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Hurricane season of 2008 forecast to be moderately more active than average

By: Dr. Jeff Masters, 5:09 PM GMT on December 07, 2007

It's going to be a modestly more active than average Atlantic hurricane season in 2008, according to the latest seasonal forecast issued by Dr. Bill Gray and Phil Klotzbach of Colorado State University (CSU) today. The CSU team is calling for 13 named storms, 7 hurricanes, 3 intense hurricanes, and an ACE index 20% above average (Accumulated Cyclone Energy (ACE) is a measure of the total destructive power of a hurricane season, based on the number of days strong winds are observed). An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The CSU forecast calls for a 15% above average chance of a major hurricane hitting the U.S. The odds for a major East Coast hurricane are put at 37% (a 31% chance is average), and odds for the Gulf Coast are 36% (30% chance is average). The CSU team predicts that the current moderate La Nina event will weaken by the 2008 hurricane season, but still contribute to lower than average values of wind shear. In addition, warm sea surface temperatures are likely to continue in the tropical and North Atlantic during 2008, due to the fact that we are in a positive phase of the Atlantic Multidecadal Oscillation (AMO), which began in 1995.

The forecasters examined the observed atmospheric conditions and ocean temperatures in October-November 2007, and came up with a list of five past years that had a similar combination of a moderate La Nina event, near average tropical Atlantic sea surface temperatures (SSTs), and warm far North Atlantic SSTs. Expect 2008 to be similar to the average of these five analogue years, they say. The five years were 2000 (14 named storms, 8 hurricanes, 3 intense hurricanes), 1999 (12, 8, and 5 of the same), 1989 (11, 7 and 2), 1956 (8, 4 and 2), and 1953 (14, 6 and 4). Hurricane Hugo of 1989 (Category 4) was the strongest hurricane to hit the U.S. in these five analogue years.


Figure 1. Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Bill Gray and Phil Klotzbach of Colorado State University (colored squares) and TSR (colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

How good are these December hurricane season forecasts?
For the first time, the CSU team presents detailed information informing users of the accuracy of their December forecasts. Past December forecasts by CSU have had no skill, and I've criticized them for not clearly stating this. I applaud their efforts in today's forecast, where it says in the 2nd paragraph of the abstract, "These real-time operational early December forecasts have not shown forecast skill over climatology during the period 1992-2007". Later in the report, they show that the correlation coefficient (r squared), a standard mathematical measure of skill, is near zero for their December forecasts. As an example of this lack of skill, consider the figures presented in the November 2007 verification report. This report stated that 65% of their December forecasts between 1999 and 2007 correctly predicted whether the coming hurricane season would be above or below normal, for forecasts of number of named storms, hurricanes, intense hurricane, and number of days these storms are present. That 65% figure sounds pretty good, but is it skillful? To answer that question, I tallied up how an almost zero-skill forecast would have done over the same period. My almost zero-skill forecast simply assumed that since we are in an active hurricane period that began in 1995, every hurricane season will have an above normal number of named storms, hurricanes, intense hurricanes, and number of days storms are present. The result? My almost zero-skill forecast got it right 65% of the time, exactly the same as the CSU December forecast.

Another way to measure skill is using the Mean Square Skill Score (MSSS), which looks at the forecast error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes (Figure 1). The skill of the December forecasts issued by both CSU and Tropical Storm Risk, Inc. (TSR) have averaged near zero since 1992. Not surprisingly, the forecasts get better the closer they get to hurricane season. The TSR forecasts show more skill than the CSU forecasts, but it is unclear how much of this superiority is due to the fact that TSR issues forecasts of fractional storms (for example, TSR may forecast 14.7 named storms, while CSU uses only whole numbers like 14 or 15). TSR does an excellent job communicating their seasonal forecast skill. Each forecast is accompanied by a "Forecast Skill at this Lead" number, and they clearly define this quantity as "Percentage Improvement in Mean Square Error over Running 10-year Prior Climate Norm from Replicated Real Time Forecasts 1987-2006."

