Tuesday, September 12, 2017

More Not So Deep Thoughts on Irma Plus Utah Weather

I'm still feeling frisky this morning about several issues, so the not so deep thoughts continue.

Anderson Cooper is clueless
With Irma still threatening the southeast, I continue to scan the news coverage and find appalling statements.  Anderson Cooper has been especially effective at getting under the nerves of this meteorologist.

Last night, while interviewing the Mayor of Jacksonville, which was hit with severe flooding yesterday, he made the dumbfounding statement that "clearly people were caught off guard."  No Anderson, people in mandatory evacuation zones were not caught off guard. 

Social media and other communications challenges
It's been clear in the snippets that I've caught of Anderson that he really likes the caught off guard/surprise narrative.  This is very common amongst reporters because people love that angle.  It makes the story more interesting.

Anderson has frequently brought up the "westward shift" of Irma and how it surprised people.  As a meteorologist, I find this to be grating as well, but in contrast to saying people in mandatory evacuation zones were caught off guard, this has some merit, depending on where you get your weather information from.

Official forecasts from the National Hurricane Center were very cautious not to endorse a specific storm track up either the east or west coast of Florida at long lead time.  They also issued hurricane and storm surge warnings on both coasts, as well as the south coast and Key West.

However, many people do not see those forecasts.  Instead, they see national news, local news, and social media.  In that echo chamber, there is a tendency to gravitate toward especially extreme model forecasts and clusters of model ensembles that do not fully account for uncertainty.

Also an issue are misinterpretations of the NHC "cone of uncertainty."  That graphic is not intuitive for the general public, and needs improvement, but even some broadcast meteorologists don't understand it.

Let me show and example of how this effects the information that people receive.  Below and at left is a summary of the Key Messages for Hurricane Irma issued about 3.5 days prior to the landfall of Irma on Marcos Island.  The cone of uncertainty, which encapsulates the entire Florida peninsula and offshore waters.  The National Hurricane Center simply says that there's a treat of hurricane impacts over the weekend and early next week, with a likelihood of hurricane watches being issued on Thursday.

The right hand side provides an example of what people are seeing on social media, which says very strongly that Irma will hit Miami at Cat 4 or 5 on Sunday.  At that time, one could find model forecasts calling for that track and intensity, and advising people to leave was warranted, but the tweet suggests much greater confidence than evident in National Hurricane Center forecasts.

Traditional and social media today provides a firehose of content that is unfiltered and often without context.  At one time, it was difficult to see the forest through the trees.  Today, it is difficult to see the information through the misinformation.  Note that not all misinformation is malicious.  Sometimes it simply doesn't provide the necessary broader perspective.

This is why, in the case of tropical storms and hurricanes, I strongly urge people to monitor forecasts from the National Hurricane Center and local National Weather Service Offices.  While no forecast is perfect, these are the most reliable available.  The National Hurricane Center, in particular, has a remarkable team of scientists, with strong ties to the research and emergency management communities.  Finally, heed the recommendation of local officials.

OK, now that I've warned you about misinformation, let me provide a snippet from the latest forecast.  A bonafide midlatitude trough is expected to move over the Great Basin later this week.  Oh, it is a thing of beauty.

And here's the summary from the National Weather Service [note to my friends their, you forgot your logo :-)]

Source: NWS
I'm not counting the minutes.  I'm counting the seconds.


  1. Love your passion Jim. Hope your mom is safe and sound and her place is undamaged. Glad the worst of the storm forecast for Florida did not verify.

    Do you have any insight on why Irma's storm track changed course from West/North West (let's say azimuth 290 degrees) to North West/North (let's say azimuth 340 degrees) at the Florida keys. If you look at the track from inception 500 miles east of Cape Verde, it is half a sine wave between 15 degrees north latitude to 20 degrees north latitude, then it hits the Leeward Islands, tracks west/north west along the coast of Puerto Rico, Hispanola, and Cuba, then turns almost due north at Havana, and tracks the west coast of Florida. Is it the open water of the Gulf of Mexico? Something else. Why the abrupt change of track?

    1. Everyone is fine. A long night and lots of vegetable debris strewn around, which is nothing compared to what others are dealing with.

      I can't explain the track shift in a couple of sentences, except to say it is a response to the large-scale flow. Irma was embedded in the tropical easterlies south of a strong upper-level as it moved across the Atlantic. As it moved along Cuba, however, it began to move around the southwest periphery of that ridge, and encountered a decaying upper-level trough over the southeast US that coaxed it northward. Why the transition was so abrupt is something I haven't thought about.

      Such a track change would probably not have been anticipated, at least with such precision, without numerical forecast models. No human can integrate the laws of physics in their heads. It is a major achievement of science that we have computer models capable of forecasting events that have no historical analog.


    2. I hope this query makes sense... I think I understand that a hurricane has angular momentum, and that this interacting with the earth's rotation nudges it poleward. Does a hurricane have net forward momentum? Is a large mass of air generally moving one direction (net, on average), or is it just a zone of low pressure moving about? (Advecting?)

    3. Yeah, I'll pile on since I'm deeply fascinated by Irma's abrupt change of track, basically up the Florida peninsula, and deeply impressed that the models were predicting this track change almost from the get go. Jim said he can't explain it in a couple of sentences, maybe we can talk him into a post. Meantime, Chistian's reference is quite helpful

      Focusing in on the "tropical easterlies" Jim mentions, we see Irma was "embedded" in this flow, which seems to be typical for this area at this time of year. The "decaying upper level trough" is now gone, so does not appear in the wind model.

      Jim's basically laid out what happened, and now that Wasatch snow impends, I'm less interested, but still quite curious why the models did so well.

  2. Great news about a proper change in seasons here in Utah. Also, I'm not sure if you've seen this site, but it's a pretty remarkable view of global wind and temperature. Clicking on the word EARTH in the bottom left will let you change different view settings. I have no affiliation with the site, just thought I would pass it along.

  3. I was watching the hurricane quite a bit, as I know people who were directly affected as well. With regard to computer models, I noticed that the EC was pretty consistently further west with the storm track than the GFS, although I feel like the GFS was more consistent with its track run to run and may have performed better (?). Particularly interesting was on the morning right before landfall (Sept 10) the EC apparently had a solution showing the storm tracking over the eastern Gulf and making landfall near the FL panhandle. Any ideas why there was this divergence so close to landfall, and if the differences are due to data sets and initialization or to the dynamics in the model itself?
    With regard to the media... a lot of people have commented on how bad the storm coverage can be and I don't disagree, but I have a feeling that is because many did not fully realize how bad the coverage has become on almost everything. Enough said on that topic I guess.

    1. My impression is that the EC was superior for the longer-range forecasts and the GFS superior for the short-range forecasts through Florida. I don't really have explanations for the varied performances between models and with lead time.

    2. Thanks, I agree based on what I saw. I have long been curious about whether the models are all using the exact same data as input, or whether the observational data sets vary significantly from one model to another.

    3. It's more than just the input data. How much weight that they put on that data, the accuracy of the underlying model, and the parameterization of physical processes, especially diabatic heating, all play a role.