****UPDATE 5-16-2014: Well NWS Raleigh did their damage survey of this storm today. An EF-1 tornado was confirmed, but not in the area I thought it would be. Unlike what I said below, the TDS was associated with the tornado as it was happening and not a delayed reaction like I thought. Either way i hope those of you who did read this enjoyed it. I have attached the PUBLIC INFORMATION STATEMENT below.****
The origin of this post begins on facebook. Someone reported seeing a possible TDS (Tornadic Debris Signature) on the KRAX radar. The time stamp of the image was 2214z. Someone made note of the face that the TDS was not directly associated with the rotational couplet on SRV (Storm Relative Velocity).
Below is my attempt at finding out why the TDS was not associated with the velocity couplet seen on the original image post. The 4 panel images below show Reflectivity (Z), SRV, KDP, and CC.
At 2158, the rotation appears to reach its strongest point as it crosses I-40. CC and KDP appear to remain at the same levels as they did back at 2149.
Using the RHI tool I made a cut across the TDS at 2214 in an attempt to see just how high the debris was lofted. It appears that whatever the debris was, was lofted somewhere between 7000 and 8000 KFT.
NOTE- The radar beam ranged from 1900-2400 KFT above the ground.
In my opinion, the tornado touchdown was around 2154 and possibly lifted around 2209? This would explain why the TDS was detached from the circulation we see in the above screen caps. The tornado was weak, which is why it took a little while for the debris to be lofted enough to be seen by radar, and also why the debris did not go above 10 KFT.
Again, just my non expert opinion. Hope you all enjoyed....LOL
***Again, This post is purely based off radar data only. At the time this was written, there were no confirmed sightings of a tornado. Second, I decided to write this because someone asked a question and I was curious to see what the answer was, or most likely was.***
Some helpful links to learn more about Dual Polarization Radar:
WDTB Dual-Pol Training
Dual-Pol Training Aid
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE RALEIGH NC 447 PM EDT FRI MAY 16 2014 ...TORNADO CONFIRMED APPROXIMATELY 3 MILES SOUTHWEST OF DURHAM IN DURHAM COUNTY NORTH CAROLINA... LOCATION...3 SW DURHAM IN DURHAM COUNTY NORTH CAROLINA DATE...MAY 15 2014 ESTIMATED TIME...610 PM TO 613 PM EDT MAXIMUM EF- SCALE RATING...EF1 ESTIMATED MAXIMUM WIND SPEED...90 MPH MAXIMUM PATH WIDTH...150 YARDS PATH LENGTH...0.8 MILES * FATALITIES...0 * INJURIES...0 * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS STORM DATA. ...SUMMARY... THE NATIONAL WEATHER SERVICE IN RALEIGH NC HAS CONFIRMED A TORNADO 3 SW DURHAM IN DURHAM COUNTY NORTH CAROLINA ON MAY 15 2014. DAMAGE CONSISTED OF DOZENS OF SNAPPED AND UPROOTED TREES...AND APPROXIMATELY 40 HOMES THAT EXPERIENCED ROOF OR OTHER STRUCTURAL DAMAGE. MOST OF THE DAMAGE TO THE HOMES WAS CAUSED BY FALLING TREES AND OTHER DEBRIS IMPACTING THE STRUCTURES. HOWEVER...THERE WERE AT LEAST A HALF DOZEN HOMES THAT EXPERIENCED MINOR ROOF DAMAGE CAUSED SOLELY BY THE WIND. IN ONE CASE...A LARGE OAK TREE WAS UPROOTED...AND IN THE PROCESS FELL ONTO A HOME AND SUBSEQUENTLY SLICED THROUGH THE ROOF AND AN EXTERIOR WALL OF THE HOME. THE EXTENT OF THE HARDWOOD TREE DAMAGE SUGGESTED MAXIMUM SPEEDS OF 90 MPH (EF1) BASED ON THE ENHANCED FUJITA SCALE. THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT WEATHER.GOV/RAH.