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

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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

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2335. mikester
5:41 AM GMT on August 18, 2007
Here is what is happening in africa.
pic
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2334. Metallica1990
5:40 AM GMT on August 18, 2007
so if the FL winds are 154 Kts and 90 percent of that is 159 mph are we dealling with a cat 5 now?
2332. H2PV
5:40 AM GMT on August 18, 2007
After Dean...

http://www.h2-pv.us/wiki_100mpg/img/wiki_up/AfterDean2.jpg
http://www.h2-pv.us/wiki_100mpg/img/wiki_up/AfterDean2.jpg
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2331. stormybil
5:36 AM GMT on August 18, 2007
looks like dean is having big babys all around him
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2330. Skyepony (Mod)
5:04 AM GMT on August 18, 2007
I'm cheering that buoy that spoon posted makes it, been watching that one with concern. They take forever to replace those when they get lost & destroyed in storms.
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2329. mikester
5:36 AM GMT on August 18, 2007
Here's a good pic of the what he dry air is doing to dean.
pic
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2328. Dan187
5:37 AM GMT on August 18, 2007
154 kt=177mph

90 percent is 159 mph
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2327. Metallica1990
5:34 AM GMT on August 18, 2007
thanks painkiller :)
2326. moonlightcowboy
5:31 AM GMT on August 18, 2007
I hear you Jaxen! ditto

...the season is ramping up!
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2325. WatchingInHouston
5:31 AM GMT on August 18, 2007
Cheyanne - Hi, neighbor! :) They are in a fairly difficult situation... they've been accused of extremes on both sides - too much hype and not enough hype. You want people to be aware, obviously, yet you don't want an event like last year with people in AUSTIN evacuating further away from Rita.

I would just keep an eye on things and an open ear. As it gets closer, we're going to get more info (more reliable info at least).

Stay safe.
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2324. sgpine
5:30 AM GMT on August 18, 2007
If it pulls just a little bit North of Brownsville but stays South of Corpus Christi it would be lucky (for most). Kenedy County, TX is the 4th least populated county in the United States and has a population density of only about 0.1 people per square mile.
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2323. ThePainkiller
5:32 AM GMT on August 18, 2007
Posted By: ThePainkiller at 5:27 AM GMT on August 18, 2007.

It may still be intensifying.

000
URNT12 KNHC 180522
VORTEX DATA MESSAGE AL042007
A. 18/05:00:30Z
B. 14 deg 55 min N
066 deg 26 min W
C. 700 mb 2498 m
D. 105 kt
E. 193 deg 004 nm
F. 291 deg 117 kt
G. 197 deg 005 nm
H. 930 mb
I. 12 C/ 3044 m
J. 20 C/ 3055 m
K. 9 C/ NA
L. CLOSED
M. C13
N. 12345/ 7
O. 0.03 / 2 nm
P. AF302 0504A DEAN OB 24
MAX FL WIND 138 KT NE QUAD 01:12:20 Z
MAX FL WIND OUTBOUND 154KT AT 05:04:00 Z

where do you find this may i have the link


I found it here Link
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2322. mikester
5:32 AM GMT on August 18, 2007
Yeah there is alot of moisture but no convection yet. Have to wait and see if any of those disturbances become a tropical depress.
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2321. weatherwonderer
5:30 AM GMT on August 18, 2007
It will be interesting to see what he looks like in the morning.I'm not surprised.
Member Since: July 16, 2005 Posts: 0 Comments: 167
2320. H2PV
5:32 AM GMT on August 18, 2007
The Dragon Spits Fire

After Dean...
http://www.h2-pv.us/wiki_100mpg/img/wiki_up/AfterDean1.jpg
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2319. Jaxen
1:30 AM EDT on August 18, 2007
Just heard TWC is sending Mike Seidel to Jamaica tomorrow. What, did Cantore go "NO WAY IN HELL!?" Seriously though, pray for those in Jamaica and the Caymans. Find a boat and start rowing to Cuba, folks! (Did I just really type that?)

Everyone is comparing this track to Emily ... but GILBERT in '88 came this dangerously close to Jamaica, then literally bounced off the Yucatan. Dean looks like ol' Gil's kin.

In the last week I started watching these blogs for the first time in 2 years. (I would've posted sooner but forgot my login) I'm in Orlando and this time last week I got that sweaty feeling on the back of my neck ... when Dean was just an INVEST, and I started thinking this thing was going to follow the steps of Andrew, Frances, David, Floyd or Hugo. I didn't worry about Charley until it turned on the right-turn blinker, but I had Frances pegged like a week out and spent the whole time pacing watching that blob chug toward me. 3 years later I'm worrying about invests. Unreal. Anymore I hate the idea of a 3,4,5 hitting ANY populated area. I don't feel better until a major becomes a fish storm ... and when it doesn't I spent too much productive time here on WU.

And by the way, airing now on TWC ... It Could Happen Tomorrow: A Category 4 Hurricane Hits Houston. Hmmmmm ....

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2318. Cheyanne
5:23 AM GMT on August 18, 2007
From reading the posts, I take it yall don't put too much faith in what the weather channel has to say..I live just east of Houston and the 10:00 news on Channel 13 only gave one possible track..Brownsville. I was very disappointed in that weather report..gives Houstonians a false sense of security. I don't want wide spread panic, but a little more honesty would be appreciated..if you don't know, say you don't know!
2317. Metallica1990
5:29 AM GMT on August 18, 2007
Posted By: ThePainkiller at 5:27 AM GMT on August 18, 2007.

It may still be intensifying.

