Superstorm Sandy and the importance of polar orbiting satellites in forecasting

By: Dr. Jeff Masters , 8:19 PM GMT on January 03, 2013

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On the 23rd of October, the 18th named storm of the 2012 Atlantic hurricane season, Tropical Storm Sandy, was born in the Central Caribbean. As is common for late-season storms in the Caribbean, Sandy moved northwards across Cuba. The official forecasts from the National Hurricane Center issued on October 23 called for Sandy to turn to the northeast after crossing Cuba, and head into the Central Atlantic. This forecast was based on the output from five of our top six computer models, which all predicted that an upper-level low pressure system in the Central Atlantic would be strong enough to pull Sandy northeastwards. However, the global weather forecast model run by the European Center for Medium-Range Weather Forecasts (ECMWF) showed a disturbing possibility: the upper-level low pressure system in the Central Atlantic would not be strong enough to turn Sandy to the northeast. The hurricane would instead get caught up in the flow associated with a trough of low pressure approaching the U.S. East Coast, and Sandy would get slung into New York or New Jersey on October 29. While the ECMWF model was the best performing model for tracking Atlantic hurricanes in both 2010 and 2011, and had done very well again so far in 2012, the American GFS model had outperformed the ECMWF model several times during the 2012 season. NHC elected to discount the ECMWF forecast for Sandy as an outlier, and went with the forecast from the GFS and other models. By October 25, it was clear that the ECMWF model had the right idea all along. More models were now showing the turn towards New York, and the official NHC forecast now called for Sandy to make landfall in New York or New Jersey on October 29. The ECMWF model's early forecast of a track for Sandy into the Northeast was critical for allowing additional time for residents to prepare for arrival of the devastating storm. So what enabled the ECMWF model to make such an excellent forecast for Sandy, six days in advance?


Figure 1. This image uses the model output from the ECMWF experiment, showing where Sandy was predicted to be located five-days out with the normal satellite data inputs into the model (left) and without any polar-orbiting satellite data (right). Both position and intensity forecasts were affected--Sandy stays out to sea without the polar-orbiting satellite data, and the closer isobar lines encircling the storm also imply a more organized and stronger system. Image credit: NOAA.

Polar satellite data: a key to ECMWF model success
The ECWMF has a very sophisticated technique called "4-D Var" for gathering all the current weather data over the Earth and putting the data on a 3-dimensional grid that is then used as the initial "reality" of the current weather for the model to use for its forecast. The old expression, "garbage in, garbage out" is a truism for weather forecast models. If you don't properly characterize the initial state of the atmosphere, the errors you start off with will grow and give a lower-quality forecast. Data from geostationary satellites, which sit continuously at one spot above the globe, are easy to assimilate, and all the models use this data. However, the ECMWF model's superior technique used to assimilate the initial data allows inclusion of data from a large number of polar-orbiting satellites, which the other models cannot do as well. Polar-orbiting satellites orbit Earth at an altitude of 540 miles twice per day, circling from pole to pole. Their data is difficult to use, since the it is only available twice per day at each spot on the Earth, and the time of availability is different for each location. According to an email I received from Jean-Noël Thépaut, the chief of the Data Division of the Research Department at the European Center for Medium-Range Weather Forecasts, the ECMWF model uses data from at least fourteen polar orbiting satellites: N-15, N-19, N-19, N-17 (ozone SBUV instrument only), Metop-A, AQUA, NPP (ATMS instrument only), AURA (ozone OMI data only), F-17, TRMM (TMI data), COSMIC, GRACE-A, TERRASAR, and the GPSRO data on top of METOP-GRAS. The data of most importance is the data collected in the infrared and microwave wavelengths, as well as atmospheric density data obtained via GPS radio occultation (as a polar orbiting satellite goes over the horizon, the GPS signals from the satellite get bent by Earth's atmosphere, with the amount of bending proportional to the density of the atmosphere. This GPS Radio Occultation data is gathered from eight polar orbiting satellites, and fed into both the ECMWF and GFS models.) You can find a nice summary of the impacts of polar orbiting satellite data on weather prediction models at this link.)


Figure 2. Forecast track error for four of our top models used to predict Hurricane Sandy, for their runs that began at 00Z October 25, 2012. By this time, the GFDL model had joined the ECMWF in predicting that Sandy would make landfall in Southern New Jersey in five days. The GFS and HWRF models made good 1 - 3 day forecasts, but failed to anticipate Sandy's north-northwestward turn towards the U.S. coast. Image credit: Morris Bender, NOAA/GFDL.

