I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

One more thing: My local area has 3 tv stations. 2 of them have their
own doppler radar. Only one station uses some software known as VIPIR.
How accurate is this VIPIR? Is it more advanced or am I relying far
too much on the VIPIR results?

Another pet peeve is that my local stations refuse to break into
programming to give updates. Sure they break in when a warning is
issued but it would be nice to have short updates on whether the storm
system is stregthing or weaking. I mean, they could literally do this
update in less than 20 seconds at most.

Since the outbreak of storms on october 24, 2001, I have developed an
irrational fear of storms. I have convinced myself that every tstorms
is going to produce a tornado. It rules my life now. I am constantly
checking the SPC outlooks, local weather, and needing to know exact
times of storm events. I do not sleep or leave home during storms, no
matter how extreme or tame they are. I share this with you because I
have wondered if anyone has this height of panic over these things
besides me? I literally have to take hand fulls of anxiety meds during
storm outbreaks. Lots of klonopin, ativan, etc.

I know this is not a therapy group of psych group but I just had to
get this off my chest. This fear is literally killing me. I do believe
if a tornado was within 5 miles of me I would die of a heart attack
well before the tornado hit the house.

Anyway, I hope some of you can answer some of my questions and help me
with this irrational fear I have of tstorms.
I also hope you can pardon me for interrupting a scientific newsgroup.

thank you for your help.
Ted

In article ,
says...
I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

Here are the annual tornado warning statistics for the US from 1986-
1994. POD is the probability that a tornado will have a warned county
associated with it. FAR is the false alarm ratio, the fraction of the
warned counties for which there is no tornado.

Year POD FAR
1986 0.338 0.813
1987 0.289 0.813
1988 0.290 0.813
1989 0.358 0.801
1990 0.438 0.715
1991 0.412 0.760
1992 0.453 0.695
1993 0.429 0.730
1994 0.459 0.743
1995 0.599 0.748
1996 0.593 0.770
1997 0.588 0.775
1998 0.652 0.802
1999 0.702 0.720
2000 0.648 0.762
2001 0.692 0.712
2002 0.757 0.750
2003 0.792 0.748
2004 0.759 0.743

If we limit attention to the strongest tornadoes (F2 or greater, roughly
10% of the tornadoes), the POD is a little over 0.8 for 2003 and 2004.


--
Harold Brooks
Head, Mesoscale Applications Group
NOAA/National Severe Storms Laboratory

On Sun, 1 Jan 2006 16:24:01 -0600, Harold Brooks
wrote:

In article ,
says...
I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

Here are the annual tornado warning statistics for the US from 1986-
1994. POD is the probability that a tornado will have a warned county
associated with it. FAR is the false alarm ratio, the fraction of the
warned counties for which there is no tornado.

Year POD FAR
1986 0.338 0.813
1987 0.289 0.813
1988 0.290 0.813
1989 0.358 0.801
1990 0.438 0.715
1991 0.412 0.760
1992 0.453 0.695
1993 0.429 0.730
1994 0.459 0.743
1995 0.599 0.748
1996 0.593 0.770
1997 0.588 0.775
1998 0.652 0.802
1999 0.702 0.720
2000 0.648 0.762
2001 0.692 0.712
2002 0.757 0.750
2003 0.792 0.748
2004 0.759 0.743

If we limit attention to the strongest tornadoes (F2 or greater, roughly
10% of the tornadoes), the POD is a little over 0.8 for 2003 and 2004.

Let me ask you then: Does this mean 8% in 2004 were FAR and 7.59% were
warned counties?
Could you explain a little more in laymen terms. I am no scientist by
any stretch..
thanks

In article ,
says...
On Sun, 1 Jan 2006 16:24:01 -0600, Harold Brooks
wrote:

In article ,
says...
I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

Here are the annual tornado warning statistics for the US from 1986-
1994. POD is the probability that a tornado will have a warned county
associated with it. FAR is the false alarm ratio, the fraction of the
warned counties for which there is no tornado.

Year POD FAR
1986 0.338 0.813
1987 0.289 0.813
1988 0.290 0.813
1989 0.358 0.801
1990 0.438 0.715
1991 0.412 0.760
1992 0.453 0.695
1993 0.429 0.730
1994 0.459 0.743
1995 0.599 0.748
1996 0.593 0.770
1997 0.588 0.775
1998 0.652 0.802
1999 0.702 0.720
2000 0.648 0.762
2001 0.692 0.712
2002 0.757 0.750
2003 0.792 0.748
2004 0.759 0.743

If we limit attention to the strongest tornadoes (F2 or greater, roughly
10% of the tornadoes), the POD is a little over 0.8 for 2003 and 2004.

Let me ask you then: Does this mean 8% in 2004 were FAR and 7.59% were
warned counties?
Could you explain a little more in laymen terms. I am no scientist by
any stretch..

For the POD, start by looking at all tornadoes. Compute the fraction of
them with warnings. In 2004, it was 0.759 (75.9%.) For the strong
tornadoes, it was a litle over 0.8 (80%.)

For the FAR, start by looking at the warnings. Compute the fraction
with no tornado. In the 2004, it was 0.743 (74.3%.)

--
Harold Brooks
Head, Mesoscale Applications Group
NOAA/National Severe Storms Laboratory

Harold Brooks wrote:
In article ,
says...

On Sun, 1 Jan 2006 16:24:01 -0600, Harold Brooks
wrote:


In article ,
says...