The June and August forecasts from CSU, TSR, and NOAA show some modest skill, and are valuable tools for insurance companies and emergency planners to help estimate their risks. The key problem with earlier forecasts is that the El Nino/La Nina atmospheric cycle that can dominate the activity of an Atlantic hurricane season is generally not predictable more than 3-6 months in advance. For example, none of the El Nino forecast models foresaw the September 2006 El Nino event until April or May of 2006. Until we can forecast the evolution of El Nino more than six months in advance, December forecasts of Atlantic hurricane activity are merely interesting mental exercises that don't deserve the media attention they get. There is hope for the December forecasts, since Klotzbach and Gray (2004) showed that their statistical scheme could make a skillful forecast in December, when applied to 50 years of historical data. However, these "hindcasts" are much easier to make than a real-time forecast. For example, before 1995, it was observed that high rainfall in the Sahel region of Africa was correlated with increased Atlantic hurricane activity. This correlation was used as part of the CSU forecast scheme. However, when the current active hurricane period began in 1995, the correlation stopped working. Drought conditions occurred in the Sahel, but Atlantic hurricane activity showed a major increase. The CSU team was forced to drop African rainfall as a predictor of Atlantic hurricane activity.

Hotel owner threatens to sue Bill Gray for bad forecasts
Central Florida's most famous hotel owner, Harris Rosen, has threatened to sue Bill Gray because his bad forecasts have cost Florida billions of dollars in tourist revenue, according to a story published in November 2007 by WKMG Orlando. I think the record-breaking hurricane seasons of 2004 and 2005 had more to do with lost tourist revenue than any forecast by Bill Gray, so this is a rather ridiculous threat. However, these sorts of ugly accusations are the inevitable result of a culture where seasonal hurricane forecasts, which are not very good, are excessively hyped by both the forecasters and the media. The forecasters have set them selves up for such shrill condemnations by putting out these very public forecasts, complete with press conferences, but not properly emphasizing the uncertainties and low skill of their forecasts. By clearly stating their lack of forecast skill, the CSU team's December 2007 forecast is a great step towards improving this situation. The public needs to know that these December forecasts as yet have no skill, and are unworthy of the media attention they get.

References
Klotzbach, P.J., and W.M. Gray, "Updated 6-11 Month Prediction of Atlantic Basin Seasonal Hurricane Activity," Weather and Forecasting 19, Issue 5, October 2004, pp 917-934.

Next blog
Next week, I'll be blogging from San Francisco. It's time for the world's largest scientific meeting on climate change, the annual meeting of the American Geophysical Union.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Don't be so thin skinned JFV. He was just trying to be funny. Wether or not it worked I better not judge as I am guilty of a pot shot or two myself.
989. weatherguy03 7:43 PM CST on December 09, 2007
We always notice you SJ. Its hard to miss all of the links to your website.:)


LOL...
The future of this thing is going to be up to whether it hits the islands.A rather strong high pressure ridge is forcast to be a place most of next week.I dont see anything in its way for the next 2-3 days that might halt some intensification. Adrian
Evening 03, great to see you, I'm sorry did you ask for a link to StormJunkie.com?

But if you know anything about weather, then you will likely just want to use the Quick Links page. Everything you need in one place!
Ok, now that I feel stupid for forgetting what direction due west was (doh!) I can at least recognize that the motion has slowed
shes due west
1008. Drakoen
989. weatherguy03 1:43 AM GMT on December 10, 2007
We always notice you SJ. Its hard to miss all of the links to your website.:)

LOL.
992. Drakoen 8:44 PM EST on December 09, 2007
"The Phsycological affects of tropical Cyclones on Human Behavior"
That should be the title of a book.


It's not the subtitle to Dr M's blog?
Colorful map here in SW Ohio...Flood watches and flash flood watches in green, freezing rain adv. in purple and dense fog adv. in gray...

1010. ShenValleyFlyFish 1:51 AM GMT on December 10, 2007
992. Drakoen 8:44 PM EST on December 09, 2007
"The Phsycological affects of tropical Cyclones on Human Behavior"
That should be the title of a book.

It's not the subtitle to Dr M's blog?


ROFL
1014. Drakoen
1010. ShenValleyFlyFish 1:51 AM GMT on December 10, 2007
992. Drakoen 8:44 PM EST on December 09, 2007
"The Phsycological affects of tropical Cyclones on Human Behavior"
That should be the title of a book.

It's not the subtitle to Dr M's blog?


