assignment3 rbb52

Super Tornado Outbreak 2011

A Hydrologic Perspective

One of the worst tornado outbreaks in recorded U.S. history

925 mb

-Surface low over OK/AR-Abundant low-level moisture over Gulf Coast states-Strong low-level jet in place over Mississippi

850 mb

-Deep layer of moisture present-Winds veering over MS, LLJ still in place

700 mb

-Continued deep layer of low-level moisture-Winds continuing to veer and increase in speed with height-Low tilting with height, appears to be coupled with another poleward low

500 mb

-Continued veering of winds with height-Mid-level divergence, diffluence-Exit region of trough over Dixie Alley area

250 mb

-Upper-level trough present-Upper-level divergence, diffluence over Ohio River Valley through to Gulf Coast states-Right-rear quadrant of jet streak over N-Mississippi

Skew-T

-High moisture in lower levels-Veering winds with speed shear with height-High CAPE levels-Moderate CIN-Dryer layer aloft


• Effectively several elements were in place for a very serious severe weather situation, and these elements panned out, in what was one of the worst tornado disasters in U.S. history. But through all of the destruction and spectacular tornado footage, what was happening with respect to our hydrologic cycle?...


• This study focuses on Smithville, MS, a small town in Monroe County, MS.

• -Image courtesy of Wikipedia

Products shown: Q2 RaDAR Only; Q2 QC’d Gauge; Q2 Gauge-Adjusted RaDAR; Satellite Hydroestimator; Stage IV

*Hydroestimator not available for 0700-0900

• Stratiform precipitation a few hours after primary severe weather threat passes

Products shown: Q2 RaDAR Only; Q2 QC’d Gauge; Q2 Gauge-Adjusted RaDAR; Satellite Hydroestimator; Stage IV

*Hydroestimator not available for 0700-0900

Situation Rundown• The precipitation within this time frame is nearly exclusively convective of nature. • Rain gauge data in this instance is likely highly unreliable due to wind undercatch,

and the possibility it was destroyed by an EF5 tornado. Moreover, or rain gauges, it is likely that between 1100 and 1200 a rain gauge in NW-Monroe County was incapacitated, noted by the hole apparent from 1200 onward in gauge only data.

• Satellite Hydroestimator values appeared to underestimate precipitation in all hourly snapshots except for 2000, which was several hours after the primary severe threat passed, and precipitation was associated with less intense convection, as well as inclusive of stratiform precipitation.

• Smithville, MS is roughly 70km from the nearest RaDAR site in Columbus, MS. This is a reasonable enough distance to be from the RaDAR without being far enough so that the beam overshoots the majority of the precipitation.

• Another consideration is the fact that an EF5 tornado-producing supercell passed through Smithville mid-afternoon, between 1500 and 1600. Precipitation estimates from this event will be skewed regardless of source due to the nature of evaporation, wind-driven displacement of hydrometeors, and presence of substantial hail.

So what does all this mean?.

• If I were the NWS hydrometeorologist responsible for providing QPE for this event, I would rely very heavily on RaDAR backed up with rainfall reports from the field.

assignment3 rbb52

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