Positive/Negative Tilt

I always see this aspect when it comes to forecasting severe weather events, but I am unsure of what is meant by a positive tilt or a negative tilt and how they relate to severe storm development. Is there a clear definition on what they are and their effects?

Thanks!
 
From Haby Hints:

TILTING OF TROUGHS ON A HORIZONTAL PLANE
http://www.theweatherprediction.com/habyhints/58/

WHAT IS A "NEGATIVELY TILTED TROUGH"?
http://www.theweatherprediction.com/habyhints/127/

From: Haby Hints:
NEGATIVE TILTED TROUGH- A trough which tilts from the northwest toward the southeast. This situation creates instability since cold temperatures in the mid and upper levels advect over warmer air at the surface. A negative tilt is a sign a trough is mature.

POSITIVE TILTED TROUGH- A trough which tilts from the northeast toward the southwest. Often a trough is positive tilted in it's development stage.

From: National Weather Service:
Negative-Tilt Trough: An upper level system which is tilted to the west with increasing latitude (i.e., with an axis from southeast to northwest). A negative-tilt trough often is a sign of a developing or intensifying system.

Positive-Tilt Trough: An upper level system which is tilted to the east with increasing latitude (i.e., from southwest to northeast). A positive-tilt trough often is a sign of a weakening weather system, and generally is less likely to result in severe weather than a negative-tilt trough if all other factors are equal.
Mike
 
How would I calculate the tilt ? I calculate the trough axis and then the angle of the trough axis makes with the north pole is the tilt ?
 
Supposing I had an inverted trough as in a easterly wave. Would the definitions be reversed (i.e. positive tilt is a sign of maturing trough and a negative tilt is a sign of a weakening trough ? )

http://www.theweatherprediction.com/habyhints/126/

While that's a good question (and I don't know the answer), I also believe it to be irrelevant. I've never heard any discussion of an easterly tropical wave tilt. You might want to consult a forum that focuses more closely on tropical weather or send a general email to the National Hurricane Center or a prominent tropical meteorology lab (perhaps at Florida State Univ., but there are probably others, too).
 
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