General Map Information
Time Stamp
All maps on this page have a time stamp at the bottom of the page, which indicates date for which the map is valid. For example, the time stamp Valid 020901/1800V030 can be decoded as follows: 02 is the year (2002), 0901 is the month and day (Sept, 01), 1800 is the hour in UTC, 030 is the forecast hour (30). The forecast hour indicates how many hours after model initialization this forecast represents.
Isopleths
All lines or contours on the following maps are isopleths. An isopleth is a line drawn on a map through all points of equal value of some measurable quantity. An example would be the isobars (iso->equal, bar->pressure) on a surface pressure map.
Description of Each Map
Surface
Analysis Precip
The estimated mean sea level pressure in millibars (mb) is given by solid white lines (isobars). The accumulated precipitation in inches, for the previous 6 hours is given as color fill using a non-linear scale.
Surface
Analysis Temperatures
The estimated mean sea level pressure is given by
solid white lines (isobars). The
surface temperature, in degrees Fahrenheit, is given as color fill. Wind barbs indicate wind direction and wind
speed in knots.
Surface
Analysis Dewpoints
The estimated mean sea level pressure is given by solid white lines (isobars). The surface dewpoint, in degrees Fahrenheit, is given as color fill. Wind barbs indicate wind direction and wind speed in knots.
Surface
Analysis Relative Humidity
The estimated mean sea level pressure is given by
solid white lines (isobars). The
surface relative humidity, as a percentage of saturation, is given as color
fill. Wind barbs indicate wind
direction and wind speed in knots.
Surface
to 30mb above Sfc. - Rel. Hum.
This product illustrates the average relative humidity for the boundary layer defined as the surface to a pressure level that is 30 millibars less than surface pressure. This is particularly useful for determining fog and marine layer coverage.
30mb
to 60mb above Sfc. - Rel. Hum.
This product illustrates the average relative humidity for the boundary layer defined as the pressure level between 30 and 60 millibars less than surface pressure. This is particularly useful for determining fog and marine layer coverage.
60mb to 90mb above Sfc. - Rel. Hum.
This product illustrates the average relative humidity for the boundary layer defined as the pressure level between 60 and 90 millibars less than surface pressure. This is particularly useful for determining fog and marine layer coverage.
CAPE
& Convective Inhibition
The Convective Available Potential Energy (CAPE) over an area in joules per kilogram is given as a non-linear color fill. CAPE indicates how much energy is available once free convection is initiated. Convective inhibition in joules per kilogram is given by alternating blue and red lines. Convective inhibition describes how much energy must be overcome before free convection occurs.
Lifted index is a measure of instability within a column of atmosphere. It is calculated by lifting a parcel of air from near the surface to the 500-millibar level. The parcel temperature is subtracted from the actual 500-millibar temperature. The result is the lifted index with a negative value indicating possible instability. For the case of the best lifted index, this calculation is performed for each of the six boundary layers within the model. The layer producing the lowest (greatest possible instability) value is displayed.