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

Permalink | A A A

Top of Page

Reader Comments

Display: 0, 50, 100, 200

Sort: Newest First - Order Posted

Viewing: 1251 - 1301

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 | 71 — Blog Index

1251. fldude99 18. elokuuta 2007 klo 01:18 (GMT)
If this isn't global warming I don't know what is Member Since: 14.07.2006 Posts: 0 Comments: 560

1252. Metallica1990 18. elokuuta 2007 klo 01:18 (GMT)
Thanks

1253. WildHorseDesertTx 18. elokuuta 2007 klo 01:18 (GMT)
Posted By: whipster at 8:15 PM CDT on August 17, 2007. Going outside now to start my Prius. I hope I'm not too late! (sarcasm) Yeah and when the Ice Age (tm) starts up it's gonna be your fault too! (sarcasm again) Member Since: 23.07.2005 Posts: 9 Comments: 107

1254. 7544 18. elokuuta 2007 klo 01:19 (GMT)
just a question i know when canes get this big they might stall if dean does stalls before 75 west . what will it mean Member Since: 6.05.2007 Posts: 0 Comments: 6020

1255. nolesjeff 18. elokuuta 2007 klo 01:19 (GMT)
Posted By: bappit at 1:15 AM GMT on August 18, 2007. A rebuttal does not refute another's argument. There is ample evidence that climate change is occurring Then why did you choose to rebut? there is ample evidence there isnt! so how about we drop it Member Since: 20.06.2006 Posts: 9 Comments: 1391

1257. Metallica1990 18. elokuuta 2007 klo 01:19 (GMT)
enough global warming stuff back to dean

1258. eaglesrock 18. elokuuta 2007 klo 01:19 (GMT)
Dean is rapidly intensifying!

1259. bappit 18. elokuuta 2007 klo 01:19 (GMT)
Cool post CajunSubbie! Member Since: 18.05.2006 Posts: 5 Comments: 4423

1260. tallahasseecyclone 18. elokuuta 2007 klo 01:19 (GMT)
Alexandra Steele is to Maria Shriver as Dean is to Wilma...Only time will tell if either of the previous will overcome the latter.

1261. bekroweather 18. elokuuta 2007 klo 01:19 (GMT)
Dean seems to be moving due west the last couple of hours, which has brought him south of the forecasted track.

1262. Bobbyweather 18. elokuuta 2007 klo 01:19 (GMT)
Dean has t# of 6.0 and has winds of Flossie! Member Since: 7.09.2006 Posts: 88 Comments: 2487

1263. ChuckieTodd 18. elokuuta 2007 klo 01:20 (GMT)
Actually, catjojo, that was Highway 90 not Interstate 10. Either way, it was a barge on a highway. not something I want to go through again.

1266. Masquer08er 18. elokuuta 2007 klo 01:20 (GMT)
People write theses on the subject of global warming without convincing the other side. No one will change their opinion due to a post here. Member Since: 16.08.2007 Posts: 0 Comments: 388

1267. TheCaneWhisperer 18. elokuuta 2007 klo 01:20 (GMT)
Yes SaBen! 11pm eastern

1268. catjojo 18. elokuuta 2007 klo 01:20 (GMT)
Xion, try these as well. Link Link

1269. 53rdWeatherRECON 18. elokuuta 2007 klo 01:21 (GMT)
THIS IS WHAT DEAN WILL LOOK LIKE IN THE MORNING. THIS IS WILMA WHEN SHE BROKE ALL THOSE RECORDS. Member Since: 5.08.2005 Posts: 2 Comments: 74

1270. PensacolaBuoy 18. elokuuta 2007 klo 01:21 (GMT)
StuccoMan, I think your Dennis comparison is an excellent one. Compact storm... big damage over relatively small area. I don't fully understand the dynamics of what makes a storm blossom into the Gargantuan storm size that Katrina and Rita were. Heat content of the gulf? I guess we'll see. If it stays small, we're in much better shape. Size really matters when it comes to major hurricanes! Member Since: 28.07.2006 Posts: 0 Comments: 348

1271. Metallica1990 18. elokuuta 2007 klo 01:21 (GMT)
yep swflboy i was thanks again :)

1272. MikeOhio 18. elokuuta 2007 klo 01:21 (GMT)
Posted By: fldude99 at 1:18 AM GMT on August 18, 2007. If this isn't global warming I don't know what is What's the point of bringing this up now?

