4/23/07: NOW: NY/PA

[HAltschule]

Very intense thunderstorm with a well define hook echo is currently Northeast of Pittsburgh, PA and is moving well right of the mean flow and has a well sustained hook and excellent gate 2 gate shear. Tornado warnings are in effect. This poss. tornado is moving through some fairly populated areas of Pittsburgh. Other Bows/LEWP's continue in that area.

Another Bow/LEWP is moving across the Tug Hill Plateua region of New York right now. 60 MPH winds were just reported at Hancock Int'l AP in Syracuse. This northern part of the line should weaken below severe limits shortly as CAPE diminishes.

 

[MatthewCarman]

What is a LEWP? I have never heard of this term before with a Bow Echo. (I know what a Bow Ech is)

Some pretty intense storms in the southern end of this line in PA.

 

[HAltschule]

LEWP= "Line Echo Wave Pattern"....aka...a Line of storms.

 

[Brandon Sullivan]

Stands for Line Echo Wave Pattern. This is an outward bulge along a squall line that is often created from strong upper level winds intersecting that segment of the squall line. A LEWP can suggest strong surface winds will occur along the LEWP's path.

 

[HAltschule]

Actually, a LEWP is just a line of echos or storms. A "Bow Echo" is when the line bulges, or bow, outward as the strong winds and/or cold pool reach the surface and enhance the forward motion of that part of the line.

 

[Brandon Sullivan]

Below is a picture of a normal LEWP. Dont think I am trying to be an ass. I dont know much about them, but here is how NWS officially defines them.

http://www.weather.gov/glossary/index.php?word=LEWP
Line Echo Wave Pattern - A bulge in a thunderstorm line producing a wave-shaped "kink" in the line. The potential for strong outflow and damaging straight-line winds increases near the bulge, which often resembles a bow echo. Severe weather potential also is increased with storms near the crest of a LEWP

 

[rdale]

Actually, a LEWP is just a line of echos or storms.

No - that's the LE part (aka squall line.) The WP = Wave Pattern, which means there will be parts of the line that bow out from the main axis. A bow echo is simply one line of bowing storms. Similar, yet not the same.

 

[HAltschule]

FYI...Here is the official definition of a LEWP:

line echo wave pattern—(Abbreviated LEWP.) A special configuration in a line of convective storms that indicates the presence of a low pressure area and the possibility of damaging winds and tornadoes.
In response to very strong outflow winds behind it, a portion of the line may bulge outward forming a bow echo.
Nolen, R. H., 1959: A radar pattern associated with tornadoes. Bull. Amer. Meteor. Soc., 40, 277–279.

 

[rdale]

Correct - not just a line of storms. It's the picture included above.

 

[HAltschule]

No - that's the LE part (aka squall line.) The WP = Wave Pattern, which means there will be parts of the line that bow out from the main axis. A bow echo is simply one line of bowing storms. Similar, yet not the same.

The definition says nothing about the requirement for there to be parts of the line that bow out. It simply states that there is a low pressure area associated with it.

 

[rdale]

Correct - the low pressure area in the picture is in the upper-left part where the big 'kink' is. A line of storms does not have to contain a low, a LEWP does (that causes the wave pattern.)