NOAA predicts a near-normal Atlantic hurricane season

By: Dr. Jeff Masters , 9:17 PM GMT on May 24, 2012

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NOAA forecasts a near-normal Atlantic hurricane season in 2012, in their May 24 outlook. They give a 50% chance of a near-normal season, a 25% chance of an above-normal season, and a 25% chance of a below-normal season. They predict a 70% chance that there will be 9 - 15 named storms, 4 - 8 hurricanes, and 1 - 3 major hurricanes, with an Accumulated Cyclone Energy (ACE) 65% - 140% of the median. If we take the midpoint of these numbers, NOAA is calling for 12 named storms, 6 hurricanes, 2 major hurricanes, and an ACE index 102% of normal. This is very close to the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2011 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 153% of the median. Only five seasons since 1995 have not been above normal--including four El Niño years (1997, 2002, 2006, and 2009), and the neutral 2007 season.


Figure 1. The strongest Atlantic hurricane of 2011, Ophelia, as seen at 1:40 pm EDT October 1, 2011. At the time, Ophelia was a Category 3 hurricane with 120 mph winds. At 11 pm that night, Ophelia peaked at Category 4 strength with 140 mph winds. Image credit: NASA.

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

1) Near-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 near-average, and are expected to remain so during hurricane season, based on current observations, climatology, and long-range model forecasts.

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 reduced vertical wind shear and weaker easterly trade winds, below-average sea-level pressure, a configuration of the African easterly jet that is more conducive to hurricane development from tropical cloud systems (aka Easterly waves) moving off the African coast, and warmer than average SSTs."

3) An El Niño event may occur 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). If El Niño fails to develop, the probability of an above-normal Atlantic hurricane season will be higher and the actual seasonal activity will likely be toward the upper end of our predicted ranges." There is currently of lot of uncertainty whether or not an El Niño event will develop in time for the August - September - October peak of hurricane season--the latest NOAA El Niño discussion is giving a 41% chance of an El Niño event during hurricane season, and a 48% chance of neutral conditions.

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 show large spreads in the ENSO forecasts for ASO, ranging from ENSO-Neutral to a moderate-strength El Niño episode. As a result, their forecasts for the Atlantic hurricane season also show a considerable spread, ranging from slightly above normal to slightly below normal."

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. Not surprisingly, NOAA's August forecasts were much better than the May forecasts, and did significantly better than a climatology forecast.


Figure 2. 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.

I'll have an update on Hurricane Bud and Invest 94L Friday morning.

Jeff Masters

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Quoting Gorty:
Any low yet with pre-beyrl?

Broad/weak circulation. It's forecasted by many models now to become Beryl, and then get shoved down by the High, into SE coast.
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Quoting NICycloneChaser:




Pretty sure that blue bit covers 2008.

Just to clarify that graph a little, the blue does cover 2008 however most of that year was in a cool neutral phase not a La Nina... I think that little cut in the middle of that long blue period represents the 2008 season- still below normal, but above the -0.5 C needed for a La Nina
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Member Since: August 6, 2011 Posts: 4 Comments: 42270
I think a little bit of energy is going to be left in the western Caribbean, should be interesting when tropical wave gets there early next week.
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Thanks Dr. Masters.....Happy Hurricane season everyone! 1887 was the last time we have had 2 storms named before June 1st. So says Rob on Crown Weather.
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Quoting MAweatherboy1:

I think 2008 was a cool neutral year coming off a La Nina.
Quoting nigel20:

2008 was a neutral year


Ok, but it was coming off a pretty strong La Nina.

Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting HurricaneDean07:

2010 = 2007 which were strong La Nina years that came off of Strong El Nino's the previous years (2006. and 2009).
2011 = 2008 Which were Weaker La Nina years that were fading into Neutral(2008 = neutral basically).
2011 and 2008 were considered 2nd year La Nina's because they were La Nina's during the beginning of the year.
What would the comparison to 2012 be, since we're going from a weak La Nina to a weak El Nino?
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Any low yet with pre-beyrl?
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35 TropicalAnalystwx13: The NHC would have upgraded to 100 knots had recon not been flying out. Recon did not find winds to support a major hurricane like they updated in ATCF, so Bud remains at 95 knots.

