WRAL WeatherCenter Blog

Wake-Franklin tornado survey

Posted April 27, 2010

Radar reflectivity image from 7:58 pm when the storm had just begun to show a faint "hook echo" development on it's southwestern flank Public reports and photos indicate that at least a funnel cloud and possibly a tornado was already underway at this time.

The Raleigh National Weather service office has completed and issued a storm damage survey for the severe thunderstorm that occurred Sunday night, April 25, 2010, along a track stretching across Wake, Franklin, Nash and (as it weakened) Edgecombe counties, and I've included the complete text of the report at the end of this post.

This was an especially interesting scenario, with the atmosphere in a pattern that was supportive of a slight risk of severe storms, but with activity greatly suppressed by the arrival of very dry air aloft earlier in the day. Toward evening, a very small shower/thunderstorm cell formed up just west of Wake County and tracked east-northeast, behaving in a quite benign fashion until suddenly intensifying and taking on a rotating, supercell structure just before 8 pm as it moved into easternmost parts of Wake County. From there into at least central Nash County, the storm showed a classic "hook echo" form in it's radar reflectivity and also signs of notable low-to-mid level rotation in Doppler velocity displays, as seen in some of the images I captured after the fact from the radar archive page at Plymouth State University.

I also included an image from the Iowa Environmental Mesonet County Warning Verification site that illustrates the application of "storm-based" warnings by the NWS. As you'll see, the warning area is much more confined to expected track of the storm in question than the older county-based warnings. Note that those are still in use for NOAA weather radios, so anyone in any part of Wake, Franklin or Nash county would have received an alarm. Also note that rather than being a simple trapezoid, the warning area has a small "notch" toward its southwestern corner. This is included to prevent all weather alarm radios in Johnston county from sounding an alert, since the tornado was considered likely to stay just north of the county line. While weather radio remains a very valuable system, this situation also highlights the benefits of a service like WeatherCall, which would only relay telephone warnings to addresses that fall within the red boxes outlining each storm-based warning update.

It is worth noting that in this case, the sudden development and reorganization of the storm and its rapid production of a weak tornado made it nearly impossible to project that a tornado would form from this cell, and meant that a tornado was already reported on the ground around 5-8 minutes before the first warning was disseminated, so that a funnel cloud or tornado likely crossed a small area west of the starting location of the warning box before any kind of warning was in place. Therefore, some owners of weather radios or subscribers to WeatherCall saw the funnel but did not hear an alarm until a bit later (weather radio) or did not receive a WeatherCall due to living at an address that was a short distance west of the beginning of the warning area. In many other cases, storms will show some signs of potential tornado production prior to a tornado forming, allowing for warnings to provide somewhat more in the way of advance notice.

As you may have already seen, this system was photographed by many of our viewers. There are also at least a couple of good videos of the tornado on YouTube, and I've included links to those here. As you'll see in the report below, this tornado was rated at EF-0, with a track about 75 yards wide by 3.5 miles in length and maximum winds estimated around 80 mph.

----------------------------

PUBLIC INFORMATION STATEMENT...UPDATED
NATIONAL WEATHER SERVICE RALEIGH NC
400 PM EDT MON APR 26 2010

...EF-0 TORNADO CONFIRMED NEAR ZEBULON IN WAKE AND SOUTHERN FRANKLIN
COUNTIES NORTH CAROLINA...

LOCATION...ZEBULON IN WAKE...AND FRANKLIN COUNTIES NORTH CAROLINA
DATE...APRIL 25 2010
ESTIMATED TIME...759 PM TO 806 PM EDT
MAXIMUM EF-SCALE RATING...EF0
ESTIMATED MAXIMUM WIND SPEED...80 MPH
MAXIMUM PATH WIDTH...75 YARDS
PATH LENGTH...3.5 MILES
FATALITIES...0
INJURIES...0

...SUMMARY...
THE NATIONAL WEATHER SERVICE IN RALEIGH NC HAS CONFIRMED AN EF-0
TORNADO WITH WINDS NEAR 80 MPH NEAR ZEBULON IN WAKE COUNTY AND
FRANKLIN COUNTY NORTH CAROLINA ON APRIL 25 2010.

