Forecast Variables

All forecast data is generated using Weather Central’s proprietary forecasting SuperMicrocast technology. This model offers some of the highest resolution forecast data available with resolutions down to 1km per gridpoint of data. Additionally Weather Central runs interpolation between gridpoints so the forecasts area truly specific to the latitude longitude pair you are requesting.

Forecast Variables

Accumulated Ice Relative Humidity Traffic 120m Wind Direction Wave Height
Accumulated Rain High Clouds Surface Wind Direction 120m Wind Speed Wave Period
Accumulated Snow Mid Clouds1 Surface Wind Speed 120m Wind Gusts Wave Direction
Clouds Mid Clouds2 Surface Wind Gusts Summary Primary Wave Direction
Dewpoint Low Clouds 60m Wind Direction Probability of Precipitation Primary Wave Period
Feelslike Supercell 60m Wind Speed UV Index  
Reflectivity Temperature 60m Wind Gusts    

Accumulated Ice

API Query:
datatype=forecast&var=accumicetotal

This is the accumulated freezing rain accumulation forecasted by the SuperMicrocast Model over the forecast period. Freezing Rain occurs when the air is above freezing but the ground is below freezing so the rain freezes to surfaces such as trees and roadways upon contact. This is a cumulative product so the data return by both the point and tile requests in an indication of how much freezing rain has fallen since the beginning of the model run (represented by the starttime attribute of the hourly or daily point xml return). The resolution of this product is 1km.

Point Data Example:

Tile Data Example:


Accumulated Rain

API Query:
datatype=forecast&var=accumraintotal

This is the accumulated rain forecasted by the SuperMicrocast Model over the forecast period. This is a cumulative product so the data return by both the point and tile requests in an indication of how much rain has fallen since the beginning of the model run (represented by the starttime attribute of the hourly or daily point xml return). The resolution of this product is 1km.

Point Data Example:

Tile Data Example:

Accumulated Snow

API Query: datatype=forecast&var=accumsnowtotal

This is the accumulated snow forecasted by the SuperMicrocast Model over the forecast period. This is a cumulative product so the data return by both the point and tile requests in an indication of how much rain has fallen since the beginning of the model run (represented by the starttime attribute of the hourly or daily point xml return). The resolution of this product is 1km.

Point Data Example

Tile Data Example

Clouds

API Query: datatype=forecast&var=clouds

This is the cloud coverage factor forecasted by the SuperMicrocast Model. More information on what the values represent can be found in the unit explanation page. The resolution of this product is 12km.

Point Data Example:

Tile Data Example:

Dewpoint

API Query: datatype=forecast&var=dewpoint

The temperature variable represents the dewpoint forecasted by the SuperMicrocast Model at two meters above ground level. The dewpoint is a measure of the total amount of moisture in the atmosphere.

Dewpoint °C Dewpoint °F Human Perception
> 26 > 80 Severely Humid
21 to 26 70 to 80 Uncomfortable
16 to 21 60 to 70 Humid
10 to 16 50 to 60 Comfortable
< 10 < 50 Dry

The resolution of this product is 1km.

Point Data Example:

Tile Data Example:

Feelslike

API Query: datatype=forecast&var=feelslike

Feelslike is a value added weather variable that takes multiple weather factors such as wind speed, humidity, and temperature to determine what the weather “Feels-like” on your skin. This is essentially a merged wind chill and heat index so that it can be used in all seasons. The resolution of this variable is 1km.

Point Data Example

Tile Data Example

Reflectivity

API Query: datatype=forecast&var=reflectivity

Reflectivity is a product that includes both the type and the intensity of the forecast precipitation for a given hour. Snowfall is represented by blue, Mixed precipitation is represented by pinks and purples, light rain is represented by greens, and heavier rain is represented by yellows, oranges, and reds. This dataset is only available in the tile request at this time.

Tile Data Example

Reflectivity With Clouds

API Query: datatype=forecast&var=reflectivity_w_clouds

This is a combination of the Reflectivity and Clouds products to make your requests more efficient if you want to show both variables on one map. This request is only available in tile format.

