Tagged: Severe Weather RSS

  • Jared Smith 10:41 am on January 21, 2010 Permalink
    Tags: , , Severe Weather   

    Tough commute possible this afternoon 

    Heavy rain and thunderstorms — a few of which could reach severe limits — are a possibility this afternoon as a storm system pushes its way east through the area. While the best severe potential remains south of here (think Beaufort), there’s still a shot of some heavy rumbling up in Charleston. We’re not included in a watch or convective outlook yet, though that could change as the day rolls on.

    Another concern is flooding. Localized totals of 3″ are forecasted. Right now, expect the heavier rains to start around noon and pick up throughout the afternoon. As with any heavy rain event, street flooding in the usual spots downtown cannot be ruled out, but a widespread flooding event is probably not so much in the cards, as tides will be receding throughout the afternoon. High tide is at 11:20 AM, followed by low tide at 5:46 PM.

    Continue to watch this thread and @chswx for updates throughout the day.

     

    • Jared Smith 2:44 pm on January 21, 2010 Permalink

      Thanks to the steady rain, severe weather won’t be a worry this afternoon. The rain has been heavy at times, but rainfall totals haven’t been anything to write home about just yet. Still watching for a chance at some local flooding — particularly in the coastal areas — but the tide situation is on our side with that. Be careful if you have to travel today, as the rain and occasionally blustery wind will make things a bit difficult, particularly on the bridges.

  • Jared Smith 10:24 am on December 9, 2009 Permalink
    Tags: , Severe Weather,   

    Tornado Watch 803 CANCELLED as line of storms weakens 

    Tornado Watch 803 has been canceled as the energy needed to kick off additional severe weather has waned considerably; this is evident in the precipitation signature of the squall line pushing eastward. We may see rain with gusty winds — and you can never rule out a clap of thunder — but things have calmed considerably. The rain will be out of here by midday; enjoy one last day in the 70s before the temperatures plunge on Thursday.

     

  • Jared Smith 9:02 am on December 9, 2009 Permalink
    Tags: Severe Weather,   

    Tornado Watch 803 until 10am; line of storms incoming 

    Look out for a rough morning ahead: The Storm Prediction Center issued Tornado Watch 803 around 6am out ahead of a very strong squall line that’s rifling through the Southeast. This line has a history of damaging winds and tornadoes cannot be ruled out. (Watch Wunderground radar in motion.) Additionally, the sun is starting to peek, which may add some instability before the line arrives.

    As of this writing, it appears the line will start to be felt in the northwestern portions of Berkeley and Dorchester counties around 8:30am; it will spread quickly through the area shortly thereafter. The line is moving at speeds up to 55 MPH, so this will be a short-term event. Things should be clearing after 10am, when the Tornado Watch expires.

    Watch @chswx on Twitter for the latest statements and any warnings that are issued.

     

    • Jared Smith 9:47 am on December 9, 2009 Permalink

      Been watching RADAR. Heavy rain being reported in some areas but not seeing any thunderstorm reports within the line, which has not looked as impressive in the last hour. Wind fields and storm motions are still impressive, though, and anything that flares up has a shot at producing damaging winds (though the only warnings right now are in NE SC).

    • Jared Smith 10:04 am on December 9, 2009 Permalink

      A weakening trend within the line is continuing. Precipitation is falling off noticeably, particularly over the portions of the Midlands and the inland Lowcountry that are still in the line. Still some stronger storms in Georgia that might hold up, but the trend is positive in terms of our severe weather threat. That being said, the watch continues — there’s still decent juice in the atmosphere — 64 degree dewpoints, for starters — that could still flare a storm.

    • Jared Smith 10:20 am on December 9, 2009 Permalink

      This watch is now canceled. The weakening trend is enough for NWS to declare the severe weather threat moot. Still will see gusty winds but it looks like the major severe threat has ended.

  • Jared Smith 11:11 pm on December 2, 2009 Permalink
    Tags: Recap, Severe Weather,   

    Tornado watch canceled; threat ends 

    The Tornado Watch which has been with us for most of the afternoon — and stuck around a little longer than anticipated — has finally been dropped for the area.

    We were very fortunate that the severe weather outbreak that had been predicted for this afternoon did not play out. One major factor was the lack of sunshine — because the clouds hung around, this kept a lid on the most explosive convection. Another factor was timing; storms did not begin to reintensify until they were largely offshore. We did notice the squall line falter and then pick up just before it pushed offshore, prompting a fairly long period where the Charleston area was warned for severe weather. After pushing offshore, very distinct rotations in the cells developed and are now moving ashore in the Grand Strand and into southeast North Carolina.

