Today's rain is associated with a low pressure system and associated warm front moving in from the southwest. On the surface analyses for 12 Z (7AM) Wednesday 11 February, 2008 (left) the low pressure system was located over the center of the U.S. A warm front extended northeastward into West Virginia. A south-southesterly flow ahead of the storm system (red arrows) transports warm, humid air from the Gulf towards the warm front. Meteorologists refer to this flow as a vapor channel. The humidity falls as precipitation to the north of the front (black circle). This is typical of of midlatitude winter storms. Light to moderate precipitation typically falls in broad regions north of warm fronts to the northeast of the low pressure center.
By 00Z Thursday 12 Feb. 2008, the storm center has moved into the Ohio valley. The vapor channel from the Gulf of Mexico is cut off by the cold front moving eastward across the southeastern states. Moist air from the Atlantic continues to stream northward ahead of the storm system (red arrows). Precipitation continues to fall ahead of the warm front (shown as a stationary front over northern New England (black circle).
This precipitation occurs because warm humid air overruns the cold air ahead of the front when it reaches the front. This leads to cloud formation and precipitation. This falls ahead of the front as frozen precipitation if the surface temperature is below freezing and rain of the surface is above freezing. See "
Precipitation along warm front" tutorial for more information.
Today's rain is associated with a low pressure system and associated warm front moving in from the southwest. On the surface analyses for 12 Z (7AM) Wednesday 11 February, 2008 (left) the low pressure system was located over the center of the U.S. A warm front extended northeastward into West Virginia. A south-southesterly flow ahead of the storm system (red arrows) transports warm, humid air from the Gulf towards the warm front. Meteorologists refer to this flow as a vapor channel. The humidity falls as precipitation to the north of the front (black circle). This is typical of of midlatitude winter storms. Light to moderate precipitation typically falls in broad regions north of warm fronts to the northeast of the low pressure center.
By 00Z Thursday 12 Feb. 2008, the storm center has moved into the Ohio valley. The vapor channel from the Gulf of Mexico is cut off by the cold front moving eastward across the southeastern states. Moist air from the Atlantic continues to stream northward ahead of the storm system (red arrows). Precipitation continues to fall ahead of the warm front (shown as a stationary front over northern New England (black circle).
