCL and moist adiabatically thereafter TE = temperature of the environment CINV - CINS computed by using virtual temperature CINV = GRAVTY * SUMN ( DELZ * ( TVP - TVE ) / TVE ) SUMN = sum over sounding layers from top of the mixed layer to LFCV for which ( TVP - TVE ) is less than zero. DELZ = incremental depth TVP = virtual temperature of a parcel from the lowest !500 m of the atmosphere, raised dry adiabatically to the LCL and moist adiabatically thereafter TVE = virtual temperature of the environment CTOT - Cross Totals index CTOT = TD850 - T500 TD850 = Dewpoint in Celsius at 850 mb T500 = Temperature in Celsius at 500 mb EQLV - Equilibrium level EQLV = level at which a parcel from the lowest !500 m of the atmosphere is raised dry adiabatically to the LCL and moist adiabatically to a level above which the virtual temperature of the parcel is the same as the environment. If more than one Equilibrium Level exists, the highest one is chosen. EQTV - EQLV computed by using virtual temperature KINX - K index KINX = ( T850 - T500 ) + TD850 - ( T700 - TD700 ) T850 = Temperature in Celsius at 850 mb T500 = Temperature in Celsius at 500 mb TD850 = Dewpoint in Celsius at 850 mb T700 = Temperature in Celsius at 700 mb TD700 = Dewpoint in Celsius at 700 mb LAPS - Temperature lapse rate in a layer LAPS = d (TMPK) / dz = d (TMPC) / dz LCLP - Pressure in millibars at the LCL from the surface LCLP = PRES * ( LCLT / ( TMPC + 273.15 ) ) ** ( 1 / KAPPA ) Poisson's equation LCLT - Temperature in Kelvin at the LCL from the surface LCLT = [1 / ( 1 / ( DWPK - 56 ) + LN ( TMPK / DWPK ) / 800 )] + 56 LFCT - Level of Free Convection by comparing temperature between a parcel and the environment LFCT = level at which a parcel from the lowest !500 m of the atmosphere is raised dry adiabatically to LCL and moist adiabatically to the level above which the parcel is positively buoyant. If more than one LFCT exists, the lowest level is chosen. If the parcel is positively bouyant throughout the sounding, the LFCT is set to be the same as the LCLP. If the parcel is negatively bouyant throughout the sounding, the LFCT is set to missing. LFCV - LFCT computed by using virtual temperature LIFT - Lifted index LIFT = T500 - Tparcel T500 = temperature in Celsius of the environment at 500 mb Tparcel = 500 mb temperature in Celsius of a lifted parcel with the average pressure, temperature, and dewpoint of the layer !100 mb above the surface LFTV - LIFT computed by using virtual temperature LHAN - Low elevation Haines Index MHAN - Middle elevation Haines Index HHAN - High elevation Haines Index MLMR - Mean mixed layer MIXR MLMR = average MIXR in the lowest !500 m MLTH - Mean mixed layer THTA MLTH = average THTA in the lowest !500 m PWAT - Precipitable water (mm) for the entire sounding RICH - Richardson number in a layer RICH = BFVQ ** 2 / SHRM ** 2 SEPA - Isentropic pressure thickness in a layer SEPA = pressure difference over a isentropic layer !5 K deep SHOW - Showalter index SHOW = T500 - Tparcel T500 = Temperature in Celsius at 500 mb Tparcel = Temperature in Celsius at 500 mb of a parcel lifted from 850 mb SHRD - Wind shear direction in a layer SHRD = direction of [ du/dz, dv/dz ] SHRM - Wind shear magnitude in a layer SHRM = magnitude of [ du/dz, dv/dz ] STAB - THTA lapse rate in a layer STAB = d (THTA) / dz STAP - THTA change with pressure in a layer STAP = - d (THTA) / dp SWET - SWEAT index SWET = 12 * TD850 + 20 * TERM2 + 2 * SKT850 + SKT500 + SHEAR TD850 = Dewpoint in Celsius at 850 mb TERM2 = MAX ( TOTL - 49, 