Rapid Refresh (RAP)

Best (4-layer) lifted index uses parcels from the lowest four model layers to assess stability at 500 hPa. More negative values indicate greater instability.

• Units: K.
• Often used alongside CAPE and CIN in convective forecasting.

Absolute vorticity combines relative vorticity and planetary vorticity from Earth's rotation. It highlights rotation and dynamical forcing in the flow.

• Units: 1/s.

Convective precipitation accumulation represents precipitation produced by the convection scheme during the output period. It isolates convective rainfall from larger-scale precipitation.

• Units: kg/m².
• Useful for identifying convectively driven rainfall contributions.

Aerosol optical thickness represents the column-integrated attenuation of solar radiation by aerosols. Larger values indicate hazier conditions and reduced surface sunlight.

• Units: dimensionless.
• Useful for visibility, air quality, and solar energy assessments.

Accumulated precipitation represents the total water-equivalent amount of rain and snow during the output period. It is a primary field for hydrologic impacts and event totals.

• Units: kg/m^2.
• Use with the model time interval to interpret totals and compare to gauges.

Accumulated snow depth is the total depth of snow on the ground over the period. It is a physical depth, not water equivalent.

• Units: m.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Baseflow‑groundwater runoff represents subsurface drainage from soil into streams. It is a slower component of runoff.

• Units: kg/m^2.

Convective Available Potential Energy (CAPE) quantifies buoyant energy available to rising air parcels. Larger values generally imply stronger potential updrafts and greater convective intensity.

• Units: J/kg.
• Often used with CIN and lifting mechanisms to assess thunderstorm potential.

Categorical indicator of freezing rain occurrence at the surface during the output period.

• Units: flag.
• Useful as a mask for icing or glaze hazards.

Categorical indicator of ice pellet (sleet) occurrence at the surface during the output period.

• Units: flag.
• Use with precipitation fields to gauge intensity.

Convective Inhibition (CIN) measures the energy barrier that must be overcome to initiate convection. More negative values indicate a stronger cap that can suppress storms.

• Units: J/kg.
• When CIN is weak and CAPE is high, convection is more likely.

Categorical indicator of rain occurrence at the surface during the output period. Useful as a yes/no mask for rain.

• Units: flag.
• Use with accumulation or rate fields for intensity.

Categorical indicator of snow occurrence at the surface during the output period.

• Units: flag.
• Use alongside snowfall/snow-water-equivalent fields.

Dew point depression is the difference between air temperature and dew point. Small values indicate near‑saturation.

• Units: K.
• When dew point is close to air temperature, fog or low cloud potential increases.

Dew point temperature is the temperature at which the air becomes saturated. It is a direct measure of moisture content.

• Units: K.
• When dew point is close to air temperature, fog or low cloud potential increases.

Equivalent potential temperature includes the effects of moisture and latent heat. It is conserved for moist adiabatic motions.

• Units: K.

Freezing rain accumulation is the water-equivalent amount of freezing rain during the period. It relates directly to ice accretion risk.

• Units: kg/m^2.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Freezing rain probability gives the chance of freezing rain during the period. It supports icing risk guidance.

• Units: percent.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Wind gust is the peak short-duration wind speed. It captures brief, hazardous bursts that can exceed sustained winds.

• Units: m/s.

High cloud cover is the fraction of the grid cell covered by clouds in the upper troposphere. It affects longwave radiation and aviation.

• Units: percent.
• Cloud fraction influences surface radiation and temperature.

Geopotential height is the altitude of a pressure surface in the atmosphere. It is the primary field for identifying ridges, troughs, and large‑scale flow patterns.

• Units: gpm.

Haines Index combines stability and moisture to estimate large fire growth potential. Higher values indicate drier, more unstable conditions favorable for fire behavior.

• Units: K.
• Typically used in wildfire forecasting and risk monitoring.

Storm-relative helicity measures the potential for streamwise vorticity to be ingested by a storm updraft. Higher values suggest a greater likelihood of rotating updrafts.

• Units: m^2/s^2.
• Commonly evaluated in the lowest 1 to 3 km layer.

Boundary layer height marks the depth of the turbulent surface-influenced layer. It affects mixing, dispersion, and surface fluxes.

• Units: m.

Soil layer thickness specifies the depth of the modeled soil layer. It helps interpret soil moisture and temperature fields.

• Units: m.
• Soil state affects evapotranspiration and boundary-layer moisture.

Low cloud cover is the fraction of the grid cell covered by low clouds. It strongly affects visibility, fog potential, and surface temperatures.

• Units: percent.
• Cloud fraction influences surface radiation and temperature.

Lifted Index compares a lifted parcel's temperature to the environment at 500 hPa. More negative values indicate greater instability and thunderstorm potential.

• Units: K.
• Values near zero indicate neutral stability.

