September 28, 2022

European Models Provide Far Better Forecasts than U.S. Models for Hurricane Ian

European weather prediction models provided to be substantially superior to U.S weather prediction systems predicting the track of Hurricane Ian.

Weather radar image near the time of Ian's landfall on the 
west coast of western Florida today.

This is an issue I have blogged about and written papers about in the past, with the most well-known past case being Hurricane Sandy in 2012.  

And it reflects the decline of U.S. national weather prediction skill versus leading international centers--a situation that is a national embarrassment and must be fixed.

Let me show you the unfortunate details for Hurricane Ian.

I will start with a graphic of forecast track error by Professor Brian Tang of the University of Albany (website here).  This figure presents the track error (in km) for various forecast lead times.

The main US global model (the GFS) is shown by the dark red color (AVNO), while the leading weather prediction center in the world (the European Center) is shown by blue (ECMF).  The high-resolution US hurricane models (HWRF and HMON) by purple and cyan, and the official forecast (with human input!) by the black line.

For the short-term forecasts (24 or 48 hr) everyone was on the same page.

But look at the extended forecasts (96 and 120 hr)!  OMG.  The European Center was the clear winner, with roughly HALF the track error of the US global model.

Furthermore, it is very concerning that the U.S. high-resolution hurricane models (HWRF and HMON) had even larger track errors.

 High resolution doesn't do you much good if you get the storm in the wrong place!

Let me show you the problem spatially by presenting the tracks of the U.S. and European ensembles of many forecasts, with each forecast providing a track of the storm.  

Below are the forecasts starting at 0000 UTC 25 September (Saturday at 5 PM PDT), with the black lines showing you the mean track of all the forecasts).  (imagery courtesy of weathernerds.org)

The European Center forecasts were very good, suggesting landfall on the central and southern western coast of Florida.  South of Tampa.  Quite close to the actual landfalling position (as shown by the radar image above)


In contrast, the US GFS ensemble was displaced much more to the west (which was wrong).  Much more spread (uncertainty).  The U.S. forecasts were MUCH more threatening to Tampa, since a storm making landfall north of Tampa could push water into the bay.


As a result of the problematic U.S. forecasts, the media went nuts talking about a catastrophic storm surge in Tampa, with calls to evacuate hundreds of thousands of people.  And people down the coast were not warned of a serious threat.


I wish this was an isolated case, but it is not. 

U.S. global weather prediction is not as good as some major international centers, and the cost to the American people is enormous (can you imagine the costs of all the evacuations in Tampa, for example).

The U.S. has the largest and best weather research community in the world. We spend more on weather prediction than anyone else.  Yet, our forecasts are not as good as others.  And a shadow of what we are capable of.

I have written a new paper describing the origins of the problem.  It is a problem of organization, of duplication of efforts, of no one group or individual being responsible, and a lack of a coherent system for improving our weather models.  

And it will take the active intervention of Congress to fix it.

September 26, 2022

Was This the Driest Summer in Northwest History?

A dry Pacific Northwest in July and August is the normal state of affairs, but this year was particularly arid.

Some media outlets have claimed this is Seattle's or the region's driest summer on record.  Is that true?

Let's find out.  

At Seattle's SeaTac Airport, this summer (June 21-September 21) was the driest in a record doing back to the late 1940s (.50 inches).  2017 was right behind (.52 inches).  



What about a nearby station with a longer record (Kent), going back to 1912?  That is shown below with a trend line.  2022 was the driest summer on record but some came close in the 1925-1945 period.  The trend shows a slight decline (maybe a half-inch) over 110 years.  The very small long-term trend will turn out to be important.


What about east of the Cascades?   This is important because of the agriculture there and the frequent wildfires.   A different story from the west.  

Spokane (going back into the late 1800s) was dry but six other years were drier.

And Kennewick, also with a record going back into the late 1800s, was not exceptionally dry at all, with 29 years more arid.


So what can we conclude?  Western Washington was exceptionally dry this summer. The driest on record for many stations.  But there is only a minimal trend toward more dryness west of the Cascade crest.   Eastern Washington had a dry year, but it wasn't exceptional.

Let me stress, there is only a slight trend toward drier summers in our region.  

That is important, because if climate change is the cause of the dry conditions you would expect to see a long-term trend.  If a very dry summer like this year was caused by climate change, there would be a long-term trend towards much drier summers.  There isn't.  

What do climate models suggest?   Here at the UW we are running high-resolution regional climate models driven by a collection of global climate models.  This is the gold standard of such work.

Here is the prediction for summer precipitation (in this case June-July-August) for Seattle and Pasco driven by a VERY aggressive increase of greenhouse gases (the RCP 8.5 scenario) for 1970-2100.  Climate models suggest VERY little change in summer precipitation through 2022 for either station.  For Seattle, there is a slight decline in precipitation by 2100.  Virtually no change in the Columbia Basin.

So what should you conclude from all this?  

We had a very dry summer in western Washington.  But there is little overall extended trend, but plenty of variability that is probably natural in origin.   This is supported by climate model simulations that show little change in summer precipitation even with large increases in greenhouse gases.


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Atmospheric Sciences 101

Like last year, I am teaching atmospheric sciences 101:  a general introduction to weather and climate, this fall.  You can learn more about the class on the class website.  I talk about everything from the basics of the atmosphere to weather prediction, thunderstorms, hurricanes, and local weather to global warming and climate.

I will be teaching the class in person at the UW, but will also make it available over zoom.  Thus, folks can take it remotely.

If you are over 60, you can take the class through the ACCESS program for a very nominal charge (something like $15).   Last year I had over 125 folks do so.

So if you are a UW student looking to learn about weather or a non-student interested in the topic, I welcome you to join me this fall.  My first class is on September 29th.






European Models Provide Far Better Forecasts than U.S. Models for Hurricane Ian

European weather prediction models provided to be substantially superior to U.S weather prediction systems predicting the track of Hurricane...