Thanks, didn't realize that the recon mission hadn't taken place before the 6pmGMT(11amPDT) ATCF figures were posted.
Still surprised that the ATCF's MaxSusWinds number hasn't already been re-evaluated&altered to reflect the recon. Woulda thought a Major-to-Minor status-change would have been enough for them to take an edit-break into their regular posting schedule.
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Quoting NICycloneChaser:




Pretty sure that blue bit covers 2008.
2008 was neutral.
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Quoting weatherman12345:
bud peaked.....

Appears so as of now.
110 Mph- Peak.
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Quoting MAweatherboy1:

See post 16 or so in the blog... I totally agree... I really don't see much value in the NOAA numbers.
Ah..I see. I didn't see your post. In any case, I totally agree with your comments in 16. We had 2 different ways of explaining how meaningless these numbers are.
.
I would have preferred if the Dr. gave his current thoughts on the tropics, but perhaps he doesn't think there's much difference between talking about it now or tomorrow.
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Quoting NICycloneChaser:


Hmmm... Wasn't it an analogue for last season? Thought it was a double-dip.

2010 = 2007 which were strong La Nina years that came off of Strong El Nino's the previous years (2006. and 2009).
2011 = 2008 Which were Weaker La Nina years that were fading into Neutral(2008 = neutral basically).
2011 and 2008 were considered 2nd year La Nina's because they were La Nina's during the beginning of the year.
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Quoting NICycloneChaser:


Hmmm... Wasn't it an analogue for last season? Thought it was a double-dip.
2008 was a neutral year
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Quoting NICycloneChaser:


Hmmm... Wasn't it an analogue for last season? Thought it was a double-dip.

I think 2008 was a cool neutral year coming off a La Nina.
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Quoting washingtonian115:
08 was not la nina....




Pretty sure that blue bit covers 2008.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting TropicalAnalystwx13:
Or just a convective burst in the NW quadrant.

It still looks good and now they are calling for it to make landfall.
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My Atlantic Hurricane Season prediction-
12-15 Named Storms
6-8 Hurricanes
3-5 Major Hurricanes
Maybe the first 8 storms wont be TS like last year. That would lower the amount of Hurricanes and Major Hurricanes.
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Quoting washingtonian115:
08 was not la nina....


Hmmm... Wasn't it an analogue for last season? Thought it was a double-dip.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting JeffMasters:


Ha, nice catch, fixed. If any of you ever see typos in my posts, please wumail me or (better) email me at jmasters@wunderground.com.

Jeff Masters


Would "Grothar" be considered a typo?

OH! Never mind. That would be a typo in my post and not yours. ;-)
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Or just a convective burst in the NW quadrant.

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Quoting CosmicEvents:
I don't understand why the NOAA numbers should have any value if they're statistically not that much different than climatology. Especially when it's within a range that's within the first derivative from the norm. And they say themselves for those who don't understand the numbers that we have a 50% chance of normal, 25% chance of below normal, and 25% for above normal. Is there anyone who sees some signifigance that I'm missing?

See post 16 or so in the blog... I totally agree... I really don't see much value in the NOAA numbers.
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Quoting HurricaneDean07:

Models are in agreement of 94L heading off to the Northeast until Saturday, then Being slowly shunted off toward the west by the blocking high over the Mid-atlantic and being pushed into North Florida/Georgia/Extreme South Carolina Coast.
The Ukmet,Canadian,Euro, (18z) Gfs, Hwrf, and Nogaps are in agreement in the formation of Beryl on Saturday/Sunday time-frame and bringing it into the U.S. Coastline.

It appears most models like a Georgia landfall, as of late.
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Quoting DavidHOUTX:
How many hurricanes have actually formed in the E Pac and went over Mexico and was a Hurricane in the Gulf of Mexico?


