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: 3185 - 3135

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

3185. IMA
1:39 PM GMT on August 18, 2007
I've found a great resource regarding taking an inventory of your home. This is good for anyone to have, not just those in hurricane-prone areas. There's good info here: Link and here: Link and then a free download from them here: Link
Member Since: Posts: Comments:
3184. StormJunkie
1:35 PM GMT on August 18, 2007
So - a landfall in the US is looking highly unlikely this morning - bad news for Mexico - but good news for Texas

Not true!!! Everyone needs to stay vigilant from LA to Mex...

BG, there should be more out around 2pm...

Models, imagery, preparedness, and more...
Quick Links

Select the first link in the model section. This is the FSU Experimental model page. For all models except for the GFDL and HWRF, I set the field to 850mb vorticity to view potential genesis or track and size of tropical systems. Select animate then scroll right and page through the model run. The surface maps are also good to look at as the 850mb map will sometimes show features which are not at the surface. The GFS, GFDL, and HWRF run four times a day; 00z, 06z, 12z, and 18z. The 00z runs usually come out around 2am Est, the 06z around 8am Est, the 12z around 2pm Est, and the 18z around 8pm Est. The CMC, Nogaps and mm5fsu only run at 00z and 12z. The FSU model site can depict the strength of a system which is something you donít get with the line models. There is a great link that shows the mb to ft comparison in the learning section. Also the GFDL and HWRF only work with the field set to Surface Pressure and they only run for active storms. The NWS NCEP model page contains the long range GFS and the NAM as well as several other models. The South Florida Water Management page has a nice spaghetti plot showing most all of the models together. The Weather Underground Tropical section also has some nice spaghetti plots of several of the major models. The GFDL track can usually be found here before it can be seen on the other sites.

Member Since: August 17, 2005 Posts: 26 Comments: 15472
3183. UnderstandingFL
1:29 PM GMT on August 18, 2007
SEFL, I still can't believe he went.

Unless they provided a CAT 5 withstandable structure, which I'm sure they didn't, I think we all know what a CAT 5 can do. I'll settle for pictures after the fact.

What resources? A camera that will go out with the first strong 120+ winds. Even the person from Jamaica mentioned that their shelters/schools are meant to hold up to CAT 3 winds.

Those that think it's cool, could've actually gone to Jamaica a couple of days ago. I don't think anyone that has ever been in a CAT 4 or 5 would voluntarily go to an island with scarce resources (due to other hurricanes), in it's direct path.
Member Since: Posts: Comments:
3181. dmaddox
1:33 PM GMT on August 18, 2007
i agree as well. it appears dean is now tracking "north" of the NHC projected path issued at 5amEDT... if you look at the latest satellite pictures and overlay the projected plots. could be temporary though but DEFINITELY more of a northerly component than yesterday thats for sure.

i want to follow up on the mike seidel issue. its one thing locating them on the us mainland where they have a place to escape if need be, but no offense - jamaica is simply a sitting duck in the water this morning. there is no place to run and hide for 3 million people there.
Member Since: Posts: Comments:
3180. fire831rescue
1:36 PM GMT on August 18, 2007
Even though this storm appears to continue moving west, I live on the MS Gulf Coast and saw first-hand what the "K" word did. I'm not letting my guard down until it hits somewhere. I'm just wondering who will win the race: the ULL or Dean...
Member Since: Posts: Comments:
3179. welshcayman
1:35 PM GMT on August 18, 2007
Cayman Islands has the best way of dealing with reporters during storms :)

As of 10pm last night nobody is allowed on the island who is not a permanent resident. After Ivan there were many news companies who were complaining that their crews were not allowed onto the island for many days after the storm. Bottom line was that there was a limited amount of fresh water, rooms with a roof and medical supplies. Last thing we needed were dozens more people to worry about.
Member Since: Posts: Comments:
3178. Pipewhale
1:37 PM GMT on August 18, 2007
LAWeatherGuy,

If it made a bee line (which generally a straight line) for Cuba now it would have to smash across Hispaniola first would it not?
Member Since: Posts: Comments:
3177. Kaea
7:35 AM MDT on August 18, 2007
Hey thanks that one worked - friends on Roatan have not answered since Thursday, worried about them....
Member Since: Posts: Comments:
3176. louisianaweatherguy
1:33 PM GMT on August 18, 2007
Posted By: KnowYourRole at 1:31 PM GMT on August 18, 2007.

