NWS Southern Region Tropical Weather - Gulf of Mexico visible satellite image

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County	Dew Point	Gusts	HDW-low	HDW-mid	HDW-high	HI	LatLon	LI	MSLP	NCEP Fronts	Pcpn
PW	Radar	RH	Roads	SST	Stn Plot	T-Pcpn	Temp	Trop Fcst Pts	Watch/Warn	WC	Wind

County	Depicts county boundaries (for the United States only).
Dew Point	The most recent surface dew point temperature (°F) from weather reporting stations. The dew point is the temperature to which, if the atmosphere was cooled, the air would become saturated with moisture. As the difference between the temperature and dew point decreases, the humidity increases. The dew point is a better measure of the moisture content near the surface than relative humidity.
Gusts	Speed (in knots) of the highest gust of wind. Gusts will be reported when the maximum wind speed exceeds the sustained wind speed by 10 knots within 10 minute of the observation time. The time of the image is in the lower left.
HDW-low	High density satellite derived wind from the surface to 10,000 feet. Values are derived from tracking cloud motion. The different colors, red or fuchsia, represents the type of image, visible or infrared, used to gather the information.
HDW-mid	High density satellite derived wind from 10,000 to 23,000 feet. Values are derived from tracking cloud motion. The different colors, light/dark green and yellow, represents the type of image, visible, infrared or water vapor, used to gather the information.
HDW-high	High density satellite derived wind from 23,000 and 50,000 feet. Values are derived from tracking cloud motion. The different color of blues, represents the type of image, infrared or water vapor, used to gather the information.
HI (Heat Index)	The heat index is the temperature the body "feels" when the heat is combined with the humidity. As the humidity increases, the ability for the body to cool itself by evaporation decreases. The body's decreased ability to cool itself makes it "feel" hotter than the current air temperature. Prolonged exposure to the heat, especially when the heat index is large can be deadly. Learn more about the Heat Index.
LatLon	Depicts the latitude and longitude across the image.
LI (Lifted Index)	The lifted index is an estimate of atmospheric stability. It represents the buoyancy which an parcel of air would experience if lifted to 18,000 feet. The lifted index value is the temperature difference (°C) between the air temperature at 18,000 feet and what the temperature of the parcel would be if lifted to that same level. A negative value (the lifted parcel is warmer than the environment) suggests positive buoyancy and continued rising whereas a positive value suggests stability or descending air. Specifically a... Lifted index 6 or Greater, Very Stable Conditions Lifted index between 1 and 6: Stable Conditions, Thunderstorms Not Likely Lifted index between 0 and -2: Slightly Unstable, Thunderstorms Possible, With Lifting Mechanism (i.e., cold front, daytime heating, etc.) Lifted index between -2 and -6: Unstable, Thunderstorms Likely, Some Severe With Lifting Mechanism Lifted index less Than -6: Very Unstable, Severe Thunderstorms Likely With Lifting Mechanism Just because the air at 18,000 feet is unstable that does not mean that thunderstorms will form. There are many other factors involved such as moisture content, both at the surface and aloft, and whether there is some feature that provides the initial lift. Quite often, the atmosphere will be "conditionally unstable" -- the lifted index indicates instability but their needs to be a feature the begins to force the air up in the atmosphere...the condition.
MSLP (Mean Sea Level Pressure)	Image of the surface pressure patterns (updated hourly). The lines are called isobars (lines of equal pressure) and are in whole millibars. The time of the image is in the lower left. Learn more about isobars.
NWS Fronts	Analysed positions of fronts, troughs of low pressure and centers of high and low pressure. The time of the position of these features is indicated in the upper left portion of the image. The image at right shows the different types of front that can be depicted. Troughs of low pressure are indicated by a yellow dashed line. The values of the high and low pressure centers are indicated, in whole millibars, just below and to the left of the blue "H" or red "L". Learn more about fronts.
Pcpn	Observed precipitation for the previous 6 hours.
PW (Precipitable Water)	The amount of water possible with all the water vapor in the atmosphere above a location condensed into liquid. Measured in inches, the higher the value the greater the moisture in the atmosphere. Summer values of precipitable water are usually larger than winter since the ability for the atmosphere to hold water increases with increase temperature. These values are derived from the GOES satellites.
Radar	Shows only the most recent NWS doppler base reflectivity radar composite. This image should coincide with the last image (most recent) in the satellite loop. The color scale at the bottom of the overlay is an indicator of the intensity of the rainfall. (Color blindness tool) Typically, the light green color is considered the beginning of light rain. The range of the radar is 248 nautical miles (286 statute miles). However, remember that as the distance from a radar increases the radar can only see reflections higher and higher in storms. Learn more about how distance from the radar affects what is seen.
RH (Relative Humidity)	The most recent relative humidity (percentage) from weather reporting stations. Relative humidity is a measure of the amount of water vapor contained in the air, divided by the maximum amount the air can hold, expressed as a percent. A relative humidity of 50% means the air contains ½ of the water vapor it can actually hold. The maximum amount of water vapor the air can hold is dependent upon the temperature (the "relative" in relative humidity). The higher the temperature, the more water (actually water vapor) the air can hold. For example, air with a temperature of 32°F can hold about 0.16 ounces of water. Air with a temperature of 80°F can hold about an ounce of water. The time of the relative humidity is in the lower left of the image.
Roads	Depicts Interstate highways (for the United States only).
SST (Sea Surface Temperature °C)	Updated daily. Ignore values over land.
Stn Plot (Station Plot)	Hourly weather plot of the temperature (upper left value - °F), dew point (lower left value), sea-level pressure (upper right value - in tenths of millibars), station call letters (lower right) and wind speed and direction (line and barbs or circles). The time of the image is in the lower left. Learn how to read a station plot.
T-Pcpn	Observed precipitation for the previous 24 hours at 12 UTC (How to read "UTC" time).
Temp	The most recent surface air temperature (°F) from weather reporting stations. The time of the temperatures is in the lower left of the image.
Trop Fcst Pts (Tropical Forecast Points)	Issued from the National Hurricane Center these are forecast points for tropical cyclones.
Watch/Warn	Displays any watches and warnings across the image (for the United States only). See all watches, warnings and advisories for the U.S.
WC (Wind Chill)	The wind chill is the effect of the wind on people and animals. The wind chill temperature is based on the rate of heat loss from exposed skin caused by wind and cold and is to give you an approximation of how cold the air feels on your body. Learn more about wind chill.
Wind	The direction and sustained speed (in knots) FROM which the wind is blowing. The time of the image is in the lower left. Learn how to read the wind barbs.

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