WeatherBeacon
http://en.wikipedia.org/wiki/Bow_echo
http://en.wikipedia.org/wiki/File:Bow_echo_diagram.svg
Typical evolution of a thunderstorm radar echo (a) into a bow echo (b, c) and into a comma echo (d). Dashed line indicates axis of greatest potential for downbusts. Arrows indicate wind flow relative to the storm. Note regions of cyclonic rotation (C) and anticyclonic rotation (A); both regions, especially C, are capable of supporting tornado development in some cases.
As I said before aside from the bow echos, The nws offices needs to follow their own warning criteria.
Yes, I saw those links the first time. I suspect the NWS explanation of bow echo is more authoritative than the wiki article. Besides, the entire wiki article mentions the word "rotation" only twice, and both occurrences are in the figure caption only. Furthermore, the caption even says: "both regions, especially C,
are capable of supporting tornado development
in some cases." The words are
capable and
some, not
likely and
most or
many. Throughout the entire wiki article, the emphasis is clearly on damaging straight line winds and much less on tornadoes. (I'm not going to cut-and-paste every statement in the wiki.) My point is that if tornadoes were the primary concern associated with a bow echo, one would think the wiki article would stress that.
NWS definition of a bow echo:
A radar echo which is linear but bent outward in a bow shape. Damaging straight-line winds often occur near the "crest" or center of a bow echo. Areas of circulation also can develop at either end of a bow echo, which sometimes can lead to tornado formation - especially in the left (usually northern) end, where the circulation exhibits cyclonic rotation.
The emphasis is on "damaging straight line winds." It also says circulation
can develop and
sometimes can lead to tornado formation.
The AMS gives a similar definition, but again the emphasis is on "damaging straight line winds."
Finally, references to "rotation," "cyclonic," or "circulation" do not necessarily mean
tornadic. A low pressure system is cyclonic. That doesn't mean every low is a tornado or produces a tornado.
Lest I be misunderstood, I agree that bow echoes can and should be taken seriously. (I get very concerned when radar shows one bearing down on us.)
Your concern is with false alarms and "The Boy Who Called Wolf" syndrome. I understand your concern. I guess I'd rather have the NWS issue a tornado warning when they believe a tornado might materialize but doesn't, than have the NWS withhold issuing a tornado warning for fear of issuing a "false alarm" and have a tornado actually materialize. As has been stated here several times, meteorology is an inexact science, as are all sciences. (That's why physicians "practice" medicine and lawyers "practice" law.) Perhaps the only way to predict a tornado with 100% certainty is to have each of us carry "Granny's weather beetle."
As I said before aside from the bow echos, The nws offices needs to follow their own warning criteria.
If you're so sure that the NWS Office in your area is not following NWS criteria for issuing alarms, have you contacted them about it? That might accomplish more than our sharing of opinions here.
Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence. --- John Adams in his defense of the British soldiers in the Boston Massacre trial, 1770.
