Tornado Warning For....San Francisco?! [Updated 1:35p PST]

By -
According to the local National Weather Service, this is the first tornado warning for the City of San Francisco, ever. 

 Below is a map of the tornado warning. 

A gust of 83 mph was clocked at the San Francisco Airport, south of the city near San Bruno. There are trees reported down in the city and 14,000+ homes and businesses are without power in the city with more without power to the south. 

But was there a genuine tornado threat? 

There was rotation in the storm (see below) but the rotation is in the wrong direction (clockwise, instead of counterclockwise). It was moving toward the northeast. Note: the wind damage symbols represent damage that occurred after the time of the radar image. 

However, there was a "hole" in the reflectivity data that was colocated with the rotation. 
In an actual tornado, the rotation can fling rain and hail out from the center and cause a weak echo area in the center of the rotation. 

Given that the San Francisco NWS office has very little experience with tornado warnings, this one wasn't too bad when you consider there was damage over the city -- but with no reports, so far, of an actual tornado. 

Additional Information Added at 1:35pm:
Regarding some of the comments on social media:
  • The radar was set to 7-minute update mode which is completely inappropriate when there is the potential for strong thunderstorms, let alone tornadoes. It should have been updating at 2  minute, or faster, intervals. I'll give the San Francisco office a pass on this one. However, when it happens in the Midwest -- which is all too often -- it is inexcusable.
  • Yes, the rotation was more impressive on the Monterey radar (see below). However, the rotation was weakening rapidly. But, this radar depiction shows the rotation in the correct counterclockwise direction. 
I continue to believe it was fine to issue this tornado warning because there was rotation and, when we have virtually no experience with tornadic thunderstorms n the Bay Area, this was one of the infrequent times where "better safe than sorry" is a good rule. 

Comments

Post a Comment

Popular posts from this blog

The East Coast Severe Weather Threat is Over

By -
Image
Midnight: The East Coast Threat for Tornadoes and Severe  Thunderstorms Has Ended 3:50pm. Tornado watch for the Middle Atlantic Region. 2:30pm Tornadoes are also forecast in the South. 2:20pm. A couple of tornadoes, hail and wind gusts to 65 mph are possible with these storms. This includes NYC and Philadelphia.  1:05pm. The tornado risk has been extended northward into New York. The brown area has a significant risk of tornadoes. Remember: if a tornado warning is issued, go to your basement and get under heavy furniture like a pool table. Of, if your basement is finished, get into the bathroom. Go ahead an put a couple of water bottles and, if appropriate, diapers in your shelter area. Wear shoes.  If you don't have a basement or safe room, go to the lowest floor and get into a bath or closet in the middle of your home. Children should be put in the bathtub.  I'll update later today. 
Read more

Today's Tornado and Severe Thunderstorm Outlook - 9:30pm

By -
Image
After 65 mph winds went through Wichita, we have been without power for 35 minutes. So, I am going to have to end coverage for the night (using backup systems to write this). Scroll down for the forecast of tornadoes and severe thunderstorms for Sunday and Sunday night.  Please read down for the latest forecasts regarding this dangerous tornado and damaging wind situation! 5:40pm, a new "regular" tornado watch has been issued for north central Kansas.  Note that wind gusts to 80 mph are likely in this storm in addition to tornadoes and giant hail. Please make sure friends and relatives in the area are aware of the danger in the area outlined in red below plus the red area outlined at 2:50pm  In addition to "several strong tornadoes," hail to 4.8" in diameter is forecast along with wind gusts to 80 mph. Now is the time for persons living in mobile homes, manufactured homes and those with mobility issues should be making plans!!  Do not wait until a tornado warn...
Read more

Updated Freezing Rain and Heavy Rain Forecast

By -
Image
Note: An Updated Forecast is Available HERE Freezing Rain The National Weather Service has now issued winter weather advisories, two warnings and a watch. It may be a bit too large but, when it comes to freezing rain and slick roads, caution is usually the better course of action.  Here's a color code: Deep purple is an ice storm warning; serious condition where power outages are possible. Pink is a winter storm warning for significant icing. Deep green is a winter storm watch. I don't know why this is still a watch. If I were on the forecast desk I would have a winter storm warning for icing.  Dark blue is a winter weather advisory, a lesser condition, for icing.  Here is a view of the entire watch/warning/advisory area. The small area of green in Illinois is for flooding and, in Nebraska, for snow.  Here is a forecast of freezing rain amounts; totals to 6am Tuesday.  Color codes: Yellow is 0.25 to 0.50 inches. Power outages may occur in this areas. Deep blue i...
Read more