DEADLY NOCTURNAL TORNADOES

A pair of tornadoes each caused a death in the wee hours of the morning on Saturday November 15 in North Carolina. This brought the death toll for the year to 125. You have to go back to 1998 to find a deadlier year (130 tornado deaths), and then all the way back to 1974 (366 deaths).

The killer tornadoes also continued a trend for November -- deadly nocturnal tornadoes. 87% of the tornado deaths in November in the last 15 years have been at night. Nocturnal tornadoes tend to be deadlier than ones in the daytime at any time of year, with 42% of all tornadoes occurring at night, but causing 57% of deaths in the 1997-2006 period. People are often asleep and can't normally see the tornado coming. And residences are often of weaker construction than the buildings where many people work during the day.

Stu Ostro wrote a blog on November 15 showing the radar from the deadly EF2 Kenly, North Carolina tornado that struck shortly after 3AM on Saturday morning, November 15. The second killer tornado that night struck about a half hour later, an EF3 just west-southwest of Elm City, NC. Its radar precipitation pattern is shown below.

The tornado is on the southeast edge of that band of red, just west-southwest of Elm City. Notice the overall S-shape of the precipitation pattern, sometimes called a LEWP (line-echo-wave-pattern) known to sometimes be conducive to tornadoes. The storm-relative velocity pattern below shows a red-green couplet inside the circle that I've superimposed. This is the tornado signature, with red indicating eastward and green indicating westward. "Storm-relative" means that the storm motion has been subtracted. This often accentuates embedded rotation signatures like this one, making then easier to spot and warn on.

Following this event, a series of cold fronts have made it too cold and stable across the United States for severe thunderstorm and tornado activity. The image below shows one of those cold fronts, from Friday November 21.

SECONDARY COLD FRONT

This visible satellite image shows what we sometimes call a "secondary" cold front.
It is a "reinforcing" cold front, bringing in even colder air into an area that was already cool. I've drawn a yellow arrow to indicate the location of the secondary front -- that band of bright clouds running basically from west to east.

The orientation of my yellow arrow indicates winds from the north-northeast and bands of clouds called "cloud streets" in the cooling air behind the front. The cloud streets are formed as the cold air is heated and moistened over the warm Gulf of Mexico behind the front. Brighter, taller clouds at the arrowhead are enhanced by the convergence in the colliding air masses right at the front. Other bands of clouds south of the cold front may be remnants of previous fronts that moved into the area and weakened.

This secondary front is already showing such signs of weakening on the surface weather map below. I've drawn blue and red arrows to indicate the winds behind and ahead of the front. The relatively small wind shift suggests a weakening front, not atypical of secondary fronts that have gone this far south (away from their Canadian cold air origin.

The cold air behind this front promises to keep conditions too stable for a tornado threat through at least Sunday.

Feel that chill in the air friends? That can mean only one thing. The Weather Channel Half Marathon (and let's not forget about Thanksgiving Day) is about a week away!

What a wild and crazy ride this has been. It's only been about 6 months since I went out for my first run (and I really do mean ... my FIRST run.) I found about this challenge back in March, so I dragged my feet long enough by waiting until May. I guess I fell back into my college procrastination ways and waited until I realized this whole half marathon thing was REALLY happening and that I didn't want to be completely embarrassed on national television.

So here we go, I've got my running shorts (and in case you haven't noticed, I'm kind of a jeans guy even when its 120 plus degrees in Death Valley, call me crazy so the short thing in of itself took some getting used to). I've got my running shoes and its go time! So I hit this trail by The Weather Channel offices. It's a very scenic and lovely -- and most importantly flat, so I stretch like I've seen on those am morning workout shows and then I'm off. Lucky for me there are markers on the side of the trail clicking off mileage ... you know ... .25, .50, .75, 1 mile so I can track my out the gate progress. Now I realize I'm not man/womankind's gift to physical prowess but I figured even I could bang out a mile without too much difficulty, I mean high school gym class wasn't THAT long ago was it? Well let me tell you something, apparently high school gym class WAS that long ago as I was sputtering along after about a half mile wondering seriously for the first time what on earth I had gotten myself into. I figured it was only a matter of time before police dogs found me on the side of the trail and I ended up on an episode of some forensic style police show. Long story short ... Thanksgiving day was CLEARLY not far enough away!

