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

Share this Blog
3
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 585 - 535

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71Blog Index

585. sociologyguy
10:20 PM GMT on August 17, 2007
thanks for the article on sea ice...
who knows what brews up there?
More frequent and stronger storms coming out of the artic?
Member Since: Posts: Comments:
584. Tazmanian
3:25 PM PDT on August 17, 2007
Pinhole eye alert
Member Since: Posts: Comments:
583. ioweitall2charley
10:22 PM GMT on August 17, 2007
Hey guys,
I visit this blog often and appreciate it as a resource and I even appreciate the bickering :-) Having lived through Charley and then Wilma I can honestly say that I don't necessarily trust tracks....I understand steering currents etc...but neither of these hurricanes were forcast for our area and SURPRISE ! I am keeping an eye on Dean...I suggest everyone in from SW Florida, Texas, Lousiana etc should as well....lets all just hope it stays on the most southern course possible.
Member Since: Posts: Comments:
582. CFL
10:21 PM GMT on August 17, 2007
you're exactly right MTJAX. several of the models are hinting at development and i assume that anything that forms soon would follow that ULL (or maybe another one yet to form) into florida
Member Since: Posts: Comments:
581. miken62
10:21 PM GMT on August 17, 2007
Posted By: bayoubrotha at 10:20 PM GMT on August 17, 2007.

The eye of Katrina came within 40 miles east of New Orleans, not 150 miles
.


Yes and damage was devastating well over a hundred miles to the eastof that . So if Dean were to go 100 to 150 miles west of NOLA ..it would still be devastating; note the storm would be coming in most likely from the southeast toward the northwest which would really pile up water into NOLA. this by the way is all hinging on this storm being a monster in both size and strength..
Member Since: Posts: Comments:
580. bayoubrotha
10:21 PM GMT on August 17, 2007
THAT'S WHY A CAT 5 LANDING WEST OF NOLA IS BAD!!

GFDL 12z has a Category 4 hurricane coming ashore at Vermillion Bay and hiting Lafayette.

That is 150 miles away. It would not destroy New Orleans, which has survived closer hurricane landfalls: the 1915 Hurricane, Betsy, Camille and Katrina.

Can we please stop the hype and scare tactics?
At this point, we do not have a clear idea of where Dean will end up.
Member Since: Posts: Comments:
579. jake436
4:16 PM CST on August 17, 2007
Just one man's opinion...mine. Today, I went and filled up several 5 gallon cans of gasoline, my truck, my wife's van, and my boat. If the storm comes to my area...I'll have plenty of gas for our generator...(about a weeks worth), and we have plenty of fuel in the vehicles...don't intend to drive much this weekend anyway.

If the storm DOESN'T affect us...fine. We have plenty of fuel to pour in our vehicles NEXT week, and we only paid $2.56/gallon for it. Try doing that next week if the thing hits TX! In fact, try doing that if the thing enters the GOM period.

Moral of the story...if you can afford it...just go do it now while you don't have to pay an arm and a leg for a gallon. Gas will still be good in a couple of weeks if the storm doesn't affect you, so you can use it then. Also, stock up on water...(I personally take empty gallon jugs and fill them with tap water NOW...so that I'll have them IF I need them later).

We, along with everyone else affected by Katrina...or any other storm recently...already have a generator...and we know the drill. Bottom line...BE PREPARED!! It can't hurt to get things in order now.
Member Since: Posts: Comments:
578. UnderstandingFL
10:18 PM GMT on August 17, 2007
MTJax, thanks for the info, even though I couldn't see the images.

I hope it doesn't develop. I don't want to even think about any storm hitting South Florida. The economy and Real Estate down here wouldn't be able to handle it right now.
577. H2PV
10:21 PM GMT on August 17, 2007
Posted By: StormJunkie at 9:35 PM GMT on August 17, 2007.
Easy with the pics y'all, the blog is busy...

We have 6 images in 50 comments...And 50 comments are flying by like every 15 minutes or so...


Just want the blog to be useful even for those with a slower connection. No offense, I like the pics myself. But I know not everyone is on cable...


When I first logged on after Charlie '04 I didn't know where to go to find pictures, which applies to lots here now. Having the pictures helped and sometimes was a real head's up about something has changed.

Most of those 50 comments are empty of content, and the blog would be better without them in the first place.

I used dial-up from '04 to early '07 because I was in a canyon shadow with no cable, no DSL, no wireless net, no net-over-powerlines and no satellite dish possible. Despite that I made my personal archives of satellite pictures on dialup and collected 80,000 images in '06.

