NOAA predicts an active Atlantic hurricane season: 15 named storms, 8 hurricanes

By: Dr. Jeff Masters , 4:08 PM GMT on May 19, 2011

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The National Oceanic and Atmospheric Administration (NOAA) issued its 2011 Atlantic hurricane season forecast today. NOAA forecasts a very active and possibly hyperactive season. They give a 65% chance of an above-normal season, a 25% chance of a near-normal season, and just a 10% chance of a below-normal season. NOAA predicts a 70% chance that there will be 12 - 18 named storms, 6 – 10 hurricanes, and 3 - 6 major hurricanes, with an Accumulated Cyclone Energy (ACE) 105% - 200% of the median. If we take the midpoint of these numbers, NOAA is calling for 15 named storms, 8 hurricanes, 4.5 major hurricanes, and an ACE index 152% of normal. A season with an ACE index over 165% is considered "hyperactive." An average season has 10 – 11 named storms, 6 hurricanes, and 2 intense hurricanes. Hurricane seasons during 1995-2010 have averaged about 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median. NOAA classifies 11 of the 16 seasons since 1995 as above normal, with eight being hyperactive. Only five seasons since 1995 have not been above normal, which include four El Niño years (1997, 2002, 2006, and 2009), and the 2007 season.

The forecasters cited the following main factors that will influence the coming season:

1) Above-average sea surface temperatures (SSTs) are expected in the hurricane Main Development Region (MDR), from the Caribbean to the coast of Africa between between 10°N and 20°N. SSTs in the MDR during April were about 0.5°C above average, the 14th warmest April SSTs in the past 100 years. This is far below last year's record 1.4°C anomaly, but still plenty warm enough to help drive above-average Atlantic hurricane activity. Long-range computer forecast models are predicting a continuation of these above-average SSTs through the peak part of hurricane season.

2) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO): "During 1995-2010, some key aspects of the tropical multi-decadal signal within the MDR have included warmer than average SSTs, reduced vertical wind shear and weaker easterly trade winds, below-average sea-level pressure, and a configuration of the African easterly jet that is more conducive to hurricane development from tropical waves moving off the African coast. Many of these atmospheric features typically become evident during late April and May, as the atmosphere across the tropical Atlantic and Africa begins to transition into its summertime monsoon state."

3) An El Niño event is not expected this year: "Another climate factor known to significantly impact Atlantic hurricane activity is the El Niño-Southern Oscillation (ENSO.) The three phases of ENSO are El Niño, La Niña, and ENSO-Neutral. El Niño events tend to suppress Atlantic hurricane activity, while La Niña events tend to enhance it (Gray 1984). Currently, the 2010-11 La Niña episode is dissipating. Based on observations and ENSO forecast models, ENSO-Neutral conditions are likely during the 2011 Atlantic hurricane season."

4) NOAA is increasingly using output from ultra-long range runs of the computer forecast models we rely on to make day-to-day weather forecasts, for their seasonal hurricane forecasts: "The outlook also takes into account dynamical model predictions from the NOAA Climate Forecast System (CFS), the European Centre for Medium Range Weather Forecasting (ECMWF), the United Kingdom Meteorology (UKMET) office, and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble. These models are indicating a high likelihood of an above normal season."

How accurate are the NOAA seasonal hurricane forecasts?
A talk presented by NHC's Eric Blake at the 2010 29th Annual AMS Conference on Hurricanes and Tropical Meteorology studied the accuracy of NOAA's late May seasonal Atlantic hurricane forecasts, using the mid-point of the range given for the number of named storms, hurricanes, intense hurricanes, and ACE index. Over the past twelve years, a forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Using another way to measure skill, the Mean Squared Error, May NOAA forecasts for named storms, hurricanes, and intense hurricanes had a skill of between 5% and 21% over a climatology forecast (Figure 2). Not surprisingly, NOAA's August forecasts were much better than the May forecasts, and did significantly better than a climatology forecast.


