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
Time	F-Scale	Location	County	State	Lat	Lon	Comments
129	UNK	6 WSW MONTALBA	ANDERSON	TX	31.84	-95.82	EM REPORTED TORNADO IN TENNESSEE COLONY (FWD)
140	UNK	MONTALBA	ANDERSON	TX	31.88	-95.73	SPOTTER REPORT OF TORNADO IN MONTALBA (FWD)
Wind Reports
Time	Speed	Location	County	State	Lat	Lon	Comments
1720	UNK	2 E NEODESHA	WILSON	KS	37.42	-95.64	A METAL SHED KNOCKED OVER ON 700 ROAD EAST OF TOWN. (ICT)
1830	UNK	7 ESE BUFFALO	WILSON	KS	37.67	-95.58	TREE KNOCKED DOWN ON TO 1800 ROAD NEAR THE WILSON AND NEOSHO COUNTY LINE. (ICT)
1830	UNK	5 NW IOLA	ALLEN	KS	37.98	-95.47	WIND DAMAGE TO A HOME AND TO TREES NORTH OF THE HOME NEAR SOUTH DAKOTA RD AND 1000 RD. (ICT)
1945	UNK	2 W INK	POLK	AR	34.58	-94.15	EMERGENCY MANAGER REPORTED TREES AND POWER LINES DOWN 5 MILES EAST OF MENA ON HIGHWAY 88. (LZK)
2045	UNK	5 NW IOLA	ALLEN	KS	37.98	-95.47	REPORT OF WIND DAMAGE TO A BARN WEST OF IOLA (ICT)
2120	UNK	COMANCHE	COMANCHE	TX	31.9	-98.6	TREE LIMBS DOWN ON VEHICLES AND POWER LINES…TIME ESTIMATED (FWD)
2221	UNK	MIDWAY	HOT SPRING	AR	34.25	-92.95	A SEVERE THUNDERSTORM PRODUCED STRONG WINDS AND A LARGE TREE DAMAGED A HOUSE. (LZK)
2235	UNK	10 E LINDEN	CASS	TX	33.01	-94.19	TREES AND POWER LINES DOWNED IN THE HUFFINES AND SMYRNA AREAS ALONG FM 1841. (SHV)
2250	60	4 ESE PAXICO	WABAUNSEE	KS	39.06	-96.1	A COUPLE OF 2 TO 3 INCH DIAMETER BRANCHES DOWNED AS WELL. (TOP)
2352	60	4 W MEXIA	LIMESTONE	TX	31.68	-96.55	WIND GUSTS TO 60 MPH FLOWING INTO STORM WEST OF MEXIA (FWD)
128	70	8 NW PALESTINE	ANDERSON	TX	31.84	-95.74	QUATER INCH HAIL WIND GUST 70 MPH IN TENNESEE COLONY (FWD)
225	UNK	FRANKSTON	ANDERSON	TX	32.06	-95.5	FRANKSTON P.D. REPORTS THE ROOF IS OFF THE DRIVE-THROUGH TELLER SECTION OF THE 1ST NATIONAL BANK (FWD)
229	60	FRANKSTON	ANDERSON	TX	32.06	-95.5	ALSO PEA-SIZE HAIL IN TOWN.. (FWD)
255	UNK	11 NW JACKSONVILLE	CHEROKEE	TX	32.08	-95.39	POWER LINES DOWNED SOUTH BOUND FROM SMITH COUNTY ON FM 346. (SHV)
300	UNK	HOLLY SPRINGS	OUACHITA	AR	33.82	-92.72	THUNDERSTORMS PRODUCED STRONG WINDS WHICH KNOCKED DOWN POWER LINES AND TREES. (LZK)
805	UNK	COLUMBUS	LOWNDES	MS	33.51	-88.4	NUMEROUS TREES DOWN AROUND THE CITY OF THE COLUMBUS. TREEES ON POWERLINES…CAUSING OUTAGES. SEVERAL HOMES DAMAGED. (JAN)
Hail Reports
Time	Size	Location	County	State	Lat	Lon	Comments
2153	125	5 W LAWTON	COMANCHE	OK	34.6	-98.51	REPORTED FROM NEAR 72ND AND GORE ON THE WEST SIDE OF LAWTON…SAME LOCATION AS THE PREVIOUS REPORT…BUT HAIL SIZE HAS INCREASED. (OUN)
2218	175	1 S MIDWAY	HOT SPRING	AR	34.24	-92.95	GOLFBALL SIZE HAIL FELL HALFWAY BETWEEN DONALDSON AND FRIENDSHIP. (LZK)
2227	88	5 E LAWTON	COMANCHE	OK	34.6	-98.33	REPORTED ALONG HIGHWAY 7. (OUN)
2229	75	13 SSW FOUKE	MILLER	AR	33.09	-93.97	1 MI. W OF DODDRIDGE. (SHV)
2242	125	5 NE PUMPKIN CENTER	COMANCHE	OK	34.65	-98.15	ALSO ESTIMATED WINDS OF 45 MPH. (OUN)
2305	88	8 S STERLING	COMANCHE	OK	34.63	-98.17	(OUN)
120	175	DUBLIN	ERATH	TX	32.09	-98.34	MEDIA RELAYED REPORT OF GOLFBALL HAIL ON THE SOUTH SIDE OF DUBLIN (FWD)
131	175	6 W MARQUEZ	ROBERTSON	TX	31.24	-96.36	(FWD)
145	125	MONTALBA	ANDERSON	TX	31.88	-95.73	EM REPORTED 1/2 DOLLAR HAIL NEAR MONTALBA (FWD)
810	75	COLUMBUS	LOWNDES	MS	33.51	-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.

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