All Weather News

Two Tornado Reports Yesterday, but No Tornado Watch?

7 Oct 2008, 2:45 pm

When discussing October tornado tendencies last week, I mentioned that we had a potential for tornadoes this week. As of this writing, yesterday there were two tornado reports, plus additional reports of severe winds and hail. Note the table below:

  Tornado Reports
TimeF-ScaleLocationCountyStateLatLonComments
129UNK6 WSW MONTALBAANDERSONTX31.84-95.82EM REPORTED TORNADO IN TENNESSEE COLONY (FWD)
140UNKMONTALBAANDERSONTX31.88-95.73SPOTTER REPORT OF TORNADO IN MONTALBA (FWD)
  Wind Reports
TimeSpeedLocationCountyStateLatLonComments
1720UNK2 E NEODESHAWILSONKS37.42-95.64A METAL SHED KNOCKED OVER ON 700 ROAD EAST OF TOWN. (ICT)
1830UNK7 ESE BUFFALOWILSONKS37.67-95.58TREE KNOCKED DOWN ON TO 1800 ROAD NEAR THE WILSON AND NEOSHO COUNTY LINE. (ICT)
1830UNK5 NW IOLAALLENKS37.98-95.47WIND DAMAGE TO A HOME AND TO TREES NORTH OF THE HOME NEAR SOUTH DAKOTA RD AND 1000 RD. (ICT)
1945UNK2 W INKPOLKAR34.58-94.15EMERGENCY MANAGER REPORTED TREES AND POWER LINES DOWN 5 MILES EAST OF MENA ON HIGHWAY 88. (LZK)
2045UNK5 NW IOLAALLENKS37.98-95.47REPORT OF WIND DAMAGE TO A BARN WEST OF IOLA (ICT)
2120UNKCOMANCHECOMANCHETX31.9-98.6TREE LIMBS DOWN ON VEHICLES AND POWER LINES…TIME ESTIMATED (FWD)
2221UNKMIDWAYHOT SPRINGAR34.25-92.95A SEVERE THUNDERSTORM PRODUCED STRONG WINDS AND A LARGE TREE DAMAGED A HOUSE. (LZK)
2235UNK10 E LINDENCASSTX33.01-94.19TREES AND POWER LINES DOWNED IN THE HUFFINES AND SMYRNA AREAS ALONG FM 1841. (SHV)
2250604 ESE PAXICOWABAUNSEEKS39.06-96.1A COUPLE OF 2 TO 3 INCH DIAMETER BRANCHES DOWNED AS WELL. (TOP)
2352604 W MEXIALIMESTONETX31.68-96.55WIND GUSTS TO 60 MPH FLOWING INTO STORM WEST OF MEXIA (FWD)
128708 NW PALESTINEANDERSONTX31.84-95.74QUATER INCH HAIL WIND GUST 70 MPH IN TENNESEE COLONY (FWD)
225UNKFRANKSTONANDERSONTX32.06-95.5FRANKSTON P.D. REPORTS THE ROOF IS OFF THE DRIVE-THROUGH TELLER SECTION OF THE 1ST NATIONAL BANK (FWD)
22960FRANKSTONANDERSONTX32.06-95.5ALSO PEA-SIZE HAIL IN TOWN.. (FWD)
255UNK11 NW JACKSONVILLECHEROKEETX32.08-95.39POWER LINES DOWNED SOUTH BOUND FROM SMITH COUNTY ON FM 346. (SHV)
300UNKHOLLY SPRINGSOUACHITAAR33.82-92.72THUNDERSTORMS PRODUCED STRONG WINDS WHICH KNOCKED DOWN POWER LINES AND TREES. (LZK)
805UNKCOLUMBUSLOWNDESMS33.51-88.4NUMEROUS TREES DOWN AROUND THE CITY OF THE COLUMBUS. TREEES ON POWERLINES…CAUSING OUTAGES. SEVERAL HOMES DAMAGED. (JAN)
  Hail Reports
TimeSizeLocationCountyStateLatLonComments
21531255 W LAWTONCOMANCHEOK34.6-98.51REPORTED FROM NEAR 72ND AND GORE ON THE WEST SIDE OF LAWTON…SAME LOCATION AS THE PREVIOUS REPORT…BUT HAIL SIZE HAS INCREASED. (OUN)
22181751 S MIDWAYHOT SPRINGAR34.24-92.95GOLFBALL SIZE HAIL FELL HALFWAY BETWEEN DONALDSON AND FRIENDSHIP. (LZK)
2227885 E LAWTONCOMANCHEOK34.6-98.33REPORTED ALONG HIGHWAY 7. (OUN)
22297513 SSW FOUKEMILLERAR33.09-93.971 MI. W OF DODDRIDGE. (SHV)
22421255 NE PUMPKIN CENTERCOMANCHEOK34.65-98.15ALSO ESTIMATED WINDS OF 45 MPH. (OUN)
2305888 S STERLINGCOMANCHEOK34.63-98.17(OUN)
120175DUBLINERATHTX32.09-98.34MEDIA RELAYED REPORT OF GOLFBALL HAIL ON THE SOUTH SIDE OF DUBLIN (FWD)
1311756 W MARQUEZROBERTSONTX31.24-96.36(FWD)
145125MONTALBAANDERSONTX31.88-95.73EM REPORTED 1/2 DOLLAR HAIL NEAR MONTALBA (FWD)
81075COLUMBUSLOWNDESMS33.51-88.4(JAN)

I have been an observer of weather phenomena (I am not fond of the term ‘chaser’ and what that concept has come to represent) for 18 plus years now. Over that time I have been in the field when PDS watches were issued and no storms formed, when tornado watches were issued and no storms formed, when no watches were issued and storms formed and so forth. The art and science of forecasting all weather types has developed a great deal over the years, but is still not an exact science, and will likely not be in our lifetimes.

