Florida Hazards Guide: Weather Radar & Other Information

The Graphicast is an NWS product that shows current hazards in a simple visual format.

A wealth of weather information is freely available if you know how to interpret it.  A full guide is available from Weather Underground. Additional info and a FAQ are available here.  Radar ranges and overlap are viewable at the NOAA NEI Site.

There are several radar products available from the weather.gov site.  You can also adjust the tilt of the radar, see how much moisture is in the clouds, and get an idea if there is hail or possible tornadoes.

The basic radar display is the Base Reflectivity.  This shows the strength of the return doppler radar signal in decibels (DBZ), at different angles of radar tilt, from 0.50 degrees to 3.45 degrees.  Distances from the radar are measured in nautical miles (NMI).  This gives you a picture of storm systems moving into range of the radar.

Radial Velocity shows how the precipitation is moving - away or towards the radar station.  This is a good indicator of whether or not there are areas of rotation in the storm.  If there are high positive Radial Velocity readings close to strong negative ones, this is a possible sign of rotation and a sign of a tornado (but not always).

Vertically Integrated Liquid determines how much precipitation is in a storm system, measured in kg/m2.  This measures the number of hydrometeors in the clouds; a hydrometeor could be a rain drop, hail stone, snowflake, or sleet crystal.

Echo Tops indicate how high the clouds go.  Higher clouds full of moisture can produce hail, since the air is colder at higher altitudes.  There are other factors involved, but for a rough estimate of possible hail stone formation, the environmental lapse rate calculation is approximately 3.56 degrees F / 1000 ft of altitude.  This means that it will become over 3 and a half degrees colder for every 1000 ft you ascend.  A sudden drop in echo top readings could also indicate a downburst of precipitation.  

Additional information in a weather forecast can include temperature, humidity, dew point, heat index, wind chill, and baromeric pressure.  Many of these factors are defined and explained here and here.  If you are looking at the mesoscale analyses, this page explains the terms used there.

Whereas radar data comes from sensor stations on the ground, satellites provide a view of the weather from space.  Like radar, there are different types of imagery available.  The two most common types are visible and infrared.  The National Weather Service provides both types of satellite imagery as well as water vapor and multispectral images. A great selection of satellite imagery can be viewed here and here.

There are other, simpler methods of tracking the weather when the complexity of radar and satellite imagery is unnecessary:

Live webcams are a useful way to see weather conditions live.  Traffic cams are available here and weather cams are available here and here.

Openweathermaps.org shows the basics - temperature, precipitation, pressure, wind speed, and clouds in a simple and easy to use format.

"Earth: a global map of wind, weather, and ocean conditions" provides real-time, animated data including winds, ocean currents, sea surface temperature, and other data.  The wind height to 500 hectopascals is a good way to determine which way the atmosphere will steer storms.

There are many live weather webcams available to stream on the internet.  These can provide a handy visual confirmation of conditions you detect on the radar and satellite maps.

CAPE (Convective Available Potential Energy) is another indicator of storm severity. It is measured in Joules per Kilogram. A storm can have a CAPE value of over 1,000 and severe storms can have one of over 5,000.  HREF and SREF data is also useful in predicting bad weather.

Barometric Pressure is available in many of the weather sites linked from this guide. Average pressure at sea level is around 1013 mbar. A typical low pressure system could be around 1000 mbar, and powerful storms like hurricanes and tornadoes can range from 980-950 mbar or below.