0 ) TOTL = Total totals index SKT850 = 850 mb wind speed in knots SKT500 = 500 mb wind speed in knots SHEAR = 125 * [ SIN ( DIR500 - DIR850 ) + .2 ] DIR500 = 500 mb wind direction DIR850 = 850 mb wind direction If TD850 is negative, then TD850 is set to 0. SHEAR is set to 0 if any of the following conditions are met: wind direction at 850mb is < 130 or > 250 wind direction at 500mb is < 210 or > 310 DIR500 - DIR850 <= 0 SPD500 <= 15 or SPD850 <= 15 TOTL - Total Totals index TOTL = ( T850 - T500 ) + ( TD850 - T500 ) T850 = Temperature in Celsius at 850 mb TD850 = Dewpoint in Celsius at 850 mb T500 = Temperature in Celsius at 500 mb VTOT - Vertical Totals index VTOT = T850 - T500 T850 = Temperature in Celsius at 850 mb T500 = Temperature in Celsius at 500 mb CLOUD PARAMETERS Cloud coverage may be defined using a cloud code, short code, fractional coverage or numeric value. The valid values of these parameters ordered from least to greatest cloud coverage, are: Cloud Coverage Cloud Short Fractional Numeric Symbol xCLD xCLO CLCx CFRT missing - 0.00 0 - clear CLR C 0.00 1 0 thin scattered -SCT -S 0.25 6 2 scattered SCT S 0.40 2 3 thin broken -BKN -B 0.60 7 5 broken BKN B 0.75 3 6 thin overcast -OVC -O 0.90 8 7 overcast OVC O 1.00 4 8 thin obscured -X -X 0.00 9 0 obscured X X 1.00 5 9 The following lists the GEMPAK parameter definitions with an example using the sample AIRWAYS cloud report: 22SCT 80-BKN 250OVC Note that the character x may be replaced by L, M, or H, indicating low, mid or high clouds. Also note that the character T indicates the value of the parameter at the level of maximum cloud coverage. xCLD - Character cloud coverage code Examples: LCLD = SCT MCLD = -BKN HCLD = OVC TCLD - xCLD at maximum cloud coverage Example: TCLD = OVC xCLO - Fractional cloud coverage Examples: LCLO = 0.400 MCLO = 0.600 HCLO = 1.000 TCLO - xCLO at maximum cloud coverage Example: TCLO = 1.00 CLCx - Numeric cloud coverage Examples: CLCL = 2 CLCM = 7 CLCH = 4 CLCT - CLCx at maximum cloud coverage Example: CLCT = 4 The next two parameters combine cloud coverage values from the three cloud levels. CLDS - Combined cloud coverage short code from three levels Example: CLDS = S-BO CMBC - Combined cloud coverage numeric from three levels Example: CMBC = 274 The next set of parameters are combined cloud height and cloud coverage. CLHx - Cloud height in hundreds of feet Examples: CLHL = 22. CLHM = 80. CLHH = 250. CLDx - Combined cloud height and short code Examples: CLDL = 22S CLDM = 80-B CLDH = 250O CLDT - CLDx at maximum coverage level Example: CLDT = 250O CLDB - CLDx at the lowest ceiling/layer Example: CLDB = 22S COMx - Numeric combined cloud height and coverage combined as CLHx * 10 + CLCx Examples: COML = 222. COMM = 807. COMH = 2504 Note: In the case when the sky is partially obscured, the value of 10000 is added on to the lowest reporting level. For example, if AIRWAYS report is -X M5 BKN 19 BKN, COML would equal 10053. COMT - COMx at maximum coverage level Example: COMT = 2504. The next two parameters combine the cloud height and coverage allowing up to three reports which do not necessarily correspond to low, middle and high level clouds. These parameters allow a means of storing cloud reports where there may be more than one report at a single level. CHCx - Numeric combined cloud height and coverage combined as CLHx * 10 + CLCx, where x is the cloud report group number from 1 to 3. Examples: CHC1 = 222. CHC2 = 807. CHC3 = 2504 Note: In the case when the sky is partially obscured, the value of 