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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The map source is Ham Weather. The dot is on Dry Tortugas, its tough to see ;) On Wed, Apr 6th Dry Tortugas recorded 0.5 inches, the old record was 0.07 inches in 1954.
Here's a Link
Don't need any further legislation on those critters thanks to Hook's Law:
No matter how charming it's friendly smile, never never handfeed a crocodile.
The Damp Tourugas?
The Moist Tortugas?
Record temps in northern Spain in some cases 15/c above normal. 33/c or about 90+F this afternoon on the north coast. Noaa said it was coming last week.
Whats with all these moderate earthquakes in ARKANSAS?
Bit more of a problem at another nuclear plant in Japan but they say they have it under control. Leaks of radioactive water etc.
Not a word of politcs there!
Agree
Then we very well may have run into each other. I was at the armory in Homestead--right next to the community center--for two days handing out relief supplies (water, diapers, infant formula, bread, etc.), then spent another three days driving through Homestead and Florida City going door-to-door--or, truthfully, debris pile to debris pile--looking for those unable to get to the center. Most of the time we were out in convoys, several vehicles working at once, and with several people in each vehicle. But I and another guy once found ourselves cut off from the group in what was left of a mobile home park, and we were robbed of all our supplies at gunpoint within, literally, minutes. When we told the cops about it later, they just shrugged and said, "Bummer. Guess you won't be going back there alone, huh?"
Good times...
I took a few dozen pictures of the damage before I started feeling guilty about doing so; I'll scan them and post them when I get a chance.
I was in Hialeah.
554 TampaTom "The Damp Tourugas? The Moist Tortugas?"
So much for their tourism promise of fun&sun with no "I'm melting... I'm melting...". Just leaves the AtacamaDesert and the McMurdoDryValleys for the Wicked. And Antarctica is colder than a Witch's
Seems a bit odd!
MAP
2.6
2011/04/08 13:16:49
35.236
-92.366
6.0
ARKANSAS
Andrew 1992
This is the way it was as far as the eye could see at the Dadeland MHP.
It was "interesting" for the first week or so untill the military moved into the neighborhood. No way to contact emergency services, and vigilante justice does have it's pros and cons.
g'morning hydrus to you as well.
Well, surface moisture is quite high, but the moisture drops way off above the near surface layer. Also, the ridge aloft is causing an inversion in the mid levels. To be honest, the atmosphere is amazingly favorable for convection considering we are sitting here in Early April with a strong ridge overhead.
This year is definitely looking much better than last year. Last year the atmosphere always was against convection. Even during El Nino early on we didn't get any severe weather and almost no thunderstorms because the air was so darn stable.
This year, there has been a general replacement of more stable air that dominated last year with more unstable air.
Hey there "killer." Good to see you.
I don't know, I can imagine dry Tortugas can actually be quite wet at times. That part of the gulf can be absolutely drenched with rain sometimes. Its just that it's April on an island off the coast of South Florida.
I would probably bet dry Tortugas is known for some huge rain events at times actually. People probably just visited it during the winter and spring and called it "dry Tortugas".
Published: Friday, April 08, 2011, 6:30 AM
Speaking of inversion layers... they suck. And have a MUCH bigger impact than you think on convection. For example, here in Houston, we have had PLENTY of moisture at the low levels, and some solid forcing the past few weeks, but very little to speak of in the way of rain. Why? A very strong cap caused by an inversion layer around 850-900mb.
RUC sounding for KIAH (Houston Intercontinental Airport). Notice the rise in temps at 1200 feet, and drop in humidity at 2600 feet. Its a textbook inversion layer, and is acting to basically destroy anything that tries to get going. Also, this inversion layer is caused by a change in wind direction around those levels. (note at the very lowest levels, the wind is from the SE, off the gulf. Above that, its out of the SW, which is over land, from Mexico, and tends to be very dry. Yes, we will get some low clouds, but nothing will drop from them.
On Friday, parts of Britain were hotter than Rome, Athens, Istanbul, LA and New York, with temperatures predicted to reach 21C (70F).
Average temperatures for this time of year are 7C (45F) in Scotland, and 12C (54F) in London.
London and the Home Counties have basked in warm sunshine for the past two days, with mid-afternoon temperatures reaching 22C (71.6F) in Gatwick, West Sussex, and Charlwood, Surrey, on Thursday.
This equalled the highest recorded 7 April temperature of 22C (71.6F) - recorded in Achnashellach, in the Highlands of Scotland, in 1974.'
21/22C up here close to the Yorkie Moors.