I'm not sure how many or if they achieved hurricane strength. Here's TS Allison part one. :)



June 26-28th, 1989 (Allison): Allison formed from the remains of Pacific hurricane Cosme, which made landfall near Acapulco and accelerated northeast into the western Gulf. A new surface circulation formed in the western Gulf of Mexico and moved north-northeast, strengthening into a tropical depression and then a tropical storm offshore the Texas coastline. Winds gusted to 56 mph at Galveston on the 26th as Allison made landfall. One tornado touched down on the Bolivar peninsula and did minor damage (Lichter). Over 30 inches of rain led to severe flooding in extreme Southeast Texas...only ten years after the extreme flooding from Claudette. Eleven died during the storm. Damage from Allison totaled $500 million, putting it on the list of the United States%u2019 most damaging storms.
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Looks like a sharp temperature contrast is on the way next week:



Unfortunately the heat remains stuck in the Southwest where the fire danger remains way up... Even worse it's forecast to stay dry out there.
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I don't understand why the NOAA numbers should have any value if they're statistically not that much different than climatology. Especially when it's within a range that's within the first derivative from the norm. And they say themselves for those who don't understand the numbers that we have a 50% chance of normal, 25% chance of below normal, and 25% for above normal. Is there anyone who sees some signifigance that I'm missing?
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Quoting NICycloneChaser:


There is almost more of a correlation between not having a La Nina and having more damaging storms. Look at the recent damaging years. OK, 2008 (Ike, Gustav) had a La Nina, and 2007 (Dean, Noel) had a late developing La Nina. But 2005 (Dennis, Emily, Katrina, Rita, Wilma and many others) was a neutral year, 2004 (Charley, Frances, Ivan, Jeanne) was El Nino, and you've mentioned many from other El Nino years. More 'homegrown' threat with more possibility of landfalls in the Carribean and US.
08 was not la nina....
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Quoting weatherbro:


Mmm...More Georgia then Florida. Don't forget that same ridge is forecasted to break-down Monday-Tuesday of next week.:)
Not sure if that is going to mean anything if the system is already making landfall and weakening inland, regardless should bring rain to drought stricken areas, which is what we want.
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My 4th Hurricane Season Forecast #

12-14 Named Storms
7-9 Hurricanes
3-5 Major Hurricanes

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Quoting HurricaneDean07:
94L made a brief landfall in southern florida a couple of hours ago, and is now headed ENE out toward the Bahamas, but watch out Florida, It will be swinging back with High pressure building into place in just a day or two.


Mmm...More Georgia then Florida. Don't forget that same ridge is forecasted to break-down Monday-Tuesday of next week.:)
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We had alot of weak troughs over the last couple months, led to a warmer winter.. Weak trough and building ridges = more percentage of landfalling storms.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Quoting CybrTeddy:


And 2002 as well.

Also, does active necessarily mean destructive? Not really, take 2010 and 2011.. both tied as the 3rd most active hurricane season ever. With the exception of Irene, those seasons where generally benign and did not, thankfully, cause mass devastation and death (Igor and Tomas where damaging, but not where near the scale of previous years) However, seasons like 2002 and 1999 where generally near average but they had storms like Floyd, Lenny, Isidore, and Lili that where very destructive.


There is almost more of a correlation between not having a La Nina and having more damaging storms. Look at the recent damaging years. OK, 2008 (Ike, Gustav) had a La Nina, and 2007 (Dean, Noel) had a late developing La Nina. But 2005 (Dennis, Emily, Katrina, Rita, Wilma and many others) was a neutral year, 2004 (Charley, Frances, Ivan, Jeanne) was El Nino, and you've mentioned many from other El Nino years. More 'homegrown' threat with more possibility of landfalls in the Carribean and US.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
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Quoting HurricaneDean07:
94L made a brief landfall in southern florida a couple of hours ago, and is now headed ENE out toward the Bahamas, but watch out Florida, It will be swinging back with High pressure building into place in just a day or two.