10000 is added on to the first reporting level. For example, if AIRWAYS report is -X M5 BKN 19 BKN, CHC1 would equal 10053. CHDx - Combined cloud height and short code Examples: CHD1 = 22S CHD2 = 80-B CHD3 = 250O The next parameter is the ceiling, defined as the height above the earth's surface of the lowest cloud layer that is reported as broken or overcast, or the vertical visibility into an indefinite ceiling. CEIL - Ceiling in hundreds of feet The following set of cloud parameters is the numeric WMO codes which are reported by airways data. CFRL - Fraction of celestial dome covered by all low and mid level clouds from WMO Code 2700 CTYL - Low-level cloud genera from WMO Code 0513 CTYM - Mid-level cloud genera from WMO Code 0515 CTYH - High-level cloud genera from WMO Code 0509 CBAS - Cloud base height from WMO Code 1600 CSYL - Cloud graphics symbol for CTYL CSYM - Cloud graphics symbol for CTYM CSYH - Cloud graphics symbol for CTYH CSYT - Cloud graphics symbol for first level reporting clouds CFRT - Cloud coverage number from CLCT (maximum clouds) SKYC - Cloud coverage graphics symbol for CFRT SKYM - Sky coverage symbol with wind barbs in m/s SKYK - Sky coverage symbol with wind barbs in knots XVFR - Categorical identification of flight rules 0 = Low Instrument Flight Rules (LIFR) 1 = Instrument Flight Rules (IFR) 2 = Marginal Visual Flight Rules (MVFR) 3 = Visual Flight Rules (VFR) The flight categories and corresponding ceiling and visibility values are listed below. Flight CEILING VISIBILITY Category (feet) (statute miles) =============================================================== LIFR < 500 ft and/or < 1 SM IFR >= 500 to < 1,000 and/or >= 1 to < 3 MVFR >= 1,000 to <= 3,000 and/or >= 3 to <= 5 VFR > 3,000 or none and > 5 =============================================================== WEATHER CODES WCOD - Character weather code WNUM - Numeric weather code The weather code WCOD may also be accessed as WTHR. The weather number consists of 3 parts, A, B, C where WNUM = A * 80 * 80 + B * 80 + C. Each part corresponds to one of the values: 0 (no value) 1 R (mod rain) 41 UP (unknown prcp) 2 L (mod drizzle) 42 3 S (mod snow) 43 4 A (mod hail) 44 5 T (thunder) 45 6 H (haze) 46 7 K (smoke) 47 8 D (dust) 48 9 F (fog) 49 ZR- (lt frz rain) 10 Q (squalls) 50 ZR+ (hvy frz rain) 11 V (volcanic ash) 51 RW- (lt rain shwr) 12 52 RW+ (hvy rain shwr) 13 R- (lt rain) 53 ZL- (lt freezing drizzle) 14 R+ (hvy rain) 54 ZL+ (hvy freezing drizzle) 15 ZR (mod frz rain) 55 SW- (lt snow shwr) 16 RW (mod rain shwr) 56 SW+ (hvy snow shwr) 17 L- (lt drizzle) 57 IP- (lt ice pellets) 18 L+ (hvy drizzle) 58 IP+ (hvy ice pellets) 19 ZL (frz drizzle) 59 SG- (lt snow grains) 20 S- (lt snow) 60 SG+ (hvy snow grains) 21 S+ (hvy snow) 61 SP- (lt snow pellets) 22 SW (mod snow shwr) 62 SP+ (hvy snow pellets) 23 IP (mod ice pellet) 63 IPW (mod ice pellet shwr) 24 SG (mod snow grain) 64 IC- (lt ice crystals) 25 SP (mod snow pellet) 65 IC+ (hvy ice crystals) 26 A- (lt hail) 66 TRW (mod thunder shwr) 27 A+ (hvy hail) 67 SPW (snow pellet shwr) 28 T- (lt thunder) 68 BD+ (hvy blowing dust) 29 T+ (hvy thunder) 69 BN+ (hvy blowing sand) 30 IF (ice fog) 70 BS+ (hvy blowing snow) 31 GF (ground fog) 71 32 BS (blowing snow) 72 33 BD (blowing dust) 73 34 BY (blowing spray) 74 35 BN (blowing sand) 75 IPW- (lt ice pellet shwr) 36 IC (mod ice crystals) 76 IPW+ (hvy ice pellet shwr) 37 IN (ice needles) 77 TRW- (lt rain thunder shwr) 38 AP (small hail) 78 TRW+ (hvy rain thunder shwr) 39 KH (smoke, haze) 79 40 PO (dust whirls) The