I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

Here are the annual tornado warning statistics for the US from 1986-
1994. POD is the probability that a tornado will have a warned county
associated with it. FAR is the false alarm ratio, the fraction of the
warned counties for which there is no tornado.

Year POD FAR
1986 0.338 0.813
1987 0.289 0.813
1988 0.290 0.813
1989 0.358 0.801
1990 0.438 0.715
1991 0.412 0.760
1992 0.453 0.695
1993 0.429 0.730
1994 0.459 0.743
1995 0.599 0.748
1996 0.593 0.770
1997 0.588 0.775
1998 0.652 0.802
1999 0.702 0.720
2000 0.648 0.762
2001 0.692 0.712
2002 0.757 0.750
2003 0.792 0.748
2004 0.759 0.743

If we limit attention to the strongest tornadoes (F2 or greater, roughly
10% of the tornadoes), the POD is a little over 0.8 for 2003 and 2004.

Let me ask you then: Does this mean 8% in 2004 were FAR and 7.59% were
warned counties?
Could you explain a little more in laymen terms. I am no scientist by
any stretch..


For the POD, start by looking at all tornadoes. Compute the fraction of
them with warnings. In 2004, it was 0.759 (75.9%.) For the strong
tornadoes, it was a litle over 0.8 (80%.)

For the FAR, start by looking at the warnings. Compute the fraction
with no tornado. In the 2004, it was 0.743 (74.3%.)


Is there any geographical bias to FAR or POD? It seems like
you'd be far more likely to have a POD where more tornadoes
are radar-detected -- which should be where there is little
population. I don't recall seeing a state-by-state mapping
of these two parameters, however. Is it online somewhere?


Scott

In article ,
says...
Harold Brooks wrote:
In article ,
says...

On Sun, 1 Jan 2006 16:24:01 -0600, Harold Brooks
wrote:


In article ,
says...

I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

Here are the annual tornado warning statistics for the US from 1986-
1994. POD is the probability that a tornado will have a warned county
associated with it. FAR is the false alarm ratio, the fraction of the
warned counties for which there is no tornado.

Year POD FAR
1986 0.338 0.813
1987 0.289 0.813
1988 0.290 0.813
1989 0.358 0.801
1990 0.438 0.715
1991 0.412 0.760
1992 0.453 0.695
1993 0.429 0.730
1994 0.459 0.743
1995 0.599 0.748
1996 0.593 0.770
1997 0.588 0.775
1998 0.652 0.802
1999 0.702 0.720
2000 0.648 0.762
2001 0.692 0.712
2002 0.757 0.750
2003 0.792 0.748
2004 0.759 0.743

If we limit attention to the strongest tornadoes (F2 or greater, roughly
10% of the tornadoes), the POD is a little over 0.8 for 2003 and 2004.

Let me ask you then: Does this mean 8% in 2004 were FAR and 7.59% were
warned counties?
Could you explain a little more in laymen terms. I am no scientist by
any stretch..


For the POD, start by looking at all tornadoes. Compute the fraction of
them with warnings. In 2004, it was 0.759 (75.9%.) For the strong
tornadoes, it was a litle over 0.8 (80%.)

For the FAR, start by looking at the warnings. Compute the fraction
with no tornado. In the 2004, it was 0.743 (74.3%.)


Is there any geographical bias to FAR or POD? It seems like
you'd be far more likely to have a POD where more tornadoes
are radar-detected -- which should be where there is little
population. I don't recall seeing a state-by-state mapping
of these two parameters, however. Is it online somewhere?

It's really complicated. Separating out the meteorological and non-
meteorological factors is almost impossible. Effectively, you can
improve both FAR and POD by getting smarter or by working harder at
collecting verification information. That's on top of detection,
population, and road network issues.

Harold
--
Harold Brooks
Head, Mesoscale Applications Group
NOAA/National Severe Storms Laboratory

In article , Harold Brooks wrote:
In article ,
says...
I have watched the refreshing screen the NWS has for all the watches
and warnings for severe storms and tornadoes. I have noticed that at
times they will display, over a period of many hours, many dozen
tornado warnings as red dots. However, when I check the pages with the
actual storm reports on the following days, it shows only a few. In
fact, in appears that of all those tornado warning dots, that perhaps
10 and at most 15% of those tornado warnings actually formed a
tornado.

Now, if this is in fact true, then what about those tornadoes that are
confirmed where a warning was _never_ even issued?

What is the accuracy rate of [issued tornado warning vs confirmed
tornadoes]?

Also, what is the percentage of times when an actual tornado hits the
ground _but_ was never associated with a warning?

Here are the annual tornado warning statistics for the US from 1986-
1994. POD is the probability that a tornado will have a warned county
associated with it. FAR is the false alarm ratio, the fraction of the
warned counties for which there is no tornado.

Year POD FAR
1986 0.338 0.813
1987 0.289 0.813
1988 0.290 0.813
1989 0.358 0.801
1990 0.438 0.715
1991 0.412 0.760
1992 0.453 0.695
1993 0.429 0.730
1994 0.459 0.743
1995 0.599 0.748
1996 0.593 0.770
1997 0.588 0.775
1998 0.652 0.802
1999 0.702 0.720
2000 0.648 0.762
2001 0.692 0.712
2002 0.757 0.750
2003 0.792 0.748
2004 0.759 0.743

If we limit attention to the strongest tornadoes (F2 or greater, roughly
10% of the tornadoes), the POD is a little over 0.8 for 2003 and 2004.

Maybe the forecasters suffer from the same problem as folk who assert
they will list data from 1986-1994, then quote twice as much. ;-)

Cheers, Phred.

--
LID