Neither is it useful to post each half-hourly updated picture, than it is to argue about a wobble on the last picture. Hurricanes don't usually change much in an hour.

That said, SEPAT went from 100 knots to 130 knots in between one 6-hour period, and Wilma did it even faster. Still it was three hours for Wilma to jump from Cat-1 to Cat-4, and half-hourly pictures would not have added much useful details.

NHC hires the best. If you (any one of you) are better, then they will offer you a job at high salary. If you are not better, then your written comments adds nothing much to their 3-hour advisories. It's not often that anybody here beats them to the punch by half an hour, and that's only because they have to be more certain when they speak than the gamblers here who are not held responsible for their bad predictions made recklessly.

IVAN was pointed straight down New Orleans throat for a time, and the national discussion was what would a direct hit on NOLA mean. Everything they said was found true one year later. RITA was aimed right on Houston's bullseye and the national discussion was on what that would mean -- we may find out how true that was come early next week.

The fact is, the NHC was wrong on IVAN, wrong on RITA, and nobody here was any better that far out. The anxiety brings out a need for information, and for some/many it brings out a need to make up information. At least the images are not made up, they are real for whatever they are worth.

I pay webhosting for images I post -- I don't link to sources, but copy them. If everybody had to pay for the pictures they post, there would be fewer of them, but that goes for text messages too.



Member Since: Posts: Comments:
576. pt100
10:19 PM GMT op 17 Augustus, 2007
a bit windy and rainy in St Croix Link
Member Since: Posts: Comments:
575. JLPR
10:22 PM GMT on Agosto 17, 2007
yeah look at the probabilities of something forming is very high off the coast of Africa
its orange!!!
Link
Member Since: Posts: Comments:
574. retaining1
10:05 PM GMT on August 17, 2007
Good things to prepare for if you choose to stay:
1) No stores, grocery or otherwise, will be open for perhaps several weeks after the storm. If you don't have your own food supplies stocked up, then don't stay.
2) Gas stations will be shut down for at least a week after the hurricane before the first ones start re-opening. If you have a generator that uses 5-10 gallons of gas a day... you better buy two 42 gallon barrels of gasoline and a hand pump now. After the storm, gasoline is currency.
3) The first several nights after the hurricane can be worse than the storm itself (Rita & Katrina). Neighborhoods are dark, police are busy elsewhere, alarms aren't working... We used six tiki torches to light up our yard at nights. It helps the bad guys know that someone is home, so they move on to easier pickings elsewhere. If you aren't prepared for four days of chaos and partial lawlessness... then don't stay.
4) Keep your credit card handy. Many places that still had gas, suprisingly, only took credit... no cash. There were people walking around offering cash for others to buy gas for them on charge cards.
5) Volunteer. There will be plenty of help needed, it kills time and helps you to meet all of the policemen, paramedics, electricians and tree service people. In one day of volunteering, you can hear all the straight news about which neighborhoods are next to have electricity, what the police are doing... all the useful news. It also helps people know who you are in case YOU have a problem.
Member Since: Posts: Comments:
572. JLPR
10:20 PM GMT on Agosto 17, 2007
a lil cloudy but there is no wind is very still
so still its creapy lol
the winds have died down since 5pm here
Member Since: Posts: Comments:
571. bekroweather
10:16 PM GMT on August 17, 2007
Rita evacuation was a joke. Took me 21 hours to Dallas. Of course Houstonians are also partially to blame, since many of us that did not have to evacuate, did so. Post-Katrina panic.

I still cant believe that there was no notion of contraflow on the highways in TX in case of an evacuation for a city like Houston. At least now this has changed.
Member Since: Posts: Comments:
570. Metallica1990
10:18 PM GMT on August 17, 2007
wow that would be very bad for ALL LA not just NO
Member Since: Posts: Comments:
569. bayoubrotha
10:11 PM GMT on August 17, 2007
The eye of Katrina came within 40 miles east of New Orleans, not 150 miles.