following correspond to a single character code: -1 TORNA (tornado) -3 WATER (water spout) -2 FUNNE (funnel cloud) WNUM - Numeric weather code, as computed from the METAR codes The weather number consists of 3 parts, A, B, C where WNUM = A * 80 * 80 + B * 80 + C. Each part corresponds to one of the values: -1 +FC (tornado or -2 FC (funnel cloud) waterspout) 0 (no value) 1 RA (mod rain) 41 UP (unknown prcp) 2 DZ (mod drizzle) 42 3 SN (mod snow) 43 4 GR (mod hail) 44 5 TS (thunder) 45 6 HZ (haze) 46 7 FU (smoke) 47 8 DU (dust) 48 9 FG (fog) 49 -FZRA (lt frz rain) 10 SQ (squalls) 50 +FZRA (hvy frz rain) 11 VA (volcanic ash) 51 -SHRA (lt rain shwr) 12 52 +SHRA (hvy rain shwr) 13 -RA (lt rain) 53 -FZDZ (lt frz drizzle) 14 +RA (hvy rain) 54 +FZDZ (hvy frz drizzle) 15 FZRA (mod frz rain) 55 -SHSN (lt snow shwr) 16 SHRA (mod rain shwr) 56 +SHSN (hvy snow shwr) 17 -DZ (lt drizzle) 57 -PL (lt ice pellets) 18 +DZ (hvy drizzle) 58 +PL (hvy ice pellets) 19 FZDZ (frz drizzle) 59 -SG (lt snow grains) 20 -SN (lt snow) 60 +SG (hvy snow grains) 21 +SN (hvy snow) 61 -GS (lt snow pellets) 22 SHSN (mod snow shwr) 62 +GS (hvy snow pellets) 23 PL (mod ice pellet) 63 SHPL (mod ice pellet shwr) 24 SG (mod snow grain) 64 25 GS (mod snow pellet) 65 26 66 TSRA (mod thunder shwr) 27 SHGR (hvy hail) 67 SHGS (snow pellet shwr) 28 68 +BLDU (hvy blowing dust) 29 69 +BLSA (hvy blowing sand) 30 FZFG (ice fog) 70 +BLSN (hvy blowing snow) 31 BR (ground fog) 71 32 BLSN (blowing snow) 72 33 BLDU (blowing dust) 73 34 BLPY (blowing spray) 74 35 BLSA (blowing sand) 75 -SHPL (lt ice pellet shwr) 36 IC (mod ice crystals) 76 +SHPL (hvy ice pellet shwr) 37 77 -TSRA (lt rain thunder shwr) 38 78 +TSRA (hvy rain thunder shwr) 39 79 40 PO (dust whirls) WTMO - Character WMO weather code WWMO - Numeric WMO weather code WSYM - Graphics weather symbol corresponding to WWMO The transformation is: 0 = 34 = BD+ 67 = ZR 1 = 35 = BD+ 68 = R-S- 2 = 36 = BS 69 = RS 3 = 37 = BS+ 70 = S- 4 = K 38 = BS 71 = S- 5 = H 39 = BS+ 72 = S 6 = D 40 = 73 = S 7 = BD 41= F 74 = S+ 8 = PO 42 = F 75 = S+ 9 = 43 = F 76 = IN 10 = F 44 = F 77 = SG 11 = GF 45 = F 78 = IC 12 = GF 46 = F 79 = IP 13 = 47 = F 80 = RW- 14 = 48 = IF 81 = RW 15 = 49 = IF 82 = RW+ 16 = 50 = L- 83 = RW-SW- 17 = T 51 = L- 84 = RWSW 18 = Q 52 = L 85 = SW- 19 = FUNNE 53 = L 86 = SW 20 = 54 = L+ 87 = IPW- 21 = 55 = L+ 88 = IPW 22 = 56 = ZL- 89 = A- 23 = 57 = ZL 90 = A 24 = 58 = R-L- 91 = R- 25 = 59 = RL 92 = R 26 = 60 = R- 93 = RS 27 = 61 = R- 94 = R+S+ 28 = 62 = R 95 = TRW- 29 = 63 = R 96 = TRW-A 30 = BD 64 = R+ 97 = TRW+ 31 = BD 65 = R+ 98 = TD 32 = BD 66 = ZR- 99 = TRW+A 33 = BD+ 105 = TSW- 107 = TSW+ 201 = V 202 = BY 203 = UP PWTH - Character past weather WMO code or graphics symbol for it PWWM - Numeric past weather WMO code The past weather WMO numeric codes are: 0 = Cloud covering less than 1/2 sky 1 = Cloud covering more than 1/2 during part of period and less than 1/2 sky during part 2 = Cloud covering more than 1/2 sky 3 = Sandstorm, duststorm or blowing snow 4 = Fog, ice fog, thick haze or thick smoke 5 = Drizzle 6 = Rain 7 = Snow, rain and snow mixed or ice pellets 8 = Showers 9 = Thunderstorm with or without precipitation The translation is: 0 = 5 = L 1 = 6 = R 2 = 7 = S 3 = BD 8 = RW 4 = F 9 = T STATION PARAMETERS STID - Character station identifier STNM - Station number STNM is the 5-digit WMO identifier for upper air data; 6 digits for surface data, usually the WMO identifier with a zero appended. SLAT - Station latitude in degrees SLON - Station longitude in degrees; West