High-Resolution Rapid Refresh (HRRR)

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.

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.

Critical Angle.

• Values retain the source encoding and units; no conversion is applied.

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.

Convective cloud cover is the fraction of the grid cell covered by clouds produced by the convective parameterization. It is useful when you need to separate parameterized convective cloud from stratiform or total cloud amount.

• Units: %.
• Interpret it alongside total cloud cover and precipitation to see how much of the cloud field is tied to deep convection.

Cloud forcing on net solar flux is the difference between clear-sky and all-sky net shortwave at the surface. It quantifies how much clouds reduce surface solar heating.

• Units: W/m^2.
• More negative values indicate stronger cloud shading.

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

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

Cloud ice is the ice-phase condensate carried in cloud, as distinct from falling snow or graupel. In NAM it is mainly used for cloud microphysics, icing diagnostics, and simulated satellite or radiation calculations.

• Units: kg/m^2.
• Compare it with cloud water, snow, and rime factor to distinguish suspended ice from precipitating frozen hydrometeors.

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

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

Cloud ice mixing ratio is the mass of ice cloud particles per mass of air. It indicates ice-phase cloud content relevant to precipitation and radiation.

• Units: kg/kg.
• Cloud fraction influences surface radiation and temperature.

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.

Cloud water mixing ratio is the mass of liquid cloud droplets per mass of air. It describes in‑cloud liquid water content.

• Units: kg/kg.
• Cloud fraction influences surface radiation and temperature.

Cloud liquid water mixing ratio emphasizes the liquid phase of cloud water. It is used in microphysics and fog diagnostics.

• Units: kg/kg.
• Cloud fraction influences surface radiation and temperature.

Plant canopy surface water is liquid water intercepted by vegetation. It represents interception storage and evaporation potential.

• Units: kg/m^2.

Column-integrated mass density is the total mass per unit area through the vertical column for the specified species. It summarizes column burden and is useful for transport diagnostics.

• Units: kg/m^2.

Percent frozen precipitation indicates the fraction of total precipitation that is falling in frozen form. It helps distinguish mixed-phase and winter precipitation impacts.

• Units: percent.
• Higher values indicate a larger frozen contribution to the total precipitation.

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.

Downward longwave (thermal) flux represents incoming energy at the surface. It is a key driver of surface heating and cooling.

• Units: W/m^2.
• Shortwave affects surface heating; longwave affects radiative cooling.

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.

Downward radiative flux represents incoming energy at the surface. It is a key driver of surface heating and cooling.

• Units: W/m^2.
• Shortwave affects surface heating; longwave affects radiative cooling.

Geometric vertical velocity (dz/dt) is the vertical speed of air in height coordinates. Positive values indicate rising motion and negative values sinking motion.

• Units: m/s.

Effective Storm Relative Helicity.

• Values retain the source encoding and units; no conversion is applied.

Enhanced Stretching Potential.

• Values retain the source encoding and units; no conversion is applied.

Friction velocity (u*) is a measure of near‑surface shear stress. It is commonly used in turbulence, dust, and air‑sea exchange calculations.

• Units: m/s.

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 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.

Ground heat flux is the conductive heat exchange between the surface and the subsurface. It is a key term in the surface energy balance.

• Units: W/m^2.

Graupel accumulation represents the water-equivalent amount of graupel in the column. It helps diagnose convective microphysics.

• Units: kg/kg.

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

• Units: m/s.

Hail represents hail size as a length measure. Larger values indicate more severe hail potential.

• Units: m.
• Use it with convective parameters and reflectivity fields to assess severe-storm potential.

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.

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.

Ice cover is the proportion of the grid cell covered by ice. It is used as a surface-state mask for sea ice and related cryosphere diagnostics.

• Units: Proportion.

Land cover is a land/sea mask where 0 indicates sea and 1 indicates land. It is used to separate land and ocean surface processes.

• Units: Proportion.

Layer thickness is the vertical distance between the bounds of a layer. It helps interpret thermodynamic and lifted-layer diagnostics.

• Units: m.

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.

Latent heat net flux represents energy exchange due to evaporation/condensation at the surface. It links moisture and energy budgets.

• Units: W/m^2.

Lightning is a dimensionless model diagnostic in these NOAA mesoscale inventories. Higher values indicate greater modeled lightning or convective electrical activity.

• Units: non-dim.

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.

Hourly maximum downward vertical velocity in the lowest 400 hPa highlights the strongest subsidence within the lower troposphere during the hour.

• Units: m/s.

Hourly maximum simulated reflectivity at 1 km AGL captures the strongest modeled reflectivity near the surface. It is used to identify peak convective intensity and heavy precipitation cores.

• Units: dBZ.

Hourly maximum upward vertical velocity in the lowest 400 hPa highlights the strongest updrafts within the lower troposphere during the hour.

• Units: m/s.

Maximum u‑component of wind is the strongest east‑west flow during the period. It helps identify peak wind directions.

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

Maximum v‑component of wind is the strongest north‑south flow during the period.

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

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.

Hourly minimum updraft helicity is the lowest helicity value during the hour. It provides a lower bound on rotating updraft potential.

• Units: m2/s2.

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.

Hourly maximum updraft helicity (2–5 km AGL) highlights the strongest rotating updrafts during the hour.

• Units: m2/s2.

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.

Pressure reduced to mean sea level is MSLP computed from surface pressure and temperature. It is used to locate highs and lows.

• 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.

Relative vorticity measures local rotation of the horizontal wind field. Positive values indicate cyclonic rotation and negative values anticyclonic rotation.

• Units: 1/s.

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.

Rain water mixing ratio is the mass of rainwater per mass of air. It describes rain content within the column.

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

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.

Surface roughness length is the effective height of surface obstacles that control drag. It strongly influences near-surface wind, turbulence, and exchange fluxes.

• Units: m.

Sensible heat net flux is turbulent heat exchange driven by temperature differences. It affects near‑surface temperature and stability.

• Units: W/m^2.

Snow mixing ratio is the mass of snow particles per mass of air. It describes suspended snow content relevant to microphysics and precipitation.

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