Tile Data Example

Relative Humidity

API Query: datatype=forecast&var=relativehumdity

Relative humidity is a pure measure of how much moisture is in the atmosphere vs. how much moisture the atmosphere can sustain. It is defined as a percentage from 0-100% For more reading please click here:

http://en.wikipedia.org/wiki/Relative_humidity" http://en.wikipedia.org/wiki/Relative_humidity

The resolution of this variable is 1km.

Point Data Example

Tile Data Example

High Clouds

API Query: datatype=forecast&var=high_clouds

This variable provides a forecast for how much relative humidity or moisture there is at the jet stream level of the atmosphere.  This is a good measurement of the amount of high cloud coverage is forecasted.  This is specifically the percentage of relative humidity that is at the 300 millibar height in the atmosphere, which is a unit of air pressure.  At the surface the air pressure is approximately 1000 mllib ars so the 300 millibar level would be the point in the atmosphere where the air pressure is 30% what it is at the surface, or approximately 30,000 ft (9,300 meters). 


Point Data Example

Tile Data Example

Mid Level Clouds 1

API Query: datatype=forecast&var=mid_level_clouds1

This variable provides a forecast for how much relative humidity or moisture there is at the upper mid level of the atmosphere.  This is a good measurement of the amount of upper mid level cloud coverage is forecasted.  This is specifically the percentage of relative humidity that is at the 500 millibar height in the atmosphere, which is a unit of air pressure.  At the surface the air pressure is approximately 1000 mllibars so the 500 millibar level would be the point in the atmosphere where the air pressure is 50% what it is at the surface, or approximately 18,000 ft (5,500 meters). 

Point Data Example

Tile Data Example

Mid Level Clouds 2

API Query: datatype=forecast&var=mid_level_clouds2

This variable provides a forecast for how much relative humidity or moisture there is at the lower mid level of the atmosphere.  This is a good measurement of the amount of lower mid level cloud coverage is forecasted.  This is specifically the percentage of relative humidity that is at the 700 millibar height in the atmosphere, which is a unit of air pressure.  At the surface the air pressure is approximately 1000 mllibars so the 700 millibar level would be the point in the atmosphere where the air pressure is 70% what it is at the surface, or approximately 10,000 ft (3,100 meters). 

Point Data Example

Tile Data Example

Low Clouds

API Query: datatype=forecast&var=low_clouds

This variable provides a forecast for how much relative humidity or moisture there is at the lower mid level of the atmosphere.  This is a good measurement of the amount of low level cloud coverage is forecasted.  This is specifically the percentage of relative humidity that is at the 850 millibar height in the atmosphere, which is a unit of air pressure.  At the surface the air pressure is approximately 1000 millibars so the 850 millibar level would be the point in the atmosphere where the air pressure is 85% what it is at the surface, or approximately 5,000 ft (1,500 meters). 

Point Data Example

Tile Data Example

 

SupercellIndex

API Query: datatype=forecast&var=supercellindex

Supercell index is a pure measurement of the potential of severe thunderstorms. This index is measured between 0-100. Even small values represent that there is a change that damaging thunderstorms could occur for that particular hour.

A general rule of thumb for this variable would be
0 Severe Thunderstorms unlikely
1-25 general thunderstorms possible, some could be severe.
25-50 a slight risk that you will see damaging winds, severe hail or tornados
50-75 a moderate risk that you will see damaging winds, severe hail or tornados
75-100 a high risk that you will see damaging winds, severe hail or tornados

The resolution of this variable is 12km.

Point Data Example

Tile Data Example

Temperature

API Query: datatype=forecast&var=temperature

The temperature variable represents the air temperature forecasted by the SuperMicrocast Model at two meters above ground level. The resolution of this product is 1km.

Point Data Example

Tile Data Example

Traffic Index

API Query: datatype=forecast&var=trafficindex

The Traffic Index is a unique variable which Weather Central has created which quantifies the weather impact on road speeds. This is a slowdown percentage for the particular hour which is based on rain, snow, accumulations, road temperature, wind speed, time of day, and mountainous terrain. A value of 0 would represent no weather impact, a value of 50 would represent traffic moving at about half the speed they normally would, and a value of 100 would represent traffic at a crawl (holding all other non-weather related variables equal). The resolution of this data is 12km.