longitude is negative SELV - Station elevation in meters RANG - Range in kilometers (specialized use) AZIM - Azimuth in kilometers (specialized use) LATI - Latitude in degrees from range/azimuth LONG - Longitude in degrees from range/azimuth LATI and LONG are calculated from the RANG and AZIM using equations developed for AOIPS/RADPAK. DELT - Delta time in seconds (specialized use) MODEL OUTPUT STATISTICS MXMN - Maximum or minimum temperature in Fahrenheit TNTF - Night temperature fcst in Fahrenheit TNCF - Night temperature climatology in Fahrenheit TNAF - Night temperature anomaly in Fahrenheit TDYF - Day temperature fcst in Fahrenheit TDCF - Day temperature climatology in Fahrenheit TDAF - Day temperature anomaly in Fahrenheit CL12 - Prevailing total sky cover fcst for a 12-hr period 1 = CL = mostly clear 4 = OV = mostly overcast 7 = PC = mixed clouds and clear skies SK12 - Maximum sustained surface wind speed fcst for a 12-hr period 5 = light = 0 - 12 knots 15 = moderate = 13 - 21 knots 25 = strong = 22 - 33 knots 40 = high = greater than or equal to 34 knots PP06 - Probability of precipitation fcst in a 6-hr period PP12 - Probability of precipitation fcst in a 12-hr period PP1C - Probability of precipitation climatology in a 12-hr period PP1A - Probability of precipitation anomaly in a 12-hr period PP24 - Probability of precipitation fcst in a 24-hr period PP2C - Probability of precipitation climatology in a 24-hr period PP2A - Probability of precipitation anomaly in a 24-hr period QP06 - Quantitative precipitation fcst in a 6-hr period 1 = 0.01 - 0.09 inches 2 = 0.10 - 0.24 inches 3 = 0.25 - 0.49 inches 4 = 0.50 - 0.99 inches 5 = 1.00 - 1.99 inches QPX2 - Maximum amount of precipitation in inches fcst in a 12-hr period. Values are same as QP12. QP12 - Quantitative precipitation fcst in a 12-hr period 0 = no precipitation expected 1 through 5 same as QP06 6 = greater than or equal to 2.00 inches QP24 - Quantitative precipitation fcst in a 24-hr period 0 through 5 same as QP12 6 = 2.00 - 2.99 inches 7 = greater than or equal to 3.00 inches TS06 - Unconditional probability of thunderstorms occurring in a 6-hr period TS12 - Unconditional probability of thunderstorms occurring in a 12-hr period TS24 - Unconditional probability of thunderstorms occurring in a 24-hr period TC06 - Conditional probability of severe weather occurring in a 6-hr period TC12 - Conditional probability of severe weather occurring in a 12-hr period PCPT - Categorical forecast of precipitation 0 = R = rain 1 = S = snow 2 = Z = freezing POZP - Conditional probability of freezing precipitation (not included during the warm season) POSN - Conditional probability of snow (not included during the warm season) SN06 - Categorical forecast of snow amount falling in a 6-hr period 0 = no snow 1 = trace to less than 2 inches 2 = greater than or equal to 2 inches SN12 - Categorical forecast of snow amount falling in a 12-hr period 0 and 1 same as SN06 2 = 2 to less than 4 inches 4 = 4 to less than 6 inches 6 = greater than 6 inches (not included during the warm season) SN24 - Categorical forecast of snow amount falling in a 24-hr period 0 = no snow or a trace 1 = greater than a trace to less than 2 inches 2 = 2 to less than 4 inches 4 = 4 to less than 6 inches 6 = 6 to less than 8 inches 8 = greater than 8 inches (not included during the warm season) PZ12 - Conditional probability of freezing precipitation in a 12-hr period PS12 - Conditional probability of snow in a 12-hr period PR12 - Conditional probability