The Perfect Storm

It really doesn't get much better than this synoptically for a coastal storm to develop and then sit and spin off the Mid-Atlantic coast for a few days.  ALL, and I do mean ALL of the ingredients came together to deliver copious amounts of rain to the Lower Susquehana Valley.  A vast high pressure system to the north, deep tropical moisture from the Gulf (Karen remnants), deep tropical moisture from the tropical Atlantic, low level vorticity from what once was TS Karen, and a cutoff upper 500 mb low over the central Appalachians, anomalously warm waters off the Mid-Atlantic coast, and a strong 700 mb-850 mb jet driving in mid-level moisture from the warm ocean, and finally the low level air upsloping the Piedmont to rain out over the KMDT region!  I'll try to show some of this...1st, here is the visible satellite of this Coastal Crawler as of midday Friday.  Note the "eye" just east of the mouth of the Chesapeake Bay.

Below is a satellite view of the Atlantic this past Monday.  In blue is the remnants of Karen; both spin and moisture.  Off to the east is deep tropical moisture from the very warm tropical Atlantic.  Thanks to the weak upper air pattern, these 2 decided to get together and create the Coastal Crawler!  For those of you who recall, this was the front that passed through and gave us 0.75" rain Monday.  The old frontal boundary also aided in the development of this storm!

As for the warm oceans...note the anomalous warmth off the Delmarva!

As for the mid-level jet, look at the initialization of the Euro...look at that fire hose, that starts out around Bermuda, pointing right at KMDT!  Unreal!  When this happens in the Pacific, and heavy rains fall in Cali, it is known as the "Pineapple" connection.  What would we connect with in Bermuda??  I was even thinking...if this were a winter set-up, that jet is so strong and so long that if this were a no-doubt about it snow storm, at the height of the storm, the precip would switch to sleet with the mid-levels warming to above freezing with the ocean air!

High pressure...ok...here is that current map!  Look at that huge dome (1032 mb) centered over Quebec ridging south and west and east blocking the Coastal Crawler from...well...even crawling!

So now we have the perfect set-up for the perfect storm. As for the upsloping; well, sea-level to 500' and then some in many places above sea level with an easterly flow spells trouble with all of the above in place.  That's why the rain has come...and will stay yet for a little while...here is the official call from NOAA for the next 6 hours...

And the current 24 hour total derived by radar...would not be surprised to see some purple show up when all is said and done!  As of 1 pm...these are quick additions...York Airport: just under 8", Cap City ~7.5", KMDT: just over 7", Smitty: same...Sky Hawk: can't tell since his gauge overflowed early this am at 5", as did my buddy from New Cumberland, the Captain from days long past, and my Bro down in Lanco.  What is it with you guys...get larger gauges or get out there and dump prior to overflow!  Seriously, I love the obs being sent my way...keep them coming!

I don't want an ob from my Hummelstown connection telling me about a severely flooding Swatty.  Here is the latest for it...

And the Breeches for the West Shore clientele...

And finally for you "River Rats"...

Speaking of "Rats" enjoy this Grateful Dead song concerning rats of a different variety...if you have 9 minutes, just let the song play in the background; it really is very good!

OK...gotta run and monitor my wet basement. The rain has picked up in its intensity once again, and there is still ample moisture advecting this direction!  Remember, that swath of rain is moving from east towards the west!  Ouch...

Enjoy your week's end!  Stay dry...

Smitty

AA:  Lots of rain...I know...No $&#!...but still not over...might see some brightening by Sunday pm...but not too much!  Lawn mowing warning for next week!