Early 2011 Atlantic Hurricane Season Forecasts
Hi everybody, this is Dr. Rob Carver filling in for Dr. Masters.
A continuation of the pattern of much above-average Atlantic hurricane activity we've seen since 1995 is on tap for 2011, according to the latest seasonal forecast issued April 6 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). They are calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes. An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is nearly identical to their forecast made in December, which called for 17 named storms, 9 hurricanes, and 5 intense hurricanes. Only six seasons since 1851 have had as many as 17 named storms; 19 seasons have had 9 or more hurricanes. The 2011 forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The Caribbean is forecast to have a 61% chance of seeing at least one major hurricane (42% is average.) Five years with similar pre-season November atmospheric and oceanic conditions were selected as "analogue" years that the 2011 hurricane season may resemble: 2008, 1999, 1996, 1955, and 2006. The first four years listed all had neutral to La Niña SST's during hurricane season, while 2006 had El Niño SST's. The average activity for these years was 12.6 named storms, 7.8 hurricanes, and 4.8 major hurricanes.
This year, the forecasters have introduced a new statistical model for their April forecasts. There are four components in this model:
1. Average sea-level pressure in March around the Azores in the subtropical Atlantic.
2. The average of January through March sea-surface temperatures (SST's) in the tropical Atlantic off the coast of Africa.
3. Average sea-level pressure in February and March for the southern tropical Pacific ocean west of South America.
4. Forecasts of September's SST in the tropical Pacific using a dynamical model from the European Centre for Medium-Range Weather Forecasts (ECMWF)
The first two components are loosely linked together. Statistical studies have shown that a weaker subtropical high near the Azores, combined with warmer SST's off the coast of Africa in March are associated with weak winds near the surface and aloft from August to October. This decrease in wind speeds reduces wind shear which can disrupt forming storms. These March conditions also are associated with warmer SST's in August to October, which is also favorable for more tropical storms. For this forecast, the first component is strongly favorable for increased hurricane activity, while the second component is weakly negative.
The last two components represent the changes in sea-surface temperature and sea-level pressure that are the El Niño-Southern Oscillation (ENSO). Briefly speaking, El Niño conditions (warm sea-surface temperatures) are not favorable for Atlantic hurricanes. For more info on ENSO and hurricanes, Jeff has this article.
Using the ECMWF model as guidance (see Figure 1), the CSU group believes that SST's in the tropical Pacific will be neutral (less than 0.5°C from normal). This would have a small negative effect on hurricane activity. However, the tropical Pacific sea-level pressure shows that the atmosphere looks like a La Niña event is still going on. This is strongly favorable for Atlantic hurricane activity in the CSU group's model.
Figure 1. Forecasts of El Niño conditions by 20 computer models, made in March 2011. The ECMWF forecast used by the CSU group is represented by the dark orange square. The forecasts for August-September-October (ASO) show that 5 models predict El Niño conditions, 7 predict neutral conditions, and 5 predict a weak to moderate La Niña. El Niño conditions are defined as occurring when sea surface temperatures in the Equatorial Pacific off the coast of South America ( the "Niño 3.4 region) rise to 0.5°C above average (top red line). La Niña conditions occur when SSTs in this region fall to 0.5°C below average. Image credit: Columbia University.
How accurate are the April forecasts? While the formulas used by CSU do well in making hindcasts--correctly modeling the behavior of past hurricane seasons--their April hurricane season forecasts have had no skill in predicting the future. This year's April forecast is using a new system and has not yet produced a verified forecast. The scheme used in the past three years successfully predicted active hurricane seasons for 2008 and 2010, but failed to properly predict the relatively quiet 2009 hurricane season. A different formula was used prior to 2008, and the April forecasts using that formula showed no skill over a simple forecast using climatology. CSU maintains an Excel spreadsheet of their forecast errors ( expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) for their their April forecasts. For now, these April forecasts should simply be viewed as an interesting research effort that has the potential to make skillful forecasts. The next CSU forecast, due by June 1, is the one worth paying attention to. Their early June forecasts have shown considerable skill over the years.
Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and Tropical Storm Risk, Inc. (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. 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.
