Hurricane season of 2008 forecast to be moderately more active than average
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
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 — Blog Index
Hey ,I know one thing for certain,hurricane season starts June 1st
lol that is true. But, sometimes tropical cyclones can be like babies, they can come a little premature lol :)
I really don't mean to be rude.But i am going to be rude.....I live in Palm Beach county Florida...I have been here for 24 years. I am sick and tired of the old man in Colorado and his freekin' forecasts. All it does is get the elderly people in a panic, Including my dear mother (RIP) He needs to go away so us Floridians can deal with it the best we know. I don't like the old man, and never will. I feel better, but I knoe old man Gray will still make the elderly here uncomfortable in years to come. He made my dear mother miserable for years.
Unfortunatly though, as in the case for some people in Florida, they take the seasonal forecasts as gospal...they are just predictions.
And sorry to hear that about your mother...best of wishes
The preliminary forecast calls for a total of 13 named storms in the Atlantic. It also says it is probable that at least one major hurricane will hit the U.S. coastline
I do agree with Dr. Gray that it is probable for at least one major to strike the US, but I think it is more wise to rather state a percentage, rather than say that in that way. No one knows for sure if at least one will. I can tell you this much though, we will see zero or more major's hit land lol
extreme.Exactly.They take it as gospel.That's why he needs to quit. My mother and many others have been stressed because of his forecasts. We will be prepared when the time comes. Not some old codger telling us months ahead
Perhaps maybe he just needs to wait till May like NOAA before giving a prediction, as him making a prediction this far away isnt very wise.
:S
Yes, we are in sync. :)
Fiji, officially the Republic of the Fiji Islands, is an island nation in the South Pacific Ocean east of Vanuatu, west of Tonga and south of Tuvalu. The country occupies an archipelago of about 322 islands, of which 106 are permanently inhabited, and 522 islets. The two major islands, Viti Levu and Vanua Levu, account for 87% of the population.
Cyclone Daman DID NOT miss "Fiji".
Link
Cyclone destroys all homes on Fiji island
Posted at 10:49am on 08 Dec 2007
Cyclone Daman has destroyed all the homes and food crops on the small Fijian island of Cikobia.
The Category Four storm passed directly over the island, which is to the northeast of Fiji's second largest island, Vanua Levu.
Fiji's Disaster Management Office says Cikobia was extensively damaged. It says about 70 people live on two villages on the island, and no homes remain standing, but it is not yet known whether anyone has been injured.
Hurricane strength winds and rain also hit the northern part of Vanua Levu, but the only damage appears to be some flooding.
Fiji's Meteorological Service says the worst is now over, but strong winds will continue for some time, and parts of the country are still getting heavy rain.
I knew about it maybe two days ago when I noticed that the pressure gradient has increased significantly when the low was located south of Iceland. The problem with these storm is their forward speed, they can cross the Atlantic within 2 days. I guess the current storm "Hannes" serves as a good example for these fast moving lows:
Situation as of Dec 4 The storm which is currently (evening of Dec 7) over Finland named Hannes has its center still over Nova Scotia. Center pressure about 985 mb.
The next day, Dec 5 the center is already south of Iceland and the pressure is below 975 mb. At that point I could tell that this might be a problem for Finland (where the fronts associated with Geoffrey are located).
On Dec 6 Hannes was at its lowest pressure with 970 when being over South Norway east of Britain.
And today Hannes is over Finland which was noticable in the wind directions and temperature, in the morning it was SW wind then it turned west and then it was NW, it got colder and the wind increased.
In my opinion forecasting these storms is quite hard because they can travel great distances in a few days so they can come as a surprise. If I were not into weather otherwise I would know about a coming storm maybe the day before from the media; following those maps above gives me another day or two in advance to know about it.
This endless chain of Atlantic storms lashing Northern Europe has been going on for nearly a month now. The last time I have seen the sun was on Nov 25, I think, but I'm not quite sure. The last longer sunny period was in October, I mean at least 2 sunny days in a row. I think there is a small chance of seeing the sun on Sunday before the next storm Isaak hits (currently NW of the British Isles) Sunday night. After that one maybe we might have a longer period of sunny weather. I really hope so, I miss the sun :-(
I still dont see whats wrong with making predictions this early...he has the right to make these predictions and if a person doesnt like it then they should just not look at them. The media is what hypes everything up. His December forecast was more accurate for 2007 than his later forecasts for the season anyway. I see nothing wrong with it. And just to let you know, Im not really responding only to you, but all the critical comments about it so dont take it personal or anything. Just my opinion :)
I have a question for you.
You blame the media for hypeing everything up and yet, isn't making a prediction for the 2008 Hurricane Season in December 2007, almost 6 months in advance...just a wee bit of hypeing as well?
We haven't even seen the winter weather patterns and someone...anyone has the temerity to suggest a prediction? Didn't someone on this list refer to that sort of prediction as 'wishcasting', earlier this year?
I believe that it is wrong to make predictions regarding weather that is going to happen in June next year. Why? Because it sets the stage for others who are sympathetic to the cause and in a position to have a say in the naming of storms to even subconciously err in favor of making his/her favorite predictor more correct than they otherwise would have been. ie. The naming of storms in the 2007 season that now look as if they jumped the gun in naming them. Even Dr. M mentioned it.