    Flooding still persists throughout the region. Downtown streets, which have been turned to rivers twice in 12 hours, will need some time to clear out — the lowering tides will help. There’s also reports of standing water in Goose Creek, Moncks Corner, and North Charleston. If you encounter standing water, please do not attempt to cross — it’s hard to judge the depth of water during the day, and it’s nearly impossible at night.

    Winds will remain strong through midday Thursday on the lakes; a Lake Wind Advisory continues for Lake Moultrie until noon. Small craft are also urged to use caution during the day Thursday. Gale warnings are still up until 5am for waters out 20 nm.

    Here’s looking toward a much calmer and drier Thursday. We might see some rain peek back into the forecast Friday night; still tough to pin that one down, though.

     

  • Jared Smith 9:47 pm on December 2, 2009 Permalink
    Tags: Severe Weather,   

    Tornado Watch extended to 11 PM 

    NWS has extended Tornado Watch 789, previously scheduled to expire at 9 PM, to 11 PM. The main line of storms is about through Charleston now, but there seems to be some activity kicking up behind it — better safe than sorry. After these last few rounds of activity clear, I suspect the watch will be dropped, especially as the highest probability of tornadic activity has moved northeast into the Grand Strand and eastern North Carolina. Will continue to watch…

     

  • Jared Smith 3:24 pm on December 2, 2009 Permalink
    Tags: Severe Weather, ,   

    Tornado Watch 789 until 9 PM 

    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 4:50 pm on December 2, 2009 Permalink

      New AFD, just released a few minutes ago:

      WITH THE IMPRESSIVE DYNAMIC FORCING AND INCREASINGLY
      FAVORABLE THERMODYNAMIC ENVIRONMENT SETTING UP OVER THE FORECAST
      AREA…EXPECT AN ACTIVE EVENING WITH THE POTENTIAL FOR SIGNIFICANT
      STRAIGHT LINE DAMAGING WINDS IN EXCESS OF 75 MPH AND STRONG LONG
      TRACKED TORNADOES OF EF2 STRENGTH OR GREATER.

      Rain is going to start again shortly in Dorchester County, sliding up the coast and eastward. Going to begin to get very rough here in the next hour or so.

  • Jared Smith 10:40 am on December 2, 2009 Permalink
    Tags: , , , Severe Weather   

    As messy as advertised, with the brunt yet to come 

    The flooding situation has been as messy as advertised this morning. NWS just reported that the high tide at Charleston Harbor this morning was 7.75 feet — well beyond the point where coastal flooding begins even without rain (typically 7 feet).

    Traffic into downtown Charleston is nearly impossible. The Crosstown is closed and it’s not likely to reopen for a little while. Stalled cars litter the streets-turned-rivers downtown. Josh Marthers at WCBD captures the flooding situation well. I also highly recommend watching traffic tweets and pictures (and there are some good ones) on Collecta.

    And as bad as this morning was, we haven’t seen the worst of it. This morning’s Day 1 Convective Outlook from the Storm Prediction Center continues the “slight risk” for severe weather in Charleston, and this could be upgraded to a “moderate risk” later today, especially if any sunshine peeks through and adds more fuel to the fire. The storm system which is expected to wreak havoc on us later this evening has already dropped several tornadoes in the Florida panhandle, and there is a good possibility we may see at least one or two tornadic cells later today in the Lowcountry. Straight-line damaging winds continue to be the primary threat from this system, though.

    There’s a good shot that we’ll have a tornado watch in effect by 3PM today. Keep an eye to Twitter as the day progresses with updates from NWS and SPC. We’ll announce watches and warnings there as they happen.

     

    • Jared Smith 1:36 pm on December 2, 2009 Permalink

      Not much has changed with the new Day 1 Outlook. Charleston is still listed as having an elevated risk of tornadoes and damaging winds. In the latest Hazardous Weather Outlook, NWS Charleston called this afternoon’s severe weather threat a “potentially dangerous situation” — something NWS does not say lightly. Here’s hoping for the best, but it does look like the ingredients are going to come together for a very rough late afternoon and evening. Some clearing was observed in Georgia — let’s just hope that doesn’t happen here.

    • Jared Smith 3:15 pm on December 2, 2009 Permalink

      Tornado Watch now in effect for a great deal of SC, including Charleston and surrounding areas, until 9 PM. More information forthcoming.