It should be lol.
Just for the record, My local weather/news channel just referred to 94L as a clump of showers and said it may be over Florida later this week...But they said nothing about it becoming a tropical threat. (I am located in Saint petersburg,Florida)
Michael, thanks for the info. I know there may have been some earlier or later. I was just looking for ones that affected the US, but I probably wasn't very clear when I posted. Thanks for the info though, I like to learn!
It's Christmas Season, Peace on Earth!!!
1018. Drakoen
1017. WeatherfanPR 1:53 AM GMT on December 10, 2007
It's Christmas Season, Peace on Earth!!!


ROFL.


1019. JLPR
Im very exited to know what my local met would say tomorrow morning about 94L
I second that WPR, well said!

Peace and joy to all during this holiday season.
Nah SJ, I will stick with Adrian Weather
1022. Drakoen
1021. weatherguy03 1:58 AM GMT on December 10, 2007
Nah SJ, I will stick with Adrian Weather


Ouch. Way to put a damper StormJunkie's fun.
Evening everybody.

I too noted the advice for E Bahamas to monitor this system. That ridge to the N of us seems pretty solid for now. Plus the fronts we have gotten through here lately have been pretty mild.

Temperatures here have been quite mild, even rather warm. Plus we've had lots of diurnal heating due to low cloud cover. Am I right to assume water heats/cools more slowly than nearby land masses?

In any case, wherever this baby ends up, it sure is an interesting addition to mid-December . . ..
Good site as well Bob.

And hey Bob, if you can find the last time I posted a link in here prior to tonight I will give you a free membership to SJ.com. See if you can't track that down.

Amazing how much folks enjoy putting others hard work down.

1011. extreme236 7:52 PM CST on December 09, 2007
Colorful map here in SW Ohio...Flood watches and flash flood watches in green, freezing rain adv. in purple and dense fog adv. in gray...




At least you don't have any ice storm warnings (purple):



Depending on what you look at, up to an inch of ice accumulations are expected tonight. Pretty soon most of Missouri will be devoid of trees if stuff like this keeps happening...
94L has no were to go but generally to the west or even a tad south of due west as strong high pressure will not go anywere.Last time i looked at some models they were sending a somewhat stronger cold front through the SE which would cause a break in the ridge later this week.
1020. StormJunkie 8:56 PM EST on December 09, 2007
I second that WPR, well said!
Peace and joy to all during this holiday season.

May I third that?
Drak, I wouldn't let you guys put a damper on my fun, it is Christmas time! ☺
1030. Drakoen
From intellicast.
ROFL? what does that mean Drak?
Yea Im glad I dont have ice storm warnings in my area...that would be bad
I'll pass SJ, but thanks for the offer. Well this Invest could be an interesting one, hang on folks! Almost a summer time pattern we are in across the Western Atlantic this week.
Rolling on the Floor Laughing....

Now how it had anything to do with your cry for peace, I have no clue...
1035. Drakoen
It means they think a low has formed. Ignore the symbols at the botton.
Naughty naughty Grinch

94l upgaded by 11 pm to td 15 in my opinion it is already td or real close
1038. 0741
have models runs from southfl water depatrment come out???
Hey 03 whats going on?

Hope your holidays are going great....For me iam kinda excited to attend my 2nd AMS meeting this upcoming week and look forward to taking some pics with Max and Jamie Rhone.Hows everything with the family?I had decent weekend took the wife to dinner and went to see the MIST from steven king.The ending of that movie was shocking.

Anyway hope you have a great week. Adrian
1040. Drakoen
I doubt this will be a depression. Not enough organization.
the next number is 17
Well, it wouldnt be a TD it would be a TS since winds are high enough
1043. 0741
have any model runs done on 94l?
This system sure looks impressive.

And, its not quite organized enough yet with a little uncertainty about an LLC
just going by the letter 456 o is the 15th letter
1047. JRRP
94L is moving wnw i think
Ok StormJunkie and Drakoen, I'm still confused about the ROFL word but don't worry. Peace!!!
KEEPEROFTHEGATE

ok
WPR, it is an acronym for Rolling On the Floor Laughing

Again, I second your Peace to all though!
Sounds like fun Adrian. Its going well here, real busy with the family and life. Just popping in to see what kind of tropical excitement we have! It kind of goes with my 80 degree weather this weekend, crazy stuff.
92B

ROFL=Rolling On Floor Laughing.

If thats what u needed help w/.
1025. StormJunkie 9:00 PM EST on December 09, 2007

Amazing how much folks enjoy putting others hard work down.


I hope u realize people are just cracking on u tonight . . .

It's the tracking fever.

