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

Share this Blog
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

Reader Comments

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.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1735 - 1685

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 | 71Blog Index

1735. mikester
2:40 AM GMT on August 18, 2007
Looks like africa has some hurricane potential coming along.
pic
Member Since: Posts: Comments:
1734. HurricaneDean2007
10:52 PM EDT on August 17, 2007
you mean northward
Member Since: Posts: Comments:
1733. DanielPC
2:54 AM GMT on August 18, 2007
11 p.m. AST public advisory is out.
Member Since: Posts: Comments:
1732. bappit
2:51 AM GMT on August 18, 2007
Interesting graphic pseabury! Wondering how you register the satellite photo with the map?
Member Since: Posts: Comments:
1730. presslord
10:48 PM EDT on August 17, 2007
a few years back I spent two astonishingly drunken months in Matamoros, Mexico, (south of Brownsville, TX)with this girl named...well..I digress...

the point is: a storm like this will do unimaginable damage to that area...many of the people (and, contrary to much current thought, they are people) live in structures so flimsy they would not withstand a stiff breeze...it will make NO look like a party...it's heartbreaking....
Member Since: Posts: Comments:
1728. Metallica1990
2:52 AM GMT on August 18, 2007
Posted By: Metallica1990 at 2:46 AM GMT on August 18, 2007.

Posted By: Metallica1990
at 2:18 AM GMT on August 18, 2007.
unless its shifted its track or slowed down at 11 it should be near

14.9N
65.96W

i just want to see how good i am at forecasting lol


damn i was right
14.9N 65.9W
woo hoo :)
1726. louisianaboy444
2:51 AM GMT on August 18, 2007
we will most likely see a southward shift in the models in the next run....
Member Since: Posts: Comments:
1722. bappit
2:44 AM GMT on August 18, 2007
FC: I guess as long as Dean keeps moving quickly the air ahead of it will be moving quickly, too, and have less effect on Dean? If Dean slows down, then the air ahead of it will also and Dean will weaken?
Member Since: Posts: Comments:
1721. sullivanweather
2:49 AM GMT on August 18, 2007
Satellite eclipse schedule
Member Since: March 8, 2007 Posts: 273 Comments: 12612
1720. whipster
8:49 PM CST on August 17, 2007
Yep and Ray Nagin is looking for a place to move "just in case"
Member Since: August 14, 2007 Posts: 0 Comments: 435
1717. Crawls
2:48 AM GMT on August 18, 2007
The Governor of LA. has issued a state of emergency - "just in case".
Member Since: Posts: Comments:
1715. WatchingInHouston
2:43 AM GMT on August 18, 2007
Is the correlation between slowing forward movement and wind intensification typical? Seems like a 20% decrease in forward motion resulted in an approximate 20% increase in winds?
Member Since: Posts: Comments:
1714. pseabury
2:47 AM GMT on August 18, 2007
Dean is definitely about 22 miles South of the 5PM NHC forecast track. Can see that on both radar and Satellite...

Dean South of Forecast Track
Member Since: Posts: Comments:
1713. sullivanweather
2:45 AM GMT on August 18, 2007
TCHP is over 100kj/cm^2 once Dean passes 70W.

If Dean could pass over this warm pocket of water looks like we'll have a CAT5 tomorrow morning
Member Since: March 8, 2007 Posts: 273 Comments: 12612
1712. COHurricanes2007
2:47 AM GMT on August 18, 2007
DEAN NOW 145 MPH
Member Since: Posts: Comments:
1711. Daveg
2:45 AM GMT on August 18, 2007
Posted By: louisianaboy444 at 2:44 AM GMT on August 18, 2007.
it looks like the models are now taking deep further south so this will be a problem for mexico in a few days.....so who said we could have a new invest out there where are yall talking about


WOW...I mean wow...seriously...the US is not out of the woods yet. To simply dismiss Dean and be ready to move onto the next invest is crazy. Everyone from Mexico to the TX/LA border should keep a close eye on this.

And let me also say ... Not a Cat 5 in Jamaica! What a blow that would be, not to mention Cozumel..which is just starting to recover.
Member Since: September 23, 2005 Posts: 0 Comments: 426
1710. kmanislander
2:46 AM GMT on August 18, 2007
By: CuriuosGa at 2:45 AM GMT on August 18, 2007.