  • Jared Smith 2:17 am on December 2, 2009 Permalink
    Tags: , day 1, , Severe Weather   

    Wednesday: Slight risk of severe weather, high probability of damaging winds 

    The Storm Prediction Center has just issued its Day 1 Convective Outlook, placing the Charleston area in a slight risk for severe weather. Currently, forecasters are pegging the severe event to take place in the late afternoon and into the evening hours. Primary threats are widespread damaging winds as well as the possibility of tornadoes, especially along the coastal regions.

    Currently, this is the thinking (or something like it) on Wednesday’s event:

    • 3AM – midday: Heavy rain with embedded thunderstorms associated with a warm front will soak the Lowcountry. The timing of the rain will line up with an already abnormally high tide at 7am. Enhanced with a brisk onshore flow, coastal areas including downtown Charleston could see potentially significant flooding. A Coastal Flood Warning goes into effect at 4am through 11am.
    • Midday – ~2-3 PM: Break in the action as the warm front lifts north, but before the cold front’s squall line reaches the coast. There’s a possibility that the sun may come out during this time; any sunshine could significantly destabilize the atmosphere further and thus enhance the intensity of severe weather.
    • 3 PM – Evening: Cold front makes its move on the Lowcountry. Squally thunderstorms with strong, damaging wind likely. Supercells also are a possibility; those storms can contain downbursts and tornadoes. Heavy rain also is expected, though the flood threat is not expected to be as pronounced in the evening. Activity will likely continue after sunset; be especially aware of rapidly changing conditions after dark because it will be much harder to see what’s happening.
    • Thursday: Conditions gradually abate themselves as the front moves through; rain tapers off through Thursday.

    The takeaway: The morning and afternoon commutes will likely be quite nasty. Allow extra time during your commute, and if you encounter a flooded area downtown in the morning, turn around! It takes relatively little water to stall out a vehicle. Streets such as Rutledge and Ashley Avenues, Jonathan Lucas, Bee Street, the Crosstown, East Bay Street, Market Street, and others could prove impassable. Have alternate routes ready to go. Other coastal communities, including Folly Beach and Isle of Palms, may also see significant flooding problems in the morning.

    Keep an eye here or to @chswx for updates throughout the day.

     

  • Jared Smith 6:11 pm on December 1, 2009 Permalink
    Tags: coastal flood, high surf, Severe Weather   

    Coastal Flood Warning to be issued 

    The 5 PM Area Forecast Discussion indicates that a Coastal Flood Warning will be issued for coastal communities, including downtown Charleston, tomorrow morning. This means flooding is expected to occur. High tide is just before 7:30am, so expect a very messy rush hour for downtown commuters tomorrow.

    From the AFD:

    THE LATEST GFS EXTRATROPICAL STORM SURGE
    GUIDANCE SHOWS TIDES REACHING CLOSE TO 7.8 MLLW IN CHARLESTON HARBOR
    AND AROUND 9.9 MLLW AT THE SAVANNAH RIVER ENTRANCE. GIVEN THE MODEL
    CONSISTENCY OVER THE LAST SEVERAL DAYS SHOWING TIDES REACHING THESE
    LEVELS…ALONG WITH IT/S TRACK RECORD OF UNDERESTIMATING THE ACTUAL
    TIDAL DEPARTURES AT THE TIME OF HIGH TIDE IN THESE UNUSUAL
    EVENTS…WILL GO AHEAD AND ISSUE A COASTAL FLOOD WARNING FOR THE
    ENTIRE SOUTH CAROLINA AND GEORGIA COAST.

    Additionally, the strong onshore flow may cause beach erosion and high surf, so a high surf advisory will be issued as well. I’ll update again when I hear the particulars on the new warnings and advisories.

     

    • Jared Smith 6:18 pm on December 1, 2009 Permalink

      The Coastal Flood Warning is official. The warning covers the entire coast, and will go into effect at 4am. NWS cited potential tides between 7.8 and 8.0 feet. Rush hour will be VERY hairy for downtown commuters tomorrow.