of mixed liquid/frozen precipitation in a 12-hr period PC12 - Categorical forecast of precipitation type in a 12-hr period 0 = R = liquid 1 = S = frozen 2 = Z = freezing 3 = RS = mixed liquid and frozen precipitation 4 = RZ 5 = SZ 6 = RSZ FCIG - Categorical forecast of ceiling height conditions 1 = less than 200 feet 2 = 200 - 400 feet 3 = 500 - 900 feet 4 = 1000 - 1900 feet 5 = 2000 - 3000 feet 6 = 3100 - 6500 feet 7 = 6600 - 12,000 feet 8 = greater than 12,000 feet or unlimited FVIS - Categorical forecast of visibility conditions 1 = less than 0.5 miles 2 = 0.5 - 0.875 miles 3 = 1.0 - 2.75 miles 4 = 3.0 - 5.0 miles 5 = greater than 5.0 miles FVSA - Categorical forecast of visibility conditions (for new MOS) 1 = less than 0.5 miles 2 = 0.5 mile to less than 1.0 mile 3 = 1.0 to less than 2.0 miles 4 = 2.0 to less than 3.0 miles 5 = 3.0 to 5.0 miles 6 = 6.0 miles 7 = greater than 6.0 miles OVIS - Categorical forecast in plain language of obstructions to vision 0 = N = none of the following: 1 = FG or F = fog or ground fog (vis. less than .625 mile) 2 = HZ or H = haze, smoke, dust 3 = BR = mist (fog with visibility greater than .625 mile) 4 = BL = blowing dust, sand, snow WXPB - Categorical weather precipitation probability or areal coverage determined by the precipitation parameter having the highest probability or areal coverage in WNUM. For probability: 1 = slight chance 2 = chance 3 = likely 4 = occasional 5 = definite For areal coverage: 1 = isolated 2 = widely scattered 3 = scattered 4 = numerous 5 = widespread TERMINAL AERODROME FORECAST (TAF) PARAMETERS TDRC - Temporary/probability wind direction in degrees TSKN - Temporary/probability wind speed in knots TGST - Temporary/probability wind gusts in knots BRGK - Gust barb feathered in knots TCHx - Temporary/probability numeric combined cloud height and coverage, as for CHCx TCEL - Temporary/probability ceiling in hundreds of feet, as for CEIL TSKC - Temporary/probability cloud coverage graphics symbol, as for SKYC TXVF - Temporary/probability categorical identification of flight rules, as for XVFR TWNM - Temporary/probability numeric weather code, as for WNUM TWSY - Temporary/probability graphics weather symbol corresponding to TWNM, as for WSYM TVSB - Temporary/probability visibility in statute miles PPRB - Probability for TAF forecast change indicator 30 = PROB30 - 30 percent probability condition 40 = PROB40 - 40 percent probability condition 50 = TEMPO - temporary condition VWNM - Vicinity numeric weather code, as for WNUM VWSY - Vicinity graphics weather symbol corresponding to VWNM, as for WSYM TVWN - Temporary/probability vicinity numeric weather code, as for WNUM WSKC - Worst case cloud coverage graphics symbol, as for SKYC WXVF - Worst case categorical identification of flight rules, as for XVFR TPWN - Temporary/probability/vicinity numeric weather code, as for WNUM TPWS - Temporary/probability/vicinity graphics weather symbol corresponding to TPWN, as for WSYM AWNM - Prevailing/temporary/probability/vicinity numeric weather code, as for WNUM AWSY - Prevailing/temporary/probability/vicinity graphics weather symbol corresponding to AWNM, as for WSYM LLWS - Low level wind shear forecast flag MOTV - Mountain obscuration threshold value in hundreds of feet CMSL - Ceiling converted to mean sea level in hundreds of feet MOBS - Mountain obscuration threshold met indicator TCMS - Temporary/probability ceiling converted to mean sea level in hundreds of feet TMOB - Temporary/probability mountain obscuration threshold met