Models are in agreement of 94L heading off to the Northeast until Saturday, then Being slowly shunted off toward the west by the blocking high over the Mid-atlantic and being pushed into North Florida/Georgia/Extreme South Carolina Coast.
The Ukmet,Canadian,Euro, (18z) Gfs, Hwrf, and Nogaps are in agreement in the formation of Beryl on Saturday/Sunday time-frame and bringing it into the U.S. Coastline.
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..they called for how Many in 05? and we got 28?

LOL

When they can tell me when and where and how Big..

I'll give it the weight I usually reserve for NFL pre-season Games.

Nada.

:P

NOAA Predicts 4-8 Atlantic Hurricanes

Of those four to eight hurricanes, NOAA expects one to three to be major. The Atlantic's six-month season begins June 1, although it got off to an early start this year, with Tropical Storm Alberto moving through the Atlantic off the U.S. East Coast last week.

NOAA also said it predicts a near-normal season for the Eastern Pacific, estimating a 70% chance of 12 to 18 named storms – with five to nine hurricanes, of which two to five would be major – for that area. The Eastern Pacific's season is May 15 to November 30.

A major hurricane, designated as Category 3 or greater, has winds of well above 100 mph. The weakest hurricanes have top sustained winds of at least 74 mph, and named storms have top winds of at least 39 mph.

NOAA officials said uncertainty over whether the El Nino weather pattern will form made it difficult to be more precise in predicting the Atlantic storm season.

"If (El Nino) develops by late summer to early fall ... conditions could be less conducive for hurricane formation and intensification during the peak months (August to October) of the season, possibly shifting the activity toward the lower end of the predicted range,” said Gerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center.

The forecasts do not predict how many of the storms will reach land.
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Does anyone see a center of 94L yet ?
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Quoting MAweatherboy1:
Bud's eye is shrinking


It's possible that the system has peaked.
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Quoting SFLWeatherman:
The 18z GFS is out

It is indeed... It looks like the storm is farther north this run

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Bud's eye is shrinking

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The 18z GFS is out
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Quoting aspectre:
HURRICANE BUD ADVISORY NUMBER 16
200 PM PDT THU MAY 24 2012
MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H

175km/h is ~94.5knots. 110mph is ~95.6knots
So Bud's MaxSusWinds have dropped from ~100knots to ~95knots?

The NHC would have upgraded to 100 knots had recon not been flying out. Recon did not find winds to support a major hurricane like they updated in ATCF, so Bud remains at 95 knots.
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94L made a brief landfall in southern florida a couple of hours ago, and is now headed ENE out toward the Bahamas, but watch out Florida, It will be swinging back with High pressure building into place in just a day or two.
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Quoting reedzone:
If the pattern does not change in a few months, people need to be aware of what could be a very active season (track wise). I personally think we will have 12-14 named storms, 6-9 hurricanes, and 6 3-6 majors. A bit above average... Just because an El Nino is forecast to form, doesn't mean it will be quiet.
Member Since: August 6, 2011 Posts: 4 Comments: 42270
HURRICANE BUD ADVISORY NUMBER 16
200 PM PDT THU MAY 24 2012
MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H

110mph is ~95.6knots. 175km/h is ~94.5knots.
So Bud's MaxSusWinds have dropped from ~100knots to ~95knots?
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Thx Doc.
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Quoting NICycloneChaser:


It is no doubt a general sign of a quiet season, but I'd say that 2004 is testament enough to your point.


And 2002 as well.

Also, does active necessarily mean destructive? Not really, take 2010 and 2011.. both tied as the 3rd most active hurricane season ever. With the exception of Irene, those seasons where generally benign and did not, thankfully, cause mass devastation and death (Igor and Tomas where damaging, but not where near the scale of previous years) However, seasons like 2002 and 1999 where generally near average but they had storms like Floyd, Lenny, Isidore, and Lili that where very destructive.
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