Friday, November 25, 2011

Starting The New Week On A Wet Note

The mild stretch of weather that we're enjoying will continue through the weekend. However, clouds will likely be on the increase later on Sunday as a storm system approaches from the west.   It's been a modeling mess of sorts so far as the storm is just now moving completely onshore on the West Coast, features energy in the Southwestern US, and computer guidance used to track this storm has painted a myriad of outcomes for the early portions of next week, with little in the way of consensus for the past few days.



What does have some consensus, operative word being some, is that it looks to rain on Sunday night and/or Monday as a cool front moves in from the west.  Computer modeling varies on timing and details with how much rain falls -- but the potential does exist that we could see an inch of rain or so in the Sunday night and early Monday timeframe.

Where the variation and variety take place is in how the storm evolves -- the GFS model (above) has generally developed a more dominant low over the Great Lakes and also provides a more potent northern stream of energy, one that picks up a storm system in the Southwestern US and pulls it along for the ride across the country.  The two pieces of energy team up and provide a steady shot of rain across the East Coast as the front moves through.  In contrast, the Euro has a much weaker northern stream of energy, which allows the southern stream of energy to cut away completely and develop a sit-and-spin southern low that gradually organizes at the surface before pushing northeast with steady rains for midweek.  The one-two punch the Euro model provides the same amount of rain as the GFS, but spits it out over two shots (showers on Monday, steadier rain on Wednesday).   The Euro has a history of "holding energy back" on its modeling...which mean that it sometimes struggles to kick southern systems along in comparison to other models.   This doesn't mean that the one-two punch is wrong...it ultimately may be poorly timed and that the one-two punch is much closer together.


In between those two ends, a pair of model runs of the GFS from this morning has shown a slower solution of sorts with the Sunday night & Monday front.  It also has taken that southern piece of energy and brought it along as a secondary punch with the first wave of rain, adding additional rain to the Mid Atlantic and north into New England Tuesday as this southern energy hits the coast and then phases into the northern jet.   This *could* be what verifies in the end -- a round of showers on Monday, tapering off Monday evening before a second round that moves over us on Tuesday -- an ultimate "in the middle" compromise between the "all on Monday" solution that earlier GFS runs had painted and a stronger second half system that the Euro had suggested.