You can now just imagine that the whole royal wedding event will end up being a cold, wet, dreary affair weather wise - using up all the good weather credits for this month.
Its not a physical sounding. Its a model sounding. Based off observations and nearby physical soundings.
My e-mail to the NWS went into a black hole apparently, but I found the site I linked by accident. (its the model soundings they talk about in the forecast discussions).
Its nothing near as accurate as the physical soundings, but it helps understand local conditions fairly well.
The source site is http://rucsoundings.noaa.gov/. You have to know the airport code to get it to pull, though.
There goes Arkansas again. Man I hope it's letting off steam, and reducing tension in that area.
Preachin' to the choir there. I have a feeling the restriction is due to the proximity of all the airports (not just IAH and Hobby - also all the smaller airports like Sugar Land Executive, West Houston, Hooks, and Scholes Field).
I know Sugar Land, West Houston, and Hooks all run jets with some frequency. (I live about 2 miles from Hooks)
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE MELBOURNE FL
858 PM EDT SAT SEP 25 2004
THE NATIONAL WEATHER SERVICE IN MELBOURNE HAS ISSUED A
* TORNADO WARNING FOR...
MARTIN COUNTY
ST. LUCIE COUNTY
IN EAST CENTRAL FLORIDA
* UNTIL 1000 PM EDT
* AT 855 PM EDT...THE NATIONAL WEATHER SERVICE HAS ISSUED A TORNADO
WARNING FOR MARTIN AND ST LUCIE COUNTIES MAINLY FOR THE ONSET OF
EXTREME HURRICANE WINDS AND EMBEDDED TORNADOES ASSOCIATED WITH THE
INNER CORE OF HURRICANE JEANNE AS THE CENTER NEARS THE COAST. WINDS
TO 100 MPH WITH GUSTS TO 120 MPH ARE EXPECTED...ALONG WITH
TORNADOES.
* OTHER LOCATIONS IN THE WARNING INCLUDE INDIAN RIVER ESTATES...SAINT
LUCIE VILLAGE...JUPITER ISLAND...LAKEWOOD PARK...NORTH RIVER
SHORES...QUEENS COVE...PORT SALERNO...PORT SAINT LUCIE RIVER
PARK...SAINT LUCIE AIRPORT...SAINT LUCIE WEST...NETTLES ISLAND AND
ROCKY POINT
THE SAFEST PLACE TO BE DURING A LANDFALLING MAJOR HURRICANE WITH
EMBEDDED TORNADOES IS IN A STRONG BUILDING ON THE LOWEST FLOOR IN AN
INTERIOR ROOM AWAY FROM WINDOWS. GET UNDER A WORKBENCH OR OTHER
PIECE OF STURDY FURNITURE. USE BLANKETS OR PILLOWS TO COVER YOUR
HEAD AND BODY.
Agreed, the weather pattern appears more like May to me, which means the wet season may come in May, that may not happen, but at the very least this year should be more active than last year. Heck I would think it has to be more active, last year was by far the lowest amount of lightning, the lowest amount of severe storms, and one of the driest years Ive seen since living here.
Inland Hurricane Wind Watch
An Inland Hurricane Wind Watch is issued by the local National Weather Service office and is issued for a 50 percent or greater chance of having hurricane or tropical storm force winds associated with a tropical storm or hurricane inland within 24 hours.
Inland Hurricane Wind Warning
An Inland Hurricane Wind Warning is issued by the local National Weather Service for hurricane force wind speeds occurring in association with a hurricane. This product is normally issued from the current hour out to 12 hours.
Hurricane Andrew - Path Of Terror
...12,787 people have been confirmed dead and 14,991 are listed as missing, bringing the total to 27,778. The figure includes [2] deaths reported after a major aftershock...Thursday evening.
In worst-hit Miyagi prefecture, 7,818 deaths have been confirmed, followed by 3,728 in neighboring Iwate Prefecture and 1,179 in Fukushima Prefecture.
About 83 percent of the recovered bodies have been identified and are being handed over to the victims' families.
The number of victims is expected to rise because officials in some coastal areas devastated by the tsunami still cannot calculate the exact number of missing people.
We've got a decent bird population in Colorado, but I'm guessing their numbers never get large enough to be noticeable on radar except for maybe during the annual crane migration through the San Luis Valley. But there's not a radar in the Valley and the Sangre de Cristo mountains stand between the Valley and the nearest radar in Pueblo, so I imagine it would be rare to see them on radar.
However, I will start looking out for starling "clouds" this summer...
:)
The GOM looks...errr, uhm..."excited"
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.
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