|JET STREAK ON RIGHT SIDE OF TROUGH
METEOROLOGIST JEFF HABY
When a jet streak is on the right side of a trough, the momentum of the jet streak has the opposite effect as it had
on the left side of a trough. The diagram below shows a time series of a jet streak on the right side of a trough and
trough lifting. Lifting of a trough means the amplitude of the trough becomes less and the axis of rotation moves to
the north or northeast.
A perspective in understanding how a jet streak on the right side of a trough lifts a trough is by studying the
left rear convergence quadrant of a jet streak. Mass is added to the left rear quadrant of a jet streak. As
the left rear quadrant moves north, the trough will lift because convergence in the base of a trough causes height
rises (due to addition of mass) and a subsequent weakening of the trough. The diagram below shows the left rear
quadrant of a jet streak that is exiting the base of a trough.
LEFT REAR QUAD
As a jet streak leaves the base of a trough, the left rear quadrant overlaps the base of the trough. Because
convergence is occurring within the axis of rotation the trough weakens. Strong upper level convergence raises
heights and surface pressure. The diagram below shows the position of the left rear quadrant with respect to
the position of the axis of rotation.
LEFT REAR QUAD W.R.T. ROTATIONAL AXIS
Adding to the convergence created by the left rear quadrant is NVA. The PVA and divergence from the left front
quadrant will be to the northeast (approximate direction) of the axis of rotation. This will promote a northeast
lifting of the trough. The diagram below shows the two mechanisms of convergence (left rear quad and NVA) within
the base of the trough and the two mechanisms of divergence (left front quad and PVA) to the northeast of
the axis of rotation.
NVA AND JET STREAK CONVERGENCE WITHIN TROUGH BASE
Haby sez: The momentum of a jet streak and convergence created from the left rear quadrant and NVA allow a jet streak
on the right side of the trough, which is exiting the base of the trough, to weaken and lift the trough to