Member Since: Posts: Comments:
568. alpha992000
10:17 PM GMT on August 17, 2007
JLPR, how's it doing near you? In here (Rio Piedras) it's been quite cloudy and gusty since midday. I say about 20mph.
Member Since: Posts: Comments:
567. MTJax
10:17 PM GMT on August 17, 2007
For those in FL that are worried about Dean, you should be also watching the system behind Dean. I see some models sending that storm into south FL.

hit the play button and watch

link
Member Since: Posts: Comments:
566. WPBHurricane05
6:16 PM EDT on August 17, 2007
Not sure what GFDL you looked at. Heres the latest one Link

Looks more like a cat 4.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
565. Biloxigal
10:14 PM GMT on August 17, 2007
I've stayed for every hurricane that hit the MS Coast - including Camille and Katrina. But after Katrina - I will never stay again. Please Please if you are in the eye of a strong storm - live. There's no reason to stay. We were lucky, but they did find a body in the water behind my house! And one in my brother's yard in a tree. In LA, MS and AL - we have so many dead and sick trees - anywhere near us will be HORRIBLE!
Member Since: Posts: Comments:
564. MichaelSTL
5:16 PM CDT on August 17, 2007
thats a huge swath how strong would it be at landfall in LA

GFDL has it at 148 kts...

Member Since: Posts: Comments:
563. PalmyraPunishment
10:15 PM GMT on August 17, 2007
GFDL has it looking like a cat 1 on landfall with Louisana... I find that hard to believe..
Member Since: Posts: Comments:
562. CFL
10:13 PM GMT on August 17, 2007
yes JPLR. some models are hinting at developement and the cyclone genesis probailities are pretty high in the area
Member Since: Posts: Comments:
561. seminolesfan
10:13 PM GMT on August 17, 2007
Adjusted t# is at 5.0

Raw is 6.3
Member Since: Posts: Comments:
560. JFLORIDA
10:12 PM GMT on August 17, 2007
I hope this is like top story all over the western gulf states. There are too many people living on the water.

What a mess, I didn't realize the Rita evacuation went so wrong, they should have done it again and again till they got it right.
Member Since: Posts: Comments:
559. weathersp
6:08 PM EDT on August 17, 2007
Posted By: bayoubrotha at 6:07 PM EDT on August 17, 2007.

if GFDL is correct ....bye bye NOLA

The GFDL 12z has Dean coming ashore 150 miles west of New Orleans.


Worst Case Scenario for NOLA..for any hurricane.. this might be 200 years in the future..

Right front quadrant has the strongest winds and pushes all that water into lake Pontchartrain which does not have an exit so the water stays in there and keeps going up then something has to fail because of the pressure on anything natural is stronger than anything man made so that would be the levees in NOLA then what happens 28ft surge swamps NO along with the water in the lake which is 10 ft before it gets to the line of natural ground then you have 38ft of water in NOLA. The highest point in the French Quarter is 36ft or something (?). Then the rainfall from the hurricane makes the Mississippi swell and over tops the levees on the other side..

THAT'S WHY A CAT 5 LANDING WEST OF NOLA IS BAD!!
Member Since: January 14, 2007 Posts: 17 Comments: 4140
558. hu2007
10:14 PM GMT on August 17, 2007
Link imppresive eye!!! just south of saint croix radar loop
Member Since: Posts: Comments:
557. WPBHurricane05
6:14 PM EDT on August 17, 2007
The GFDL has Dean moving slower than the other models which is one of the reasons it has it curving north.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
556. wederwatcher555
10:13 PM GMT on August 17, 2007
wow the gfs has turned into an outlier lol. it takes dean WAY south..south mexico
Member Since: Posts: Comments:
555. StuccoMan
5:10 PM CDT on August 17, 2007
Posted By: WatchingInHouston at 5:10 PM CDT on August 17, 2007.
TxKiwi - I put together an animated GIF of the forecast history... here's the link:

Link

what a loser...You stole that from NHC and claimed as yours.Click

Here is NHC Link
Member Since: Posts: Comments:
554. Baybuddy
10:10 PM GMT on August 17, 2007
Ya know...two days ago, the East Coast folks were arguing with the fish storm people.
Member Since: Posts: Comments:
553. ajcamsmom
5:09 PM CDT on August 17, 2007
I agree with Biloxigal...Having lost everything of any value to me in Katrina...I will run if this thing looks like it will come anywhere near me
Member Since: Posts: Comments:
552. JLPR
10:10 PM GMT on Agosto 17, 2007
thats some heavy convection 35W eastward
could something popup from this?
Central Atlantic
Member Since: Posts: Comments:
551. Metallica1990
10:08 PM GMT on August 17, 2007
thats a huge swath how strong would it be at landfall in LA
Member Since: Posts: Comments:
550. miken62
10:08 PM GMT on August 17, 2007
150 miles west of NOLA...would still be very bad......especially if he's large in size and covers a lot of real estate....Katrina caused incredible damage well over 150 miles from the eye....best to be cautious....
Member Since: Posts: Comments:
548. sngalla
6:09 PM EDT on August 17, 2007
Channel 10 said that Max will be back later to talk about the possible impact on South Florida, if any.
Member Since: Posts: Comments:
547. MichaelSTL
5:08 PM CDT on August 17, 2007
Bottom line: the effect of the storm will reach out and touch a large junk of the GOM states.