THE TORNADO INITIALLY TOUCHED DOWN NEAR BELL STREET JUST WEST OF
GLAXO-SMITH-KLEIN AND THE ZEBULON MUNICIPAL BUILDING. BOTH OF THESE
FACILITIES EXPERIENCED LARGE FALLEN TREES WHICH DAMAGED FENCING BUT
NO STRUCTURAL DAMAGE OCCURRED TO ANY OF THE BUILDINGS. ONE OAK TREE
AT THE MUNICIPAL BUILDING WAS AROUND 4 FEET IN DIAMETER. THE TORNADO
MOVED EAST ACROSS HIGHWAY 96 (NORTH ARENDELL AVE.) CAUSING MINOR
DAMAGE TO SEVERAL BUSINESSES IN THE TRIANGLE EAST CENTER. A
MCDONALDS...PIZZA HUT AND OTHER BUSINESSES IN THE SHOPPING CENTER
EXPERIENCED VERY MINOR DAMAGE. A FOUR HUNDRED POUND CONDENSER ON THE
ROOF OF THE MCDONALDS WAS MOVED SIDEWAYS. A COUPLE OF VEHICLES IN
THE SHOPPING CENTER PARKING LOT WERE MOVED ABOUT 10-15 FEET AND A
NUMBER OF VEHICLES HAD THEIR WINDOWS SHATTERED BY DEBRIS IN THE
TORNADO. MANY PATRONS AT THE LOCAL RESTAURANTS SAW THE TORNADO
BEFORE IT STRUCK AND TOOK COVER. TORNADO WIND SPEEDS IN THE SHOPPING
CENTER WERE AROUND 70 MPH.

THE TORNADO CROSSED HIGHWAY 64/264 NEAR SHEPARDS SCHOOL ROAD
TRAVELING PARALLEL TO THE HIGHWAY BEFORE CROSSING OLD BUNN ROAD.
NUMEROUS TREES WERE BLOWN DOWN AND ONE SHED WAS DESTROYED ALONG OLD
BUNN ROAD...HOWEVER...THE STRONGEST TORNADO DAMAGE WAS EVIDENT AT
1311 OLD BUNN ROAD. WINDS IN THIS AREA INCREASED TO AROUND 80 MPH.
AT THIS RESIDENCE A FAIR AMOUNT OF MINOR ROOF DAMAGE WAS NOTED...A
CARPORT COLLAPSED AND NUMEROUS OUTBUILDINGS WERE DESTROYED BY A
COMBINATION OF TORNADIC WINDS AND FALLING TREES. MANY OF THE TREES
WHICH FELL WERE LARGE HARDWOOD TREES BETWEEN 3-4 FEET IN DIAMETER.

AFTER STRIKING THE RESIDENCE ON OLD BUNN ROAD THE TORNADO AGAIN
CROSSED HIGHWAY 64 EVENTUALLY CROSSING PARKS VILLAGE ROAD WHERE
ANOTHER LARGE HARDWOOD FELL DESTROYING AN OUTBUILDING. THE TORNADO
THEN MOVED INTO A SWAMPY AREA BEFORE CROSSING HIGHWAY 39 JUST NORTH
OF THE INTERSECTION OF HIGHWAY 39 AND HIGHWAY 97. NUMEROUS TREES AT
A RESIDENCE WERE UPROOTED OR SNAPPED. A HOME IN THE AREA LOST
SEVERAL SHINGLES AND SOME SIDING WAS DAMAGED. WINDS IN THIS AREA
WERE AROUND 70 TO 75 MPH. THE TORNADO MOVED INTO SOUTHERN FRANKLIN
COUNTY THEN LIFTED OFF THE GROUND.

THE OVERALL STORM TRACK WAS AROUND 3.5 MILES AND IT APPEARS TO BE A
CONTINUOUS TRACK TORNADO. THE AVERAGE PATH WIDTH WAS AROUND 75 YARDS
AND THE MAXIMUM WIND SPEED WAS AROUND 80 MPH.

ALTHOUGH INITIALLY ATTRIBUTED TO THE TORNADO...DAMAGE TO A
CARPORT/STORAGE SHED IN NASH COUNTY NEAR SPRING HOPE ON WORTH ROAD
WAS NOT COINCIDENT TO THE TORNADO TRACK AND HAS BEEN DETERMINED TO
HAVE RESULTED FROM STRAIGHT LINE WINDS. RESIDENTS ALONG WORTH ROAD
REPORTED LARGE HAIL AT LEAST THE SIZE OF QUARTERS AND A BROKEN
WINDOW AND SIDING DAMAGE WERE ATTRIBUTED TO THE HAIL. STRAIGHT LINE
WINDS NEAR SPRING HOPE WERE ESTIMATED AROUND 65 MPH.

THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT WEATHER.GOV/RAH.

FOR REFERENCE...THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO
THE FOLLOWING CATEGORIES:

EF0...WIND SPEEDS 65 TO 85 MPH.
EF1...WIND SPEEDS 86 TO 110 MPH.
EF2...WIND SPEEDS 111 TO 135 MPH.
EF3...WIND SPEEDS 136 TO 165 MPH.
EF4...WIND SPEEDS 166 TO 200 MPH.
EF5...WIND SPEEDS GREATER THAN 200 MPH.
 

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