Likely tornado in San Francisco

[John Farley]

I know today was a chase day for some of you and certainly a day to practice forecast skills for many of us, but I am still a little surprised nobody has commented on the likely tornado that occurred in San Francisco yesterday. A news report, with pictures, including one of the likely tornado, can be found at:

http://www.sfgate.com/cgi-bin/article.cgi?...MNGPVBSH2P1.DTL

 

[Sam Sagnella]

Mark Strobin, a meteorologist with the National Weather Service in Monterey, said that tornados are extremely rare in the Bay Area. He said meteorologists will survey the damage in South San Francisco today to determine whether, in fact, the twister was a tornado or a funnel cloud. The difference, he said, is that tornadoes touch the ground while funnel clouds do not.

Funnel clouds are not nearly as destructive as tornadoes.

No wonder so many people are ignorant to the vast differences between the two! :roll:

 

[Glenn Rivers]

tornadoes vs funnel clouds

The distinction between tornadoes and funnel clouds is not very simple. When a condensation funnel does not reach the ground it is still possible that destructive tornadic winds are at ground level. For a condensation funnel to reach the ground, the pressure in the tornadoes' vortex has to be low enough for water to condense at ground level. If the relative humidity is very high, even a weak vortex will likely condense to ground level. If the relative humidity is low, a vortex may have to be very strong for condensation to reach all the way to the ground.

On the Tornado Video Classics tape 2, a violent tornado at North Platte NE did not have a complete condensation funnel, but was doing F3 or F4 damage.

 

[rdale]

"The distinction between tornadoes and funnel clouds is not very simple."

Actually there is a clear distinction... Funnel clouds cannot cause damage.

 

[Jeremy Lemanski]

Re: tornadoes vs funnel clouds

The distinction between tornadoes and funnel clouds is not very simple. When a condensation funnel does not reach the ground it is still possible that destructive tornadic winds are at ground level. For a condensation funnel to reach the ground, the pressure in the tornadoes' vortex has to be low enough for water to condense at ground level. If the relative humidity is very high, even a weak vortex will likely condense to ground level. If the relative humidity is low, a vortex may have to be very strong for condensation to reach all the way to the ground.

On the Tornado Video Classics tape 2, a violent tornado at North Platte NE did not have a complete condensation funnel, but was doing F3 or F4 damage.

This isn't a discussion if the tornado had a condesation funnel on the ground or not, it is did the tornado even touch down and thus was a tornado? Funnel clouds, as Mr. dale said, don't cause damage as they never touch down.

Another thing this met. said: "If it is a fairly narrow area or a very distinct area that had the damage, then it is a tornado."

Well, if every met. who did a survey of damage went by that, then every small mircoburst would be called a tornado too.

 

[Khristian Snyder]

Interesting if it was indeed a tornado. Another one for California.

Does anyone know of a source that displays the tornado count this year by state?? It would be interesting to see how much twisters California has had so far.

 

[Robert Dewey]

"The distinction between tornadoes and funnel clouds is not very simple."

Actually there is a clear distinction... Funnel clouds cannot cause damage.

And IF there was damage at the ground level, it would obviously be a tornado :wink:

I don't think that a tornado *MUST* have a condensation "funnel" touching the ground... But in order for it to be a "touch down", there must be SFC damage. So, if tornadic winds are touching ground level, in my book, that's a tornado...

 

[Karen Politte]

Re: tornadoes vs funnel clouds

The distinction between tornadoes and funnel clouds is not very simple. When a condensation funnel does not reach the ground it is still possible that destructive tornadic winds are at ground level. For a condensation funnel to reach the ground, the pressure in the tornadoes' vortex has to

Whaaa?......oh dear.

Funnel cloud = A condensation funnel extending from the base of a towering cumulus or Cb, associated with a rotating column of air that is not in contact with the ground (and hence different from a tornado). A condensation funnel is a tornado, not a funnel cloud, if either a) it is in contact with the ground or B) a debris cloud or dust whirl is visible beneath it.

Tornado = A violently rotating column of air in contact with the ground and extending from the base of a thunderstorm. A condensation funnel does not need to reach to the ground for a tornado to be present; a debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado, even in the total absence of a condensation funnel.

Taken from http://www.srh.noaa.gov/oun/severewx/glossary.php - a very useful link.

KR

 

[Mike Peregrine]

California actually led the country in tornadoes last month - 13 I believe. More than any of the southern or midwestern states! I saw video of this particular one on TWC yesterday ... looked like something straight out of the alley. I'm sure Californians are thrilled to add tornadoes to a long list of potential natural disasters that can affect the state. Though there have always been reports out of CA, it seems like this year we've witnessed a dramatic increase in incredible weather out there.

By the way - last year we saw more incomplete condensation funnels that had true tornadic ground circulation than I've seen in quite some time. The 5/29 Concordia storms being the prime example.

 

[Sam Sagnella]

...NATIONAL WEATHER SERVICE CONFIRMS F1 TORNADO IN SOUTH SAN FRANCISCO ON SUNDAY...

http://www.wrh.noaa.gov/mtr/gettext.php?pi...pil=PNS&sid=MTR

 

[Andy Wehrle]

Strange that this was never reported to the SPC. Just 1 report of low-end severe hail out of Sacremento.

http://www.spc.noaa.gov/climo/reports/050320_rpts.html

 

[Mike Kruze]

There was just this LSR for thunderstorm wind damage, issued 90 minutes later. I don't believe the storm was ever warned.

http://kamala.cod.edu/ca/latest.nwus56.KMTR.html

343 PM TSTM WND DAMAGE SOUTH SAN FRANCISCO 37.67N 122.38W
3/20/2005 UNKNOWN SAN MATEO CA SPOTTER

POSSIBLE TORNADO WITH NUMEROUS REPORTS OF SHINGLES TORN
OFF ROOF TOPS. WIND BLEW OFF TWO AIR CONDITIONING UNITS
INTO NEARBY TRUCK. REPORTS OF POWER LINES DOWN.

Did anyone save radar from this event? There were a few unimpressive convective showers moving ashore about 45 minutes prior to the tornado; max reflectivity around 40-45 dBZ. Unfortunately I didn't have access to radar after about 3:00.

 

[Glen Romine]

http://kamala.cod.edu/ca/latest.nous46.KMTR.html

3 mile track, 30 yd max width, F1, $400k

 

[Khristian Snyder]

Another one in the bag for California!!!