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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2251. FMTXWMAN 18. elokuuta 2007 klo 05:07 (GMT)
I do not know about anyone else, but it seems from the wv imagery over Florida, that the ULL is starting to sink to the southwest. Which could be in response to Dean and other forces acting on it over the continental US. If things evolve this way dean could be punted north due to the effect of which I can not remember the name of. All we need is a cat 5 to wipe out Houston's oil facilities. Then again there'd be a silver lining where it may finally force the government to do something about the refinery crunch. Member Since: 1.05.2007 Posts: 2 Comments: 66

2252. MrNiceville 18. elokuuta 2007 klo 05:08 (GMT)
I consider anyone that attended a "real" aggie - I should have appended LOL to the end of the comment - apologies... It doesn't matter how you support our school - just that you support it! I have ties as well, not going back that far, though! Sounds like a proud heritage. Seriously - I'm sure that the Met School will have interesting things on their web site if the storm winds up coming that way. If you need info here are a few links... MLC Patrap StormW Tropical Lagniappe

2253. moonlightcowboy 18. elokuuta 2007 klo 05:08 (GMT)
Hey, Niceville! Prolly resting a lil easier now. Jamaica, Caymans, Mexico...maybe a lit south Texas,heh? Just know that it's going to be a bad one for someone! The GFDL is coming back around! Member Since: 9.07.2006 Posts: 179 Comments: 28118

2254. KnowYourRole 18. elokuuta 2007 klo 05:08 (GMT)
Posted By: DG136 at 1:06 AM EDT on August 18, 2007. Interesting how the NHC newest run is way right of the others (notice up in Master's entry he says the NHC tends to out preform the models). I may be color blind, but it appears on that graphic that the NHC shows landfall around the US/Mexico border. The one all the way to the right is not the NHC the one to the right, the CLP5 has not moved all day.

2255. sammo 18. elokuuta 2007 klo 05:08 (GMT)
Posted By: exexec at 5:04 AM GMT on August 18, 2007. Can't believe anyone would ever cheer for a hurricane. My parents' house was blasted during Ivan. We nearly lost everything we had. It's easy to cheer for disaster when you believe you are invincible -- and have no morals at the same time. If that applies to you and bothers you, good. It should. True. There's a fine line btw weather freak and cane cheerleader. Some here cross it... Member Since: 30.08.2006 Posts: 0 Comments: 149

2256. Daveg 18. elokuuta 2007 klo 05:09 (GMT)
Gah...nevermind on that slight WNW turn...was yet another wobble. Crazy hurricane. Member Since: 23.09.2005 Posts: 0 Comments: 426

2258. C2News 18. elokuuta 2007 klo 05:09 (GMT)
With gas prices as high as they are now, a cat 5, even just a major hurricane in the Gulf would cause major price hikes that would take many people off the streets as far as driving goes...many middle class families would not be able to afford it, let alone lower class families...it would be a sad and frightening event that may be enevitable Member Since: 17.07.2006 Posts: 73 Comments: 622

2259. nola70119 18. elokuuta 2007 klo 05:09 (GMT)
By the way, is it any surprise that the NHC forecast outperforms the models....they forecast after looking at the models, not before they come out, right? Member Since: 16.06.2006 Posts: 0 Comments: 1535

2261. iahishome 18. elokuuta 2007 klo 05:10 (GMT)
Newest Buoy data is in: Conditions at 42059 as of 0450 GMT on 08/18/2007: Unit of Measure: Time Zone: Wind Direction (WDIR): NNE ( 20 deg true ) Wind Speed (WSPD): 36.9 kts Wind Gust (GST): 48.6 kts Wave Height (WVHT): 22.6 ft Dominant Wave Period (DPD): 13 sec Average Period (APD): 8.8 sec Atmospheric Pressure (PRES): 29.61 in Pressure Tendency (PTDY): -0.14 in ( Falling Rapidly ) Air Temperature (ATMP): 81.1 �F Water Temperature (WTMP): 83.8 �F Dew Point (DEWP): 73.2 �F Heat Index (HEAT): 86.2 �F Let's hope we see some unexpected drops. Member Since: 24.07.2005 Posts: 5 Comments: 499

2262. nola70119 18. elokuuta 2007 klo 05:10 (GMT)
What time is the next GFDL? Member Since: 16.06.2006 Posts: 0 Comments: 1535

2263. MrNiceville 18. elokuuta 2007 klo 05:10 (GMT)
Atmo - I've been in the regular population toooooo long - LOL - and married and MSU graduate. She has had a detrimental influence on me, but I still proudly display my memorabilia, have taught my kids to "saw Varsity's horns off", and taught them that it's TU, not UT....