True; if (God forbid) the GFDL is correct, effects will be felt across a VERY large area and VERY far inland (this also only shows the windswath through the end of the run):



Hurricane warnings for Oklahoma and Arkansas? That is about 600 miles across with a 300 mile hurricane windfield...
Member Since: Posts: Comments:
546. fatcat475
10:09 PM GMT on August 17, 2007
weathersp i agree with you maybe even a little more to the east
thanks fatcat
Member Since: Posts: Comments:
545. SWFLdrob
10:07 PM GMT on August 17, 2007
Dean has really gotten his act together in the last couple of hours. IR picture looks frightening
Member Since: Posts: Comments:
544. Keys99
10:05 PM GMT on August 17, 2007
Max Mayfield was just on. he pointed out that the gfdl is still the out liyer but has not been discounted as of yet since it preformed best on average over the years. Shows a more northern track. just have to wait and see all up to the ULL
Member Since: Posts: Comments:
543. bayoubrotha
10:05 PM GMT on August 17, 2007
if GFDL is correct ....bye bye NOLA

The GFDL 12z has Dean coming ashore 150 miles west of New Orleans.
Member Since: Posts: Comments:
542. Crisis57
10:06 PM GMT on August 17, 2007
WOW DEAN!!!
wow
Member Since: Posts: Comments:
541. finnadat
10:04 PM GMT on August 17, 2007
steelmagnolia44 - it is more about the clean or dirty side - the left side of the cone is better than the right side. You have to watch out if the cone is on or near you, but depending on intensity and if you end up on the left hand side you can get not much more than some wind..
Member Since: Posts: Comments:
540. castnblast
9:52 PM GMT on August 17, 2007
HERE'S MY PREDICTION: 100% CHANCE OF GAS PRICES GOING THROUGH THE ROOF...Gas here in Corpus Christi went up .20 just today. !@#@$%2! !#@$!$% !#%@%....o.k...I've vented...

Seriously, as I have been saying, and still say...Morgan City LA down to Brownsville is my best guess...This is not a wish cast. My wish cast is a direct hit between Baffin and CC Bay...That will put me in the eye...I just gotta see this phenomena at some point in my life...
Member Since: Posts: Comments:
539. weatherboyfsu
10:04 PM GMT on August 17, 2007
I just looked at the infrared of Dean........

Dean is one bad boy..........

IN my opinion, he has obtained cat 3 status and is approaching cat 4.......I am out of here until tomorrow..........see ya......
Member Since: Posts: Comments:
538. TXKiwi
10:02 PM GMT on August 17, 2007
finnadat

That said, nobody will have a clue for another 48 hours and if it does hit south of Galveston/Houston we'll still get some significant bands, but if it is south of corpus or east of beaumont houston will be fine.

And where did Erin make landfall, and what level of rain and flooding did it bring? I don't think you can say that if Dean is 30 miles west of where Erin made landfall (i.e. South of Corpus) then Houston will be fine. Unless you can predict, 6-7 days out, the rain bands and intensity from a Hurricane within a given radius?
Member Since: Posts: Comments:
537. ThadBeier
10:02 PM GMT on August 17, 2007
My wife is planning to fly into Houston on Saturday the 18th and fly out the 19th for my sister-in-law's kids' baptisms. It appears that this should be OK, I can't think that there would be any issues before Monday -- but am I being naive?

Thanks for all the comments, it's very interesting!
Member Since: Posts: Comments:
536. Crisis57
10:04 PM GMT on August 17, 2007
Posted By: sngalla at 10:04 PM GMT on August 17, 2007.

Max Mayfield on channel 10 just said for the last 3 years that the GFDL model has been the most accurate. The ULL not moving as predicted is one reason for this being the most outlier of the models.


Glad to know Max saw it and i'm not going blind that the ULL hasn't moved since this morning
Member Since: Posts: Comments:
535. miken62
10:04 PM GMT on August 17, 2007
if GFDL is correct ....bye bye NOLA
Member Since: Posts: Comments:

Viewing: 585 - 535

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71Blog Index

Top of Page

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.

Local Weather

Overcast
54 °F
Overcast