A dry line, dew point line, or Marfa front[1] is a boundary separating moist and dry air masses, and an important factor in severe weather frequency in the Great Plains of North America. It typically lies north-south across the central and southern High Plains states during the spring and early summer, where it separates moist air from the Gulf of Mexico (to the east) and dry desert air from the southwestern states (to the west). Hotel Paisano and the Presidio County courthouse Marfa is a city located in the high desert of far West Texas. ... In meteorology, an air mass is a large volume of air having fairly uniform characteristics of temperature, atmospheric pressure, and water vapor content. ... NOAA scientists observe severe weather using a mobile doppler radar and a helicopter (in the distance) Severe weather phenomena are weather conditions that are hazardous. ... The Great Plains covers much of the central United States, portions of Canada and Mexico. ... World map showing North America A satellite composite image of North America. ... The High Plains are a subregion of the Great Plains in the central United States, located in eastern Colorado, western Kansas, western Nebraska, central and eastern Montana, eastern New Mexico, western Oklahoma, western Texas, and southeastern Wyoming. ... Gulf of Mexico in 3D perspective. ...

Vertical Structure

Near the surface, warm moist air is more dense than dry air of greater temperature, and thus the warm moist air wedges under the drier air like a cold front.^[1] At higher altitudes, the warm moist air is less dense than the cooler, drier air and the boundary slope reverses. In the vicinity of the reversal aloft, severe weather is possible, especially when a triple point is formed with a cold front.

Daily Progression

The dry line typically advances eastward during the afternoon and retreats westward at night, mainly due to the increased mixing down to the surface of drier air aloft, rather than the air mass' surface density contrast. However, a strong storm system can sweep the dry line eastward into the Mississippi Valley, or even further east, regardless of the time of day. A typical dry line passage results in a sharp drop in dew point, clearing skies, and a wind shift from south or southeasterly to west or southwesterly. (Blowing dust and rising temperatures also may follow, especially if the dry line passes during the daytime; see dry punch). These changes occur in reverse order when the dry line retreats westward. Severe and sometimes tornadic thunderstorms often develop along the slope reversal zone east of the surface dry line, especially when it begins moving eastward. Ver ycool Length 6,270 km Elevation of the source 450 m Average discharge 16,200 m³/s Area watershed 2,980,000 km² Origin Lake Itasca Mouth Gulf of Mexico Basin countries United States (98. ... Dew on a spider web The dew point or dewpoint of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for the water vapor component to condense into water, called dew. ... Wind, tacuinum sanitatis casanatensis (XIV century) Wind is the rough horizontal movement of air (as opposed to an air current) caused by an area of lo pressure and an area of hi pressure near eachother and the wind will blow from the hi pressure point to the lo pressure point... After just three years of use, dust has blocked this laptop heat sink, making the computer unusable Dust is a general name for minute solid particles with diameters less than 500 micrometers (otherwise, please see sand or granulates and, more generally, finely divided matter). ... Fig. ... A dry punch is meteorological slang for a surge of drier air; normally a synoptic scale or mesoscale process. ... A tornado in central Oklahoma. ... A shelf cloud associated with a heavy or severe thunderstorm over Enschede, The Netherlands. ...

See Also

• Surface weather analysis

ethan has a z-400 and its freekin sweet and he can ride a wheelie for blocks and Donny T has a go cart that has no brakes A surface weather analysis for the United States on October 21, 2006. ...

References