Which model do you trust? And, Arctic sea ice reaches a record minimum

By: Dr. Jeff Masters , 7:33 PM GMT on August 17, 2007

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Hurricane Dean, now a major Category 3 hurricane with 125 mph winds, continues to intensify and grow larger in size. Dean pounded Martinique and St. Lucia this morning, and claimed its first victim when a 62-year old man died on St. Lucia while trying to save his cow from raging flood waters.

Dean's eye is now visible on long range radar out of Puerto Rico. Buoy 42059 is in Dean's path, and should be interesting to watch.

We're fairly confident of the 1-2 day forecast, which has Dean headed west to west-northwest over the Central Caribbean, very close to Jamaica and the Cayman Islands, then into the Western Caribbean. After that, things become murkier. The latest 12Z runs of the NOGAPS, UKMET, GFS, and HWRF computer models all show Dean hitting the Yucatan Peninsula, and continuing on into the Gulf of Mexico towards a second landfall near or south of the Texas border. The HWRF run is slower, and does not take Dean to the coast at the end of its forecast period. The big outlier is the GFDL model, which now takes Dean northwest into central Louisiana. Which model is correct? The problem is that each model has a different solution for the behavior of an upper-level low pressure system expected to be over the Gulf of Mexico early next week. Which model should we trust?

In 2006, the official NHC forecast performed better than any of the individual computer forecast models. However, several "consensus" forecasts made using an average of the "big four" computer models (GFDL, GFS, UKMET, and NOGAPS), slightly outperformed the official forecast at some time periods (Figure 1). The Florida State Super-Ensemble (FSSE), for example, combines the "big four" models on the basis of past performance in an attempt to correct for biases in those models. (The FSSE is owned by a private company, which makes it available to NHC but not the general public). The Florida State Super Ensemble slightly out-performed the official NHC forecast at most forecast times.

The "big four" models are plotted on wunderground.com's computer model page for Dean, (along with the inferior BAMM model, which is plotted since it is always available quickly, and has done well at longer range forecasts in the past). We do not get tracking points for the ECMWF or HWRF models at this point, so you'll have to go the raw plots to see those forecasts. Note that three of the "big four" models performed well in 2006, with the GFDL and GFS performing the best. The UKMET had a very poor showing in the Atlantic in 2006. However, the UKMET was the best-performing model in the Eastern Pacific in 2006, along with the GFDL and BAMM models.

The European Center's model (ECMWF) outperformed the "big four" consensus models for 72, 96, and 120 hours forecasts in the Atlantic. However, the ECMWF model was generally not available in time to be used by forecasters. Efforts are being made to make the ECMWF available in a more timely fashion for the 2007 season, which would be a big help. We also have the new HWRF (Hurricane Weather Research Forecast) model this year. In tests done on a number of hurricanes for past years, the HWRF performed about as well as the GFDL (Figure 2).



Figure 1. Track forecast skill in 2006 of the official forecast and the various models, compared to a "zero skill" forecast using NHC's CLIPER5 model. The CLIPER model (short for CLImatology and PERsistence) is a model that makes a forecast based on historical paths hurricane have taken, along with the fact that hurricanes tend to keep moving in the direction they are going (i.e., their current motion persists). Note that many models had a negative skill for their 120 hour (5 day) forecast. The official NHC forecast had about 10% skill at 5 days. Image credit: NHC.

Figure 2. Track errors for 48-hour forecasts from the 2006 version of the GFDL model (black) and the new HWRF model (red). The HWRF model performed better on some hurricane than the GFDL, and worse on others. Overall, the two models had about the same performance on the cases tested. Image credit: Naomi Surgi, NOAA Environmental Modeling Center.

In conclusion, the official NHC forecast outperforms all the individual models, particularly at long ranges. Looking at the individual model plots can be helpful to determine the uncertainty in the forecast, but it's tough to beat the NHC. In the case of Dean, where one model is an outlier from the rest, it is usually better to believe the consensus of the other models.

If you want to look at plots of the individual models, I've written a description of the various models and where to find these plots on our tropical weather page.

Arctic sea ice shrinks to record low
The National Snow and Ice Data Center announced today that Arctic sea ice has just surpassed the previous single-day (absolute minimum) record for the lowest extent ever measured by satellite. Satellite measurements began in 1979. Sea ice extent has fallen below the 2005 record low absolute minimum and is still melting. Sea ice extent is currently tracking at 5.26 million square kilometers (2.02 million square miles), just below the 2005 record absolute minimum of 5.32 million square kilometers (2.05 million square miles). This new record was set a full five weeks before the usual late September minima in ice extent, so truly unprecedented melting is occurring in the Arctic. The most recent images from the North Pole webcam show plenty of melt water and rainy conditions near the Pole.