2011 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2011 Atlantic hurricane season forecast on April 5. They are also calling for a very active year: 14. 2 named storms, 7.5 hurricanes, and 3.6 intense hurricanes. We would round that to 14 named storms, 8 hurricanes, and 4 intense hurricanes. This compares to their forecast issued in December of 15.6 named storms, 8.4 hurricanes, and intense hurricanes. TSR predicts a 55% chance of an above-average hurricane season, 28% chance of a near-normal season, and only a 17% chance of a below normal season. TSR bases their April forecast on predictions that sea surface temperatures this fall in the tropical Atlantic will be above about 0.08°C above average, and trade wind speeds will be about 0.2 m/s slower than average. The decrease in the trade wind speeds is favorable for enhanced hurricane activity, while the forecast SST's are expected to be neutral for hurricane activity.
TSR puts their skill level right next to the forecast numbers: 13% skill above chance at forecasting the number of named storms, 11% skill for hurricanes, and 10% skill for intense hurricanes. That's not much skill, and really, we have to wait until the June 1 forecasts by CSU, NOAA, and TSR to get a forecast with reasonable skill.
Rob's critiques of the April forecasts
I have to note that Jeff and I wrote this article together. He wrote the general framework before the forecasts were issued, while I wrote the details based on the actual forecasts. So the preceding text is a joint production. However, I have a few observations to make that are my responsibility alone.
First, I am disappointed that the CSU group has changed forecast models only after three seasonal forecasts. This makes it very difficult to assess the skill of the current forecast using past performance. This is very important for forecast users, and they do it everyday. For example, I tend to discount a forecast of rain if it comes from a source that over-forecasts rain (The boy who cried wolf problem).
In the documentation that came with the April forecast, the CSU group argue that the hindcasts show the new forecast model has skill. However, I think hindcasts are a poor substitute for real forecasts in understanding the skill of a statistical forecast model, like that of the CSU's group. As Jeff noted, the previous forecast model did well with the hindcasts and yet had mixed results with the actual forecasts. This does not give me confidence that the new forecast model will be superior to the previous model.
From a philosophical viewpoint, I am inherently cautious about statistical forecast models like the one used by the CSU group. Essentially, they look at what happened in the past and use that to predict the future. However, for making forecasts, we assume that the relationships in space and time between the predictors (such as the average March sea-level pressure around the Azores) and the predictands (Atlantic hurricane activity) does not change as we move forward in time. In a world with climate change, that's a tricky assumption to make.
In any event, it is customary in the meteorological community to continue running older forecast guidance models after the introduction of newer models. This allows forecasters and forecast users to leverage their knowledge of the forecast skill of the older model and gain insight into the forecast skill of the new model. The CSU group really should have included the forecast from the previous statistical forecast system in this forecast.
I am uneasy with some of the methodology choices made in implementing the forecast model. Data for the first three predictors was obtained from the Climate Forecast System Reanalysis (CFSR), NOAA's newest and most advanced reanalysis product. However, CFSR data for 2010 and 2011 has not been released yet, so the CSU group used NCEP/NCAR Reanalysis (NNR), NOAA's first-generation reanalysis, to fill in the gaps. Due to differences in design, resolution, etc., CFSR and NNR can have different depictions of the state of the atmosphere. So using NNR's March 2011 average SLP instead of CFSR's could alter the forecast in unexpected ways. It would be interesting to see how CFSR's 2010-2011 data changes the results.
In any event, we will have to wait and see what the Atlantic hurricane season of 2011 brings.
Reader Comments
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On 08.04.2011 at 03:04 GMT 2
It's been almost a year since the explosion of BP's Deepwater Horizon oil rig, and scientists are finding an increased number of dolphins and sea turtles in the Gulf of Mexico. Some of those deaths are being connected to the BP oil spill. Since last April's oil spill, nearly 300 dolphins have been found "stranded" - either dead in the Gulf or dying on its beaches. That's according to an update from the National Oceanic and Atmospheric Administration. NOAA scientist Blair Mase says that's an unusually high number. But since many were found decomposed, it's hard to determine what killed them. Mase says 15 dolphins have been confirmed dead from oil poisoning, with eight being directly connected to the BP spill. "Here, almost a year after the oil spill, we're still seeing evidence of dolphins washing ashore with oil in them," she says. Mase says most of the deaths have been in Louisiana, but one dolphin was found washed ashore on Florida's panhandle. As for the turtles, most of the ones found washed ashore are Kemps-Ridley, an endangered species.
