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)

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

Categories: Climate Change

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901. WPBHurricane05 17. elokuuta 2007 klo 23:55 (GMT)
VORTEX DATA MESSAGE AL042007 A. 17/17:17:00Z B. 14 deg 46 min N 063 deg 16 min W C. NA mb 2763 m D. 110 kt (surface wind) E. 011 deg 010 nm F. 107 deg 124 kt G. 011 deg 011 nm H. 966 mb I. 7 C/ 3046 m J. 19 C/ 3040 m K. 9 C/ NA L. CLOSED WALL M. C17 (eye is 17 miles large) N. 12345/7 O. 0.02 / 2 nm P. AF304 0404A DEAN OB 28 MAX FL WIND 124 KT N QUAD 17:13:30 Z Member Since: 31.07.2006 Posts: 56 Comments: 7930

902. Crazman 17. elokuuta 2007 klo 23:55 (GMT)
LMAO Stormkats Hurricane warning office. More like his moms living room... Member Since: 3.08.2006 Posts: 0 Comments: 32

903. KYhomeboy 17. elokuuta 2007 klo 23:56 (GMT)
JF... i know what you mean. I am doing the same thing....PRAYING for a nice big northward or westward jog...so that it wont make landfall here like its scheduled too!

904. Tropicnerd13 17. elokuuta 2007 klo 23:56 (GMT)
hi guys. i just finished making a cone of uncertainty. no, it is not a wishcaster cone, but i feel as though if that ULL goes slow enough, dean will go more north than most of the models are predicting right now. and i am not a wish caster. i just feel that this may be a possible storm track. the black bands represent a day. the thick colorful bands represent the possible storm location and strength. you ought to be able to figure out what the strength means. and please dont jump me for making it. i just feel as though dean will rapidly intensify soon.

905. littlefish 17. elokuuta 2007 klo 23:56 (GMT)
The GFDL is fine and dandy, but I still don't see that ULL moving much. Am I wrong?

906. StormJunkie 17. elokuuta 2007 klo 23:56 (GMT)
Also great MIMIC of Dean starting to clear out the eye and intensify. Posted By: Fl30258713 at 11:47 PM GMT on August 17, 2007. The UKMET 18Z moved to the track for GFDL 12Z Not sure where you get that... The 18z Ukmet only goes out 48hrs on the FSU site. Have to wait for WU to update the Ukmet to see what it says... Member Since: 17.08.2005 Posts: 26 Comments: 15218

907. Tropicnerd13 17. elokuuta 2007 klo 23:57 (GMT)
omg lmao on visible sattelite erin looks like a cat 3!

909. Dropsonde 17. elokuuta 2007 klo 23:57 (GMT)
Thanks SJ. Fan of your site BTW, very helpful to me to find all my tropical info after my hard drive crashed a few months ago and I hadn't backed up my bookmarks. It just struck me how dead on the model was, based on what the HH seem to be finding. Member Since: 22.08.2006 Posts: 10 Comments: 414

910. Crisis57 17. elokuuta 2007 klo 23:58 (GMT)
Posted By: littlefish at 11:56 PM GMT on August 17, 2007. The GFDL is fine and dandy, but I still don't see that ULL moving much. Am I wrong? i see it to

911. tallahasseecyclone 17. elokuuta 2007 klo 23:58 (GMT)
Does anyone know what percentage of hurricanes turn north vs south after passing over or near the yucatan?

912. weatherguru 17. elokuuta 2007 klo 23:58 (GMT)
anything could happen i'm going to keep watching til it makes landfall

913. Tazmanian 17. elokuuta 2007 klo 23:59 (GMT)
this is old 05 VORTEX DATA MESSAGE AL042007 A. 17/17:17:00Z B. 14 deg 46 min N 063 deg 16 min W C. NA mb 2763 m D. 110 kt (surface wind) E. 011 deg 010 nm F. 107 deg 124 kt G. 011 deg 011 nm H. 966 mb I. 7 C/ 3046 m J. 19 C/ 3040 m K. 9 C/ NA L. CLOSED WALL M. C17 (eye is 17 miles large) N. 12345/7 O. 0.02 / 2 nm P. AF304 0404A DEAN OB 28 MAX FL WIND 124 KT N QUAD 17:13:30 Z Member Since: 21.05.2006 Posts: 5088 Comments: 111361

915. Fl30258713 17. elokuuta 2007 klo 23:59 (GMT)
Posted By: OUFan919 at 11:53 PM GMT on August 17, 2007. I have a question: It looks like there is an upper level low about 1000 miles little NNE of Dean and it is moving at a pretty good clip, possibly faster than Dean. Anybody think that if the ULL entering Florida right now weakens and this low replaces it when Dean is over the Western Caribbean that this will draw Dean farther North?? Look at it here. http://www.goes.noaa.gov/HURRLOOPS/huirloop.html Yep, that idea hasbeen discussed several times in the last couple of days. Still waiting and watching to see how they will interact with each other. Member Since: 24.07.2006 Posts: 1 Comments: 976

