Four Troughs Dance Around the CONUS

500 mb height and Water Vapor satellite imagery Date: 05/26/16 06UTC

Sometimes I like to sit back and just watch the dynamics. Four separate troughs have been significant rain & weather makers over the last two days. Working from left to right:
 The first mid level trough dives southward down western British Columbia propagated by a mid/upper level jet max as it moves around the trough. The associated lift begins prompting some showers in central Alberta and Montana.
 The second trough moves slowly northeastward starting in central Montana to southern Manitoba. It assists with the generation of a shortwave trough that later forms into an afternoon MCS over Iowa, Illinois, and Kentucky.
 The third is a classic deep trough with a pivoting positive to negative tilt axis. Over the two day loop the mid/upper level flow shifts from zonal to meridional allowing for advection of steep lapse rates (seen be the dry mid-level air), isentropic lift, and PVA. All this occurs above an already moist environment. The resulting upper level divergence is the final ingredient for a long lasting convective mode. The storms over southeast Texas have been seemingly non-stop while causing widespread flooding in an already flood prone area.
 The last trough is associated with Tropical Depression 2 (02L) which formed in a sweet spot right under the upper ridge axis off the east coast. The coastal/Atlantic waters are just warm enough above 26°C and the shear is below 20 kts for this depression to form off previous convection. The models are very consistent in showing a northwest moving track and NHC has 02L reaching South Carolina by sometimes early Sunday morning as a Tropical Storm.
 So much more can be said from this one satellite loop, but I’ll just end my discussion here.

Originally published at on September 1, 2016.

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