Figure 1. Mean absolute error for the May and August NOAA seasonal hurricane forecasts (1999 - 2009 for May, 1998 - 2009 for August), and for forecasts made using climatology from the past five years. A forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

How do NOAA's seasonal hurricane forecasts compare to CSU and TSR?
Two other major seasonal hurricane forecasts will be released over the next two weeks. On June 1, Phil Klotzbach and Bill Gray of Colorado State University (CSU) issue their forecast, and the British firm Tropical Storm Risk (TSR) will issue their outlook on May 24. A three-way comparison of the forecast accuracy of the three groups' forecast (Figure 2) reveals that all three organizations enjoy some success at making accurate seasonal forecasts, with NOAA and CSU making the best late May/early June forecasts overall. While the skill of these forecasts is low, they are useful for businesses such as the insurance industry.


Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August). using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

Jeff Masters

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XX
Member Since: July 15, 2006 Posts: 163 Comments: 52200
I wonder if there were more storms in 1950 than were reported, as all of them formed east of 50 degrees and 6 of them were land-falling.
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did they do sst maps in 1950?
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Quoting Jax82:


The number of hurricanes chart goes to 1944, if you look at 1950 it has 11 hurricanes to go with the high ACE.


Thanks, I looked at the 1950 archive and it is interesting that in that year, the total was 12-11-8, with the following breakdown, 1 cat 5, 2 cat 4, 5 cat 3, 2 cat 2, and 1 cat 1, 1 TS.

I find it amazing that almost all of the storms were hurricanes and 66% were majors.
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149. sotv
6.0 earthquake in Turkey, quite shallow depth
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Landsat Offers Stunning Comparison Of Flooding "NASA"

Link
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Quoting Kahlest:
Been lurking here for a while, learning lots from you guys but don't really feel like I know enough to speak yet.


Ah, but surely if you've been lurking long enough you know that ignorance never stops people from posting here! (I offer up myself as Exhibit A)

:)

I kid, of course.

"Wise men, when in doubt whether to speak or to keep quiet, give themselves the benefit of the doubt, and remain silent." -Napoleon Hill

Welcome to the famdamly.
Member Since: March 26, 2006 Posts: 44 Comments: 1520
Quoting HurricaneDevo:


1950 really had a 240+ ACE? with only 5 storms? I think I am reading these graphs correctly.

BTW, thanks for the information.


1950 had 13 storms, 11 hurricanes, 8 majors, giving a seriously high ACE.
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Quoting Jax82:


The number of hurricanes chart goes to 1944, if you look at 1950 it has 11 hurricanes to go with the high ACE.


8 of them major hurricanes, at that.
Member Since: October 15, 2008 Posts: 11 Comments: 2305
144. Jax82
Quoting HurricaneDevo:


1950 really had a 240 ACE? with only 5 storms? I think I am reading these graphs correctly.

BTW, thanks for the information.


The number of hurricanes chart goes to 1945, if you look at 1950 it has 11 hurricanes to go with the high ACE.
Member Since: September 2, 2008 Posts: 1 Comments: 1261
Quoting TampaSpin:








1950 really had a 240+ ACE? with only 5 storms? I think I am reading these graphs correctly.

BTW, thanks for the information.
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Been lurking here for a while, learning lots from you guys but don't really feel like I know enough to speak yet.
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138. beell
Moderate risk

Click for full Outlook
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I think our first Atlantic system will probably develop in the SW Caribbean sometime within the net week or first week of June. We sure need rain
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Quoting ILwthrfan:


Whoops...I meant surface winds lol. Is the MJO still forcasted to increase in this area over the next weeks or have the models backed off on that idea lately?


It has already been in our area of the world for a few days now. The signal is forecast to weaken, but possibly loop right back into octants 7 and 8. That says a lot about the warm water in the Atlantic compared to the rest of the world.

Member Since: November 24, 2005 Posts: 628 Comments: 26454
Quoting blsealevel:


What is the cause of the high heat blob in the gulf
wouldnt that hole area be warm?