Kmanislander

JUst remember when you silcone up everything that water will come up through the sewage pipes when it floods

Yea I know. It depends on the water level outside. There is a limit to what you can do
Member Since: Posts: Comments:
1709. Baybuddy
2:47 AM GMT on August 18, 2007
How West?
Member Since: June 26, 2006 Posts: 0 Comments: 1115
1708. Xion
2:46 AM GMT on August 18, 2007
2am, next HH mission into Dean

How long do they typically stay in for?
Member Since: Posts: Comments:
1707. ForecasterColby
2:44 AM GMT on August 18, 2007
Forecast to reach Cat 5 in 24 hours and hold it on his entire trek through the Caribbean.
Member Since: Posts: Comments:
1706. Caymanite
2:40 AM GMT on August 18, 2007
Seems like if the storm is not headed for Fla or N.O. that a lot of people here really dont care a #$%&@@#$ and start talking about global warming and other topics that should be left for inactive times when there is not a MAJOR hurricane about to affect peoples lives. IMHO.
Member Since: Posts: Comments:
1705. Broward1975
2:37 AM GMT on August 18, 2007
Been lurking for a few years...I've learned a lot from the posts. Thanks to all who take the time to answer rudimentary questions with detailed and well-explained information. I appreciate it.

As far as Dean goes, lets hope it takes the path that affects as little human life and property as possible.

Kmanislander, I've always valued your input, hope you stay safe
Member Since: Posts: Comments:
1703. Metallica1990
2:46 AM GMT on August 18, 2007
Posted By: Metallica1990
at 2:18 AM GMT on August 18, 2007.
unless its shifted its track or slowed down at 11 it should be near

14.9N
65.96W

i just want to see how good i am at forecasting lol


damn i was right
14.9N 65.9W
woo hoo :)
1702. Crisis57
2:44 AM GMT on August 18, 2007
wow so DR and Hati have a warning hmmm
1701. Skyepony (Mod)
2:28 AM GMT on August 18, 2007
Cloudsat Club.... from 16:55 today. click yellow 17 & scroll down.

It's 2 passes back still a firstlook, will have to check out the finished on Navy tommarrow.
Member Since: Posts: Comments:
1700. CuriuosGa
2:41 AM GMT on August 18, 2007
Kmanislander

JUst remember when you silcone up everything that water will come up through the sewage pipes when it floods.
1698. WPBHurricane05
10:44 PM EDT on August 17, 2007
gulp cat 5

Member Since: Posts: Comments:
1697. Xion
2:42 AM GMT on August 18, 2007
No change in strength for 11 PM.
Member Since: Posts: Comments:
1696. louisianaboy444
2:43 AM GMT on August 18, 2007
it looks like the models are now taking deep further south so this will be a problem for mexico in a few days.....so who said we could have a new invest out there where are yall talking about
Member Since: Posts: Comments:
1695. sayhuh
2:41 AM GMT on August 18, 2007
If you believe tropical entities such as hurricanes have an "intuition", then that would be the desire to live and thrive. That being the case, in general, they will avoid things that would end them such as land and other inhibiting factors. It is not suprising if you sense this - that wobbles, jogs, and other movement may happen to avoid tropical "land mines"
Member Since: Posts: Comments:
1694. bappit
2:43 AM GMT on August 18, 2007
FC: I saw all the dry air ahead of it earlier this evening. I was wondering how it would keep intensifying if that air gets pulled in.
Member Since: Posts: Comments:
1693. extreme236
2:43 AM GMT on August 18, 2007
11pm advisory is out
Member Since: Posts: Comments:
1692. Dan187
2:43 AM GMT on August 18, 2007
ZCZC MIATCMAT4 ALL
TTAA00 KNHC DDHHMM
HURRICANE DEAN FORECAST/ADVISORY NUMBER 20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007
0300 UTC SAT AUG 18 2007

AT 11 PM AST...A HURRICANE WARNING IS ISSUED FOR THE SOUTHWESTERN
PENINSULA OF HAITI...FROM THE HAITI/DOMINICAN REPUBLIC BORDER TO
PORT-AU-PRINCE...AND A TROPICAL STORM WARNING IS ISSUED FROM
PORT-AU-PRINCE TO THE NORTHERN HAITI/DOMINICAN REPUBLIC BORDER.

AT 11 PM AST...THE HURRICANE WARNING FOR GUADELOUPE AND ITS
DEPENDENCIES HAS BEEN DISCONTINUED...AND ALL TROPICAL STORM
WARNINGS HAVE BEEN DISCONTINUED FOR THE FOLLOWING ISLANDS OF THE
LESSER ANTILLES...MONTSERRAT...ANTIGUA...NEVIS...ST
KITTS...BARBUDA...AND ANGUILLA.

A HURRICANE WARNING IS IN EFFECT FOR THE SOUTH COAST OF THE
DOMINICAN REPUBLIC FROM BARAHONA WESTWARD TO THE HAITI-DOMINICAN
REPUBLIC BORDER. A HURRICANE WARNING MEANS THAT HURRICANE
CONDITIONS ARE EXPECTED WITHIN THE WARNING AREA WITHIN THE NEXT 24
HOURS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED
TO COMPLETION.

A TROPICAL STORM WARNING REMAINS IN EFFECT FOR THE BRITISH VIRGIN
ISLANDS....U.S. VIRGIN ISLANDS AND PUERTO RICO. THESE WARNINGS
WILL LIKELY BE DISCONTINUED ON SATURDAY MORNING.