Posted By: louisianaweatherguy at 9:29 AM EDT on August 18, 2007.
OK NOW... I believe DEAN has begun more than just a wobble to the WNW...Just as I had suspected last night with a slow down come s a change in direction...

Expect MAJOR shifts in the models during the day today...

I doubt it. The NHC has been right on with their forecasted path. Nothing has changed enough to warrant Dean changing direction greatly.

All I'm saying is... if Dean continues gaining latitude like he's doing rapidly as we speak, the models will begin to shift eastward... it's a fact... and you know what happens when the models shift: the NHC track changes... although they wait many runs (understandably)

Member Since: Posts: Comments:
3175. StormJunkie
1:31 PM GMT on August 18, 2007
few people who frequent this blog who would like to be in his place with the resources he will have.

looks around...Can't imagine who those folks would be !~)
Member Since: August 17, 2005 Posts: 26 Comments: 15472
3174. BiloxiGirl
1:33 PM GMT on August 18, 2007
When will new model graphics be posted on sfwmd.gov site?
Member Since: Posts: Comments:
3173. Wecouldoit
1:25 PM GMT on August 18, 2007
Rather than try visual inspection of sat images...if we think its not following track...best use the data from the guys on the scene...recon plots at
http://my.sfwmd.gov/portal/page?_pageid=2854,19644915,2854_19644936:2854_19645082&_dad=portal&_sche ma=PORTAL
Member Since: Posts: Comments:
3172. CocoaLove
9:29 AM EDT on August 18, 2007
Posted By: SEFL at 9:29 AM EDT on August 18, 2007.

"I would expect there are more than a few people who frequent this blog who would like to be in his place with the resources he will have. Aren't you interested in seeing what happens? Better than trying to analyze the most recent four frames of a satellite loop!
"

Thank you for typing this. If new stations didn't send reporters to cover this event folks on this blog would be highly incensed. What more do you want?

Seidel said he is staying in the mountain area of Jamaica, about 600 feet above sea level. He will be okay. He is a reporter as well as a meteorologist. This is what he's trained to do.
Member Since: Posts: Comments:
3171. Kaea
7:30 AM MDT on August 18, 2007
What am I doing wrong? Tried to ask if Roatan was OK, did Dean pass by it, almost 30 mins ago, comment never appeared - help? Please if anyone knows if Roatan got hit (or will) or help me figure out how to post here?
Member Since: Posts: Comments:
3170. StormJunkie
1:28 PM GMT on August 18, 2007
OSMS, no offense, but the NHC had to demand to talk to the locals in La and NO due to the slow proceedings...There was a lot of poor management prior to and after Kat.

But seriously we should be focusing on Dean, the Islands, The Mex and Gulf Coast for now.

Member Since: August 17, 2005 Posts: 26 Comments: 15472
3169. louisianaweatherguy
1:29 PM GMT on August 18, 2007
Posted By: obxrox at 1:28 PM GMT on August 18, 2007.

the last model runs and the TPC plots are biased too far south...it's clearly at 15.6N and gaining latitude as we blog...my clearly uneducated guess is that the center passes north of jamaica, either over w cuba or right through the channel, and then on to central tx or even w la...hope not, but i bet we see the next run of the gfdl go back e and n.


VERY TRUE... I do believe Dean has begun his turn to the WNW... he has headed due WEST for the longest time yesterday evening...

He's headed for a bee-line straight towards the central or Western parts of Cuba...
Member Since: Posts: Comments:
3168. atmoaggie
1:30 PM GMT on August 18, 2007
TWC just reported Dean as a minimal hurricane?? Cat 4 is minimal??