Point Data Example

Tile Data Example

Surface Wind Direction

API Query: datatype=forecast&var=winddirection_10m

The wind direction variable represents the direction the wind is coming from at 10 meters above the surface. A North Wind would be represented by 0, East Wind by 90, South wind by 180, and West wind by 270. This data is only accessible by the point request type. The resolution of the data is 1km.

Point Data Example

Surface Wind Speed

API Query: datatype=forecast&var=windspeed_10m

The wind speed variable represents the wind speed forecasted by the SuperMicrocast Model at ten meters above ground level for a given hour. Wind is officially measured at ten meters above the ground to avoid the frictional effects of the objects on the ground such as buildings and trees. The resolution of this product is 1km.

Point Data Example

Tile Data Example

Surface Wind Gust

API Query: datatype=forecast&var=windgust_10m

The wind gusts variable represents the wind gust speed forecasted by the SuperMicrocast Model at ten meters above ground level for a given hour. Wind is officially measured at ten meters above the ground to avoid the frictional effects of the objects on the ground such as buildings and trees. The resolution of this product is 1km.

Point Data Example

 

Tile Data Example

 

60 meter Wind Direction

API Query: datatype=forecast&var=winddirection_60m

The wind direction variable represents the direction the wind is coming from at 60 meters above the surface.  This is specifically useful for the wind energy industry to help with maintenance planning and energy yield forecasting.  A North Wind would be represented by 0, East Wind by 90, South wind by 180, and West wind by 270. This data is only accessible by the point request type. The resolution of the data is 1km.


Point Data Example


60 meter Wind Speed

API Query: datatype=forecast&var=windspeed_60m

The wind speed variable represents the wind speed forecasted by the SuperMicrocast Model at 60 meters above ground level for a given hour.  This is specifically useful for the wind energy industry to help with maintenance planning and energy yield forecasting.  The resolution of this product is 1km.

Point Data Example

Tile Data Example

60 Meter Wind Gust

API Query: datatype=forecast&var=windgust_60m

The wind gusts variable represents the wind gust speed forecasted by the SuperMicrocast Model 60 meters above ground level for a given hour.  This is specifically useful for the wind energy industry to help with maintenance planning and energy yield forecasting.  The resolution of this product is 1km.

Point Data Example

Tile Data Example

 

120 meter Wind Direction

API Query: datatype=forecast&var=winddirection_120m

The wind direction variable represents the direction the wind is coming from at 60 meters above the surface.  This is specifically useful for the wind energy industry to help with maintenance planning and energy yield forecasting.  A North Wind would be represented by 0, East Wind by 90, South wind by 180, and West wind by 270. This data is only accessible by the point request type. The resolution of the data is 1km.

Point Data Example

 

120 meter Wind Speed

API Query: datatype=forecast&var=windspeed_120m

The wind speed variable represents the wind speed forecasted by the SuperMicrocast Model at 60 meters above ground level for a given hour. This is specifically useful for the wind energy industry to help with maintenance planning and energy yield forecasting. The resolution of this product is 1km.


Point Data Example

Tile Data Example

120 Meter Wind Gust

API Query: datatype=forecast&var=windgust_120m

The wind gusts variable represents the wind gust speed forecasted by the SuperMicrocast Model 120 meters above ground level for a given hour.  This is specifically useful for the wind energy industry to help with maintenance planning and energy yield forecasting.  The resolution of this product is 1km.

Point Data Example

 

Tile Data Example

 

Summary

API Query: datatype=forecast&var=summary

The summary variable is only accessible by the point request type and provides a summary for the time period of all the commonly accessible variables.  This serves as a easy way to batch a variable request.
The summary request will return all of the following variables


Hourly Request

Point Data Example

Daily Request

Point Data Example

 

Probability of Precipitation

API Query: datatype=forecast&var=pop

Probability of Precipitation measures the chance of precipitation occurring within a 60 mile radius around a specified lat/lon point. It is defined as a percentage from 0-100%.

The resolution of this variable is 1km.