LOL
1051. weatherguy03 9:15 PM EST on December 09, 2007
Sounds like fun Adrian. Its going well here, real busy with the family and life. Just popping in to see what kind of tropical excitement we have! It kind of goes with my 80 degree weather this weekend, crazy stuff.

Awsome buddy thanks for responding...If i dont speak to you again this year i wish you and your family the best in 08. Keep in touch. Adrian
Amazing how much folks enjoy putting others hard work down.

I second that
we got a summer flow going on 23 thats why the 80's
On Tuesday, December 4, 2007, GOES-12 (GOES-East) experienced an anomaly in its attitude following a scheduled North-South station keeping maneuver. Various attempts to restore GOES-12 to normal on-orbit mode have been unsuccessful. GOES-12 is safe, continued attempts will be made to return GOES-12 to normal on-orbit mode. Investigation is continuing. At this time, we do not have an estimated Return to Service for GOES-12. GOES-10 is being utilized with GOES-East schedule and COMM services including GVAR being relayed through GOES-12.
Thanks Baha, and great to see ya!

It is all good, I am pretty thick skinned (and use to the hacking on I take from some) ☺
The NHC is probably going to wait a bit longer; after all, they were recently getting flak over naming storms that some people thought that shouldn't have been named, although I don't see any problems with any of the storms this year, even if some would have been missed before satellite (if you applied the same to 2005 and adjusted the numbers for 1933 to account for the storms that might of been missed, 1933 might still be the most active season).
That is killing me 456, thanks for the info though. That is the reason the GHCC site is off line as far as I can tell.
Tracking.. snacking..
My forecast for invest 94.. twill become a tropical storm, near hurricane force, then move off to NE becoming extratropical or is that subtropical?

My sources? Climatology and my favorite psychic weather Link.

LOL. Good to see you all having fun tonight. Everybody Wang Chung.
OK thanks for the ROFL explanation. I just learned something new today.
ok, no problem, glad when i can help. :)
Quicksat from a few hours ago doesn't look closed.
1062. Weather456 8:26 PM CST on December 09, 2007
94L has move westward alot. Its now over Haiti.


That has to be some kind of error... NRL still has it NE of the Leewards:

Evening BFOTR :~)

Everybody Wang Chung.

That is taking it back a decade or two there!

Speaking of Wang, anyone remember Wang computers?
GOES
Engineers have confirmed the cause of the attitude disturbances on GOES-12 that started after the North/South maneuver. We believe there is a leak in the oxidizer line of thruster 2B. We were successful yesterday in isolating the thruster. This evening, we are planning to go into normal attitude control mode. Engineers will be monitoring the spacecraft through out the weekend. On Monday we will determine whether to begin normal imaging and sounding operations. GOES-10 continues to support the East satellite imaging and sounding operations. Since yesterday GOES-10 GVAR and all auxiliary services, including EMWIN, were broadcast simultaneously through GOES-10 and GOES-12.
Evening nrti, great to see you, and thanks for more great info! Would love to have the GHCC site back in the next day or so!
1054. BahaHurican 2:16 AM GMT on December 10, 2007
I hope u realize people are just cracking on u tonight . . .

It's the tracking fever.


...lol, more like just plain ego "fever"! Remember the line, "That's what we call an overbaked ham!" lol, weather watching gets a bit too serious sometimes!

Adrian and SJ both have great weather/link sites. SJ's site has got a great tutorial on models, Qscat and other things. SJ, I appreciate your hard work over there and visit frequently! The tutorials are awesome. Site, too!

1062. Weather456 8:26 PM CST on December 09, 2007
94L has move westward alot. Its now over Haiti.


That has to be some kind of error... NRL still has it NE of the Leewards:


Its an error....I think they used a GOES-12 background fro GOES-10 images.
Thats whats odd...QS doesnt show a closed low but microwave imagery indicates some spiral banding and a possible LLC...mixed signals, so thats another reason why the NHC is waiting
Thanks mlc, and great to see you! Going to get some more of those tutorials done as soon as I finish a couple of things I am working on now. They aren't a great help for professional mets, but for us weather junkies, they can sure speed the learning process a little.
236, I have not looked at QS or microwave, but is there a significant time difference in the two? May be part of the reason for the discrepancy between the two?
This what microwave shows



Good night all



That is taking it back a decade or two there!
LOL, SJ, and not a gray hair to be found.