As originally reported by the Washington Post's Capital Weather Gang, then confirmed in a NOAA press release, a study done by ECMWF research scientist Tony McNally found that if the ECMWF model did not have all of the data from the fourteen polar orbiting satellites, the five-day forecast of the model for Hurricane Sandy would have shown Sandy missing the Northeast U.S. This brings up a concern, since the U.S. polar orbiting satellite program is behind schedule. As explained by Andrew Freedman of Climate Central, the program is plagued by mismanagement, billions in cost overruns, and technical development challenges. The next polar orbiting satellite is not scheduled to be launched until 2017, and one or more of the existing polar orbiting satellites are expected to fail before then. This will result in a degradation of our ability to observe and predict the weather, and may result in poorer forecasts for storms like Hurricane Sandy. Given that the ECMWF model used data from fourteen polar orbiting satellites, the failure of just one satellite may not have made a significant difference in its forecast for Sandy. But if we lose several of these key satellites by 2017, our hurricane forecasts in 2017 may be worse than they were in 2012. To figure out how to cope with the loss of satellite-derived data, NOAA is conducting a Gap Risk Study that seeks ideas from researchers and the public on how NOAA can preserve the quality of its weather model forecasts in the event of the failure of one or more polar orbiting satellites in the coming years.


Figure 3. A tanker rests on the southern shore after being swept onto land by a storm surge due to Superstorm Sandy, Friday, Nov. 2, 2012, in the Staten Island borough of New York. (AP Photo/ John Minchillo)

Links
Eric Berger of the Houston Chronicle has an interview with Jean-Noël Thépaut, chief of the Data Division of the Research Department at the European Center for Medium-Range Weather Forecasts, on why the European model did so well with Hurricane Sandy.

Jeff Masters

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898. Ighuc
One year ago, 24.08% of Minnesota was in severe or extreme drought. As of a week ago, that number is now 83.44%:



Gosh I love snow, but we really need some rain!
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Quoting 1900hurricane:
Looks pretty saturated in the forecast soundings.

Ahhh, da's beautiful....
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Quoting LargoFl:
wow mid week get the row boats ready folks...........
Not in this part of the world. Too dry. Wetlands are dry. Lakes/ponds are very low. Streams are very low to dry.
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Quoting TropicalAnalystwx13:

It's the GGEM (CMC) we're talking about here...you know how it likes to exaggerate.

The GFS is much more realistic.

Still shows much-needed rainfall across all of Texas.



Well, the GEM ensembles are a much better unit than the operational by itself. Totals are very realistic on the GEM ensemble mean:

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894. VR46L
Quoting LargoFl:
yeah hopefully the drought stricken states will get some much needed rain huh...


Only problem with heavy rain on parched ground it tends to run off and not make an impact on the ground.. slow constant drizzle for a few days is better to kill drought than it all falling in one go ..
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even south Texas......
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892. VR46L
Two systems moving in from the west

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.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY...

A VIGOROUS UPPER LEVEL STORM SYSTEM WILL DIVE INTO NORTHERN MEXICO
MONDAY AND SLOWLY MEANDER EASTWARD TOWARDS THE SOUTHWEST BIG BEND
AREA OF TEXAS BY WEDNESDAY. AT THIS TIME...IT APPEARS LIKE RAIN
WILL BE INCREASING ACROSS THE WESTERN HALF OF OUR REGION INCLUDING
NORTHEAST TEXAS DURING THE DAY TUESDAY...WITH MORE WIDESPREAD
RAINFALL EXPECTED TUESDAY NIGHT INTO WEDNESDAY ACROSS THE
REMAINING PORTIONS OF THE FOUR STATE REGION. DUE TO THE SLOW
MOVEMENT OF THIS UPPER TROUGH TO OUR WEST...VERY HEAVY RAINFALL
WILL LIKELY SET UP ACROSS THE REGION TUESDAY NIGHT THROUGH AT
LEAST WEDNESDAY NIGHT...AND PERHAPS EVEN INTO THURSDAY. FLASH
FLOODING WILL LIKELY BECOME A CONCERN ACROSS AT LEAST PORTIONS OF
THE REGION WEDNESDAY THROUGH WEDNESDAY NIGHT. SEVERE WEATHER
PROBABILITIES ARE MUCH MORE DIFFICULT DO DISCERN THIS FAR OUT IN
THE FORECAST BUT THERE IS AT THE VERY LEAST...A RISK OF STRONG TO
SEVERE THUNDERSTORMS ALONG AND SOUTH OF THE INTERSTATE 20 CORRIDOR
OF NORTHEAST TEXAS AND NORTHERN LOUISIANA WEDNESDAY THROUGH
WEDNESDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF EMERGENCY MANAGEMENT PERSONNEL...AMATEUR RADIO
OPERATORS...AND STORM SPOTTERS WILL NOT BE NEEDED.