2264. Metallica1990 18. elokuuta 2007 klo 05:11 (GMT)
Posted By: nola70119 at 5:10 AM GMT on August 18, 2007. What time is the next GFDL? 5 am i think

2266. bappit 18. elokuuta 2007 klo 05:12 (GMT)
Interesting disclaimer on the model plot Skyepony posted. If anything on this graphic causes confusion, ignore the entire product. Member Since: 18.05.2006 Posts: 3 Comments: 4371

2269. KnowYourRole 18. elokuuta 2007 klo 05:12 (GMT)
Posted By: Daveg at 1:09 AM EDT on August 18, 2007. Gah...nevermind on that slight WNW turn...was yet another wobble. Crazy hurricane. Unless you see it in about 3-4 frames, it's not even worth mentioning a possible turn. I still have yet to see it move off 15N since about 8:00pm EST.

2270. punkasshans 18. elokuuta 2007 klo 05:12 (GMT)
The SREF (short range ensemble) has an average 4 day position in the central gulf. The models are moving north, and the entire Texas region needs to be getting ready, or at least have a plan of action. The NGM has also shifted far north compared to the last run (just north of Jamaica now), along with the GFS as already discussed.

2272. KnowYourRole 18. elokuuta 2007 klo 05:13 (GMT)
later nola70119.

2273. Spoon 18. elokuuta 2007 klo 05:13 (GMT)
Has anyone done the math -- what time will Dean be closest to 42059?

2276. weatherwonderer 18. elokuuta 2007 klo 05:14 (GMT)
good night atmoaggie. Good luck tomorrow. Member Since: 16.07.2005 Posts: 0 Comments: 167

2279. Aggie92 18. elokuuta 2007 klo 05:15 (GMT)
Good Bull Mr. Niceville. On a more storm related note. I work at the Riverside Campus, an old military base that has been turned into offices, wharehouses, and what not. We got an e-mail today saying that Gov. Perry has declared a State of Iminent Danger and they were going to start staging supplies and search and rescue aircraft at Riverside Campus. Sounds like our State Gov't is on the ball.

2282. weathersp 18. elokuuta 2007 klo 05:16 (GMT)
How low can ya go I say how low can ya go? Dean Buoy Pressure Member Since: 14.01.2007 Posts: 17 Comments: 4112

2284. WatchingInHouston 18. elokuuta 2007 klo 05:16 (GMT)
C2News: I've tried not to chime in on posts like this... but, really... a "sad and frightening event" regarding gas prices? I think that we need to really put things in scale here - a sad and frightening event would be the people whose lives are being drastically affected by Dean... whose lives have been taken, whose livelihoods have been swept away, whose homes are no more. A sad and frightening event is the people that's already happened too and the people that it IS going to happen too. Let's keep things in perspective here. Gas prices are a simple reflection of market supply and demand. The people that can't afford to buy gasoline take demand away from the pool, thus creating a sense of increased supply, or increasing the supply to those whom can afford it. The natural market reaction to this is lower prices. Sorry for the OT post, folks.

2285. catjojo 18. elokuuta 2007 klo 05:16 (GMT)
Surf's up !Be careful in the carrib............ Conditions at 42059 as of 0450 GMT on 08/18/2007: Unit of Measure: English Metric Time Zone: Station Local Time Greenwich Mean Time [GMT] British Summer Time [GMT+1] Eastern Greenland [GMT-1] Azores [GMT-2] Western Greenland [GMT-3] Atlantic Standard [GMT-4] US/Eastern Standard US/Central Standard US/Mountain Standard US/Pacific Standard Alaska Standard [GMT-9] Hawaii-Aleutian Standard [GMT-10] Samoa Standard [GMT-11] International Date Line West [GMT-12] Western European [GMT+0] Central European [GMT+1] Eastern European [GMT+2] Moscow [GMT+3] USSR Zone 3 [GMT+4] USSR Zone 4 [GMT+5] USSR Zone 5 [GMT+6] USSR Zone 6 [GMT+7] China Coast [GMT+8] Japan Standard [GMT+9] Guam Standard [GMT+10] GMT+11 International Date Line East [GMT+12] Click on the graph icon in the table below to see a time series plot of the last five days of that observation. Wind Direction (WDIR): NNE ( 20 deg true ) Wind Speed (WSPD): 36.9 kts Wind Gust (GST): 48.6 kts Wave Height (WVHT): 22.6 ft Dominant Wave Period (DPD): 13 sec Average Period (APD): 8.8 sec Atmospheric Pressure (PRES): 29.61 in Pressure Tendency (PTDY): -0.14 in ( Falling Rapidly ) Air Temperature (ATMP): 81.1 �F Water Temperature (WTMP): 83.8 �F Dew Point (DEWP): 73.2 �F Heat Index (HEAT): 86.2 �F