Fun. Something to watch anyway... though we'll never see Zeta again. Well, I'll leave the floor to all of you.

I dont think there was that much of a time difference.
Evening SW, great to see ya!

Night 456.

Wasn't sure 236, just thought I would throw it out there.
Hey, StormW...I thought we'd closed the door on the tropics! What gives? lol
yea, it was a good point you brought up though SJ about a possible time difference...I guess that would normally explain it, but I guess its just an odd situation lol
Buoy/ship wise not much near at the moment.

StormW, you know man, you're the "go to" guy for weather on here for many of us!
What's your take on this thing? Little chance or none?

Hey, SKYE! BFoot, Extreme, 456, Drakoen, STL, JFV, HG, Baha, Keeper, Adrian, all!

Top of the Sunday evening to everyone!
Can't believe no one commented/remembers the Wang computers? Was one of the first computers my family owned. Think that was even before the TRS-80/COCO
Evening Skye :~) If I try to make the Jan 2nd launch, any chance you could direct me in to a good location to watch it?

Sorry for the off topic, but back to the computers for a minute, our TRS-80 even had one of those modems you sit your phone on, like in War Games. Use to log on to what were called Bulletin Board Services where in several hours you could download very small programs, post messages, etc...
Hey MLC
Not sure if this has been mentioned yet, but SSD is calling 94L a tropical depression:

09/2345 UTC 19.2N 58.3W T1.5/1.5 94L -- Atlantic Ocean
STL, just curious, then why does it still say

09/2345 UTC 19.2N 58.3W T1.5/1.5 94L -- Atlantic Ocean
the 94L above if its a Depression.
Thanks
Good night all!
1095. HurricaneGeek 9:08 PM CST on December 09, 2007
STL, just curious, then why does it still say

09/2345 UTC 19.2N 58.3W T1.5/1.5 94L -- Atlantic Ocean
the 94L above if its a Depression.
Thanks


Well, it is still an invest, but at depression intensity (usually T1.5-T2.0). Also notable that they are calling it tropical and not subtropical.
1099. Rodek
Hi folks. Just got back from a roadtrip and am super tired. I couldn't resist checking out the latest in the tropics. To my surprise, 94l is sitting out there. Can someone share the latest and greatest with me in layman's terms?
Ok, STL thank you.
nhc may issue something at 11 pm it looks like a mod to strong td to me trackin due w slightly sw good wrap how long it can maintain is anyones guess
it appears near 19.2n/59.1w
later storm
A local news reporter said that the NHC issued a special statement and said that 94L could become a subtropical depression and we can expect up to two inches of rain and winds up to 45mph specially on elevations above 1,000ft.
Thanks for the update WPR

Night SW, see ya soon
1111. AndyN
What are the odds of 94L getting into the Gulf and being anything except a high wind event and rain maker? Could this be the drought buster for the South?
Evening Andy, seems unlikely, but I am not really up on it either. I looked at the models a little yesterday and it seemed all of them wanted to take it towards the Yuc Pen
according to NHC it has no closed cir.
as per 1030 update
Heavy rains and breezy conditions right now here in Carolina PR.
1115. JLPR
yep WeatherfanPR although is calm right now here
For us in Puerto Rico it doesn't matter if 94L develops or not because in any case we are going to feel rain and wind and it's just starting here.
could this td 94l take right off an go on a rapid organization phase just a hunch it appears to be getting itself together better every sat update
1118. JLPR
yeah weatherfan its kinda funny you live so close to me :P
there isnt such a big difference between a strong invest and a TD
ur experienceing the little tropical monsoon before the big tropical monsoon
Says 40 mph, it should have been upgraded.
Hey JLPR, I live in Villa Fontana,Carolina near Plaza Carolina. and you?
Personally I doubt it keeper, but the tropics often keep us guessing. Still looks a little rough to me right now though. Granted for a Dec system it does look fairly well organized.

Night y'all ☺
1123. JLPR
not so far about 15minutes from you
Country Club in front of La Ciudad Deportiva Roberto Clemente
nite sj
Ok, right now it's calm here.
1126. JLPR
yeah tomorrow should be a rainy and windy day here well take care WeatherfanPR and everyone
goodnight :)
whats that popin up at 10n/96w
Nite JLPR, I'm going to bed also Nite All.
1129. JRRP
is no a td couse 94L don´t has the enough convection as to be tropical ciclone