Sunday, June 10, 2012

Rainfall not as promising

I hate to be the messenger of bad news, but I have to give you the truth. Heavy rainfall for Monday does not look near as promising as it did yesterday.  In fact, some parts of the area may only receive a tenth of an inch by Monday night. Here's what's likely to happen. Right now, a rather weak upper level shortwave is located over the Gulf Coast, while a strong upper level trough is swinging into the Northern Plains, forcing a cold front eastward, which at the same time is sparking severe weather over Minnesota. The weak shortwave near the Gulf Coast is currently "trying" to move eastward, but its forward progress is being halted by the strong upper level ridge which is currently located over the area.  This is forcing to slowly move northward, especially in advance of the upper level trough over the Northern Rockies.  Overnight, this will cause the deep layer mean wind to becoming southerly, as the upper level shortwave is absorbed into the main upper level storm system.  These southerly winds will "pump" an incredibly moisture "rich" air mass into the region, with precipitable water (the total amount of "useable" water vapor in the atmosphere above a location, usually it is a good indication of heavy rainfall) values approaching 2 inches by the morning hours. Convergence from a surface trough and weak upper level forcing (along with moisture convergence along the initial surge of rich moisture) will cause the development of scattered showers tomorrow morning.  At this point, thunderstorms are unlikely tomorrow morning (from 8-noon is the best chance for rain), due to the advection of a mid level cap into the region, limiting atmospheric instability.  After this first wave of rain, skies should clear for a while before the initial storm system arrives, as a pocket of drier air aloft arrives in the area.  As for afternoon and evening, if the initial moisture surge has not shifted eastward yet, the cold front should be able to produce a few showers and thunderstorms across the area, but they will not likely be numerous, although some could be strong (assuming they do form). As for temperatures, depending on the amount of rainfall and cloud cover, temperatures should range from the low to mid 80's across the area.  Current model trends have been toward the moisture surge shifting eastward rapidly, bringing a rapid end to the rainfall, or the rainfall completely missing us.  Right now, I very skeptical of this, as the NAM may be having convective feedback issues associated with the closed low over the Gulf of Mexico, pushing the low too far east.  For now, we will have to see because this is a very unusual situation.  The cold front will push through sometime Monday night, still allowing warm overnight temperatures in the upper 60's.  By Tuesday, much cooler air will arrive with highs nearing the lower 80's (depending on the amount of rainfall we receive Monday).  Wednesday and Thursday, temperatures should start out in the middle 70's for highs on Wednesday, then jumping upward into the lower 80's.  By the weekend, highs will likely be in the 90's yet again as yet another ridge of high pressure builds into the area.

1 comment:

  1. Joshua, have you seen this?
    http://news.yahoo.com/blogs/sideshow/chunk-ice-falls-sky-crashes-california-home-154220049.html

    ReplyDelete