(Fast forward 6 months)

That was then, this is now and while I'm not ready to call myself a professional runner just yet it's truly amazing what a little determination and lack of wanting to be embarrassed will get you when you put your mind to it. I can't tell you how thankful I am that The Weather Channel decided to sponsor this year's half marathon down Atlanta's most famous street (Peachtree). Because it gave me the kick in the pants I've needed for years and I hope this challenge may have even helped you out a little bit in that department as well!

Over the past 6 months I've run on the scenic beaches of Nantucket, through the oxygen light Rocky Mountains and even over the burning sand of Death Valley (where the temperature topped out at just over 120 degrees thank you very much). Each of these locations and climates provided their own unique challenges and I've met runners from all over the country who helped me to get ready to achieve my goal of finishing my first half marathon. You can check out some of the video online, but I found it incredibly interesting to hear and see first hand how these runners deal with the different situations Mother Nature throws at them throughout the year.

So, it's been an adventure -- I hope some of you have been enjoying the programming surrounding the marathon. It's not over yet, I still have to actually finish the 13.1 miles followed by a guilt free Thanksgiving feast unlike any the world has ever seen! Check back here in about two weeks and I'll let you know how everything turned out, but come heck or high water I'll be crawling over that finish line and I wish the best of luck to any of you who will be joining me for the finish of this wild ride!

No, that's not a typo in the title. In 2005 I posted an entry titled "November 15," followed in 2006 by "November 15 strikes again."

So this follows from those.

As I noted in the original entry, November 15 is notorious for having been the date of major severe thunderstorm & tornado outbreaks on three consecutive years in the late 1980s, culminating in the F4 Huntsville tornado in 1989.

Then it happened again in back-to-back years in 2005 with scores of tornadoes including an F4 in Madisonville, KY and in 2006 with widespread wind damage from Mississippi to the Carolinas including injury-producing tornadoes (followed by the deadly Riegelwood, NC tornado around sunrise on the 16th).

Now it's happened yet again, with reports of destructive tornadoes in eastern North Carolina during the wee hours Saturday morning. Kenly is one of the communities that has been hit.

[Kenly, N.C.; AP Photo / Gerry Broome]

This was not a classic standalone supercell -- the tornado formed within a cluster of thunderstorms as part of a line -- but the "velocity" radar image indicated rotation by way of the reds and greens, showing air moving rapidly in different directions and juxtaposed closely to each other.

[Source of radar images: GRLevelX]

This is all a result of a strong cold front interacting with warm, humid air out ahead of it, plus a deep dip in the upper-level jet stream and a strong "low-level jet," with showers and thunderstorms in the Mid-Atlantic and Northeast this afternoon capable of producing additional wind damage and possibly tornadoes.

SATURDAY EVENING ADDENDUM

The University of Wisconsin CIMSS Satellite Blog has a new entry (a cropped image from it is below) which shows that the low-level remnants of Paloma came into the Florida Panhandle early Friday morning and resulted in a big flare-up of thunderstorms with heavy rain and lots of lightning.

Although the large-scale drivers for the North Carolina tornadoes during the wee hours Saturday were the deep trough approaching from the west and unstable air surging northward up the coastal plain on the heels of strengthening low-level winds, the timing and location relative to what happened in the FL Panhandle early Friday had me wondering whether the Paloma remnants were a factor.

An examination of radar imagery shows that the early morning thunderstorms weakened to an area of showers over Georgia during midday Friday and then dissipated as they later moved into South Carolina, while new clusters of showers and thunderstorms developed over the Florida Panhandle and south Georgia and combined with those associated with an impulse from Alabama.

That's the stuff which later moved into North Carolina and got out of hand, and it was solidly in the warm, humid air well ahead of the cold front. And the CIMSS animation of low-level spin in the atmosphere showed a maximum in the Carolinas out ahead of the main trough, at least some of which appears to have been injected from the Gulf.

So while Paloma's remnants certainly didn't singlehandedly cause the rash of tornadoes, perhaps their last vestiges played a role?

If nothing else, it's an interesting coincidence ...

Meanwhile, no tornadoes reported yet today despite all the watches which were issued, but there has been wind damage in a few places from Virginia to New England, and in New Jersey unfortunately a man was killed when a tree fell on him.

A couple of folks posting comments to recent entries have asked about what happened in Maine the afternoon of October 28, when several huge anomalous waves suddenly surged onshore. Indeed, it was a very curious and interesting case!

From this article in The Boston Globe:

>>>
Dockworker Marcy Ingall saw a giant wave in the distance last Tuesday afternoon and stopped in her tracks. It was an hour before low tide in Maine's Boothbay Harbor, yet without warning, the muddy harbor floor suddenly filled with rushing, swirling water.

