Dr. Jeff Masters' WunderBlog

Which model do you trust? And, Arctic sea ice reaches a record minimum
Posted by: Dr. Jeff Masters, 17. elokuuta 2007 klo 19:33 (GMT) +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
Categories: Climate Change
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751. nrtiwlnvragn 17. elokuuta 2007 klo 23:21 (GMT)    
Short term on radar looks moving due west

Link
Member Since: 23.09.2005 Posts: 11 Comments: 8922
752. HurricaneJoe 17. elokuuta 2007 klo 23:21 (GMT)    
any ideas on if dean will hit LA?
753. ezziboo 17. elokuuta 2007 klo 23:21 (GMT)    
Just saw the link about the Louisiana governor declaring a state of emergency....which means that, because I'm employed by a Louisiana social service agency, I have to pack a bag and wait to be called out to man a shelter...even if the storm would be headed straight for my area...not fun.
Member Since: 8.06.2006 Posts: 0 Comments: 0
754. wederwatcher555 17. elokuuta 2007 klo 23:21 (GMT)    
on the 18z run the GFS has become an outlier
755. nawlinsdude 17. elokuuta 2007 klo 23:21 (GMT)    
WOW She did. I thought that was a joke. Unbelievable
756. silverstripes 17. elokuuta 2007 klo 23:22 (GMT)    
SJ,

I know I recently allowed the auto update of Java to occur and I think that coincides with the problems I was having with it loading properly.
Member Since: 26.07.2006 Posts: 5 Comments: 594
758. Pachanga 17. elokuuta 2007 klo 23:22 (GMT)    
Governor declares state of emergency

To me that’s just another example of her incompetence. IMO, it's way too early to declare such an emergency, just think of the panic this will cause those who went through Rita and Katrina. I wouldn’t be surprised if this state of emergency declaration doesn’t cause someone to literally be scared to death before Dean even entered the GOM.
759. Xion 17. elokuuta 2007 klo 23:22 (GMT)    
Wow.

The ADT's latest estimate absolutely plummeted (rose in intensity) in T#, especially when lookin at the graph HERE.

It estimates wind speeds of 117 knots. That would make it a Cat 4.
Member Since: 29.08.2006 Posts: 0 Comments: 726
760. icepilot 17. elokuuta 2007 klo 23:23 (GMT)    
Re:Arctic sea ice shrinks to record low

The loss of so much summer sea ice is very frightening. What’s really amazing is the sat picture which apparently shows open water in McClure Strait, between Banks Island and Melville Island,

I was aboard the USCGC Polar Sea which transited the NW passage above Canada in the summer of 1985.
We had to go through the Prince of Wales Strait, East of Banks Island because McClure Strait was packed with a jumble of multi year ice – we tried McClure Strait but could make no headway through the thick rubble of multi yr ice. This is significant as I had personally seen the Polar Sea transit 5-6 ft thick Ice at 10 Kts and had personally driven through ridges of ice up to 100 ft (measured) thick (albeit - there was some open water on the other side, so the ice had somewhere to move to which helped it break) The ship, Polar Sea, is a Polar Class Icebreaker and is one of the 2 most powerful non-nuclear Icebreakers in the world. Her sister ship Polar Star is the other - 13000 tons, 399 feet long and 60,000+ HP – 75k Hp in short bursts)

If the world’s glaciers are keeping pace (and it seems they are) we could see the ocean levels rise faster than anyone has yet predicted. While the melting sea ice won’t affect sea levels - think of ice in a glass of water, as the ice melts the water level stays the same – the added fresh water and lack of cooling effect will effect water circulation, and the reduction in the reflection of the sun’s energy just adds to the equation. Melting ice cover on Greenland and Antarctica are sure to follow.


I have watched Arctic sea ice conditions since the early 80’s. I have 6 yrs of service on Polar Icebreakers and 6 years doing Oceano data collection and tracking Icebergs in the North Atlantic for the International Ice Patrol. My career as a Oceano tech spans 20 yrs. And this scares the *&^% out of me.

Member Since: 9.07.2005 Posts: 0 Comments: 379
761. snowboy 17. elokuuta 2007 klo 23:23 (GMT)    
with the pinhole eye, Dean is at least Cat4 by now..
Member Since: 21.09.2005 Posts: 10 Comments: 2546
762. Baybuddy 17. elokuuta 2007 klo 23:23 (GMT)    
Hurricanes are like Police Chases on t.v. all of the media cover it, everyone watches and then expresses shock that someone actually got killed.
Member Since: 26.06.2006 Posts: 0 Comments: 1115
763. DonnaGalveston 17. elokuuta 2007 klo 23:24 (GMT)    
Our neighborhood home owners association has scheduled an emergency meeting on Sunday afternoon to discuss Dean.
764. StormJunkie 17. elokuuta 2007 klo 23:24 (GMT)    
Well this kept telling me that I had "virtual machines running too many instances of java"...