Figure 2. Current extent of the polar sea ice, compared to the normal for this time in August (pink line). Image credit: National Snow and Ice Data Center.

I'll have an update Saturday morning.
Jeff Masters

Hurricane Dean near the island Puerto Rico (Hector777)
the ciclonic surge hard mind in Salinas,Puerto Rico mines the Community Las Ochenta in the south of Puerto Rico
Hurricane Dean near the island Puerto Rico

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3435. scaldisnoel
3:09 PM GMT on August 18, 2007
cyclone boz,

I may be alone in this, but I would appreciate it if you provided links to the video, not embed the video in your post. It just eats up more bandwidth and makes it take longer to refresh.

Thanks
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3433. BeenThereinMiami
3:06 PM GMT on August 18, 2007
Any one out there able to explain trochoidal wobbles ? What they are and how they look relative to the track ? I am pretty sure I remember them being scalloped looking wobbles up and down along the track, but I can't find an easy to understand diagram or explanation.
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3432. extreme236
3:08 PM GMT on August 18, 2007
image

Yellow box with the convection at 30-35W. should be interesting
Member Since: August 2, 2007 Posts: 19 Comments: 19234
3431. centex
3:06 PM GMT on August 18, 2007
It's not a wobble. The wobble is the minor variation within the bump to the north.
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3430. Drakoen
3:07 PM GMT on August 18, 2007
Posted By: Meteorologist1969 at 3:07 PM GMT on August 18, 2007.

The new GFS has another storm in the central GOM in 15 days, long way out, but the GFS is good at picking up long term lows and with the Bermuda High expected to stay strong and in place, could realistically occur.


No, you need consistency. There is no consistency 15 days out. It could be another ghost storm by the GFS.
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3429. weatherboyfsu
3:04 PM GMT on August 18, 2007
Good morning,

Dean continues to impress and speed along...Its amazing that a hurricane of this strength can be moving along at this rate.......I have been looking up others and have been hardpressed to find similar numbers.......The pinwheel eye.......14 miles in diameter moving that fast for that period of time......and yes it has been jogging a little more to the WNW but I believe it will right itself like it has been..........its almost like going up stairs..........but you never know..........do you?
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3428. littlefish
3:05 PM GMT on August 18, 2007
TXKiwi, CMC is known for its cyclogenesis hyperactivity... I wouldn't trust it unless other models were showing similar.
3427. Meteorologist1969
3:07 PM GMT on August 18, 2007
The new GFS has another storm in the central GOM in 15 days, long way out, but the GFS is good at picking up long term lows and with the Bermuda High expected to stay strong and in place, could realistically occur.
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3426. StormJunkie
3:06 PM GMT on August 18, 2007
Looks as if Dean will be under going a EWRC over the next 12-24...
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3424. scwindsaloft
3:05 PM GMT on August 18, 2007
"Ok, this Dr. Lyons guy on TWC is officially out of his mind"
Remember...this broadcast is for the general public. They must be careful not to prematurely alert the general public.
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3423. Meteorologist1969
3:07 PM GMT on August 18, 2007
The new GFS has another storm in the central GOM in 15 days, long way out, but the GFS is good at picking up long term lows and with the Bermuda High expected to stay strong and in place, could realistically occur.
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3422. CycloneBoz
2:58 PM GMT on August 18, 2007
ATTAINED! Tropical Storm Erin’s Center of Circulation at Landfall – 8/16/2007

Thanks to the invaluable help of Doug from Florida, I was able to arrive at the center of circulation of Tropical Storm Erin as it made landfall just south of Port Aransas, Texas on Thursday, 8/16/2007.

It was a wild ride through the wall surrounding the center of circulation. Heavy wind and massive amounts of rain blasted my car as I drove along Texas 361 towards Port Aransas. It was barely becoming daylight, but I knew as I traveled down the road alone that Erin was making landfall, and I was experiencing the very worst part of the storm.
Suddenly, the wind and rain stopped. I had Doug on the phone and he told me that I was right there and to find someplace to pull off. I chose “Gulf Beach Access Road 1” which is just south of Port Aransas.

Please look at the following images:

TS Erin's Path At Landfall - 8/16/2007

This image was obtained using coordinates provided by the NHC and Google Earth. Please notice that the path crosses land just south of Port Aransas, Texas.

Zoomed In View of TS Erin's Path At Landfall

This image is a zoomed in view of TS Erin's path at landfall.

"X" marks the spot where I shot the following video:



At the end of the video, I'm facing towards the west. You can see a structure there. If you launch Google Earth and enter coordinates 27.47N 97.05W, and zoom all the way in, you'll see the structure I caught on tape.

