Wednesday, October 30, 2013

The Forecasting and Climate Lessons of Superstorm Sandy

A year has passed since Superstorm Sandy raked the northeast U.S., with over 60 billion dollars of damage to Long Island, New York City, and New Jersey and the loss of over 100 lives.    What did we learn from this storm?    Was it a harbinger of things to come under global warming?   As we will see some of the accepted "truths" about this storm were really fictions.

Reality Check:  U.S. Weather Prediction is Good, But Not the Best

     For the first time, a "secret" among U.S. meteorologists became generally known to the general population:  although very good, U.S. numerical weather prediction is no longer the best in the world.   During the week and a half run up to the storm, it became obvious that the global forecasts of the European Center for Medium Range Weather Forecasting (ECMWF) were superior.  Several days before the U.S. global model (the GFS), the ECMWF forecast model accurately forecast the path and intensity of the storm:  a  triumph of the technology.  This superiority of the ECMWF was no fluke and in the subsequent months the media highlighted other cases where the U.S. model was inferior.   But there was a silver lining to this revelation:  the origins of the U.S. modeling problems

were discussed, including the National Weather Service's inferior computers.  And the concerns of the American people and their representatives in Congress led to nearly 25 million dollars of the Sandy Supplement being dedicated to a new computer for weather prediction.   As the new head of the National Weather Service Louis Uccellini has stated on several occasions:  the implications of this powerful new computer (available in about a year) will be revolutionary.  Good news.

Miscommunication:  A Hurricane By Any Other Name Can Still Be Devastating

A major communication snafu occurred with Sandy.   As the storm approached the coast, it was losing its tropical characteristics and becoming more like a midlatitude storm (the fancy name for this is extratropical transition).   So right before landfall, the National Weather Service downgraded Sandy to a post-tropical cyclone and responsibility for forecasting it was handed off to local Weather Service forecast offices.  Hurricane watches and warnings were dropped, as one of the most dangerous storms of the century approached the Northeast coast.  Keep in mind that the storm was still as strong as a hurricane, with maximum winds of 85 mph. And Sandy was much larger than the typical hurricane.  The name change was terribly confusing to the media and many local authorities, some of which started to downplay the storm.  Big mistake.   The National Weather Service recognizes these problems in the post-storm review and has changed its strategy...next time the Hurricane Center will stay with such storms through landfall, and the warnings/watches will continue.


Will Storms Like Sandy Be More Frequent Under Global Warming?   Probably NOT.

The media and politicians seem to believe something that is not true.  That under global warming we can expect more storms like Sandy.   Let me say this clearly:  there is absolutely no reason to expect this.

First, consider the unusual track of Sandy.  Most hurricanes turn right and move out to sea.  The track of Sandy, a sharp left hook to the coast is nearly unprecedented during the past century.  And it appears that the probability of taking such a left turn will become LESS PROBABLE under global warming.  How do I know this?   Professor Elizabeth Barnes and colleagues of Colorado State University have published a paper that analyzed the output of a large collection of climate models forced with increasing greenhouse gases.  To quote from this paper:

"we demonstrate that climate models consistently project a decrease in the frequency and persistence of the westward flow that led to Sandy’s unprecedented track, implying that future atmospheric conditions are less likely than at present to propel storms westward into the coast."

 Just wrong

Second, theoretical and modeling studies of the effects of global warming on hurricanes and tropical storms have determined that there will be no increase in the frequency of weaker hurricanes under global warming.   Superstorm Sandy was a weaker hurricane (category 1) before landfall.  So there is NO reason to expect more of such storms under global warming.

But the facts noted above have not stopped governors, mayors, newspapers, and the general media from repeating this canard, time and time again.  Really frustrating!  Global warming is a serious issue and society deserve facts, not baseless hype.

Announcement:  Special Dinner and presentation (by me) on the storm that destroyed Ivar's Mukilteo landing restaurant in 2003.  Where? When?  At the rebuilt restaurant, next Thursday, November 7.  More information here.  Limited to 40 people.

9 comments:

codetalker said...

Cliff,

How about a talk about AGW here in Seattle?

Jack said...