916. zingocat 18. elokuuta 2007 klo 00:00 (GMT)
Where's the update? Member Since: 15.07.2007 Posts: 0 Comments: 170

918. Dan187 18. elokuuta 2007 klo 00:00 (GMT)
000 URNT12 KNHC 172356 VORTEX DATA MESSAGE AL042007 A. 17/23:32:00Z B. 14 deg 52 min N 065 deg 02 min W C. NA mb 2632 m D. 119 kt E. 302 deg 006 nm F. 048 deg 130 kt G. 309 deg 010 nm H. 946 mb I. 8 C/ 3045 m J. 18 C/ 3045 m K. 13 C/ NA L. CLOSED M. 16 N. 12345/7 O. 0.02 / 2 nm P. AF302 0504A DEAN OB 03 MAX FL WIND 130 KT NW QUAD 23:29:00

919. KEEPEROFTHEGATE (Mod) 18. elokuuta 2007 klo 00:00 (GMT)
track mark 15,66 C4/H/D 15.2,67 16.1,72 C4/H/D 16.6,75 17.2,77 C5/H/D 17.3,79 18,81 C4/H/D 19,82 21,85 STOP...... Member Since: 15.07.2006 Posts: 144 Comments: 40670

920. ClearH2OFla 18. elokuuta 2007 klo 00:00 (GMT)
Little fish you are right i have been watching it all day not moving to much at all. Dean appears to move moving faster

921. Metallica1990 18. elokuuta 2007 klo 00:00 (GMT)
Posted By: zingocat at 12:00 AM GMT on August 18, 2007. Where's the update? there waiting on the HH

922. AnthonyJKenn 18. elokuuta 2007 klo 00:00 (GMT)
Oh..and this just in: The models have all shifted south again: even the doomsday GDFL now has landfall near Galveston-Houston rather than Morgan City/Vermilion Bay. And as for Stormkat, who always seems to want any storm in the Gulf to hit Louisiana, even when they don't (Rita, Emily, Wilma): You may have lucked out on Katrina's ultimate path, but I'd no more trust you than I would a finger in the wind. Trofs usually don't make it that far south these days to turn a system that rapidly, and the path of least resistance is still more to South Texas and Mexico, not Louisiana. We'll see what happens, but I'll roll with the experts on this one, thank you very much. Anthony Member Since: 20.09.2005 Posts: 0 Comments: 187

924. Skyepony (Mod) 18. elokuuta 2007 klo 00:01 (GMT)
That vortex message is 6 hrs old Member Since: 10.08.2005 Posts: 144 Comments: 29376

926. drusierDMD 18. elokuuta 2007 klo 00:01 (GMT)
tropic i like it good job

927. Crazman 18. elokuuta 2007 klo 00:01 (GMT)
edit reposted from other blogger Member Since: 3.08.2006 Posts: 0 Comments: 32

928. Wundermobay 18. elokuuta 2007 klo 00:01 (GMT)
Dean Cat.4

929. Tropicnerd13 18. elokuuta 2007 klo 00:01 (GMT)
we have a cat 4 dean

930. seflagamma 18. elokuuta 2007 klo 00:01 (GMT)
info just in now a Cat 4, got it from TWC. Member Since: 29.08.2005 Posts: 286 Comments: 40485

931. hahaguy 18. elokuuta 2007 klo 00:01 (GMT)
dean 130 Member Since: 12.08.2007 Posts: 2 Comments: 2838

932. cirrocumulus 18. elokuuta 2007 klo 00:02 (GMT)
One statistic I found fascinating was that of the previous ten wettest Julys on record in Texas, six had major hurricanes hit the Texas Gulf Coast the same year. Texas had one of the wettest Julys ever this year. Member Since: 30.09.2005 Posts: 0 Comments: 1606

933. calder 18. elokuuta 2007 klo 00:01 (GMT)
dean cat 4 Member Since: 26.07.2006 Posts: 0 Comments: 412

934. Crisis57 18. elokuuta 2007 klo 00:02 (GMT)
Posted By: ClearH2OFla at 12:00 AM GMT on August 18, 2007. Little fish you are right i have been watching it all day not moving to much at all. Dean appears to move moving faster it moved this mornign then after stopped and hasn't really moved after

935. OUFan919 18. elokuuta 2007 klo 00:02 (GMT)
AT LEAST 130mph winds 946mb pressure Category 4 Member Since: 31.07.2007 Posts: 0 Comments: 329

936. samspade 18. elokuuta 2007 klo 00:02 (GMT)
Newbie posting/not an expert - not in Houston area, but used to live there and have family there. This latest GFDL run is not headed for Houston, but rather just east of Matagorda Bay about 50-100 miles from Galveston. Kind of reminds me of where Carla hit. Wouldn't be too bad for Galveston/Freeport, though they'd probably still get Cat 1/2 force storm surge etc, since they'd be on the bad side of the storm. Actually, in the scheme of things, that's not the worst place for it to hit. Matagorda Bay is sparsely populated, with the exception of Victoria (~50,000) which is about 50 miles off the coast. The only better place for it to hit to keep loss of life/property down is the King Ranch/Kenedy County in between Brownsville and Corpus Christi where the cows live. Hitting Central America/Mexico would be terrible for loss of life - worse than the US. Terrible to hear someone say that.