A TROPICAL STORM WARNING IS IN EFFECT ALONG THE SOUTH COAST OF
THE DOMINICAN REPUBLIC FROM CABO ENGANO WESTWARD TO BARAHONA.

A HURRICANE WATCH IS ALSO IN EFFECT FOR JAMAICA.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED WITHIN THE WARNING AREA WITHIN THE NEXT 24 HOURS. A
HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN
THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

A TROPICAL STORM WATCH IS IN EFFECT FOR PORTIONS OF CUBA...FROM THE
PROVINCE OF CAMAGUEY EASTWARD TO THE PROVINCE OF GUANTANAMO. A
TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

INTERESTS ELSEWHERE IN THE CENTRAL AND WESTERN CARIBBEAN...INCLUDING
WESTERN CUBA...THE CAYMAN ISLANDS...AND THE YUCATAN PENINSULA OF
MEXICO...SHOULD CLOSELY MONITOR THE PROGRESS OF DEAN.

HURRICANE CENTER LOCATED NEAR 14.9N 65.9W AT 18/0300Z
POSITION ACCURATE WITHIN 10 NM

PRESENT MOVEMENT TOWARD THE WEST OR 275 DEGREES AT 16 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 937 MB
EYE DIAMETER 10 NM
MAX SUSTAINED WINDS 125 KT WITH GUSTS TO 155 KT.
64 KT....... 50NE 30SE 30SW 50NW.
50 KT.......100NE 60SE 50SW 100NW.
34 KT.......180NE 120SE 100SW 180NW.
12 FT SEAS..375NE 210SE 75SW 375NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 14.9N 65.9W AT 18/0300Z
AT 18/0000Z CENTER WAS LOCATED NEAR 14.9N 65.1W

FORECAST VALID 18/1200Z 15.5N 68.4W
MAX WIND 130 KT...GUSTS 160 KT.
64 KT... 50NE 30SE 30SW 50NW.
50 KT...100NE 60SE 60SW 100NW.
34 KT...200NE 120SE 120SW 200NW.

FORECAST VALID 19/0000Z 16.4N 71.7W
MAX WIND 135 KT...GUSTS 165 KT.
64 KT... 50NE 30SE 30SW 50NW.
50 KT...100NE 60SE 60SW 100NW.
34 KT...200NE 120SE 120SW 200NW.

FORECAST VALID 19/1200Z 17.3N 75.0W
MAX WIND 135 KT...GUSTS 165 KT.
64 KT... 50NE 30SE 30SW 50NW.
50 KT...100NE 60SE 60SW 100NW.
34 KT...200NE 120SE 120SW 200NW.

FORECAST VALID 20/0000Z 18.2N 78.4W
MAX WIND 135 KT...GUSTS 165 KT.
50 KT...100NE 60SE 60SW 100NW.
34 KT...200NE 120SE 120SW 200NW.

FORECAST VALID 21/0000Z 20.0N 85.5W
MAX WIND 140 KT...GUSTS 170 KT.
50 KT...100NE 60SE 60SW 100NW.
34 KT...200NE 120SE 120SW 200NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 225 NM
ON DAY 4 AND 300 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY

OUTLOOK VALID 22/0000Z 22.5N 91.5W...INLAND
MAX WIND 110 KT...GUSTS 135 KT.

OUTLOOK VALID 23/0000Z 25.0N 97.5W
MAX WIND 110 KT...GUSTS 135 KT.
1691. Baybuddy
2:38 AM GMT on August 18, 2007
Mr. Colby, as a matter-of-fact, NASA Does have a Massive, Space-Borne, Hurricane Destroying Lazer (M.S.B.H.D.L. for short).....they just forgot to bring batteries.
Member Since: June 26, 2006 Posts: 0 Comments: 1115
1690. AndyN
2:42 AM GMT on August 18, 2007
I feel like a proud parent. I have seen Dean emrge as a wave from the motherland...Africa...and after much struggle.....began to grow...and now he is almost grown....they grow right before your very eyes...
Member Since: December 29, 2005 Posts: 1 Comments: 551
1688. AnthonyJKenn
2:40 AM GMT on August 18, 2007
Sorry, misread..that was the NOGAPS, not the GFS, that was tracking into the Pacific.

Still interesting..

Member Since: Posts: Comments:
1687. CajunSubbie
2:41 AM GMT on August 18, 2007
is it me.. or is foward speed slowed down big time?
Member Since: Posts: Comments:
1686. HurricaneDean2007
10:42 PM EDT on August 17, 2007
let's hope Dean maintains speed...so he'll catch the ULL.
Member Since: Posts: Comments:

Viewing: 1735 - 1685

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 | 71Blog Index

Top of Page

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.

Local Weather

Scattered Clouds
78 °F
Scattered Clouds