2286. PtOConnorTXfisherman 18. elokuuta 2007 klo 05:17 (GMT)
Been lurking for 2 years here, first time posting... Does anyone have link to updated GFS path? Thx Member Since: 18.08.2007 Posts: 0 Comments: 134

2287. VEROBEACHFL1 18. elokuuta 2007 klo 05:17 (GMT)
someone quoted---Unless you see it in about 3-4 frames, it's not even worth mentioning a possible turn. I still have yet to see it move off 15N since about 8:00pm EST. --its going to wobble a bit and gradually go WNW till 80W....I dont think its going to ride the line the whole way--almost sure of it......... so i guess i do agree somewhat with the NHC BUT a little more northward of the track that i see in the "trop fcst pts" checked box.......for the next 36 or so hrs

2288. Daveg 18. elokuuta 2007 klo 05:17 (GMT)
Posted By: KnowYourRole at 5:12 AM GMT on August 18, 2007. Unless you see it in about 3-4 frames, it's not even worth mentioning a possible turn. I still have yet to see it move off 15N since about 8:00pm EST. You're right there. He's riding 15N like a beam. Member Since: 23.09.2005 Posts: 0 Comments: 426

2289. MrNiceville 18. elokuuta 2007 klo 05:17 (GMT)
ROFL Atmo! I prefer Friends over in Madisonville. Sit out on the "dock" with a pitcher and a glass and watch the world float by. But then, us older folks tend to slow down after 40...

2290. guygee 18. elokuuta 2007 klo 05:18 (GMT)
Posted By: FMTXWMAN at 5:07 AM GMT on August 18, 2007. "Then again there'd be a silver lining where it may finally force the government to do something about the refinery crunch." Hear, hear FMTXWMAN. I would hate to see it go down this way, but it is coming sooner or later anyways. Nearly all of The Blood has been squeezed from The Stone, and we are always just three meals away from the revolution. Member Since: 16.09.2005 Posts: 0 Comments: 2830

2291. MrNiceville 18. elokuuta 2007 klo 05:18 (GMT)
MLC - u gotta understand - it's an AGGIE thing now...

2292. DG136 18. elokuuta 2007 klo 05:18 (GMT)
Anyone on the Gulf Coast is at risk, so long as there is a storm out there, EVERYONE needs to pay attention to it. We can make guesses all day long about where it will or wont go, but we have all seen storms do strange, unexpected things before. It's not wishcasting if you are just concerned. The people who keep shooting down the possibilities almost sound like they are wishcasting. This thing is still days away, when it's 2 or 3 days out, we'll know a lot better about where it will be.

2293. WatchingInHouston 18. elokuuta 2007 klo 05:19 (GMT)
FMTXWMAN - unfortunately, there is a little that the Gov. could immediately do (besides rationing) to help with the actual finished product supply crunch. There is such an extreme backlog of construction at this time, it would take 2-3 plus years to get a refinery off the ground and running. Part of this is the availability of supplies, part is the amount of work currently backlogged, a large part of this is the amount of workers available.

2294. KRL 18. elokuuta 2007 klo 05:19 (GMT)
Since there have been so many unexpected places getting hit with unusual weather it makes sense that this hurricane season will see some strange events also. That's one of the reasons I think Florida will see limited action this year, and states that haven't gotten hit recently will. I still can't believe they had a 4.3 earthquake in Saudi Arabia today. That is just completely out of the normal scope of seismic location action. That'd be like an earthquake happening in South Florida. LOL Just never happens. Member Since: 31.07.2006 Posts: 0 Comments: 229

2296. MrNiceville 18. elokuuta 2007 klo 05:20 (GMT)
Well, gotta hit the rack. (no wise cracks - MLC) It will be interesting to see what the models cook up overnight...

2297. atmoaggie 18. elokuuta 2007 klo 05:21 (GMT)
I prefer Friends over in Madisonville. Sit out on the "dock" with a pitcher and a glass and watch the world float by. But then, us older folks tend to slow down after 40... Been there done that. During the boat parade this year. My kids are somewhere in the photo section of their page, cannot link it, though. Member Since: 16.08.2007 Posts: 6 Comments: 12461

2298. weatherwonderer 18. elokuuta 2007 klo 05:21 (GMT)
good post guygee Member Since: 16.07.2005 Posts: 0 Comments: 167

2300. stormybil 18. elokuuta 2007 klo 05:22 (GMT)
look real quick looks like a meteor just shot south off jamacia a big red ball that was cool .

2301. iahishome 18. elokuuta 2007 klo 05:22 (GMT)
If Dean stays near 18 mph and keeps headed west, closest approach should be approximately 8:00 GMT (around 2.5 hours). I don't think the buoy will keep reporting until then though... would be nice if it does. Member Since: 24.07.2005 Posts: 5 Comments: 499

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