Waterspout-turned-tornado strikes Surf City, NC on July 19, 2017

path of the Surf City waterspout/tornado on July 21, 2017

Track of the Surf City waterspout/tornado on July 19, 2017

During the morning of July 19, 2017 a waterspout developed within a cluster of showers off the coast of Pender County, NC. The waterspout approached the beaches and at 11:23 AM moved ashore with wind speeds estimated around 70 mph. The waterspout, now called a tornado since it was occurring over land, moved over the front row of beach homes, crossed South Shore Drive and Seahorse Ave, then dissipated just before reaching South Topsail Drive (NC 50) and the marshes beyond.

Damage occurred to a wooden fence and to roofs on three houses. Strong winds also scattered outdoor patio furniture. Based on a survey of the damage, the tornado's path width was approximately 25 yards. Thankfully there were were no injuries.

Multiple witnesses took pictures and recorded video of the waterspout before and during its transition into a tornado.

So this happened today...
Posted by Andrew Kirsch on Wednesday, July 19, 2017

The atmosphere on July 19th contained ingredients favorable for the development of fair-weather waterspouts. What is a fair-weather waterspout? While most tornadoes develop beneath severe thunderstorms, fair-weather waterspouts develop over the ocean beneath cumulus clouds or showers that produce no other hazardous weather. According to in-house research conducted at NWS Wilmington, NC, fair-weather waterspouts locally occur most often from June through September. Three factors are needed to produce fair-weather waterspouts:

Modified 12Z sounding from Morehead City, NC (MHX) on July 19, 2017 shows an unstable atmosphere, good vertical depth of moisture, and lack of significant wind shear.

Instability provided by decreasing temperatures aloft.
Humid air (relative humidity > 75%) extending up to 10,000 feet up above the Earth's surface. Any significant dry air aloft will interfere with the growth of the cumulus clouds that ultimately spawn waterspouts.
Lack of wind shear below 10,000 feet. This is opposite to what is found in tornadoes formed in severe thunderstorms where winds blowing from different directions and speeds at various altitudes is required. For fair-weather waterspouts, any significant wind shear would tilt and destroy the circulation.

Once these conditions are met, developing cumulus clouds or showers will have the potential to produce waterspouts. In many cases, boundaries produced by earlier shower activity or by the early morning landbreeze can help develop these clouds and showers.

Because fair-weather waterspouts are so much smaller and weaker than their stronger tornado cousins, radar is not a very effective tool to observe or forecast them. The entire circulation of a waterspout can fit within a single pixel of radar data unless the storm is close to the radar antenna. As shown below in the reflectivity (left) and velocity data (right) from the Surf City waterspout/tornado event, there was little indication using radar that a waterspout had developed and was approaching the coast of Pender County.

Public Information Statement
National Weather Service Wilmington NC
544 PM EDT Wed Jul 19 2017

...TORNADO CONFIRMED NEAR SURF CITY IN PENDER COUNTY NORTH
CAROLINA...

Location...Surf City in Pender County North Carolina
Date...July 19 2017
Estimated Time...1123 AM EDT to 1125 AM EDT
Maximum EF-Scale Rating...EF-0 
Estimated Maximum Wind Speed...70 MPH 
Maximum Path Width...25 Yards 
Path Length...0.14 Miles 
Beginning Lat/Lon...34.4181N / 77.5553W 
Ending lat/Lon...34.4200N / 77.5566W
* 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 Wilmington NC has confirmed a
tornado near Surf City in Pender County North Carolina on July
19 2017.

A waterspout moved onshore near 1003 S. Shore Dr. tossing patio
furniture and causing minor damage to wooden patio fencing. The
tornado quickly moved across S. Shore Dr near the intersection of
Seahorse Ave and caused minor roof damage to the house on the
corner of this intersection. The tornado caused more roof damage
to a home on the north side of Seahorse Ave as well as a town
house before lifting. There was considerable video evidence of the
waterspout/tornado during this event.

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

$$

Pfaff

Additional Reading:

WECT News: Waterspout causes minor damage in Surf City after coming onshore as a tornado (includes photo and video)

WWAY News: Waterspout turned EF0 tornado causes minor damage in Surf City (includes photo)

Research & Page Author: Tim Armstrong
Page Created: July 21, 2017
Last Updated: July 21, 2017