MrMixon~ Your welcome.. My bookmark into WUnderground is to my local radar. Fires, bugs, birds, chaff & rain..it's like a third eye.
Not necessarily a bad trait, arguing with the devil.
:)
As you may know, there is some question whether or not the increased activity in AR is due to injection wells operated by two companies engaged in natural gas fracking. The injection wells have been shut down since March 4. The two companies involved have agreed this shutdown will continue till the AR Oil and Gas Commission can listen to science on both sides of the question at a hearing scheduled for April 26. Earthquake activity has slowed since Mar 4, but, as you have noted, it does continue. Here's a recent news article summary . Also a 2.4 aftershock(?) at 10:36. Looks like 22 quakes in past 2 1/2 days. USGS link
The big quake(s) in Japan might make the human vs. natural cause of Arkansas swarms harder to evaluate.
December 15, 1995 through January 5, 1996. The first shutdown was not long enough to affect pay checks, and DOD was not affected by the second because defense appropriations were enacted on December 1, so funding was available. This is why they got paid. I don't know of any DOD appropriations have been enacted this time to allow them not to defer payroll for DOD.
Those pesky facts...
This is weird, a Tsunami Station is in event mode in the Caribbean SSW of PR. Must be a malfunction. The one closest to it is normal.
We are all DOOM!
Warm sector, dry line, low pressure. Severe weather in Washington, D.C. Which feature you assign to whom is up to you.
:)
Same old questions, though... Where and when will the cap break and what will be the aftermath?
Have a good day, folks.
Was there a Viagra spill?
If this keep "up" more than 4 hours......
You and I are talking about entirely different things.
The military is already deemed as "essential". Each department determines who is "essential" internally. Congress decides if furloughed workers are paid for time they were not at work, due to the shutdown. Anyone who works is deemed essential, and is paid once the budget impasse is resolved, that isn't in question. Whats in question is whether the furloughed workers get paid or not.
One side says "they didn't work, they don't get paid". The other side says "they didn't work because we *couldn't* pay them without a budget".
It requires a username and password... Looks fantastic, though!
Plaza, Here is a helicoder reading near that area, kinda gives another perspective....
Heh... you're seeing everything on radar but rain today...
:)
The fact that Florida has enough bugs that you can occasionally pick them up on radar reminds me of another reason I live at 8,300 above sea level (fewer bugs)! :)
Yeah~ I'd trade it all for rain.
Gates was just on TV addressing our men and women in uniform at a base. He stated to them " the good news is you will get paid, the bad news is I don't know when".
So yes you are correct, they will get paid but it would be a deferred payment once the government is opened back up from business if they shut down
I hear ya... we're way behind on precip around here too. The Western Slope is looking good, but things are downright crispy out on the plains at the moment...
Hi, Jeffs713.
There are some that will not allow the facts to deter them from their opinions. I have seen twincomache side with the facts before. Just keep giving him the facts and I believe he will go with the facts.
Where's Grothar?
I know TC will side with the facts, once they are proven to be facts, as opposed to conjecture or rumor. I know quite a few people who refuse to side with facts if they disagree with their opinion or ideology, but TC isn't one of the stubborn sheeple.
+1000
The plains and front range didn't get much in the way of "upslop" storms this year. A lot of the systems either came across the great lakes and northern plains, or came up from the gulf - not much went across the middle, through the TX panhandle.
The recent update of the 4/4/11 storm. Big numbers
I agree, Jeffs.
I think I found Grothar:
Yeah, I think that would qualify as "significant". And OMG did they try to make a pointillistic painting with blue?
I'm VERY glad he has a good sense of humor. :)
Uh, oh. I think that one will wake the sleeping giant. :-0
+1000
I think the wisdom gained by age tends to thicken the skin...
I can personally testify to that. Someday, I hope to be as thick as Grothar! ..... did that come out wrong?
Yes,..but,..... that photo gave a whole new meaning to "thick Skin"......lol
Revenge is a dish best served cold. Keep your eyes open.
Exactly. This was Boulder's driest March since 1911. The Front Range can usually count on a handful of upslope snowstorms to dump 6-12" of snow a piece and we haven't gotten a single one so far this spring. I'm still holding out hope for a good upslope storm in April or even May, but if we don't get one in the next few weeks then things could get real ugly around here in terms of wildfire (it's already bad enough...)
Does anyone have a sense for what the Southwestern Monsoon season is supposed to be like this summer?
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