I have known of a memory problem with Java for sometime and have a link that will help fix it. I'll post that when I get off this dang laptop!
Member Since: 17.08.2005 Posts: 26 Comments: 15218
765. Metallica1990 17. elokuuta 2007 klo 23:26 (GMT)    
anyone wanna take a guess at how wide the eye is?
766. cirrocumulus 17. elokuuta 2007 klo 23:26 (GMT)    
icepilot: And there you have it: The huge air conditioner Dean is about to work overtime on the melting ice.
Member Since: 30.09.2005 Posts: 0 Comments: 1606
767. wederwatcher555 17. elokuuta 2007 klo 23:26 (GMT)    
the 18z gfs is crazy. it has dean going completely west and then turning sw instead of nw like the other models
768. DonnaGalveston 17. elokuuta 2007 klo 23:26 (GMT)    
I am going to go try to relax a bit. When will there be another update? I need to follow this very closely.
769. Baybuddy 17. elokuuta 2007 klo 23:27 (GMT)    
This placehas actually slowed down. I thought it crashed for a sec...
Member Since: 26.06.2006 Posts: 0 Comments: 1115
770. Metallica1990 17. elokuuta 2007 klo 23:27 (GMT)    
next update will be within the hour
771. bekroweather 17. elokuuta 2007 klo 23:27 (GMT)    
Is there a link for the 18Z GFDL? Is it out?
772. DonnaGalveston 17. elokuuta 2007 klo 23:28 (GMT)    
Thank you Metallica1990, I will stay around until it comes in. This has made me a very nervous person. My husband is a doctor, so I believe if we evacuate we may be able to get back into town easier should the storm hit.
773. cirrocumulus 17. elokuuta 2007 klo 23:29 (GMT)    
I'm still sticking with a Texas landfall even though the GFS is still in Mexico. I think Dean will catch a little more of the ULL at the huge forward momentum of 22mph and it tilted farther north on a jog earlier today.
Member Since: 30.09.2005 Posts: 0 Comments: 1606
774. BigToe 17. elokuuta 2007 klo 23:29 (GMT)    
Nice Link water vapor loop. shows the ull e of Fl. Just toggle back & forth.
Member Since: 12.06.2006 Posts: 0 Comments: 239
775. tristanh72 17. elokuuta 2007 klo 23:30 (GMT)    
I am going to go try to relax a bit. When will there be another update? I need to follow this very closely.

A very good idea on both counts. Mentally prepare, relax, nothing you can do about it anyways. Someone else can tell you the model times, keep an eye on them, that's all we can do.
Member Since: 16.07.2007 Posts: 0 Comments: 82
776. gatagus07 17. elokuuta 2007 klo 23:30 (GMT)    
Just as I thought....even the GFDL is joining the crowd.....Mexico/Texas border is your landfall....
777. Metallica1990 17. elokuuta 2007 klo 23:30 (GMT)    
np and best of luck to you
778. Neponset 17. elokuuta 2007 klo 23:30 (GMT)    
I live in Charleston S.C, and do not have a dog in this fight, but I take this stuff very seriously. We are in sort of a holding pattern as we watch this storm progress and I think there is a little space for the periphials of living with storms. I evacuated for Hugo and lived/worked thru the aftermath. Some one earlier mentioned differiculty of returning to their homes after an evacuation - this can be a real problem. The folks who had homes on the barrior islands were not permitted to return for repair work/salvage of stuff for many weeks. My refuge for Hugo was 75-100 miles inland and we got hammered - need to go inland and to left of anticipated path.
779. Metallica1990 17. elokuuta 2007 klo 23:30 (GMT)    
anyone wanna take a guess at how wide the eye is?
780. medicroc 17. elokuuta 2007 klo 23:31 (GMT)    
Hurricanes are like Police Chases on t.v. all of the media cover it, everyone watches and then expresses shock that someone actually got killed
I vote this as one of the greatest analogies of all time
Member Since: 14.09.2005 Posts: 0 Comments: 452
781. JLPR 17. elokuuta 2007 klo 23:31 (GMT)    
well i see a cloud comming from the east here in carolina PR and the wind has picked up a lil bit
Member Since: 4.09.2007 Posts: 36 Comments: 5223
782. JRRP 17. elokuuta 2007 klo 23:31 (GMT)    
This afternoon here in Santo Domingo
we had winds from NE 45K-50Km/h
Member Since: 16.08.2007 Posts: 0 Comments: 4304
783. WPBHurricane05 17. elokuuta 2007 klo 23:31 (GMT)    
Just as I thought....even the GFDL is joining the crowd.....Mexico/Texas border is your landfall....

Link? The GFDL I'm looking at has it in Louisiana.
Member Since: 31.07.2006 Posts: 55 Comments: 7897
784. Patchmedic 17. elokuuta 2007 klo 23:31 (GMT)    
Donna is your husband on a DMAT team?
785. Baybuddy 17. elokuuta 2007 klo 23:31 (GMT)    
Donna always err on the side of caution. If you are full of nervous energy, you can get all of your important documents and prepare them to travel. I feel tupperware works well. Also, if you have any valuables in a safe deposit at a bank close to the coast, I would pull it.
Member Since: 26.06.2006 Posts: 0 Comments: 1115
786. icepilot 17. elokuuta 2007 klo 23:32 (GMT)    
Cirro,
unfortunatly Hurricanes are considered small, locallized weather patterns/events in world weather.

but not really to me- grin - I live in Fl
Member Since: 9.07.2005 Posts: 0 Comments: 379
787. IMA 17. elokuuta 2007 klo 23:32 (GMT)    
Well, we're northwest of San Antonio, in the Hill Country, and we had to evacuate our house last night. We did not flood, thank God; however, we lost yards and yards of bank & the bridge we share with about 6 other homes, the only way we have in and out, was destroyed. We are packing up all keepsakes this weekend and will get them to San Antonio, just in case.