That's the main eddy of the loop current, where warm water extends to a great depth.
Member Since: November 24, 2005 Posts: 628 Comments: 26454
Quoting Levi32:


Shear is still strong over the Caribbean due to upper-level winds. The surface trade winds are starting to resume at a slow speed, but the models don't seem to increase them very much during the next couple of weeks.


Whoops...I meant surface winds lol. Is the MJO still forcasted to increase in this area over the next weeks or have the models backed off on that idea lately?
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Quoting MississippiWx:


The Gulf loop current. It's very warm at great depths.


Yep; forgot about that "sorry"
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Quoting blsealevel:


What is the cause of the high heat blob in the gulf
wouldnt that hole area be warm?


The Gulf loop current. It's very warm at great depths.
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Quoting Levi32:
Navy analysis also shows the warming:



What is the cause of the high heat blob in the gulf
wouldnt that hole area be warm?
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Quoting ILwthrfan:


How long is the light shear supposed to last down there?


Shear is still strong over the Caribbean due to upper-level winds. The surface trade winds are starting to resume at a slow speed, but the models don't seem to increase them very much during the next couple of weeks.
Member Since: November 24, 2005 Posts: 628 Comments: 26454
Navy analysis also shows the warming:

Member Since: November 24, 2005 Posts: 628 Comments: 26454
Quoting Levi32:
TCHP in the Caribbean has skyrocketed over the last week due to the absence of trade winds and clouds.



It's like you read my mind. You posted that while I was typing my long SST and TCHP post. Lol.
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Quoting Levi32:
TCHP in the Caribbean has skyrocketed over the last week due to the absence of trade winds and clouds.



How long is the light shear supposed to last down there?
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Pretty amazing how fast SSTs can heat up when winds are light. Winds have been very low over almost the entire Caribbean this past week and look at the result:

May 11, 2011:



May 18, 2011:



A 2-3C increase in temps is widespread across the Caribbean. The GOM has recently halted its cooling due to record low temps across the Southern US this week. These record lows temps are going to be followed by temps about 5-10 degrees above average this weekend into next week, which will help get the Gulf sizzling. In the overall Tropical Atlantic, we are behind last year still, but made big strides this past week, especially in the Caribbean, towards the record temps of last year. In fact, a lot of the Caribbean is warmer than this time last year...

May 18, 2010:



Also, check out the increase in heat potential over the past week...

May 11, 2011:



May 18, 2011:



Still behind last year at this time, but not by much now...

May 18, 2010:

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TCHP in the Caribbean has skyrocketed over the last week due to the absence of trade winds and clouds.

Member Since: November 24, 2005 Posts: 628 Comments: 26454
Sibi Pakistan -
Temperature

120 °F . Heat Index: 125 °F.
http://www.wunderground.com/global/stations/41697 .html
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122. beell
Quoting MrMixon:


Which parts of the article were wrong? I'm ignorant and genuinely curious.


There are almost too many parts wrong to mention.

The most glaring:

Since the Red River and Atchafalaya Basin are really the same river, Red River Landing is an ineffective dam. In reality, the Corps of Engineers term %u201Cfloodway%u201D means %u201Cwhere we hope the water will flow.%u201D %u201CSpillway%u201D is the Corps%u2019 terminology for a dam. The Army Corps has opened the Morganza Dam. Apparently, the dam at the Red River has not been opened

I can only guess that the dam at Red River Landing is a reference to the Old River Control Structure (ORCS). It is open year-round. Diverting 30% of the Mississppi River flow into the THE Atchafalaya Basin. There are not two Atchafalaya Basins. It has been running at/near capacity for at least a couple of weeks.

There is no "Red River Dam".

This is a piece of crap journalism.
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Quoting beell:


Some of the stuff about the rivers history may be accurate-but the stuff about the 2011 flood is pretty much wrong...the author is very much misinformed.