As I left Texas, the remnants of Erin pretty much filled the skies over the state. So much rain has fall now, that I fear if Dean were to go into that area, it could remain a strong storm well inland, because of all the humidity and water that's on the ground right now in Texas.
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3421. NeverPanic
2:57 PM GMT on August 18, 2007
Hi all,
Been busy at work lately so have very little time to keep up with all thats going on. Just snuck in for a moment and can only linger for about 10 so no time to catch up on the blog, that will take 2 days 24/7 by the looks lol.
Anywho just one quick question.
What are your thoughts on the wave located at @9.5N 35W. Looks to have something going on.
THX.
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3420. Meteorologist1969
3:05 PM GMT on August 18, 2007
The new GFS has another storm in the central GOM in 15 days, long way out, but the GFS is good at picking up long term lows and with the Bermuda High expected to stay strong and in place, could realistically occur.
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3419. Melagoo
3:06 PM GMT on August 18, 2007
What a storm!

Photo Sharing and Video Hosting at Photobucket
Member Since: July 31, 2006 Posts: 19 Comments: 1555
3418. PBG00
3:06 PM GMT on August 18, 2007
What is the thing off Florida?

The cmc being crazy.
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3417. weatherboykris
3:06 PM GMT on August 18, 2007
The plane's SW of the eye....80kt SFMR winds.
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3415. TXKiwi
3:03 PM GMT on August 18, 2007
In the CMC run for T=126, it shows another system where Dean has just been, but something else off Florida.

What is the thing off Florida?
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3414. TerraNova
11:02 AM EDT on August 18, 2007
Does anyone know of a link to high res visual satellite imagery?

Link
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3413. comtrader
2:59 PM GMT on August 18, 2007
the latest ngm run puts the ull well south and east of the gfs forecast 48 hours out. it also appears to be stronger. all things being equal this will increase the likelihood of a hit higher up the gulf. if there is going to be a change in the model forecasts i would say the biggest worry would be houston.
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3412. Tampalookout54
3:01 PM GMT on August 18, 2007
Guys,
What do you think would cause the ridge that is supposed to build over Florida to weaken? Some of you are throwing that possibility out there and wanted to know what would cause this and what are the possibilities of it happening.
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3411. nola70119
3:00 PM GMT on August 18, 2007
Kenner, on the Thursday before Katrina it was on the other side of Florida and the models were drawing circles.
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3410. Drakoen
3:02 PM GMT on August 18, 2007
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3409. Masquer08er
2:57 PM GMT on August 18, 2007
Bani in the DR. looks like it has a bullseye. This is what my eyes tell me. I do not pretend to be an expert. I'm just asking for a second opinion. Thanks
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3408. PBG00
3:00 PM GMT on August 18, 2007
I disagree, TX and MX have the best chance. FL/AL/MS have the least chance

I agree with you CJ5..Not that it means MS doesn't have any chance of getting, just that as of now, mex/tx have the best chance.
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3407. scaldisnoel
3:00 PM GMT on August 18, 2007
buffalosnow,

You said:
"Ok, this Dr. Lyons guy on TWC is officially out of his mind"

He is hardly a dunce or nuts. His reasoning for the track south of Texas was that the ULL would move fast enough to not have an effect on Dean for much longer, then high pressure to the north of Dean will put it back on a course more to the west.
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3406. Drakoen
3:01 PM GMT on August 18, 2007
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3405. Xion
2:51 PM GMT on August 18, 2007
Does anyone know of a link to high res visual satellite imagery?
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3403. PensacolaDoug
2:58 PM GMT on August 18, 2007
FL302!


Good link!
Thanx!
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3402. nola70119
2:58 PM GMT on August 18, 2007
SJ, yes, I meant to say later in the forecast.....
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3400. Hellsniper223
2:52 PM GMT on August 18, 2007
Posted By: leftovers at 2:50 PM GMT on August 18, 2007.

Get over it guys no NW turn with this bad boy at least until the gulf. I bet the folks at NHC got their 500$ ruler out.

It's already north of the Forcast track. And Is heading northward. Maybe not quite NW but certainly WNW.
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3399. Bootsie1
9:57 AM CDT on August 18, 2007
just wondering. I need to know I live in MS
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3398. KennerLA70065
2:59 PM GMT on August 18, 2007
Trust me, we remember the guessing that went on for Katrina. We watched the trend and decided on Thursday that we were leaving on Saturday morning. We made our reservations for our hotel and the closest that we could get, on Thursday afternoon, was Natchitoches, LA, which isn't that far from Shreveport. We loaded up the kids and all our necessary gear (including our one month old) and headed out early Saturday morning. We didn't have any traffic to speak of and made excellent time. My in-laws left after noon and it took them 9 and a half hours to make the same trip we made in four. My father in law left that night, and it took him over 12 hours to make it.

