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 1000/500 thickness, which represents the vertical distance between the 1000 and 500mb levels, is given in meters by dashed yellow lines. The accumulated precipitation in inches, for the previous 3, 6, or 12 hours is given as color fill using a non-linear scale.

 

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.

 

850 mb temp, hght, wind

The height in decameters of the 850mb pressure surface is contoured by solid white lines. The air temperature, in degrees Celsius, is given as color fill. Wind barbs indicate wind direction and wind speed in knots.

 

850 mb rh, hght, wind

The height in decameters of the 850mb pressure surface is contoured by solid white lines.  The relative humidity is given as color fill.  Wind barbs indicate wind direction and wind speed in knots.

 

700 mb omega, hght, wind

The height in decameters of the 700mb pressure surface is contoured by solid white lines.  The vertical velocity of the air in microbars per second is given as color fill.  Positive values represent upward movement or rising air, and negative values represent sinking air.  Wind barbs indicate wind direction and wind speed in knots.

 

700 mb rh, hght, wind

The height in decameters of the 700mb pressure surface is contoured by solid white lines.  The relative humidity is given as color fill.  Wind barbs indicate wind direction and wind speed in knots.

 

500 mb vort, hght, wind 

The height in decameters of the 500mb pressure surface is contoured by solid white lines.  The absolute vorticity, or “storminess” of the air, is given as color fill.  Wind barbs indicate wind direction and wind speed in knots.

 

500 mb rh, hght, wind

The height in decameters of the 500mb pressure surface is contoured by solid white lines.  The relative humidity is given as color fill.  Wind barbs indicate wind direction and wind speed in knots.

 

500 mb temp, hght, wind

The height in decameters of the 500mb pressure surface is contoured by solid white lines. The air temperature, in degrees Celsius, is given as color fill. Wind barbs indicate wind direction and wind speed in knots.

 

300 mb hght, isotachs

The height in decameters of the 300mb pressure surface is contoured by solid white lines.  Areas of similar wind speed are color filled. Wind barbs indicate wind direction and wind speed in knots. This map is helpful for locating the polar jet stream.

 

300 mb rh, hght, wind

The height in decameters of the 300mb pressure surface is contoured by solid white lines.  The relative humidity is given as color fill.  Wind barbs indicate wind direction and wind speed in knots.

 

200 mb hght, isotachs

The height in decameters of the 200mb pressure surface is contoured by solid white lines.  Areas of similar wind speed are color filled.  Wind barbs indicate wind direction and wind speed in knots. The sub-tropical jet stream is often visible in this map between 25 and 35 degrees north.

 

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.

 

Bulk Lapse Rate for 700 to 500mb

The decrease in temperature in degrees Celsius per vertical kilometer between the height of the 700mb pressure level and the height of the 500mb pressure level is given by color fill.  Bulk lapse rates in this case describe the environmental lapse rate of the 700mb to 500mb layer.