Which parts of the article were wrong? I'm ignorant and genuinely curious.
Member Since: March 26, 2006 Posts: 44 Comments: 1520
Flooding In Louisiana's Great Basin: A Good Thing?
by Greg Allen, National Public Radio
May 18, 2011



The Army Corps of Engineers opened another bay on the Morganza Spillway Wednesday — diverting more water off the Mississippi through the bayous and rivers of Louisiana's Atchafalaya Basin.

The corps says it will divert as much water as necessary to keep the Mississippi no higher than 45 feet as it passes through Baton Rouge.

But some of that water might actually be welcome.

'We Need Good Water'

Few people pay closer attention to water conditions in the Atchafalaya Basin than those who make their living catching crawfish.

Lee Wisdom and other craw fishermen in St. Martin Parish are launching their boats, not off the ramps, but from the levee. They can't get to the ramps. Water has already risen several feet on Bayou Benoit. And water from the Morganza Spillway hasn't even reached this area yet.

Mike Bienvenu, head of the Louisiana Crawfish Producers Association, says he's not sure whether the coming flood will improve the crawfish crop or not.

"We don't like high water. High water is not good. We need good water. All we need is three or four feet [of] water to crawfish in, that's all we need," he says.

Craw fishing has declined here in recent years. Bienvenu and others blame the web of canals and levees that oil and gas companies have put in the Atchafalaya Basin, keeping fresh water from some bayous.

When the high water hits this area in coming weeks, it will flush out stagnant ponds with fresh water full of oxygen and sediment. Harold Schoeffler, who has fished these waters his whole life, says that's bound to improve things in the basin.

As water washes up on levees and other formerly dry areas, he says long-dormant crawfish will come out of the mud and start breeding.

"So you get this phenomenal production," Schoeffler says. "And then shrimp. This is an estuary where shrimp from the Gulf come into this system and reproduce. So you have this phenomenal amount of nutrients and water that's going to cause an enormous growth of shrimp that feeds speckled trout and redfish and flounder. And the whole thing just takes off."

Short term, the high water is threatening a huge animal population including as many as 150 black bears, plus many deer and smaller mammals. Schoeffler, who is the longtime chairman of the Sierra Club in this part of Louisiana, says, for the most part, the animals should do fine. Water is rising slowly, and he says, even at the crest, there will be plenty of high ground in the basin.

"We have spoil banks up there 50, 55 feet above sea level," he says. "Many hills in the 35- to 45-foot range, which are really an island for wildlife."

A Natural Part Of The Basin Ecology

It might be surprising that, although 1.5 million cubic feet of water per second may soon be released into this basin, those living here are remarkably undisturbed. That's in part because flooding is a natural part of this area's ecology.

This flood event, the largest since 1973, will reshape the basin — filling in some swamps with sediment and turning them into hardwood forests.

For Louisiana's long-eroding coastal wetlands, though, this flooding is a good thing.

Ivor van Heerden, a marine scientist formerly with Louisiana State University, says the tons of sediment washing down the river will spur plant and animal life and help build new wetlands.

"In the central part of the coast, because of the Atchafalaya, we're going to definitely be creating new marshes. We're going to be rejuvenating a huge area of marsh, so a lot of benefits," he says.

Paul Kemp of the National Audubon Society agrees. Unfortunately, he says, the place where new sediment and new marshes are needed most desperately — below New Orleans at the mouth of the Mississippi — won't be helped by the flood. Because of efforts to keep the Mississippi wide open for navigation, any sediment flowing down the river is likely to be dredged and dumped, not in coastal areas, but off the Continental Shelf.

"And I would have loved to say, 'This was the event we were waiting for. We were prepared and we were able to do 50 years of restoration in one year.' I can't say that today," Kemp says.