$$

13
Member Since: August 6, 2011 Posts: 4 Comments: 46973
Quoting VR46L:


One thing for sure the US is going to see alot of precipitation next week . The North West looks on course to catch the system south of Alaska and Quite alot of the Rest of the US will catch some of the system that is building west of Mexico
yeah hopefully the drought stricken states will get some much needed rain huh...
Member Since: August 6, 2011 Posts: 4 Comments: 46973
889. VR46L
Quoting LargoFl:
yes I hope they get thru this ok,nws is getting nervous i think,tons of rain and maybe severe weather..when I see warnings like this i worry about tornado's too..we'll see mid week what happens


One thing for sure the US is going to see alot of precipitation next week . The North West looks on course to catch the system south of Alaska and Quite alot of the Rest of the US will catch some of the system that is building west of Mexico
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Member Since: August 6, 2011 Posts: 4 Comments: 46973
The GFSe indicates that parts of Texas could see several inches.

Member Since: August 2, 2006 Posts: 47 Comments: 11883
Quoting VR46L:


Have a couple of blog friends here in that area , hope they are aware of your warnings Largo..
yes I hope they get thru this ok,nws is getting nervous i think,tons of rain and maybe severe weather..when I see warnings like this i worry about tornado's too..we'll see mid week what happens
Member Since: August 6, 2011 Posts: 4 Comments: 46973
885. VR46L
Quoting LargoFl:
Plse pay attention to your Local warnings Texas.....


Have a couple of blog friends here in that area , hope they are aware of your warnings Largo..
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883. wxmod
China (top) and India (bottom) Modis satellite photos taken today (and every day until the world ends).



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4-6 inches causes flooding dont it?............
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Quoting fabian171017:
When will the next forecasts for the 2013 Atlantic season be issued?



off topic...
love to see 17 there....that's my favorite number Fabian
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Plse pay attention to your Local warnings Texas.....
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Bohonk,you have a ton of rain coming,stay safe......
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Quoting bohonkweatherman:
Not going to get too excited we started off 2012 Very wet also then it just stopped after the first few months but this looks very promising and very much needed.



A potential multi-inch rain event in a drought stricken area is much better than the alternative (dry as a bone). Enjoy every drop while you can!
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the pic I posted this morning post828..he was only 15 and died....................TAMPA --
The driver who died early Sunday after crashing over a guardrail on the Laurel Street Bridge and plummeting into the Hillsborough River was only 15 years old, authorities said.
Tampa police have identified the victim as William Brockerick of Tampa

According to police, Broderick was traveling east on the bridge about 4:40 a.m. when he lost control of his vehicle and struck the guardrail. The vehicle flipped into the river and sank about 20 feet below the water line.

Tampa Fire Rescue crew members descended into the river on a roof ladder, reached the submerged vehicle and removed the Broderick. But paramedics were not able to resuscitate him because he had been submerged for too long, authorities said.

The Laurel Street Bridge spans the Hillsborough River near downtown Tampa just south of I-275.

At least one witness attempted to save Broderick, and that witness was rescued by Tampa Fire Rescue firefighters, authorities said. There were no passengers in the vehicle.
The Tampa police dive team removed the vehicle and the bridge has been re-opened in both directions.

Authorities are continuing to investigate.
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Texas drought Map........
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well tonight and tomorrow is Florida's turn...........
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Nam 84 hours....
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mid south gulf states already have flood warnings from last weeks rain, miss,LA ala etc..going to be a very watchful week coming up.
Member Since: August 6, 2011 Posts: 4 Comments: 46973
all the way to 192 hours...watersheds full along the gulf coast...
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Quoting wxchaser97:

It won't just be heavy rain, severe weather will also be a threat in S Texas.
Not going to get too excited we started off 2012 Very wet also then it just stopped after the first few months but this looks very promising and very much needed.
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gee from 84 to 144 hours..flooding for sure along the gulf....
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Quoting wxchaser97:

It won't just be heavy rain, severe weather will also be a threat in S Texas.
yes folks really need to pay attention to their local warnings this coming week
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12z CMC






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Looks pretty saturated in the forecast soundings.