1273. KnowYourRole 18. elokuuta 2007 klo 01:22 (GMT)
Posted By: bekroweather at 9:19 PM EDT on August 17, 2007. Dean seems to be moving due west the last couple of hours, which has brought him south of the forecasted track. Difference between yesterday and today is that it seems to be moving almost directly west now, rather than wobbling around WNW.

1276. kimpy 18. elokuuta 2007 klo 01:20 (GMT)
this was discovered in the Library of Congress: A headline in the Nov. 2, 1922 edition of The Washington Post reads: "Arctic Ocean Getting Warm; Seals Vanish and Icebergs Melt." This was one of several articles from this era about "global warming". Also noted - Four of the 10 hottest years in the U.S. were actually in the 1930s, with 1934 the hottest of all.

1277. KEEPEROFTHEGATE (Mod) 18. elokuuta 2007 klo 01:21 (GMT)
track mark 15,67 16.1,72 C5/H/D 16.5,75 17.2,77 C5/H/D 17.2,79 18,81 C4/H/D 19,62 21,85 21,86 C3/H/D 23,88 25,90 C4/H/D 27,91 29,92 C5/H/D 29,93 29,94 C4/H/D 30,95 FINAL DESINATION MOVIN INLAND Member Since: 15.07.2006 Posts: 147 Comments: 41318

1278. cormit 18. elokuuta 2007 klo 01:23 (GMT)
Recon just passing throgh shows max flight level wind of 136 kt and lowest pressure of 935.8 mb.

1279. atmoaggie 18. elokuuta 2007 klo 01:23 (GMT)
Posted By: bappit at 1:15 AM GMT on August 18, 2007. A rebuttal does not refute another's argument. There is ample evidence that climate change is occurring. Like what? Melting ice we didn't measure until within the last 30 to 40 years? Airport temperature measurents made in different places with different instruments all while the grass/trees around them turned into asphalt and they measured a 1 degree C change in 100 years? That is within the error, standard deviation, and instrument biases for the last 100 years too. Sure something is happening, the ice is melting, so? I expect that it has melted before. Member Since: 16.08.2007 Posts: 6 Comments: 12461

1280. WPBHurricane05 18. elokuuta 2007 klo 01:23 (GMT)
Eastern time is currently in daylight savings time, AST is the same as EDT. Next advisory is at 11pm. Member Since: 31.07.2006 Posts: 56 Comments: 8004

1281. catjojo 18. elokuuta 2007 klo 01:23 (GMT)
Thanks Chuckie... I was going from memory on the interstate but I knew I still had a link to it.

1284. atmoaggie 18. elokuuta 2007 klo 01:24 (GMT)
sorry, now I'm done...regardless of whatever/whoever rebuts Member Since: 16.08.2007 Posts: 6 Comments: 12461

1285. bappit 18. elokuuta 2007 klo 01:24 (GMT)
I like the global warming posts because they cool off some of the hype about Dean. Member Since: 18.05.2006 Posts: 5 Comments: 4423

1287. cirrocumulus 18. elokuuta 2007 klo 01:25 (GMT)
Soon enough even ol' Dr. Gray will be convinced of global warming. He just needs to put his thinking cap on and start studying the multitude of factors besides his chosen few! Member Since: 30.09.2005 Posts: 0 Comments: 1606

1288. Metallica1990 18. elokuuta 2007 klo 01:25 (GMT)
T# is droping like a rock

1290. WPBHurricane05 18. elokuuta 2007 klo 01:26 (GMT)
Hey storm! What do you think about Dean's intensity? Getting strong..... Member Since: 31.07.2006 Posts: 56 Comments: 8004

