Rain Totals Through Noon Wednesday

A swath of much-needed rain tracked from the southwest to the northeast over central Virginia last night and into much of this morning. These are the radar-estimated accumulations over the last 24 hours (through Noon Wednesday), which match up pretty well with totals reported in by weather watchers.

An upper wave is tracking over the Commonwealth while a surface front remains stalled over central Virginia. With this boundary lingering in the area this afternoon, new scattered showers and embedded thunderstorms are developing, especially where there are some breaks in the clouds. Keep your umbrella handy because these showers can produce locally heavy rainfall. I am not anticipating a severe threat today, but some of these heavy showers may have occasional lightning with them.

La Nina Update Mid-August

While our Summer months have been the hottest on record so far in Richmond and central Virginia, the Equatorial Pacific has been cooling significantly into La Nina conditions (above: blue shades indicate ocean cooling along the equator. For your reference, here's a broader view below).

You can see the deviation below the long-term average ocean surface temperature in this chart below where there is blue coloring:

The different Nino levels (1+2, 3, etc.) are simply different indicators used to determine the strength of the La Nina/El Nino event. Our dip out of El Nino toward La Nina began in late February, reaching negative anomolies by late April. La Niña conditions are likely to continue through early 2011, according to the Climate Prediction Center forecast data:

(Outlook figure provided by the International Research Institute for Climate and Society, updated 16 July 2010.)

What does this mean for Virginia through October? We should keep running warmer than average into the Fall. As for rainfall, we can go either way in a La Nina setup in the Fall with being wetter or drier than normal. Let's hope we are wetter than average so we get out of this drought!

Tropics Update Monday

The remnants of Tropical Depression Five from last week have drifted south back over the northeast Gulf of Mexico. As a result of being back over the warm, moist Gulf waters, the remnants could organize over the next couple of days to be re-dubbed a tropical depression. Tropical model data indicates the low could loop back in a circle over some of the same locations it affected upon its first landfall last week:

A curve east through the Mississippi Valley region may occur if what's left of this low is swept up into an upper disturbance that should be tracking through the Midwest at the end of the week. As far as intensification goes, the low will likely not be able to reach tropical storm strength. You can see all forecast intensities (except assumed consistent intensification in the red line) keep wind speeds below 39 mph (the threshhold for tropical storm strength):