      From the warning issuance:

      SALT WATER WILL RISE INTO YARDS…STREETS AND DRIVEWAYS ACROSS
      PARTS OF DOWNTOWN CHARLESTON…ESPECIALLY IN LOCATIONS THAT OFTEN
      EXPERIENCE FLOODING DURING HIGH TIDE EVENTS. HIGHWAY 80 LEADING
      TO TYBEE ISLAND GEORGIA WILL ALSO BE IMPACTED…WITH HIGH WATER
      POSSIBLY MAKING THE ROADWAY IMPASSABLE. MANY OTHER COASTAL
      LOCATIONS WILL ALSO BE IMPACTED…INCLUDING BUT NOT LIMITED TO
      ISLE OF PALMS…SULLIVANS ISLAND…SEABROOK ISLAND…EDISTO
      ISLAND…EDISTO BEACH…HUNTING ISLAND…LADYS ISLAND…SAINT
      CATHERINES ISLAND AND SAPELO ISLAND.

    • Jared Smith 6:41 pm on December 1, 2009 Permalink

      The High Surf Advisory will start at 5am and last until 5PM Thursday. Not sure I’d go surfing in this weather, though — maybe Thursday if you’re into that Polar Bear thing. :)

  • Jared Smith 11:18 am on December 1, 2009 Permalink
    Tags: , Severe Weather   

    Coastal flooding possible tomorrow AM; “widespread severe event” possible afterward 

    We’re watching with great interest a fairly good possibility for a widespread severe weather event Wednesday. A very strong low pressure system is coming together in the Gulf of Mexico and will push eastward during today and tomorrow. We’ll start feeling the effects of this low late tonight in Charleston, as strong onshore winds will begin to kick up the coastal waters, causing beach erosion and coastal flooding. NWS has the Charleston coast under a Coastal Flood Watch from late tonight through Wednesday morning, as it’s expected that heavy rain and wind will impact the area right at the time of high tide. Tides up to 7.8′ are currently expected in Charleston Harbor. This is a prime setup for a fairly significant downtown flooding event right at rush hour, as high tide is at 7:30am.

    Later Wednesday, this storm system will bring along with it a favorable setup for severe weather — a bit unusual for December, but certainly not unprecedented. The entire SC coastal area is in a “slight risk” of severe weather for Wednesday. Damaging winds, hail, and tornadoes cannot be ruled out. Plan accordingly for your Wednesday if you are traveling. We’ll keep an eye on things and update as the forecast becomes more clear.

     

    • Jared Smith 2:32 pm on December 1, 2009 Permalink

      From the latest area forecast discussion — things are looking ripe for a rough day:

      INGREDIENTS APPEAR TO BE COMING TOGETHER FOR A POTENTIALLY
      SIGNIFICANT SEVERE WEATHER EVENT. IF THE MODELS ARE CORRECT WITH
      THE TEMPERATURE AND BOUNDARY LAYER MOISTURE EVOLUTION…SURFACE
      BASED INSTABILITY OF AROUND 400-900 J/KG OF CAPE AND LI/S OF -2 TO
      -4C ACROSS THE ENTIRE FORECAST AREA…WITH NO CONVECTIVE INHIBITION
      WILL BE REALIZED. THIS COMBINED WITH STRONG MID-LEVEL QG FORCING…
      ENTRANCE REGION FORCING FROM A 130+ KT UPPER JET… MID- LEVEL
      LAPSE RATES STEEPENING TO BETWEEN 6.5 AND 7.0 C/KM ALONG WITH 0-6
      KM BULK SHEAR VALUES OF 65 TO 75 KT…WILL BE SUPPORTIVE OF
      ORGANIZED LINEAR CONVECTION WITH OCCASIONAL SUPERCELL STRUCTURES.
      WITH 850MB WINDS INCREASING TO AROUND 70 KT PROGGED BY BOTH THE GFS
      AND NAM…ENERGY HELICITY INDICES CLIMBING TO AROUND 1…AND 0-1
      KM HELICITY VALUES MAXING OUT IN THE 400-500 M2/S2…DAMAGING
      STRAIGHT LINE WINDS AND TORNADOES APPEAR TO BE THE PRIMARY SEVERE
      WEATHER THREATS WITH MARGINALLY SEVERE HAIL POSSIBLE AS WELL. THE
      SPC CONTINUES TO SHOW A SLIGHT RISK FOR THE REGION WEDNESDAY WITH
      30 PERCENT PROBABILITIES OF DAMAGING WINDS AND A LARGE HATCHED
      AREA FOR SIGNIFICANT SEVERE WEATHER ALONG MUCH OF COASTAL SOUTH
      CAROLINA AND GEORGIA. THE POTENTIAL IS CERTAINLY THERE FOR A FEW
      STRONG…LONG TRACK TORNADOES. WILL CONTINUE TO MENTION SEVERE
      WORDING IN THE ZONES AND FORECAST GRIDS FOR THE ENTIRE FORECAST
      AREA.

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