937. NASA101 18. elokuuta 2007 klo 00:02 (GMT)
Officially a CAT 4 now!! Member Since: 16.08.2007 Posts: 0 Comments: 276

938. adrianalynne 18. elokuuta 2007 klo 00:02 (GMT)
Florida seems to be out of the woods Member Since: 7.08.2006 Posts: 0 Comments: 134

939. Melagoo 18. elokuuta 2007 klo 00:02 (GMT)
Charleston TV said... hits Mexico oh well... guess what.. we are going to pay for those illegals anyway.. I always find it hidious when you think back a few hundred years and how we took everything from the native people and pretty much slaughtered them ... they lived here for 1,000s of years. Member Since: 31.07.2006 Posts: 19 Comments: 1510

940. Metallica1990 18. elokuuta 2007 klo 00:03 (GMT)
CAT 4 I was close with the pressure :)

941. sngalla 18. elokuuta 2007 klo 00:03 (GMT)
NHC 8pm AT 800 PM AST...0000Z...THE CENTER OF HURRICANE DEAN WAS LOCATED NEAR LATITUDE 14.9 NORTH...LONGITUDE 65.1 WEST OR ABOUT 800 MILES... 1290 KM...EAST-SOUTHEAST OF KINGSTON JAMAICA AND ABOUT 255 MILES... 410 KM...SOUTH-SOUTHEAST OF SAN JUAN PUERTO RICO. DEAN IS MOVING TOWARD THE WEST NEAR 19 MPH...31 KM/HR. THIS MOTION IS EXPECTED TO CONTINUE THROUGH SATURDAY WITH A GRADUAL DECREASE IN FORWARD SPEED. ON THIS TRACK...THE CORE OF THE HURRICANE WILL BE MOVING WELL SOUTH OF PUERTO RICO TONIGHT. REPORTS FROM AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT INDICATE THAT MAXIMUM SUSTAINED WINDS HAVE INCREASED TO AT LEAST 130 MPH...215 KM/HR...WITH HIGHER GUSTS. DEAN IS NOW A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE. SOME ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS. Member Since: 18.02.2003 Posts: 57 Comments: 5363

942. franck 18. elokuuta 2007 klo 00:03 (GMT)
Ohhhh!! Pinhole eye. Think Dean's gonna do the Gilbert thing..except maybe on Brownsville? Member Since: 30.08.2005 Posts: 0 Comments: 1150

943. Fl30258713 18. elokuuta 2007 klo 00:03 (GMT)
StormJunkie Here's the link again Link for UKMET. The 12Z UKMET was headed due west and 18Z to the NW Member Since: 24.07.2006 Posts: 1 Comments: 976

945. Dan187 18. elokuuta 2007 klo 00:03 (GMT)
south a bit, 14.9

946. DonnaGalveston 18. elokuuta 2007 klo 00:03 (GMT)
On television they say the fact that the storm is slowing in forward motion means it may be about to have a change in course. Is that true?

947. WPBHurricane05 18. elokuuta 2007 klo 00:03 (GMT)
000 URNT12 KNHC 172356 VORTEX DATA MESSAGE AL042007 A. 17/23:32:00Z B. 14 deg 52 min N 065 deg 02 min W C. NA mb 2632 m D. 119 kt Surface winds 140mph from Recon! Member Since: 31.07.2006 Posts: 56 Comments: 7930

948. scottflorida 18. elokuuta 2007 klo 00:03 (GMT)
http://i28.photobucket.com/albums/c205/scottflorida/Untitled-2.jpg

949. ThePainkiller 18. elokuuta 2007 klo 00:03 (GMT)
000 URNT12 KNHC 172356 VORTEX DATA MESSAGE AL042007 A. 17/23:32:00Z B. 14 deg 52 min N 065 deg 02 min W C. NA mb 2632 m D. 119 kt E. 302 deg 006 nm F. 048 deg 130 kt G. 309 deg 010 nm H. 946 mb I. 8 C/ 3045 m J. 18 C/ 3045 m K. 13 C/ NA L. CLOSED M. 16 N. 12345/7 O. 0.02 / 2 nm P. AF302 0504A DEAN OB 03 MAX FL WIND 130 KT NW QUAD 23:29:00

950. Cavin Rawlins 18. elokuuta 2007 klo 00:04 (GMT)
cat 4 REPEATING THE 800 PM AST POSITION...14.9 N...65.1 W. MOVEMENT TOWARD...WEST NEAR 19 MPH. MAXIMUM SUSTAINED WINDS...130 MPH. MINIMUM CENTRAL PRESSURE...946 MB. Member Since: 24.07.2005 Posts: 407 Comments: 19076

951. Tropicnerd13 18. elokuuta 2007 klo 00:04 (GMT)
i still think the storm will go more north than mexico. jmho. i also have the next set of model runs in 2 days or less. that is what they will be.

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