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Quoting LargoFl:
wow get ready Texas.............

It won't just be heavy rain, severe weather will also be a threat in S Texas.
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wow mid week get the row boats ready folks...........
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wow get ready Texas.............
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12z ECMWF has a monster -EPO ridge in Canada at 240 hours.

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862. VR46L
Two Clouds of Interest for next week ...

Loop Embedded


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Quoting fabian171017:
When will the next forecasts for the 2013 Atlantic season be issued?

Depends on which agency you are talking about.
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JMA model

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Quoting TropicalAnalystwx13:

It's the GGEM (CMC) we're talking about here...you know how it likes to exaggerate.

The GFS is much more realistic.

Still shows much-needed rainfall across all of Texas.


Yeah, you just must have missed my edit; I went ahead and put a similar disclaimer on my post afterwards. However, most AFDs are mentioning that the GFS depicts one of the faster events, so I wonder if the GFS totals are perhaps underdone since the NWS offices think the system is going to stick around a bit longer than what the GFS shows. For what it's worth, the GFS appears to be in pretty good agreement with the HPC at the moment.

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When will the next forecasts for the 2013 Atlantic season be issued?
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Quoting 1900hurricane:

12Z output went even higher!


It's the GGEM (CMC) we're talking about here...you know how it likes to exaggerate.

The GFS is much more realistic.

Still shows much-needed rainfall across all of Texas.

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Quoting bohonkweatherman:
Hope that happens. 3 Hottest Years in Austin's History are 2011 with 2006 and 2012 tied for 2nd, see a trend here.

12Z output went even higher!



Like I said before though, it is the CMC, which often puts out way too much rain. Regardless, it looks like a multi-inch event is very probable.
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Member Since: August 6, 2011 Posts: 4 Comments: 46973
853: ever-armed with umbrella (and Pac-a-mac, for good measure),

Well, I learned a new word. Charming those in the U.K. But watch out as my Sister and her Daughter are in London. Just a heads up...... lol
Member Since: February 29, 2012 Posts: 0 Comments: 6682
Just found on The Independent about the strange weather in the UK last year:

Weather: Could every cloud have a sinister lining?

So, farewell 2012 and, meteorologically speaking, good riddance, says David Randall for whom our weather is beyond a joke

Sunday 06 January 2013

When it came to weather, my parents were like those two little figures who alternate in emerging from the barometrically sensitive model house. My mother was the gloomy one, ever-armed with umbrella (and Pac-a-mac, for good measure), ever-ready with gloomy forebodings ("Sun before seven, rain by 11" was a favourite way to greet a cheery morning). My father was the sunny type, able to discern patches of incipient blue in the most leaden skies and who would describe each fall of rain, however prolonged or torrential, as "a clearing-up shower". Whatever it would have taken to dampen his spirits, the British climate never came up with it.

I inherited his eye for a silver lining, his dismissal of an ill wind. But 2012 tested my optimism to the limit.
Read the whole article
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The 6z GFS brings a dramatic change in the weather for many next week, especially across North Texas. The Dallas/Fort Worth area goes from having highs in the upper 60s over next Saturday to 20s and 30s with ice and snow that Sunday and into Monday.

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Quoting pcola57:
Link to meteoalarm.eu





That's... weird. Thunderstorms, in Iceland? It makes the news here whenever there's lightning. Random example:

---

http://www.mbl.is/frettir/innlent/2012/08/23/eldi ngin_klauf_staurinn/

Translating the first paragraph: "I've never experienced anything like it. I thought that I wasn't in Iceland!" said Slveig Stolzenwald, a resident of Hella, but much thunder and lightning came over the southerlands in sudden storms yesterday. Lightning struck, among other things, a power pole and cleaved it.
----

Vedur.is says nothing about thunderstorms, just light rain as usual.

Not like anyone would notice; people are still shooting off fireworks. Hard to believe that there's still things in the country that haven't yet been burned or exploded after that New Years fireworks display and the bonfires, but there you go... ;)
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Quoting 1900hurricane:
I'd take this.

Hope that happens. 3 Hottest Years in Austin's History are 2011 with 2006 and 2012 tied for 2nd, see a trend here.
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Good Morning All - Rain Mode here .02 so far.
Low 46.4 Currently 47.9 Yesterday 41.2/67.1
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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