April 18, 2009 Wake Low Event

A slow moving upper-level storm system over the Texas panhandle and associated surface low and cold front across central Texas spawned several lines of slow-moving thunderstorms during the afternoon and evening hours of April 17-18. During the late evening/early mid-night hours of April 17/18 the storm developed a Wake Low over northern and northeast Louisiana as well as southeast Arkansas as the line began to decrease in intensity. The trailing edge of the line showed stratiform type precipitation, common with Wake Lows, and areas of stronger wind fields evident with a succession of forward bows most likely attributed to stronger areas of rear inflow jets.

Wind damage was reported across all of northeast Louisiana and southeast Arkansas with speeds in excess of 50 mph and gusts of over 60 mph likely. The trace below showed the windspeed, wind direction, and barometric pressure. In one hour, the barometric pressure (blue trace) dropped from 30.19" to 29.89" - a change of 10.2 mb!

The following evening a second Wake Low event occurred, although not as severe as the first. Another similar squall line developed over east Texas during the early afternoon hours of the 18th. The bottom data chart shows both events. The pressure drop for the second event was from 29.97" to 29.84" - only 4.3 mb. Still winds gusted to near 40 mph in some locations.

 

The cross-section shown at the left (schematic cross section through wake low,
from Johnson and Hamilton - 1988) shows the "not-well-understood" dynamics of a wake low (Handal and Santos).

Greg Stumpf (1991) continued, "Stratiform precipitation regions can be dynamically significant phenomena, generating
rapidly descending inflow jets at their back edges,
capable of producing lower-tropospheric warming,
intense low level pressure gradients, and strong low
level winds."

 

 

 

 

 

 

 

 

 

 


Round 2!