Cliff, I think you're right about the connection between the meteorological side of hurricanes, etc. But a big part of what people are talking about is the contribution of sea-level rise to the storm surge that was so damaging. NOAA did find that sea-level rise due to climate change will make Sandy-like storm surges much more common in the New York area, even from weaker storms. (link: http://www.noaanews.noaa.gov/stories2013/20130905-extremeweatherandclimateevents.html)

John Monteverdi said...

While it is important to separate hype from legitimate concerns, it's also important not to overgeneralize in the other direction. For me, the meteorological issue with Sandy was not its track. Its true that GW impacts can't be reasonably attributed to a change in storm or hurricane tracks.

However, a hybrid wave cyclone-tropical system (meaning much of the tropical system's circulation embedded in the warm sector of the frontal cyclone) , such as Sandy poses a different set of issues. The higher mixing ratios/PWATS expected off of warm ocean currents such as the Gulf Stream should conceivably lead to storm intensification due to diabatic warming effects.

As you know, there were some spectacular examples of this kind of synergy on the West Coast recently, and a great example from this time of year back in 1962 (with the remnants of Typhoon Freda) feeding back to the "bomb" formation west of the California coastline.

So I disagree that ALL comments about GW's possible impact on future hybrid storms have no basis in evidence. I agree that many to most such comments are not correct, though. So your main point is one I agree with.

Cliff Mass said...

John,
The track is important because the trajectory was so very unusual. I know very well about the 1962 storm...very famous out here...the Columbus Day event. At this point, there is no solid information about hybrids becoming either more intense or more frequent in the area...so I think we have to be very careful about such speculations. We need to get beyond handwaving speculations...cliff

Unknown said...

"Will Storms Like Sandy Be More Frequent Under Global Warming?"

The "left hook" of the storm was interesting, and deserves more study (you don't directly address the arctic amplification theory).

But, like Katrina, Sandy's "killer" characteristic was the inundation it caused.

Yet you don't reference sea level rise. Admittedly it played a negligible role with Sandy, but "flood" hurricanes (as opposed to extreme wind damage ala Andrew) will surely become more common "under global warming."

Would you buy property on the SE US coast? I sure wouldn't, though I'm probably a fair bit younger than you...

Joseph Ratliff said...

Disclosure: IANAC (I am not a climatologist)

I'm with Cliff on this one. I do believe that GW exists, now, and that the majority of the cause is due to humans.

That said, to immediately predict, without careful analysis, that more storms like Sandy will happen directly resulting from GW is premature at best.

Sea level rise in and of itself seems to be a separate issue from whether or not Sandy will happen again.

From what I've seen in the IPCC findings (ipcc.ch), sea level rise will be a given, and logic dictates any storm would therefor have that much more impact on the coastal locations.

So, bottom line I think something like Sandy (with track, storm combination, etc...) is not likely to happen again in our natural lifetimes, probably not for 100 years.

Unknown said...

Another interesting aspect of Sandy was its size. The largest Atlantic hurricane on record. Focusing only on its Saffir-Simpson rating overlooks this.

Apparently the five largest Atlantic hurricanes have occurred since 1996, though our ability to measure hurricane diameter is probably better now.

A storm that makes a weird left turn, was the largest on record, and inundated the Big Apple... You can see why mayors and city planners might be scared, especially with the added expectation of future sea level rise.

The pinocchio pic looks a bit unfair in this context.

- Douglas

Unknown said...

Hi Cliff,

What role would the displaced high have out over the northern Atlantic due to the lower amounts of polar ice on the north pole?

I think I read that displaced highs can be more common due to lack of sea ice?

Thanks

Ansel said...

I wish they would not call it a "Superstorm"! After all it was only a Class 1.

The East had been spared severe hurricanes- until Sandy- for several decades now and I think people had been starting to forget. Even some scientists, forgetting New England history, started blaming Global Warming. (There was an "authority" on KUOW, just recently, talking as though hurricanes were something new.) But my father clearly remembers the severe storms of 1954, 1955, and the granddaddy of the last century, the great hurricane of 1938 (I think they did not have names for them back then).

Wake up Easterners! Hurricanes are part of your weather. Put those cottages back from the beach a ways.