It’s official, and about an hour before I thought: the Charleston area — and indeed, all of eastern SC — is now under a tornado watch. Primary threats cited in the watch discussion include damaging winds in excess of 70 MPH, half-inch sized hail, frequent and dangerous lightning, and of course tornadoes. The discussion in full:
Tornadoes…hail to 0.5 inch in diameter…thunderstorm wind
gusts to 70 mph…and dangerous lightning are possible in these
areas.
The Tornado Watch area is approximately along and 80 statute
miles either side of a line from 55 miles west southwest of
Savannah Georgia to 45 miles east northeast of Orangeburg South
Carolina. For a complete depiction of the watch see the
associated watch outline update (wous64 kwns wou9).
Remember…a Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.
Other watch information…continue…ww 788…
Discussion…a mesolow/MCV in central GA will track newd along a
retreating warm front into central SC through the afternoon…and
ongoing pre-frontal storms will continue to spread newd over se GA
into srn SC. The moist and weakly unstable warm sector will surge
nwd across SC in advance of the low…while low-mid level vertical
shear will remain quite favorable for embedded supercells capable of
producing a few tornadoes and damaging winds.
Storms in southern Georgia have been kicking up a lot of lightning this afternoon, and as I write this, there are two active tornado warnings there. This is definitely something to watch closely as the afternoon progresses and we get into that rush hour time.
For the record, the time of next high tide is around 7:30. That is expected to be a lower high tide, forecasted at 5.15 feet; however, any rapid rainfall on top of an already soaked Downtown could once again put streets underwater this evening. RADAR is not estimating the same rainfall rates out of the Georgia storms as we saw this morning; however, anything above half an inch per hour could prove problematic for an already overwhelmed drainage system.
Jared Smith 12:06 am on December 15, 2009 Permalink
Rain is taking hold throughout the Charleston metro — it will be with us for a day or so. Expect to hear some embedded rumbles of thunder, as well. Rainfall rates are heaviest further south into Beaufort and Jasper counties; locally heavy rainfall is possible through tonight and tomorrow morning. Given that an inch or two of rain overnight is not out of the question, flooding problems may start downtown well before high tide.
Jared Smith 12:35 am on December 15, 2009 Permalink
Fully expecting to see at least a flood advisory go up for low-lying and poor drainage areas soon — rainfall has been steady over the past hour with decent RADAR-estimated rates of up to 8 tenths of an inch per hour in some spots, including West Ashley. The more impressive rainfall rates are south of here and offshore; seeing estimations near 2″ per hour on a line between Beaufort and Hilton Head Island.