Point Data Example

Tile Data Example

UV Index

API Query: datatype=forecast&var=uvindex

The UV Index forecasts the level of intensity of the sun’s ultraviolet (UV) radiation that may reach the earth’s surface and pose health risks to people who are overexposed.  The UV Index is derived from the 0.5° GFS model and is updated four times a day.  Hourly forecasts are available out to 96 hours.  UV Index values are unitless and typically range from 0 to 15.  Information on what the values represent can be found in the unit explanation page

Point Data Example:



Tile Data Example:

Wave Height

API Query: datatype=forecast&var=waveheight

The Wave Height data is derived from the NOAA Multi-wave Wavewatch III model.  The data is a composite of a global 30 minute grid (~55-kilometers) and regional 10 minute and 4 minute grids (~18-kilometers and ~7-kilometers, respectively).  Forecasts are available out to 126 hours, except 84 hours for the Great Lakes.  The Wave Height is the significant height due to both wind waves and swells.  Wave Height values are in feet and typically range from 0 to 20.  Information on what the values represent can be found in the unit explanation page.  Locations of the regional grids are shown here:

Great Lakes: All 5 great lakes.
Alaska 4 minute:  Red areas on map east of the dateline
Alaska 10 minute: Dark blue areas on map east of the dateline
West coast 4 minute: Orange areas along west coast and around Hawaii
West coast 10 minute: Light blue areas along west coast
Pacific 10 minute:  Light blue areas around Hawaii
Atlantic 4 minute: Orange areas along Gulf of Mexico and Atlantic coasts
Atlantic 10 minute: Light blue areas along Gulf of Mexico and Atlantic coasts
Global 30 minute: Yellow shading on map

Point Data Example:

Wave Period

API Query: datatype=forecast&var=waveperiod

The Wave Period data is derived from the NOAA Multi-wave Wavewatch III model.  The data is a composite of a global 30 minute grid (~55-kilometers) and regional 10 minute and 4 minute grids (~18-kilometers and ~7-kilometers, respectively).  Forecasts are available out to 126 hours, except 84 hours for the Great Lakes.  The Wave Period identifies either the period (the time between waves) associated with the locally generated wind sea (in cases with strong local winds) or the dominant wave system (swell) that is generated elsewhere.  Wave Period values are in seconds and typically range from 0 to 20.  Information on what the values represent can be found in the unit explanation page.  See Wave Height variable for a map of regional grids. 

Point Data Example:

Wave Direction

API Query: datatype=forecast&var=wavedirection

The Wave Direction data is derived from the NOAA Multi-wave Wavewatch III model.  The data is a composite of a global 30 minute grid (~55-kilometers) and regional 10 minute and 4 minute grids (~18-kilometers and ~7-kilometers, respectively).  Forecasts are available out to 126 hours, except 84 hours for the Great Lakes.  The Wave Direction identifies the directional movement of the wave systems.  Wave Direction is in degrees from 0 to 360.  Information on what the values represent can be found in the unit explanation page.  See Wave Height variable for a map of regional grids. 

Point Data Example:

Primary Wave Direction

API Query: datatype=forecast&var=primarywavedirection

The Primary Wave Direction data is derived from the NOAA Multi-wave Wavewatch III model.  The data is a composite of a global 30 minute grid (~55-kilometers) and regional 10 minute and 4 minute grids (~18-kilometers and ~7-kilometers, respectively).  Forecasts are available out to 126 hours, except 84 hours for the Great Lakes.  The Primary Wave Direction identifies the directional movement of the primary wave swells.  Primary Wave Direction is in degrees from 0 to 360.  Information on what the values represent can be found in the unit explanation page.   See Wave Height variable for a map of regional grids. 

Point Data Example:

Primary Wave Period

API Query: datatype=forecast&var=primarywaveperiod

The Primary Wave Period data is derived from the NOAA Multi-wave Wavewatch III model.  The data is a composite of a global 30 minute grid (~55-kilometers) and regional 10 minute and 4 minute grids (~18-kilometers and ~7-kilometers, respectively).  Forecasts are available out to 126 hours, except 84 hours for the Great Lakes.  The Primary Wave Period is the time between waves of the dominant wave system (swell) that is being generated.  Primary Wave Period values are in seconds and typically range from 0 to 20.  Information on what the values represent can be found in the unit explanation page.   See Wave Height variable for a map of regional grids. 

Point Data Example: