1000 Year Rain Event Wrap. “This just doesn’t happen.”

October 5, 2015

Above, CNN Weather man’s description of the Weekend’s events in South Carolina.  River gauges washed away – “..that’s something that just doesn’t happen.”

Signals mixed on the role of Hurricane Joaquin, but obviously there was some impact.  Similar to Sandy, the storm interacted in complex ways with an onshore system, drew on abnormally warm sea surface temps,  and both storms were affected by unusual jetstream configurations.

Below, extraordinary radar loop.

Here, Governor Nicki Haley’s press conference on Sunday.

Although we’ll have to wait for serious forensics to tease out all the wrinkles in this very complex event, the Washington Post has a long and detailed piece, worthwhile, excerpts here:

Washington Post:

According to statistics compiled by the National Oceanic and Atmospheric Administration, South Carolina’s torrential weekend rain has well surpassed a 1,000-year rainfall event — one that, on average, we would expect to see about every 1,000 years. A three-day, 1,000-year rainfall event for Charleston County would have been 17.1 inches. A four-day, 1,000-year event would have been 17.5 inches. Boones Farm Plantation, just north of Mount Pleasant, in Charleston County, reported more than 24 inches of rain through Sunday morning, which essentially blows NOAA’s 1,000-year events scale out of the water.

As Hurricane Joaquin tracked north, well east of the coast, a separate, non-tropical low pressure system was setting up shop over the Southeast late last week. This system drew in a deep, tropical plume of water vapor off the tropical Atlantic Ocean. At the same time, this upper-level low pressure system tapped into the moist outflow of Hurricane Joaquin.

The moisture pipeline fed directly into a pocket of intense uplift on the northern side of the non-tropical vortex. Within this dynamic “sweet spot,” thunderstorms established a training pattern, passing repeatedly over the same location and creating a narrow corridor of torrential rain stretching from Charleston to the southern Appalachians.

The remarkable thing about this process is that it was sustained for three days.

For review, here is Kerry Emanuel of MIT, and his “play by play” analysis of Hurricane Sandy.

3 Responses to “1000 Year Rain Event Wrap. “This just doesn’t happen.””

  1. philip64 Says:

    This week-end’s flash floods in the South of France (19 dead and counting) are also unprecedented. The area is estimated to have received more than 10% of its average yearly rainfall in two days alone.

  2. dumboldguy Says:

    “The remarkable thing about this process is that it was sustained for three days”.
    Yes, and gave SC 20+ inches of rain, and once the flooding subsides, it will be back to BAU.

    Maybe if the oceans keep warming, the atmosphere warms more so that it can hold more moisture, and we see more “unusual jet stream configurations”, we will see more of these “complex interactions. Sandy did what no hurricane ever did, and this event in SC is less than a 1 in 1000 year event.

    Will we see these “complex interactions” happening every five years and will it be “sustained” for FIVE days next time and with a rain total over 30 inches? We are whistling past the graveyard.

  3. This violent weather provides yet more harsh and affirming truth that climate change is here to stay.

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