Monday, July 23, 2018

Upper Level Low Creates a July Woe

In terms of rainfall, we've had quite a week of precipitation beginning with a cold frontal passage last Tuesday, a hybrid type coastal system Saturday, and now a stalled upper level low where we here in PA are getting a continuous supply of deep tropical moisture from the south.  As of this time, our humble abode and rain gauge has received over 5" of rain in the last week!  And there will be much more heading our way through mid-week.  Here is a water vapor image from early Monday morning.  The yellow is dry air in the mid-levels of the troposphere while the whites and greens are quite moist.  As you can see from this, the flow is clearly from the tropics and although some dry air is wrapping into the upper low, the high dew point air at the surface will supply the fuel for more showers and thundershowers over the next couple of days...
And the concern of "training" convection can lead to excessive rainfall.  Here is an snap shot of the storms overnight.  Note how they were aligned moving from south to north in response to the upper level low...
And the streams are responding in kind...1st the Yellow Breeches in my "back yard"...
Next the Swatty at Hershey...
And the Susquehanna at Harrisburg...
And here is a graphic showing the rainfall from the last 48 hours in the Mid-Atlantic region...

So we did need rain heading into this week, but we may end up with too much liquid sunshine if this upper low remains stalled to our south and west...this last graphic shows the 5 day 500 mb average with a large 4 corners high and a elongated low from the north central states down towards the SE USA creating our southerly flow on the east side of that trough.  So showers and thundershowers do look likely throughout the upcoming week...
OK...enough said.  I'll leave y'all with this classic song about rain...


Smitty

AA:  Lots of rain the next several days to keep the green things growing.  

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