That IS twc. Maybe sure you catch the "Outdoor activity forecast" while you are there. What a dumb name for a forecast.
Member Since: Posts: Comments:
3166. KnowYourRole
9:28 AM EDT on August 18, 2007
Posted By: louisianaweatherguy at 9:29 AM EDT on August 18, 2007.
OK NOW... I believe DEAN has begun more than just a wobble to the WNW...Just as I had suspected last night with a slow down come s a change in direction...

Expect MAJOR shifts in the models during the day today...


I doubt it. The NHC has been right on with their forecasted path. Nothing has changed enough to warrant Dean changing direction greatly.
Member Since: Posts: Comments:
3164. extreme236
1:30 PM GMT on August 18, 2007
Posted By: atmoaggie at 1:29 PM GMT on August 18, 2007.

But, Dean is in the best shear environment right now. He is catching up to higher shear. Might save some lives in Cuba/Yucatan.


apparently the hurricane center doesnt think shear will be a problem. i know there is a anticyclone near by
Member Since: August 2, 2007 Posts: 19 Comments: 19234
3163. calder
1:27 PM GMT on August 18, 2007
dean2007 u love to forecast 200mph+
Member Since: Posts: Comments:
3162. WhereIsTheStorm
1:21 PM GMT on August 18, 2007
Posted By: welshcayman at 1:19 PM GMT on August 18, 2007.

It is abhorent to send a reporter to a place where a Cat 5 storm is about to land. With the camera and sound crew that is probably 3-4 more mouths to feed and people to protect for the emergency services.

I could understand if they were there for a scientific reason but it is simply for ratings and nothing else.

My respect for TWC just keeps falling. Do they not think that there would be a local Jamaican reporter on the ground that could have provided them with the same service via sattelite feed?


TWC has always sent in their own people as long as I can remember. There have only been a few times where they couldn't get into an area and had to rely on the local news people for help. I don't have the faintest idea why they need to send there people into CAT 5 conditions under any circumstances. Doesn't seem like one of the best ideas for people that understand what a CAT 5 storm will do.
Member Since: Posts: Comments:
3161. tinkahbell
1:29 PM GMT on August 18, 2007
TWC just reported Dean as a minimal hurricane?? Cat 4 is minimal??
Member Since: Posts: Comments:
3160. watchingnva
1:28 PM GMT on August 18, 2007
i bet being inside that stadium eye right now would be a beautiful sight with the sun peaking over the edge of those cloud tops...simply amazing...
Member Since: Posts: Comments:
3159. louisianaweatherguy
1:25 PM GMT on August 18, 2007
OK NOW... I believe DEAN has begun more than just a wobble to the WNW...Just as I had suspected last night with a slow down come s a change in direction...

Expect MAJOR shifts in the models during the day today...

Member Since: Posts: Comments:
3158. dmaddox
1:29 PM GMT on August 18, 2007
Nightmare Scenario for Jamaica? DEAN Threatens to be worst Hurricane on Record... *DEVELOPING*

http://www.drudgereport.com/
Member Since: Posts: Comments:
3157. SEFL
1:27 PM GMT on August 18, 2007
"VegasRain, I completely agree with your post.

I can't believe he went, either."

I would expect there are more than a few people who frequent this blog who would like to be in his place with the resources he will have. Aren't you interested in seeing what happens? Better than trying to analyze the most recent four frames of a satellite loop!
Member Since: Posts: Comments:
3156. weathermanwannabe
9:27 AM EDT on August 18, 2007
I'll BBL but it looks like Dean is going to remain in the high intensity category for a few days...Prayers out to our folks in the Greater Antilles....
Member Since: Posts: Comments:
3155. atmoaggie
1:27 PM GMT on August 18, 2007
But, Dean is in the best shear environment right now. He is catching up to higher shear. Might save some lives in Cuba/Yucatan.

shear amon
Member Since: Posts: Comments:
3154. obxrox
1:26 PM GMT on August 18, 2007
the last model runs and the TPC plots are biased too far south...it's clearly at 15.6N and gaining latitude as we blog...my clearly uneducated guess is that the center passes north of jamaica, either over w cuba or right through the channel, and then on to central tx or even w la...hope not, but i bet we see the next run of the gfdl go back e and n.
Member Since: Posts: Comments:
3153. watchingnva
1:24 PM GMT on August 18, 2007
hot will the weak cold front pushing through the southeast interact w/ the ull...and in turn, how will that interact with dean?...hmm...
Member Since: Posts: Comments:
3152. StormJunkie
1:26 PM GMT on August 18, 2007
SEFL...