1291. nolesjeff 18. elokuuta 2007 klo 01:26 (GMT)
Posted By: cirrocumulus at 1:25 AM GMT on August 18, 2007. Soon enough even ol' Dr. Gray will be convinced of global warming. He just needs to put his thinking cap on and start studying the multitude of factors besides his chosen few! LET IT GO! Member Since: 20.06.2006 Posts: 9 Comments: 1391

1293. TXWeatherNewb 18. elokuuta 2007 klo 01:26 (GMT)
Is that mess behind Dean too far south to be of concern??

1294. KnowYourRole 18. elokuuta 2007 klo 01:26 (GMT)
Posted By: cormit at 9:23 PM EDT on August 17, 2007. Recon just passing throgh shows max flight level wind of 136 kt and lowest pressure of 935.8 mb. where did you get the info. I can't get my page to load.

1295. Relix 18. elokuuta 2007 klo 01:27 (GMT)
Meh... I am going to bed. I wanted some rains and winds here in PR, but so far its been lacking. Boo Dean =P. Oh and btw... my PC is on 24/7, that is contributing to global warming right? Aaah... whatever =P Member Since: 3.08.2006 Posts: 0 Comments: 2359

1296. Wishcasterboy 18. elokuuta 2007 klo 01:27 (GMT)
I just checked the stats, and it doesn't look promising. The only slightly good news about Dean is that it has slowed down, and has developed a small eyewall. And even that has downsides. Unfortunately, I can see Dean becoming a category 5 hurricane by tomorrow.

1297. StuccoMan 18. elokuuta 2007 klo 01:27 (GMT)
Posted By: PensacolaBuoy at 8:21 PM CDT on August 17, 2007. StuccoMan, I think your Dennis comparison is an excellent one. Compact storm... big damage over relatively small area. I don't fully understand the dynamics of what makes a storm blossom into the Gargantuan storm size that Katrina and Rita were. Heat content of the gulf? I guess we'll see. If it stays small, we're in much better shape. Size really matters when it comes to major hurricanes! Katrina is the biggest media hyped storm in history.It was not as poerful or big as ivan.If you look at side by side wind swath and sattelite of ivan and katrina.ivan was bigger.Katrina just happen to put NO under water from the soup bowl theory and hit 2 majorly populated areas.Katrina was not that powerful.It made landfall as a cat 3.Andrew was the most impressive storm next to ivan.katrina Not a chance.

1298. nolesjeff 18. elokuuta 2007 klo 01:27 (GMT)
Posted By: swFLboy at 1:26 AM GMT on August 18, 2007. Peak wind of 158 just reported fron dropsonde by HH's in Dean Where did you get that? link? also swfl guy Member Since: 20.06.2006 Posts: 9 Comments: 1391

1299. VEROBEACHFL1 18. elokuuta 2007 klo 01:27 (GMT)
HELLO ALL, taking a quick break from the ballgame and popping in here------- im still in agreement for the w and sometimes wnw movements for now BUT anytime it will gradually continue NORTHWARD------not a sharp drastic N movement but a definite change in direction and models sometime before 80W...... i been saying this for oh hmm, 3 days now and we will just have to see....some agree, some disagree, ULL is in favor-- somewhat, also the intensity facotor.my "2 cents again".........bye I'll back after the game.............

1300. Stormchaser2007 18. elokuuta 2007 klo 01:27 (GMT)
Posted By: cormit at 9:23 PM EDT on August 17, 2007. Recon just passing throgh shows max flight level wind of 136 kt and lowest pressure of 935.8 mb. Where was this? Member Since: 9.06.2007 Posts: 4 Comments: 15294

1301. 53rdWeatherRECON 18. elokuuta 2007 klo 01:28 (GMT)
Dean will most likely have the 155 mph winds needed for CAT 5 by 11pm. There is only warmer water and low shear ahead. The eywall replacement cycles will be the only thing to chop him down. Member Since: 5.08.2005 Posts: 2 Comments: 74

Viewing: 1251 - 1301

Top of Page

New Comment

Community Standards Policy 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.

About JeffMasters