indicator WCMS - Worst case ceiling converted to mean sea level in hundreds of feet WMOB - Worst case mountain obscuration threshold met indicator TCTL - Temporary/probability low-level cloud genera from WMO Code 0513, as for CTYL TCSL - Temporary/probability cloud graphics symbol for TCTL, as for CSYL MARINE PARAMETERS WHGT - Wave height in meters WHFT - Wave height in feet WPER - Wave period in seconds HOWW - Height of wind wave in meters POWW - Period of wind wave in seconds HOSW - Height of predominant swell wave in meters POSW - Period of predominant swell wave in seconds DOSW - Direction of predominant swell wave in degrees HOS2 - Height of secondary swell wave in meters POS2 - Period of secondary swell wave in seconds DOS2 - Direction of secondary swell wave in degrees WAV2 - Combined wind wave period and height in feet ("2 group") WAV3 - Combined predominant and secondary swell wave direction in tens of degrees ("3 group") WAV4 - Combined predominant swell wave period and height in feet ("4 group") WAV5 - Combined secondary swell wave period and height in feet ("5 group") WPHM - Combined wave period and height in half meters WVSW - Combined swell wave direction, period and height in half meters SWEL - Character combined swell wave direction, period and height in half meters DAWV - Swell wave direction arrows of uniform length IDTH - Thickness of ice on ship in meters ROIA - Rate of ice accretion on ship from WMO Code 3551 0 = Ice not building up 1 = Ice building up slowly 2 = Ice building up rapidly 3 = Ice melting or breaking up slowly 4 = Ice melting or breaking up rapidly IGRO - Rate of ice accretion on vessel in salt water in inches per three hours IGRO = ( A*PR + B*PR*PR + C*PR*PR*PR ) * CVFAC A = 2.73 * 10E-2 B = 2.91 * 10E-4 C = 1.84 * 10E-6 PR = ( SPED * ( -1.7 - TMPC ) ) / ( 1 + 0.4 * ( SSTC + 1.7 ) ) (priesendorfer regression) CVFAC = 1.1811, to convert cm/hr to in/3hr DIGR - Character rate of ice accretion in inches per three hours SHPD - True direction from which ship is moving (for 3 hours before obs) in degrees SHPK - Ship's average speed (for 3 hours before obs) in knots DASH - Ship's true direction arrows of uniform length PMN1 - Lowest 1-minute average pressure in previous hour in mb PMNT - Time of lowest 1-minute average pressure, as hhmm PKWD - Direction of 1-minute peak wind in previous hour in degrees PKWK - Highest 1-minute mean wind speed in previous hour in knots PKWS - Highest 1-minute mean wind speed in previous hour in m/sec PKWT - Time of highest peak 1-minute wind in previous hour, as hhmm BRPK - Wind barb (knots) for highest peak 1-minute wind AIRCRAFT PARAMETERS TURB - Amount of turbulence 0 = No turbulence 2 = Light turbulence 3 = Light to moderate turbulence 4 = Moderate turbulence 5 = Moderate to severe turbulence 6 = Severe turbulence 8 = Extreme turbulence TBSE - Base of turbulence in feet TTOP - Top of turbulence in feet HBOT - Base of turbulence in meters HTOT - Top of turbulence in meters FQOT - Frequency of turbulence 1 = Occasional 2 = Intermittent 3 = Continuous TPOT - Type of turbulence 1 = Clear air turbulence 2 = Chop 3 = Low level wind shear 4 = Turbulence in cloud TBSY - Graphics symbol for turbulence ICNG - Amount of airframe icing 0 = No icing 1 = Trace icing 2 = Trace to light icing 3 = Light icing 4 = Light to moderate icing 5 = Moderate icing 7 = Moderate to severe icing 8 = Severe icing IBSE - Base of icing in feet ITOP - Top of icing in feet HBOI - Base of icing in meters HTOI - Top of icing in meters TPOI - Type of icing 