For New Orleans survival, there are really two different areas: The East bank, including the CBD, the French Quarter, and most of Tourist Attractions and the West bank, which is largely residential and moderate industry, including much of the fishing fleet. Landfalls from the south or to the immediate west are of greater risk to the West Bank as it is South of the city. Landfalls that track up along the river, especially just to the west of the channel, are bad for the whole city. Landfalls that come in from the East, like Elena's second strike, are mainly bad for the East bank and the coastal communities along Lake Ponchartrain.

Katrina didn't strike far enough West to spare the East Bank, and was packing enough storm surge to wash completely over the river levees closer to its mouth (they are much lower there). Katrina may have only been a Cat 3 at landing (although, some unofficial wind measurements from along the coast had three minute averages in the "barely cat 4" range) but she was still toating a Cat 5 storm surge that she collected on the loop.

What still scares many of us here is that, as long as Dean is where it is, if it makes a turn for us, it has to cross the loop current. That's not exactly what we like to call "good" down here.
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3397. pcshell
2:57 PM GMT on August 18, 2007
guys anyone on here on the gulf coast should pay attention to dean i don't care what steve leons says they never truly now until it passes cuba and the channel i have seen way to many tracks change buy many thousand miles after that point
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3396. CJ5
9:54 AM CDT on August 18, 2007
Posted By: Bootsie1 at 9:54 AM CDT on August 18, 2007.
Mississippi or Louisiana have the best chance of getting this monster?


I disagree, TX and MX have the best chance. FL/AL/MS have the least chance.
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3395. tallahasseecyclone
2:54 PM GMT on August 18, 2007
Is this just a wobble north?

http://www.wunderground.com/hurricane/at200704.asp#a_topad
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3394. Fl30258713
2:50 PM GMT on August 18, 2007
Posted By: PensacolaDoug at 2:49 PM GMT on August 18, 2007.

Anyone know of a radar link out of Haiti or D.R.?



http://www.weatherfx.net/radar.html


Streaming radio from Jaimaca

http://www.go-jamaica.com/power/index.html

real player direct streaming link:

http://war.str3am.com:7550/

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3393. nola70119
2:55 PM GMT on August 18, 2007
According to NHC 2am everything is in play in W and N Gulf, but obviously there are a lot of opinions.
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3392. PensacolaDoug
2:54 PM GMT on August 18, 2007
Doug! I confirmed it! I was almost dead on the center of circulation as Erin came ashore.

I can't thank you enough for spotting me



Aw shucks! It twernt nutin'
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3391. jake436
8:55 AM CST on August 18, 2007
Dean back to WNW and a Yucatan hit it looks like... The ULL is moving out now and Dean has slowed a bit. The outlier has corrected itslef more each time to the track of the others.
That's not entirely correct. Wednesday, the GFDL was in Brownsville...since then, it's been alternating back and forth from LA to TX. I wouldn't be surprised to see it back east on it's next run.
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3390. scwindsaloft
2:55 PM GMT on August 18, 2007
Dean continues to wabble...but maintain course!
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3389. FrenchKheldar
2:53 PM GMT on August 18, 2007
Jim Cantore is going to Cancun (per TWC). I guess that rules out Dean threading the needle through the Yucatan channel...
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3388. StormJunkie
2:53 PM GMT on August 18, 2007
nola, that is not exactly what SW said...but he does hint that later in the forecast period there could be a NWish movement.

Great analysis of the blog CajunSub, I could not agree more!
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3387. Melagoo
2:55 PM GMT on August 18, 2007

I'll have an update Saturday morning.
Jeff Masters


When will Dr Masters have his update?
Member Since: July 31, 2006 Posts: 19 Comments: 1555
3386. PBG00
2:54 PM GMT on August 18, 2007
Posted By: Bootsie1 at 2:54 PM GMT on August 18, 2007.

Mississippi or Louisiana have the best chance of getting this monster?


Who said that??
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3385. weatherwonderer
2:47 PM GMT on August 18, 2007
Neponset no problem here. Again, your right specifically. I happen to be more a big picture type. It takes both big picture and small picture (for the details) for most things to be worked out. None of has a lot to contribute here since we are relying on data provided and most of us are amateurs at best. But hey, thats what makes it interesting. Believe me, I worry about Jamaica and the Caymens right now. Any more to the right even Cuba will have to start worrying. I must say I have learned alot on this site 2005. Esp. from lefy, swflyboy, stormjunkie and many others. You are a good poster as well. I certainly don't have problem being corrected.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.