Kemp, van Heerden and others active in coastal restoration, hope this event will persuade the Army Corps of Engineers and other public agencies to take steps allowing not just the Atchafalaya but also the Mississippi to actually benefit from the flood. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.
Broadcast Dates

* All Things Considered, May 18, 2011
Member Since: July 3, 2005 Posts: 414 Comments: 125503
Quoting aquak9:
the pets don't get to go- we covered that yesterday


Yes. I saw that yesterday. We are talking about then and now. Now, "No Pets Allowed!". Back in the day, Grothar remembers, "Please! Do NOT Forget to Bring Your Pets!", by order of Captain Noah.
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Thus,note the History part of my post beell.


2011,,well,most didnt know we have two Relief Spillways either,,thats how important Se. La. is to the Nations Commerce.

Now,,most do.

Now,,can we get some below NOLA for replenishing the Miss River estuary?, is what we should be asking.
Member Since: July 3, 2005 Posts: 414 Comments: 125503
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115. beell
Quoting Patrap:


Actually that is a EXCELLENT article on the River's history.

Thanx for the link to it.


Some of the stuff about the rivers history may be accurate-but the stuff about the 2011 flood is pretty much wrong...the author is very much misinformed.
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Quoting MrMixon:


What, no pity for the UV-starved? ;-)

I'm afraid all the rain/snow we're getting here is Mississippi-bound (Boulder Creek -> South Platte River -> Platte River -> Missouri River -> Mississippi River). Boulder Creek's contribution is just a drop in the proverbial bucket, but the next system is officially "across the divide" and adding moisture to the overly-wet Mississippi Basin.


Yes I have pity for you as I experience almost 45 days of rain and overcast skies on a Pacific Island some year ago. Natives were restless and so we're us GI's.
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Some interesting stats on TWC about how fortunate we've been regarding hurricane landfalls:

No hurricanes have made landfall in the United States for two straight years; the first time since 2000-01.

Following the landfall of Hurricane Ike (2008) in Texas, there have been 18 consecutive Atlantic basin hurricanes without a hurricane making landfall in the United States.

This is not (yet) the longest stretch of “misses," however. A longer such string of 22 hurricanes occurred during 1999-2002.

No major hurricanes have struck the U.S. since 2005, or for five straight years (2006-2010), the first time that has happened since 1910-1914.


Wonder how much longer these "misses" are gonna go on? Unfortunately, probably not much longer.
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the pets don't get to go- we covered that yesterday
Member Since: August 13, 2005 Posts: 163 Comments: 25494
110. Jax82
Quoting HarleyStormDude52:
I'm ready for the first TD............


I'm ready for an invest at least, or a blob, or a spin, or an interception return for a touchdown.
Member Since: September 2, 2008 Posts: 1 Comments: 1261
Quoting NavarreMark:


Since they built Chatfield & Cherry Creek reservoirs, the metro area of Denver has been relatively immune to major floods.

Ya can still get the Big Thompson like event though.


Yep - our reservoirs still have plenty of flood control capacity at the moment.

The canyons are always going to be prone to "Big Thompson like" events unless we start placing dams every few miles. Speaking of which, I should add one of the "In case of flood, climb to safety" signs to my wunderphoto collection.
Member Since: March 26, 2006 Posts: 44 Comments: 1520
Quoting USAprimeCreditPeggy:
33. geepy86 1:23 PM EDT on May 19, 2011
I wonder who will have the last post when the apocolypse hits?


I am betting Taz.


I am betting on Grothar making the last post. He always seems to know just when to post. I think he may have seen the coming of days before. I think it may have been on and Ark with a few friends and their pets.
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I'm ready for the first TD............
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Quoting aquak9:
honestly no- I do not care about the difference between 153% and 165%

but I do care about the difference between 153% and 200%

d'fly! :) happy to see you

I am lost with all these new people here


Good to see you to water pup
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Quoting aquak9:
honestly no- I do not care about the difference between 153% and 165%

but I do care about the difference between 153% and 200%

d'fly! :) happy to see you

I am lost with all these new people here


Another lurker here since 2009 but decided to participate fully this year.
Member Since: April 29, 2009 Posts: 75 Comments: 13274

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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.