Lightning indicates flash frequency or density, a proxy for convective intensity. Higher values suggest stronger or more frequent thunderstorms.

• Units: flashes/km2/s.

Mass density (concentration) represents mass per unit volume of the named species or medium. It is used for concentration and transport analyses.

• Units: kg/m^3.

Mid-level cloud cover is the fraction of the grid cell covered by clouds in the middle troposphere. It influences both shortwave and longwave radiation.

• Units: percent.
• Cloud fraction influences surface radiation and temperature.

Mean sea level pressure anomaly is the departure of MSLP from a reference or climatology. It highlights large-scale pressure patterns.

• Units: Pa.

Moisture availability represents how much moisture is available at the surface for evaporation. It is used in land-surface and fire-weather diagnostics.

• Units: percent.

Pressure of the level from which the parcel was lifted indicates the parcel source level used for stability indices. It helps interpret lifted index and CAPE products.

• Units: Pa.

Potential temperature is the temperature a parcel would have if brought dry‑adiabatically to a reference pressure. It is used for stability.

• Units: K.

Precipitation rate is the total intensity of precipitation over the period. It combines convective and stratiform contributions.

• Units: kg/(m^2 s).
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Pressure is the atmospheric pressure at the specified level. It is a fundamental mass-field variable for dynamics and thermodynamics.

• Units: Pa.

Precipitable water is the total column water vapor from the surface to the top of the atmosphere. It is a key moisture indicator.

• Units: kg/m^2.

Composite reflectivity is the maximum reflectivity in the column. It is a standard radar‑style field for identifying convective cores and precipitation intensity.

• Units: dBZ.

Reflectivity is a radar‑style measure of hydrometeor concentration at a given level. Higher values generally correspond to heavier precipitation.

• Units: dBZ.

Echo top height is the altitude of the highest reflectivity in the column. It is a proxy for storm depth and convective vigor.

• Units: m.

Relative humidity describes how close the air is to saturation at the specified level. High values favor cloud formation.

• Units: percent.
• Higher values indicate more atmospheric moisture and greater cloud or precip potential.

Relative humidity with respect to precipitable water is a column‑scale moisture indicator based on total water vapor content.

• Units: percent.
• Higher values indicate more atmospheric moisture and greater cloud or precip potential.

Simulated brightness temperature for GOES-11 channel 3 represents modeled radiance converted to an equivalent blackbody temperature. It supports satellite comparison and cloud diagnostics.

• Units: K.

Simulated brightness temperature for GOES-11 channel 4 represents modeled radiance converted to an equivalent blackbody temperature. It supports satellite comparison and cloud diagnostics.

• Units: K.

Simulated brightness temperature for GOES-12 channel 3 represents modeled radiance converted to an equivalent blackbody temperature. It supports satellite comparison and cloud diagnostics.

• Units: K.

Simulated brightness temperature for GOES-12 channel 4 represents modeled radiance converted to an equivalent blackbody temperature. It supports satellite comparison and cloud diagnostics.

• Units: K.

Snow depth is the physical thickness of the snowpack. It is distinct from snow water equivalent, which measures water content.

• Units: m.

Specific humidity is the mass of water vapor per mass of air at the specified level. It is central to moisture transport.

• Units: kg/kg.
• Higher values indicate more atmospheric moisture and greater cloud or precip potential.

Storm surface runoff represents overland flow generated by rainfall or snowmelt. It responds quickly to heavy precipitation.

• Units: kg/m^2.

Total cloud cover is the fraction of the grid cell covered by clouds at any level. It influences radiation, temperature, and visibility.

• Units: percent.
• Cloud fraction influences surface radiation and temperature.

Air temperature is the thermal state of the atmosphere at the specified level. It influences density, stability, and energy exchange.

• Units: K.

U‑component of wind is the east‑west component of the horizontal wind. Combine with v for speed and direction.

• Units: m/s.
• Combine u and v components to compute speed and direction.

U‑component of storm motion is the east‑west component of the storm translation vector.

• Units: m/s.

V‑component of wind is the north‑south component of the horizontal wind. Combine with u for speed and direction.

• Units: m/s.
• Combine u and v components to compute speed and direction.

Horizontal visibility at the surface. Lower values indicate reduced visibility due to fog, precipitation, or aerosols.

• Units: m.

Vertical speed at maximum wind represents vertical motion near the strongest wind level. It can be linked to jet dynamics and turbulence.

• Units: m/s.

U‑component of shear velocity represents the east‑west component of bulk wind shear.

• Units: m/s.

V‑component of shear velocity represents the north‑south component of bulk wind shear.

• Units: 1/s.

Vertical velocity in pressure coordinates (omega). Negative values indicate upward motion (rising air); positive values indicate subsidence.

• Units: Pa/s.

Snow water equivalent (SWE) is the total liquid water stored in the snowpack. It integrates depth and density of existing snow.

• Units: kg/m^2.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.