You would prefer to spend 6 months constantly worrying about the next possible hurricane?

Thank goodness it is no longer then 6months! I think I would loose it. Although I completely understand that my addiction for the tropics is not for everyone!
Member Since: August 17, 2005 Posts: 26 Comments: 15472
3150. al3112
1:24 PM GMT on August 18, 2007
I've got a question, that seems like a pretty strong ULL and its been there for a while, I was wondering as strong as that ULL is could that basically have a impact on that ridge to the north of dean like cause a weakness or push on the ridge and cause it to go north
Member Since: Posts: Comments:
3149. KnowYourRole
9:27 AM EDT on August 18, 2007
keep the politics out of the blog!
Member Since: Posts: Comments:
3147. dean2007
1:24 PM GMT on August 18, 2007
Check out my blog. My thoughts on Dean. Could Dean at this time remind you of Hurricane Camille in cloud structure.
Member Since: Posts: Comments:
3145. KnowYourRole
9:24 AM EDT on August 18, 2007

Posted By: ridercs at 9:20 AM EDT on August 18, 2007.
new on the blog

does anyone think that the wave in the west Atlantic looks like it is developing?


you mean the one is the East atlantic?
Member Since: Posts: Comments:
3144. atmoaggie
1:19 PM GMT on August 18, 2007
Look at the ocean heat content. Dean has even tapped the highest parts of the Caribbean yet.

OHC
Member Since: Posts: Comments:
3143. CocoaLove
9:25 AM EDT on August 18, 2007
Can we keep politics out of a weather discussion, please?
Member Since: Posts: Comments:
3142. Masquer08er
1:22 PM GMT on August 18, 2007
The levees are not up to par,

True. And, never have been.
Member Since: Posts: Comments:
3141. i12BNEi
1:20 PM GMT on August 18, 2007
At some point,Does it become a battle between the Coriolis effect and the ULL in competition for the North turn?
Member Since: Posts: Comments:
3140. SEFL
1:14 PM GMT on August 18, 2007
"its amazing how once you feel like a storm isnt coming your way you no longer pay attention to it and go on with life-until the next one"

You would prefer to spend 6 months constantly worrying about the next possible hurricane? :)
Member Since: Posts: Comments:
3139. StormJunkie
1:22 PM GMT on August 18, 2007
Welcome comtrad and rider ☺

It could riders, I think everyone is keeping there third eye on it right now. It is a long way off. Front two on Dean.

comtrader, mayabe you can help me here. I answered/asked this question a couple of times...

I think in Deans case the ULL is what will ultimately decide the outcome. Help me out here maggie or anyone, If the ULL were to stay slow Dean could get caught up in front of it and then get "tugged" N. If the ULL travels in tandem then Dean continues W at a decent rate of speed. Not likely to happen in this case, but if Dean/a storm were to get behind an ULL then it would likely be pulled N and then W if it could get over the top of it? Y'all correct/help me understand here, thanks
Member Since: August 17, 2005 Posts: 26 Comments: 15472
3138. weathermanwannabe
9:21 AM EDT on August 18, 2007
Dean has been "chasing" the low so as mentioned by many yesterday, follow the low to figure out what happens to Dean...If the low slows or stalls in any way, then this could cause Dean to shift North...Keep you eyes on the Water Vapor loops for the next several days...
Member Since: Posts: Comments:
3136. KEEPEROFTHEGATE (Mod)
1:16 PM GMT on August 18, 2007
track mark 15.5,68
16.1,72 C5/H/D
16.5,75
17.2,77
17.4,79
18,81 C4/H/D
19,82
21,85
STOP......
Member Since: Posts: Comments:

Viewing: 3185 - 3135

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 JeffMasters

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

Mostly Cloudy
59 °F
Mostly Cloudy