1 = Rime 2 = Clear 3 = Mixed 4 = Rime in cloud 5 = Clear in cloud 6 = Mixed in cloud 7 = Rime in precipitation 8 = Clear in precipitation 9 = Mixed in precipitation 10 = Frost 11 = Non-persistent contrails 12 = Persistent contrails ICSY - Graphics symbol for icing WBSE - Base of weather in feet WTOP - Top of weather in feet HBWX - Base of weather in meters HTWX - Top of weather in meters CLC1 - Numeric cloud coverage 1 CBS1 - Cloud base 1 in feet CTP1 - Cloud top 1 in feet CB1M - Cloud base 1 in meters CT1M - Cloud top 1 in meters CLC2 - Numeric cloud coverage 2 CBS2 - Cloud base 2 in feet CTP2 - Cloud top 2 in feet CB2M - Cloud base 2 in meters CT2M - Cloud top 2 in meters ACRT - Aircraft report type 1 = AIREP - Aircraft report 2 = PIREP - Pilot report 3 = RECCO - Reconnaissance flight report 4 = AMDAR - Aircraft report (aircraft meteorological data relay) SELV - Flight level in meters FELV - Flight level in hundreds of feet ITSY - Icing type symbol TTSY - Turbulence type symbol TFSY - Turbulence frequency symbol ACTP - Character aircraft type ATP1 - Numeric aircraft type The numeric aircraft type is a real representation of up to four characters from the character aircraft type. ATP1 = v4 * 40 * 40 * 40 + v3 * 40 * 40 + v2 * 40 + v1. Each character corresponds to one of the values: 1 = - 9 = 5 17 = D 25 = L 33 = T 2 = . 10 = 6 18 = E 26 = M 34 = U 3 = / 11 = 7 19 = F 27 = N 35 = V 4 = 0 12 = 8 20 = G 28 = O 36 = W 5 = 1 13 = 9 21 = H 29 = P 37 = X 6 = 2 14 = A 22 = I 30 = Q 38 = Y 7 = 3 15 = B 23 = J 31 = R 39 = Z 8 = 4 16 = C 24 = K 32 = S Any character not defined above is treated as a /. MISCELLANEOUS PARAMETERS VSBY - Visibility in statute miles VSBK - Visibility in kilometers VSBN - Visibility in nautical miles VSBF - Character visibility in fractions of statute miles for visibilities between 0. and 1. VSBC - Character visibility in fractions of statute miles for all visibility numbers PnnI - Precipitation over last nn hours in inches nn = 01, 03, 06, 09, 12, 18 or 24 PnnM - Precipitation over last nn hours in millimeters nn = 01, 03, 06, 09, 12, 18 or 24 DPRC - Character daily weather map precipitation in inches PR24 - Precipitation over last 24 hours in inches, as sum of four successive 6-hour precip amounts SNOW - Snow depth in inches SNEW - Amount of new snow in inches SNRT - Forecast snow and ice pellet accumulation to watch threshold ratio SI12 - Forecast snow and ice pellet 12-h accumulation in inches SNIP - Snow and ice pellet watch threshold in inches FZRT - Forecast freezing rain accumulation to watch threshold ratio FZ12 - Forecast Freezing rain 12-h accumulation in inches FZRN - Freezing rain watch threshold in inches WEQS - Water equivalent of snow on the ground in inches HAIL - Hail flag HLSZ - Hail size in centimeters DDEN - Density of dry air in kg/(m**3) PSYM - Montgomery stream function in m**2/(100*s**2) HEAT - Heat index in Fahrenheit HMTR - Humiture (apparent temperature) in Fahrenheit WCEQ - Wind chill equivalent temperature in Fahrenheit WCHT - Revised wind chill temperature in Fahrenheit MSUN - Duration of sunshine in minutes FFnn - Flash flood guidance for next nn hours in inches nn = 01, 03, 06, 12 or 24 TOST - Type of station (manned or automatic) 0 = automatic 1 = manned STIM - Report hour and minutes as hhmm TEXT - Undecoded data SPCL - Undecoded special reports MARK - Markers FOSB - Fosberg Index, also called Fire Weather Index SPACING PARAMETERS BLNK - Plot a blank, not accounted for in FILTER SPAC - Plot a space, accounted for in FILTER