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Weather Element Definitions Key

Weather Element Name ID (grib2) ID (text bulletins) Desciption of the weather element
[additional information (hover or tab)]
Additional information
  • In the ID names, (xx) stands for a time period for the product (example: 6-hour QPF is qpf06)
  • In the ID name (PP) stands for a quantile level
  • An (n/a) for an ID means that the element is not available in that format

Weather Element Definitions

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Weather Element grib2 ID text ID Definition
apparent temperature appt (n/a) Perceived temperature derived from either a combination of temperature and wind (Wind Chill) or temperature and humidity (Heat Index) for the indicated time. When the temperature at a particular grid point falls to 50 F or less, wind chill will be used for that point for the Apparent Temperature. When the temperature at a grid point rises above 80 F, the heat index will be used for Apparent Temperature. Between 51 and 80 F, the Apparent Temperature will be the ambient air temperature.
ceiling height cig CIG Height from surface of the lowest layer of clouds (or obscuring phenomena) when reported as broken, overcast, or obscuration and not classified "thin" or "partial." The ceiling is termed unlimited when the foregoing conditions are not satisfied
lowest cloud base cldbse LCB Lowest altitude at which the air contains a perceptible quantity of cloud particles
dew point dewp DPT Temperature to which air must be cooled for saturation to occur at 2 meter height, valid at forecast time
probability of dry thunder dryts(xx) (n/a) Probabliliy of widespread or numerous thunderstorms that produce little wetting rain (<0.10 in) where dried fuels exist
18 dBZ echo top height echotop (n/a) Maxiumum height at which 18dBZ refectivity is present in a vertical column
flat ("total") ice accumulation flatice(xx) I(xx) Amount of new ice accretion on all exposed surfaces accumulated over a given time period ending at the specificed time
line ice accumulation lineice(xx) (n/a) Amount of ice forecast to accumulate on radial surfaces (e.g. power lines, tree branches) over a given period, computed utilizing the Freezing Rain Accumulation Model.
low-level wind shear direction llwsdir (n/a) Direction of wind at maxiumum low-level wind shear height
low-level wind shear height llwshgt (n/a) Height of the top of the maximum wind shear layer between 0-2000 ft above ground level
[1]
Shear is computed for the following 10 layers. These shear values are then normalized and the layer of max normalized wind shear is determined: (1) 0-500 ft (2) 0-1000 ft (3) 500-1000 ft(4) 0-1500 ft (5) 500-1500 ft (6) 1000-1500 ft (7) 0-2000 ft (8) 500-2000 ft (9) 1000-2000 ft (10) 1500-2000 ft
low-level wind shear speed llwspd (n/a) Speed of wind at maxiumum low-level wind shear height
Fosberg fire weather index (6-hour maximum) maxffwi (n/a) A non-linear filter of meteorological data developed by first transforming temperature and relative humidity to equilibrium moisture content, then transforming the equilibrium moisture content to combustion efficiency; NBM uses blended MAEW 2m temp, 2m RH, and 10m wind speed used according to Goodrick,2002 (International Journal of Wildland Fire)
Haines Index (6-hour maximum) maxhi (n/a) Snapshot index based on stability and moisture used for Fire Weather
maximum reflectivity (1-hour, 1km) maxref (n/a) Maxiumum observed radar reflectivity (dBZ) at 1km over the previous hour
mixing height mixhgt (n/a) Height where the fire sounding (surface temperature + 0.5K) crosses the environmental sounding (where the model virtual potential temp is higher than the fire potential temp); based on Stull method
maximum relative humidity maxrh (n/a) Maximum relative humidity (%) expected for the 12-hour period between 06Z-18Z
maximum temperature maxt X Maximum temperature during an 18-hour period between 12Z-06Z
minimum relative humidity minrh (n/a) Minimum relative humidity (%) expected for the 12-hour period between 18Z-06Z
minimum temperature mint N Minimum temperature during an 18-hour period between 00Z-18Z
maximum wetbulb temperature aloft mxwbalft (n/a) Maximum wet bulb temperature in the layer between 2000 feet above ground level up to 400 hPA - used to assess precipitation type.
negative energy of near surface cold layer negengy (n/a) Bourgouin precipitation type method parameter, totaling the amount of area colder than 0 deg C below the warm nose aloft
probability of precipitation pop(xx) P(xx) Probability that a threshold amount (the equivalent of 0.01 inches) of precipitation will fall during a time period ending at the specified time. (Example: 00Z PoP12 lists the probability precipitaition will fall between GMT noon to midnight)
positive energy of warm nose aloft posengy (n/a) Bourgouin precipitation type method parameter, totaling the amount of area warmer than 0 deg C above 2000 ft AGL
precipitation potential index ppi(xx) (n/a) A means to show confidence as to the location of precipitation at each forecast time across the forecast area. PPI values range from 0 to 100 and resemble PoP12 values in magnitude. The PoP12 for any 12- hour period can be derived by taking the maximum PPI value within the desired period.
predominant weather predomwx (n/a) Expected weather (precipitating or non-precipitating) valid at the indicated hour. Precipitating weather includes type, probability, and intensity information. In cases of convective weather, coverage may be substituted for probability
probability of freezing rain prfzrn PZR Probability that if precipitation occurs, it will fall in the form of freezing rain
probability of ice present probiceprsnt (n/a) Precipitation type diagnostic parameter: the probability that ice nuclei exists in the clouds and where the mean RH > 85% through the lowest 1 km AGL