In 15 minutes, the water rose 12 feet, then receded. And then it happened again. It occurred three times, she said, each time ripping apart docks and splitting wooden pilings.

"It was bizarre," said Ingall, a lifelong resident of the area. "Everybody was like, 'Oh my God, is this the end?' "

...

Residents and business owners in Boothbay said they were glad the phenomenon didn't happen at high tide, when it might have caused massive flooding and more extensive damage. Janice Newell, who lives nearby in Head of the Harbor, told the local newspaper the rushing water "was of biblical proportion."

"There were three large whirlpools in the inner harbor, up to within a foot of my neighbor's wall," she told the Boothbay Register. "It was beautiful, but it was scary."

Elena Smith, a waitress and part-owner of McSeagull's restaurant overlooking the harbor, said the late-afternoon lunch crowd sat speechless as the waters rose and receded. She was stunned to see the normally safe and placid harbor suddenly run like rapids. Some residents reported seeing massive whirlpools of water that disappeared, leaving clam shells and seaweed in vortex patterns on the harbor floor.

"It felt like somebody took the plug out somewhere" in the ocean, Smith said. "It felt like there must have been water missing in the ocean someplace."
>>>

This was the meteorological setup that afternoon:

The big, unusually-early snowstorm I wrote about at the time was in progress over the interior Northeast.

Eventually stronger winds and higher waves circulating around from the west and south sides of the cyclone (where the "pressure gradient" was tighter) made it to the Maine coast, but were not present at mid-afternoon when the strange event occurred.

The 3pm EDT (19 UTC) observation at this buoy just offshore of the area on the coast which was hit shows winds of 7 meters per second (~16 mph) with gusts to only 8 m/s (18 mph), and significant wave heights of only 1.2 meters (4 feet).

Here's the official statement from the National Weather Service:

The Globe article goes into additional detail, including referencing the possibility of the culprit being a "squall line surge" like one which hit Daytona Beach 16 years ago. As this section of the book Coastal Processes with Engineering Applications states, "squall line surges are caused by the movement of a relatively small atmospheric pressure perturbation at the approximate speed of the waves generated."

It then describes the 1992 event: "On the evening of July 3, 1992, at Daytona Beach, Florida, a freak wave about 2 m high surged up on the beach on an otherwise calm night. ... Observers soon reported a sudden increase in wind speed occurred with the change from a warm and humid evening to cool and windy conditions. Later, radar images demonstrated that a squall originated offshore of Georgia and moved south first along the Georgia and later the Florida coast ..."

A NOAA satellite image from that evening around the time the wave hit depicts a band of clouds curving in a gigantic backward S all the way from Hudson Bay to the southeast U.S. and on into the Atlantic, including a line of showers and thunderstorms near the northeast Florida coast. Radar showed that about 20 minutes before the ocean wave reached the northern Daytona Beach area and proceeded southward, there was a cluster of thunderstorms which had moved south from the Georgia coast; the storms then dissipated.

Those radar analyses are from the definitive meteorological analysis of that event, this paper published in the Bulletin of the American Meteorological Society, which concluded that "analysis of tide gauge and atmospheric data strongly suggests the water wave was generated by a squall line." (An interesting account of how a meteorite had been suspected is on pages 46-62 of this magazine.)

With the Maine event, there was that potent system in the Northeast, which at the time was swinging a band of locally heavy rain across northern New England:

[Image source: GRLevelX]

However, the band had already passed through Boothbay Harbor and thereabouts, and the buoy observations above gave no indication of a significant change in weather or water parameters when it came through there around 2pm EDT (18 UTC).

Thus (and having discussed with TWC's wave expert, Dr. Steve Lyons), there's nothing weatherwise which jumps out as having been the cause, suggesting that the "rogue" wave may have been a tsunami rather than something meteorological. That's based on this quick perusal of the data as opposed to an exhaustive investigation; more study would be necessary for a conclusive determination, although as the NWS notes we may never know for sure exactly what happened. The only earthquakes in the Atlantic that day were many hours earlier, very small, and far away near Puerto Rico. The process of elimination suggests that if weather or earthquakes were not the cause maybe it was an underwater slumping/landslide, but it'd be difficult to precisely determine that.

This report which includes the history of Maine tsunamis indicates that there have been two other tsunami events recorded in the state, in 1872 and 1926. (In regard to that article, note that tsunami is