000
URNT12 KNHC 180522
VORTEX DATA MESSAGE AL042007
A. 18/05:00:30Z
B. 14 deg 55 min N
066 deg 26 min W
C. 700 mb 2498 m
D. 105 kt
E. 193 deg 004 nm
F. 291 deg 117 kt
G. 197 deg 005 nm
H. 930 mb
I. 12 C/ 3044 m
J. 20 C/ 3055 m
K. 9 C/ NA
L. CLOSED
M. C13
N. 12345/ 7
O. 0.03 / 2 nm
P. AF302 0504A DEAN OB 24
MAX FL WIND 138 KT NE QUAD 01:12:20 Z
MAX FL WIND OUTBOUND 154KT AT 05:04:00 Z


where do you find this may i have the link
2316. stormybil
5:28 AM GMT on August 18, 2007
well the ull is working gettting heavy thunder here in so fla it about to pour .
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2315. RyanFSU
5:29 AM GMT on August 18, 2007
HWRF Swath

Interesting how HWRF is initialized for 00Z and has such a northerly track, since it has been hugging the 15N parallel for a while now...

Yet, the 00Z GFS is doing the same thing: Link
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2314. KRL
5:29 AM GMT on August 18, 2007
Man, the latest GFDL really kicks this one up.

http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2007081718-dean04l&field=Sea+Level+Pressure&hour=An imation
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2313. katadman
5:29 AM GMT on August 18, 2007
Almost a Cat5, then.
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2312. weatherwonderer
5:23 AM GMT on August 18, 2007
Been an interesting night. I'm going to see Joe Walsh and Grand funk tomorrow night and enjoy a night out. It has been HOT here in the mid-west. Pray for those that encounter this beast and enjoy
life. Ying and Yang...one does not do to well without the other. Good night.
Member Since: July 16, 2005 Posts: 0 Comments: 167
2310. KEEPEROFTHEGATE (Mod)
5:25 AM GMT on August 18, 2007
maybe a distress signal
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2309. Metallica1990
5:27 AM GMT on August 18, 2007
i beleive im starting to see a slight movement a little more north of west
2308. Tazmanian
10:24 PM PDT on August 17, 2007
hello cat 5


By: weatherboykris at 10:16 PM PDT on August 17, 2007.

It's in...and it sucks.The minimum pressure is 927..and in the NE eyewall,strongest SFMR winds were 121kt.HOWEVER,the SFMR was not reporting for some reason for a 60 second period right outside the eye(peraps too strong of winds?),and the plane had flight level winds at 150 kt.


that would make it 135kt to 140kt at sea level right?
Member Since: May 21, 2006 Posts: 5091 Comments: 115437
2307. ThePainkiller
5:23 AM GMT on August 18, 2007
It may still be intensifying.

000
URNT12 KNHC 180522
VORTEX DATA MESSAGE AL042007
A. 18/05:00:30Z
B. 14 deg 55 min N
066 deg 26 min W
C. 700 mb 2498 m
D. 105 kt
E. 193 deg 004 nm
F. 291 deg 117 kt
G. 197 deg 005 nm
H. 930 mb
I. 12 C/ 3044 m
J. 20 C/ 3055 m
K. 9 C/ NA
L. CLOSED
M. C13
N. 12345/ 7
O. 0.03 / 2 nm
P. AF302 0504A DEAN OB 24
MAX FL WIND 138 KT NE QUAD 01:12:20 Z
MAX FL WIND OUTBOUND 154KT AT 05:04:00 Z



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2306. Metallica1990
5:26 AM GMT on August 18, 2007
yeah that does look pretty cool :)
2305. stormybil
5:24 AM GMT on August 18, 2007
I think you mean hati


oh yeah did you see it sorry got dizzt=y ther
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2303. Metallica1990
5:23 AM GMT on August 18, 2007
Posted By: stormybil at 5:22 AM GMT on August 18, 2007.

look real quick looks like a meteor just shot south off jamacia a big red ball that was cool .


I think you mean hati
2302. mikester
5:20 AM GMT on August 18, 2007
You do know earthquakes can happen anywhere. In nystate we have had earthquakes. This is the least expected place to have earthquakes and we have had them. Back to dean it seems to have pulled in some dry air from the looks of things. Still has potential to become very powerful but rather small hurricane.
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2301. iahishome
5:16 AM GMT on August 18, 2007
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.
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2300. stormybil
5:21 AM GMT on August 18, 2007
look real quick looks like a meteor just shot south off jamacia a big red ball that was cool .
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2298. weatherwonderer
5:19 AM GMT on August 18, 2007
good post guygee
Member Since: July 16, 2005 Posts: 0 Comments: 167
2297. atmoaggie
5:18 AM GMT on August 18, 2007
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: August 16, 2007 Posts: 6 Comments: 12463
2296. MrNiceville
5:20 AM GMT on August 18, 2007
Well, gotta hit the rack. (no wise cracks - MLC)

It will be interesting to see what the models cook up overnight...
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2294. KRL
5:14 AM GMT on August 18, 2007
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.

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2293. WatchingInHouston
5:16 AM GMT on August 18, 2007
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.
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2292. DG136
5:06 AM GMT on August 18, 2007
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.
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2291. MrNiceville
5:17 AM GMT on August 18, 2007
MLC - u gotta understand - it's an AGGIE thing now...
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2290. guygee
5:07 AM GMT on August 18, 2007
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.
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2289. MrNiceville
5:16 AM GMT on August 18, 2007
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...
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2288. Daveg
5:16 AM GMT on August 18, 2007
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.
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2287. VEROBEACHFL1
5:12 AM GMT on August 18, 2007
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
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2286. PtOConnorTXfisherman
5:06 AM GMT on August 18, 2007
Been lurking for 2 years here, first time posting...

Does anyone have link to updated GFS path?

Thx
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2285. catjojo
5:08 AM GMT on August 18, 2007
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
Member Since: July 11, 2006 Posts: 0 Comments: 1

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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.

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