General Map Information

Time Stamp

All maps on this page have a time stamp at the bottom of the page, which indicates the 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 isohumes (iso->equal, hume->humidity) on the cross sections.

Cross Section Location

The cross section is centered on the location specified by the link title. One cross section projection runs north south for a total of 15 degrees latitude, and the other cross section projection runs east west for a total of 15 degrees of longitude. Each endpoint is marked with a latitude longitude pair for reference.

Description of Cross Section Maps

Pot. Temp, Vert. Velocity & RH

Potential temperature (K) is given by white lines in increments of three degrees. Lines spaced closer together show areas of greater atmospheric stability, while lines spaced farther apart show lower atmospheric stability. Vertical velocity of the air in microbars per second is given as color fill with positive values showing upward motion. Relative humidity of 70% or greater is given as dashed blue isohumes. Values of 70% are chosen to show likely areas of cloud cover.

Total Wind w/ Directional Barbs

The anemometer wind speed (kts) is given as color fill. Wind barbs give the wind speed in knots along with wind direction. (NOTE: The wind direction is given in a plane projection sense, i.e., north is up, east is to the right, etc.)

Pot. Temp, RH, Pot. Vort. & Ageo Circ

Potential temperature (K) is given by white lines in increments of five degrees. Lines spaced closer together show areas of greater atmospheric stability, while lines spaced farther apart show lower atmospheric stability. Relative humidity of 70% or greater is given as dashed blue isohumes. Values >70% are chosen to show likely areas of cloud cover. Isentropic potential vorticity (K/Pa/second * 0.1) greater than 1.5 is given as color fill, with black lines showing in between intervals. Areas with filled color show the approximate location of stratospheric air. The ageostrophic circulation is given by green vectors.

Equiv. Pot. Temp, RH & Wet Bulb Frez. Lvl.

Equivalent potential temperature (K) is given every five degrees by dashed red lines. Equivalent potential temperature shows the potential temperature a parcel of air would have if all the vapor were condensed to liquid. The wet bulb freezing level is given by a solid yellow line. The wet bulb freezing level can be helpful for determining snow level. If no wet bulb freezing level line exists then the wet bulb temperature everywhere above the surface is below zero Celsius. Relative humidity of 70% or greater is given as blue color fill with black isohumes showing in between intervals. Values >70% are chosen to show likely areas of cloud cover.