That said, there's a difference between being smart/prepared & being an alarmist. I can not freakin' believe that the gov. of LA already declared a state of emergency. As someone else said, it could scare someone to death. Conversely, if Dean comes nowhere close, it could very well lead to complacency with the next one. It's just irresponsible and obviously just a way for her to be able to say, "...but I TOLD you!" if it does hit. Disgusting.
Member Since: 8.07.2005 Posts: 22 Comments: 1261
788. wederwatcher555 17. elokuuta 2007 klo 23:33 (GMT)    
new gfdl looks like its back to galveston
789. presslord 17. elokuuta 2007 klo 23:33 (GMT)    
amen Neponset...I live on Johns Island...evaced to Manning....90 mins north...bad move....it was still awful
Member Since: 13.08.2007 Posts: 0 Comments: 10377
790. sngalla 17. elokuuta 2007 klo 23:33 (GMT)    
The GFDL has gone back to the left. Link
Member Since: 18.02.2003 Posts: 57 Comments: 5363
791. StuccoMan 17. elokuuta 2007 klo 23:33 (GMT)    
Posted By: gatagus07 at 6:30 PM CDT on August 17, 2007.
Just as I thought....even the GFDL is joining the crowd.....Mexico/Texas border is your landfall

Thats a pretty reckless comment considering the 18z puts it further east.


http://euler.atmos.colostate.edu/~vigh/guidance/northatlantic/track_early1.png
792. CosmicEvents 17. elokuuta 2007 klo 23:33 (GMT)    
Posted By: DonnaGalveston at 11:24 PM GMT on August 17, 2007.

Our neighborhood home owners association has scheduled an emergency meeting on Sunday afternoon to discuss Dean.
Hi Donna......My sister lived in Galveston for 10 years...nice place.
I would strongly advise that you listen to your local emergency management, and watch the storm track closely yourself, using NHC and this site....to make your evacuation decision. Don't rely on your homeowner's association meeting in 2 days in considering when and where to evacuate. If it was me I'd be packing, waiting and watching. Best of luck to you and yours.
Member Since: 3.08.2005 Posts: 10 Comments: 5098
793. iahishome 17. elokuuta 2007 klo 23:33 (GMT)    
It's good if Dean peaks too early right?

It's very rare that storms stay cat 5 for days right?

Scary Dean
Member Since: 24.07.2005 Posts: 5 Comments: 499
794. bekroweather 17. elokuuta 2007 klo 23:34 (GMT)    
18Z GFDL solution moved to a landfall north of Corpus Cristi, close to Matagorda in 4.5 days.
795. tampahurricane 17. elokuuta 2007 klo 23:33 (GMT)    
the only way it would turn north is if the ULL erodes at the high which could happen.
Member Since: 28.05.2007 Posts: 0 Comments: 287
796. ForecasterColby 17. elokuuta 2007 klo 23:34 (GMT)    
Let me emphasize again - Dean's eye is not pinhole. A pinhole is a stable eye that's only ~5-6 miles in diameter (Wilma's got as small as 2). Dean's eye, per the 5PM, is 15nm wide.
797. JLPR 17. elokuuta 2007 klo 23:35 (GMT)    
Luiz Munoz International Airport
Lat: 18.43 N Lon: 66 W Elev: 9 ft
Last Update on Aug 17, 6:56 pm AST


Partly Cloudy and Breezy

82°F
(28°C) Humidity: 79 %
Wind Speed: E 21 G 25 MPH
Barometer: 29.91"
Dewpoint: 75°F (24°C)
Heat Index: 89°F (32°C)
Visibility: 10.00 mi.
More Local Wx: 2 Day History:


Soon i should get some TS gusts
Member Since: 4.09.2007 Posts: 36 Comments: 5223
798. littlefish 17. elokuuta 2007 klo 23:35 (GMT)    
IMA- after Katrina, the earlier the better in trying to organize for a mass evacuation if you ask me. If youy only get 2 days to plan and you are not extremely organized, it'd be tough to evacuate high population areas (remember the Houston mess with people running out of gas, etc on the freeways?). Better to be saf As the saying goes... but ya it seems early.
800. Daveg 17. elokuuta 2007 klo 23:35 (GMT)    
Crossing 15N 65W right exactly where the NHC said it would. So far the NHC track is a good one, but we've got a long way to go.
Member Since: 23.09.2005 Posts: 0 Comments: 426
801. Metallica1990 17. elokuuta 2007 klo 23:35 (GMT)    
Link

to answer your question about how long cat 5s can last

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About JeffMasters
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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