NOAA predicts a near-normal Atlantic hurricane season

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

Share this Blog
33
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 29 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 — Blog Index


Member Since: Posts: Comments:
Appears, at this point in time, if 94L were to form it would likely be Sub-tropical Storm Beryl. Very Sub-tropical at this time, I'm very interested to see what the models do with it, but im sure the models will likely treat it like they did with Alberto, poor Beryl, she never gets attention xD
Member Since: Posts: Comments:
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.


It is no doubt a general sign of a quiet season, but I'd say that 2004 is testament enough to your point.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
I don't remember ever the MJO basically staying put across the Caribbean. If this stays the course thru the upcoming season then the Caribbean and the SE US is going to be in for a bad season.

Member Since: October 26, 2011 Posts: 0 Comments: 2651
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
Your blogs are still appreciated.
Member Since: Posts: Comments:
24. JeffMasters (Admin)
Quoting HurrAndrew:
I never usually type/confer etc. However there is a typo in Figure 1, should be strongest in 2011, not 2012. Do with this what you wish, just trying to help :P


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
Derived from (NHC)ATCF data for HurricaneBud for 24May6pmGMT:
15.3n106.9w has been re-evaluated&altered
15.2n107.1w, 16.0n106.5w are now the 2 most recent positions

Its vector had changed from NNEast at ~8.2mph(13.2k/h)* to NEast at ~11.3mph(18.2k/h)
MaxSusWinds had increased from ~90knots(104mph)167k/h to ~100knots(115)185k/h
And minimum pressure had decreased from 970millibars to 961millibars

For those who like to visually track H.Bud's path... ZLO is Manzanillo
LZC is LazaroCardenas . ZIH is Ixtapa-Zihuatanejo . ACA is Acapulco

The easternmost connected dot is where TropicalDepressionBud became TropicalStormBud
The next dot to the northwest on that kinked line is where TSBud became HurricaneBud
The southwesternmost dot on the longest line-segment was H.Bud's most recent position

The longest line-segment is a straightline-projection through H.Bud's 2 most recent positions
to the coastline of a continent or an inhabited island
The unconnected coastline dot was the endpoint* of the 24May12pmGMT*straightline projection
On 24May6pmGMT, H.Bud was headed toward passing ~8miles(14kilometres) southeast of Manzanillo in ~20hours from now

Copy&paste zlo, 18.78n103.84w, lzc, zih, aca, 10.2n102.6w, 10.8n103.6w, 11.7n104.6w, 12.6n105.6w, 12.9n106.6w,13.1n107.5w, 13.6n107.7w, 14.0n107.7w, 14.0n107.7w-14.6n107.5w, 14.6n107.5w-15.2n107.1w, 15.2n107.1w-16.0n106.5w, 15.2n107.1w-18.982n104.21w into the GreatCircleMapper for more^information
The previous mapping for comparison.

^ For even more info, replace the 'comma&space's between 10.2n102.6w and the first 14.0n107.7w with dashes, AND leave the comma&space between the first and second 14.0n107.7w,
(The forum program inserts spaces into overly long strings of letters&numbers&characters.
So I couldn't leave a "copy&paste"able copy of what generated my map.)

* 15.3n106.9w was re-evaluated&altered to 15.2n107.1w. So an incorrect vector(direction&speed) was calculated for 24May12pmGMT from using the original incorrect position.
Through recalculation using the correct position, the vector has been corrected to reflect that change.
The original incorrect vector produced an incorrect straightline projection leading to an incorrect endpoint
Nonetheless I am reposting it to maintain historicity with the previous map.
Member Since: August 21, 2007 Posts: 0 Comments: 4860
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: July 1, 2008 Posts: 13 Comments: 7387

Quoting CybrTeddy:
Generally speaking, the predictions made for Hurricane season are for June 1st - November 30th. So, if 94L does become Beryl, we'll probably be sitting at at least 12 named this year if the forecasts do verify. By no means an inactive season.

Yeah, i agree...i think we'll see about 11+ named systems this season
Member Since: Posts: Comments:
I'm on the higher end with 15 storms.
Member Since: Posts: Comments:
Quoting Autistic2:
We need 94 to dump some rain on us here in St. Augustine. Maybee Monday?


According to NOAA - yes

Member Since: May 18, 2012 Posts: 0 Comments: 519
Quoting reedzone:


The pattern is looking 2004ish, not good for the Southeast.


I was thinking the same. Storms come up and then get pushed back west due to a blocking high over the Mid Atlantic. Boy I hope this doesn't become a trend this year.
Member Since: October 26, 2011 Posts: 0 Comments: 2651
Oh wow, I've missed SO MUCH today!
94L is getting a good chance to become Beryl,
and Bud is BECOMING A MONSTER. Bud is definately not Mexico's best friend at this point.
Hurricane warnings have been posted.
Member Since: Posts: Comments:
Thanks Dr. Masters... I have to go on a little rant now though: The NOAA hurricane season forecast is not much more than useless... Saying that 9-15 storms will form is pretty much saying 1-100 storms will form... Just about every other forecast, whether proffesional or just from someone on the blog, has fallen into the 9-15, 4-8, 1-3 range... It's really no surprise at all that these were the numbers... I like the discussion NOAA wrote and found that very helpful, but giving this big range like they do every year doesn't help. Either they should bring the range down or just issue a discussion without any official numbers.

Just my thoughts... I don't know if anyone else feels the same.
Member Since: Posts: Comments:
Thanks Dr. Masters
Member Since: Posts: Comments:
Quoting CybrTeddy:
Generally speaking, the predictions made for Hurricane season are for June 1st - November 30th. So, if 94L does become Beryl, we'll probably be sitting at at least 12 named this year if the forecasts do verify. By no means an inactive season.


The pattern is looking 2004ish, not good for the Southeast.
Member Since: July 1, 2008 Posts: 13 Comments: 7387
**Tropical Update**




Member Since: Posts: Comments:
A lot of Floridians are probably hoping for some rainfall from 94L. All except that guy with a very large sink hole in his backyard in Western Gainesville.
Member Since: Posts: Comments:
Quoting trHUrrIXC5MMX:
Keep watching Bud... who knows when the nhc could issue a special adv to make it a major hurricane

They wouldn't have a basis to do so.
Member Since: Posts: Comments:
Interesting.
Member Since: Posts: Comments:
Generally speaking, the predictions made for Hurricane season are for June 1st - November 30th. So, if 94L does become Beryl, we'll probably be sitting at at least 12 named this year if the forecasts do verify. By no means an inactive season.
Member Since: Posts: Comments:
I never usually type/confer etc. However there is a typo in Figure 1, should be strongest in 2011, not 2012. Do with this what you wish, just trying to help :P
Member Since: Posts: Comments:
Thanks Doc!

Member Since: October 26, 2011 Posts: 0 Comments: 2651
We need 94 to dump some rain on us here in St. Augustine. Maybee Monday?
Member Since: Posts: Comments:
Thanks Dr Masters
Member Since: Posts: Comments:
How many hurricanes have actually formed in the E Pac and went over Mexico and was a Hurricane in the Gulf of Mexico?
Member Since: Posts: Comments:
Keep watching Bud... who knows when the nhc could issue a special adv to make it a major hurricane
Member Since: Posts: Comments:
Thanks, Dr. M.
Member Since: Posts: Comments:
Thanks Dr. Masters.
Member Since: Posts: Comments:

Viewing: 29 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 — Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
81 °F
Overcast