probability of re-freeze sleet probrefzslt (n/a) Probability that liquid precipitation falling through a sub-freezing layer will refreeze into sleet before reaching the surface
probability of rain prrain PRA Probability that if precipitation occurs, it will fall in the form of rain
probability of sleet prsleet PPL Probability that if precipitation occurs, it will fall in the form of sleet or ice pellets
probability of snow prsnow PSN Probability that if precipitation occurs, it will fall in the form of snow grains or pure snow
probability of thunderstorms ptsm(xx) T(xx) Probability of 1 or more cloud-to-ground lightning strikes in a 40-km grid box during the period
quantitative precipitation forecast qpf(xx) Q(xx) Amount of liquid-equivalent precipitation expected to fall over a time period ending at the specified time. (Example: 12Z qpf06 forecasts the amount of precip that will fall between 06Z and 12Z)
relative humidity rh (n/a) Ratio, expressed as a percent, of the amount of atmospheric moisture present relative to the amount that would be present if the air were saturated. It is a function of both moisture content and temperature.
significant wave height sigwv SWH Average height (from trough to crest) of the one-third highest waves valid for the top of the designated hour. Wave Height is a combination of wind waves and swell
sky cover sky SKY Percent of the sky with opaque cover at the forecast time
sleet accumulation sleet(xx) (n/a) Total accumulation of new sleet during a period ending at the specified time
snow liquid ratio slrblend (n/a) Number of inches of snow expected per one inch of precipitable water
snow accumulation snow(xx) S(xx) Total accumulation of new snow during a period ending at the specified time
snow level snowlvl SLV Height below which only rain is observed (all snow has melted); used as a proxy for freezing level in NBM
temperature temp TMP Temperature at 2 meter height, valid at forecast time
transport wind direction trwdir (n/a) Vector of average U and average V from surface to mixing height
transport wind speed trwspd (n/a) Average wind speed magnitude from surface to mixing height
vertically integrated liquid vil (n/a) Vertical integral of liquid water content obtained from radar observations at different elevation angles within a precipitation echo (mass/area); the liquid water is calculated using equivalent reflectivity factor Ze using the Marshall-Palmer drop-size distribution. The presence of hail in a storm produces larger VIL values than otherwise would be expected.
visibility vis VIS Maximum number of (statute) miles an object can be seen and identified in the horizontal. The maximum distance is determined for a minimum area of one half of the horizon circle. Visibility greater than six statute miles is considered unrestricted.
ventilation rate vrate (n/a) Product of transport wind speed and mixing height
wind direction wdir WDR Average 10 meter wind direction, calculated from u-wind and v-wind components. (Note: v3.1 winds used a clustered weighted average method
[1])
Wind directions from each model are placed into 8 bins (4 bins if at 120 h projection or later), and then bins are sorted from highest to lowest number of members. The bin with the largest number of members is then averaged to obtain a mean wind direction within that bin. In the case of a tie among 2 or more bins, the bin with the lowest MAE is chosen and averaged
wind gust wgust GST Maximum wind speed within 10 minutes of the top of the hour. (10 meter height)
wind speed wspd WSP Mean wind speed at 10m height (30m and 80m are also available)
oceanic mean sea level pressure CDF  mslp_cdf-(PP)p (n/a) Oceanic domain atmospheric pressure at sea level. Percentiles obtained by cumulative distribution function
oceanic 2 m temperature CDF temp_cdf-(PP)p (n/a) Oceanic domain temperature at 2 m height. 50th percentile obtained from cumulative distribution function
oceanic visibility CDF vis_cdf-(PP)p (n/a) Oceanic domain surface visibility. 50th percentile obtained from cumulative distribution function
oceanic 10 m wind gust CDF gust_cdf-(PP)p (n/a) Oceanic domain 10 m wind gust. 50th percentile obtained from cumulative distribution function.
oceanic 10m wind speed CDF wspd_cdf-(PP)p (n/a) Oceanic domain 10 m wind speed. Percentiles obtained from cumulative distribution function.
probabilistic calibrated QPF qmd_qpf(xx)p(PP) Q(xx)P(P) Calibrated 6-hour QPF with (P)0th-percent probability of non-exceedance. There is a (P)0% chance that less than the given number of inches of precipitation will fall during the previous (xx) hours, ending at the valid time. (Example: 12Z Q12P1 = 0.10" means there is a 10% chance between 0-0.10" of precipitation will fall between 00z and 12z, and there is a 90% chance that more than 0.10" of precipitation will fall.)
calibrated probability of precipitation qmd_pop(xx) (n/a) Calibrated xx-hour probability of precipitation using a quantile mapping method. The details of the calibration procedure are described in a publication by Hamill, 2017.
probabilistic maximum temperature [coming soon] XP(P) Maximum 18-hour temperature with (P)0th-percent probability of non-exceedance. There is a (P)0% chance that the maximum temperature during the 18-hour period between 12Z-06Z(following day) will be less than or equal to the given number. (Example: XP1 = 50F means that there is a 10% chance the maximum temperature will be 50F or less between 12Z-06Z, and there is a 90% chance that the maximum temperature will be greater than 50F).
probabilistic minimum temperature [coming soon] NP(P) Minimum 18-hour temperature with (P)0th-percent probability of non-exceedance. There is a (P)0% chance that the minimum temperature during the 18-hour period between 00Z-18Z will be less than or equal to the given number. (Example: NP1 = 50F means that there is a 10% chance the minimum temperature will be 50F or less between 00Z-18Z, and there is a 90% chance that the minimum temperature will be greater than 50F).