If the trend continues, it won't be long before someone makes a prediction for a hurricane season two years out. Isn't there a point where we all say, collectively, enough is enough?
I still dont see whats wrong with making predictions this early...he has the right to make these predictions and if a person doesnt like it then they should just not look at them. The media is what hypes everything up. His December forecast was more accurate for 2007 than his later forecasts for the season anyway. I see nothing wrong with it. And just to let you know, Im not really responding only to you, but all the critical comments about it so dont take it personal or anything. Just my opinion :)
I have a question for you.
You blame the media for hypeing everything up and yet, isn't making a prediction for the 2008 Hurricane Season in December 2007, almost 6 months in advance...just a wee bit of hypeing as well?
We haven't even seen the winter weather patterns and someone...anyone has the temerity to suggest a prediction? Didn't someone on this list refer to that sort of prediction as 'wishcasting', earlier this year?
I believe that it is wrong to make predictions regarding weather that is going to happen in June next year. Why? Because it sets the stage for others who are sympathetic to the cause and in a position to have a say in the naming of storms to even subconciously err in favor of making his/her favorite predictor more correct than they otherwise would have been. ie. The naming of storms in the 2007 season that now look as if they jumped the gun in naming them. Even Dr. M mentioned it.
If the trend continues, it won't be long before someone makes a prediction for a hurricane season two years out. Isn't there a point where we all say, collectively, enough is enough?
It is hyping in some way, but not in the way that the media hypes it up as. Im glad there hasnt been much hype so far with these new predictions that I have seen. Yes, it is stupid to may predictions this early. Im not saying that its not stupid.
Now for the naming of storms this year, every storm this year that was named earned that name and the NHC stated the reasons each storm was named. I havent read about any storms this year that did not earn a name. There is a point where we can say enough is enough, but I think every knows a prediction cant be made 2 years away. A prediction made six months in advance is not likely to be accurate (well the december forecast for this hurricane season wasnt too bad) but it isnt just a random number it is based on something, such as how its unlikely to see another cool or warm ENSO year again. Also SSTs are likely to be above average. But, once again, IMO December predictions are a bit stupid.
In comparison to that the last winter's strongest storm Kyrill had a minimal pressure of 964 mb over Germany and later even 961 further inland in Eastern Europe but gusts up to 225 km/h (140 mph or 121.5 kts) so between a 6 and a 6.5 Dvorak (115-127 kts) which have pressures of 948-935, a Cat. 4 on the Saffir Simpson scale. The 10 min sustained was about 120-150 km/h (65-80 kts) so a Cat. 1. The reason for the strong winds was in the high pressure gradient which was at the maximum 42 mb difference between a 966 over NW-Germany and 1010 over SE-Germany.
The strongest storm I remember is Lothar on Dec 26 1999 with a minimum pressure of 962 and maximum gusts of 272 km/h (169 mph or 147 kts, a Cat. 5), the 10 min sustained were also slightly higher than with Kyrill. The meteorological institute in Caen at the Atlantic coast of France noted a drop of 27.7 mb from in 3 hours and then after the storm a rise of 29 in only 3 hours which has never occured in recorded history in Europe.
In contrary to Kyrill which was well anticipated about 2 days ago Lothar struck quite surprisingly, it developed of a strong frontal system south of Ireland, became a "wave disturbance" (I don't know the correct term for this in English, probably the non-tropical equivalent of a tropical wave which can develop into a Major hurricane) which deepened rapidly within hours before striking N-France nearly out of nowhere. In Germany people also had no warning because the DWD did not issue a storm warning. It caused 11.5 billion Euros (approx. 16.8 billion $) damage in Europe and 110 people died.
I don't really understand how these rapid deepenings in non-tropical lows happen and neither does the German Meteorological Service (DWD), they don't have an explanation for it in their report on the system, it's rather descriptive.
MichaelSTL and extreme236, I agree with you that the NHC usually has reasonable requirements and adequate data to justify the naming of a storm. The question about TDs out in the ocean without any future - well, for scientific records on the overall activity of the bassin I think it is alright to appoint them TD status if they have it at least for a couple of advisories. I admit that counting all these little systems in makes it rather impossible to compare the last two decades to seasons prior to the advanced satellite technique but this is just a fact we have to live with. I'd rather say it is good we have them now and the masses of data collected in the last decades will help future mets to - hopefully - make more exact predictions and in some decades we might be able to say something about the matchlessness of 2005 when we'll have seen more highly active seasons with the eyes of satellites. By then we might also be able to evaluate the actual influence of MGW on tropical weather which is currently quite probable but we're still missing long term data to prove it 100 %.
How frequent are subtropical storms? If I recall right the last couple of years there have been maybe 1-3 of them per season, not more.
Could it be possible to measure their PDI or ACE separately from the purely tropical ones? As far as I read their ACEs are not counted towards the overall ACE of a season. Why is that so? Is it hard to estimate it based on figures like the sustained wind or central pressure?
Viewing: 51 - 101
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 — Blog Index