An item that has concerned me, and continues to, is when tornadoes are reported and no watches were issued prior to, and especially after the events have commenced. Yesterday is a fine example. The 12z SPC convective outlooks and probabilistic graphics issued by Forecaster Goss showed the potential for tornado development (note graphics below).



  SPC Convective Outlook & Probabilistic graphics for 12z October 6, 2008
12z Convective Outlook 12z Tornado Probabilistic Graphic

Note that yesterday morning Forecaster Goss identified his area of concern for tornado development. As it turns out his forecast was quite good! Notice the geographic location of the storm reports listed above in the graphic below, and compare to his forecast.

SPC Storm Reports Graphic for October 6, 2008

As an old weather geek, I find it difficult to say anything that may be interpreted as negative of the various weather agencies. The longer one works with weather and climate interests, the stronger the ‘kinship’ becomes toward the agencies since I admire, appreciate, and understand the work, forethought, and stress that are involved in their duties. Unfortunately I must also consider the safety of the general public.

How can a tornado form, however small it might be, when a watch of any kind is not issued beforehand? Especially when the morning forecaster had the foresight to identify the area of concern? We also must keep in mind that the SPC issues the watch areas for severe thunderstorms and tornadoes, while local NWS agencies issue the associated warnings.

To examine the above questions we will begin with how the SPC defines thunderstorm watches and tornado watches:

SPC Definition for Thunderstorm Watch
A Severe Thunderstorm Watch outlines an area where an organized episode of hail 3/4 inch diameter or larger and/or damaging thunderstorm winds are expected during a three to eight hour period.
SPC Definition for Tornado Watch
A Tornado Watch includes the large hail and damaging wind threats, as well as the possibility of multiple tornadoes.

Notice the first definition of a thunderstorm watch, and compare with the table at the top of this post. Did hail of 3/4″ or greater occur yesterday? Yes. Did damaging winds occur? Yes.

I should also add here that the NWS defines a thunderstorm warning as a: Product issued by the National Weather Service when a severe thunderstorm is occurring, is imminent, or has a high probability of occurring. A severe thunderstorm is a thunderstorm that produces: a tornado, wind gusts of at least 58 mph (50 knots), and/or hail at least ¾” in diameter. This is also included in the above reports.

So the variables defined as necessitating the issuance of a thunderstorm watch were achieved, and also identified by the morning forecaster but a watch was not issued.

Now we address the definition for a tornado watch. Here is a snippet that has troubled me for some time in that the definition states: as well as the possibility of multiple tornadoes. Why multiple tornadoes? Granted in the case above two reports were received, likely the result of a single cell, however historically multiple tornadoes are often reported and archived that were the result of a single thunderstorm, but once again, why multiple?

Is it possible that an environment primed for deep convective development can result in the production of only one single thunderstorm, or even a single massive classic supercell on the entire landscape? Of course, I have seen it more times than I can count, and those single storms often do produce tornadoes, granted they often result in multiple reports from one storm.

Still, why limit the defining parameters of a tornado watch to incidents where more than one tornado is forecast to occur? More importantly, why was a tornado, or even thunderstorm watch not issued for yesterday’s environment?

This reminds me of another occasion when such an event occurred. The ‘infamous’ Atlanta tornado of March 14-15 of this year. I stayed up that night doing constant mesoscale analysis while watching the news etc., and uploaded a loop of our HAMrad II product covering the storm to youtube. I have included the video below, as well as the synopsis I provided online at that time.

HAMrad II Animation of the Atlanta Tornadoes

Synopsis
This is composite radar loop of the March 14, 2008 tornado in Atlanta, Georgia with an overlay of thunderstorm warnings (orange), and tornado warnings (red). Some important points to note in the loop are the timing of when the warnings were issued (note timestamps on the bottom left corner of loop) versus the location of the storms. An additional point, and probably more important is notice the tornado watch (box) pop up at the bottom left of the screen at the end of the loop (timestamp 00.12). However a tornado watch was NEVER issued for the Atlanta area; either before, during, or after the tornado and associated storms moved through the area. I have made the loop ‘slow enough’ that you can easily distinguish the timing on warnings versus storm location etc. Tornado watches are issued by the SPC (storm prediction center) only, and each individual NWS office is responsible for thunderstorm / tornado warnings. You may view my associated youtube post here.

Associated links of interest

  • Wikipedia entry of the Atlanta tornadoes
  • CNN online article covering the events
  • CNN online article covering the search for victims
  • New York Times online article covering the events
  • USA Today online article covering storm damage

The question remains, if forecasters are aware of an environment prone to severe convective activities, why not issue the watches? I can guess of a few reasons, but will not share them. Instead the purpose of this post was to give you, our users, something to think about =)

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!

cheers,

–patrick

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