NOAA's forecast: a very active, possibly hyperactive Atlantic hurricane season
The National Oceanic and Atmospheric Administration (NOAA) issued its 2010 Atlantic hurricane season forecast today. NOAA forecasts a very active and possibly hyperactive season. They give an 85% chance of an above-normal season, a 10% chance of a near-normal season, and just a 5% chance of a below-normal season. NOAA predicts a 70% chance that there will be 14 - 23 named storms, 8 - 14 hurricanes, and 3 - 7 major hurricanes, with an Accumulated Cyclone Energy (ACE) in the 155% - 270% of normal range. If we take the midpoint of these numbers, NOAA is calling for 18.5 named storms, 11 hurricanes, 5 major hurricanes, and an ACE index 210% of normal. A season with an ACE index over 175% is considered "hyperactive." An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The forecasters note that in regards to the oil spill in the Gulf of Mexico,
"Historically, all above normal seasons have produced at least one named storm in the Gulf of Mexico, and 95% of those seasons have at least two named storms in the Gulf. Most of this activity (80%) occurs during August-October. However, 50% of above normal seasons have had at least one named storm in the region during June-July."
The forecasters cited the following main factors that will influence the coming season:
1) Expected above-average SSTs in the hurricane Main Development Region (MDR), from the Caribbean to the coast of Africa. SSTs in the MDR are currently at record levels, and the forecasters note that several climate models are predicting record or near-record SSTs during the peak portion of hurricane season (August - October.) "Two other instances of very warm SSTs have been observed in the MDR during February-April (1958 and 1969). In both years, the SST anomaly subsequently decreased by roughly 50% during the summer months. For 2010, although the record SST departures may well decrease somewhat, we still expect a continuation of above average SSTs throughout the Atlantic 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 1995-2009, 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) There will either be La Niña or neutral conditions in the Equatorial Eastern Pacific. El Niño is gone, and it's demise will likely act to decrease wind shear over the tropical Atlantic, allowing more hurricanes to form. "La Niña contributes to reduced vertical wind shear over the western tropical Atlantic which, when combined with conditions associated with the ongoing high activity era and warm Atlantic SSTs, increases the probability of an exceptionally active Atlantic hurricane season (Bell and Chelliah 2006). NOAA's high-resolution CFS model indicates the development of La Niña-like circulation and precipitation anomalies during July."
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 next week. On June 2, 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 June 4. 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.
Central American disturbance
The Atlantic is currently quiet, with the non-tropical storm (90L) that we were watching now no longer a concern. There is an area of disturbed weather (90E) just off the Pacific coast of Mexico that will be a major concern for southern Mexico and much of Central America over the next 3 - 4 days. The disturbance will bring heavy rains to Central America during the remainder of the week, potentially bringing serious flooding rains to portions of Mexico, Guatemala, El Salvador, Honduras, and Nicaragua. NHC is giving the disturbance a high (>60% chance) of the disturbance developing into a tropical depression by Saturday. There is the potential for disturbed weather accompanying the disturbance--or the disturbance itself--to push into the Western Caribbean early next week and pose a threat to develop into a tropical depression. While there is high wind shear over the northern Caribbean, shear may be low enough to allow development should the disturbance stay in the southern reaches of the Caribbean. None of the models are currently calling for this to happen, and I think the threat is low. Any storm that develops in the Caribbean in the coming week would get steered to the northeast and will not pose a threat to the Gulf of Mexico. Wunderbloggers Weather456 and StormW have more on the tropics.
Figure 3. Visible satellite image of the Central American disturbance 90E this morning.
Oil threat for the coast of Louisiana to decrease this weekend
Light winds from the north or west are expected to prevail across the northern Gulf of Mexico through Friday, resulting in a lessened threat of oiling to the Louisiana shoreline, according to the latest trajectory forecasts from NOAA. However, the latest runs of the GFS model indicate a return to onshore winds out of the southwest for most of next week, which will likely bring oil back towards shore. At greatest risk will be the coast of Louisiana, and there will be heightened risk to Mississippi, Alabama, and the Florida Panhandle. I'll a have a more in-depth discussion of the oil spill forecast in Friday's blog.
Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA trajectory forecasts
Deepwater Horizon Unified Command web site
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Surface current forecasts from NOAA's HYCOM model
Synthetic Aperture Radar (SAR) imagery from the University of Miami
Join the Hurricane Haven with Dr. Jeff Masters: a new Internet radio show
Beginning next week, I'll be experimenting with a live 1-hour Internet radio show called "Hurricane Haven." The show will be aired at 4pm EDT on Tuesdays, with the first show June 1. Listeners will be able to call in and ask questions. Some topics I'll cover on the first show:
1) What's going on in the tropics right now
2) Preview of the coming hurricane season
3) How a hurricane might affect the oil spill
4) How the oil spill might affect a hurricane
5) New advancements in hurricane science presented at this month's AMS Conference on Hurricanes and Tropical Meteorology
6) Haiti's vulnerability to a hurricane this season
I hope you can tune in to the broadcast, which will be at http://www.wunderground.com/wxradio/wubroadcast.h tml. If not, the show will be recorded and stored as a podcast.
Jeff Masters
Reader Comments
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Quoting Weather456:
Excuse me?
90L did everything I expected it to do. It was initiated by an upper trough, move towards the Carolinas and became vertically stacked. Most, if not all the aspects of what I forecasted with 90L verified, even down to it becoming subtropical as per the Dvorak numbers which used tropical cloud patterns to give 90L a T# of 1.0. So before you begin to question what I said, go and read my blog entries on 90L.
He said he wasn't badgering you and you still took it to heart. You did not nailed it in it being subtropical; it is and always has been nontropical. Admit the mistake and move on.
Exactly Drak.....i just asked a simple question....as to what happened that it did not strengthen as he was suggesting.....hey everyone makes forecast errors and i didn't even say he was in Error of his forecast...UNREAL!
Yup.
I'll try and stay as an innocent bystander.
Looks like top-kill hasn't worked...so far.
The Hershey Box
An imaginary box in the Pacific waters off central America created by Patrap, a world class rake, to confuse newcomers to the blog and create chaos and confusion among the regulars (as if any more chaos and confusion is required). While the Hershey Box has no bearing whatsioever on the weather, it's similarity to the mythical "Hebert Boxes" in the Ecarib make people double take and starts numerous conversations about the possibilty of landfalling storms that have passed through the "Hershey Box".
JFV Box.... nevermind
You wouldn't be able to keep up with 10,000 posts in 24 hours on here. You would be better off talking to yourself.
As for the top kill, if that does not work we are looking at no relief until mid-august. I work for a wholesale marine supplier and trust me we are feeling the pinch from not having the same rush for supplies as we have had in the previous years. Most of our business is around Memorial day and the fourth.
Right behind you, man.
You are a very good liar. You are making up things. I read W456 blog entries and he always maintained the idea that 90L would never be named but acquire some subtropical characteristics. He never indicated from what I understand was a definite possibility that 90L would be named.
Never ever even suggest i was good. That is what i depend on StormW for as the expert. I just simply was trying to find out from his thinking as to why things did not come together. I was trying to learn something for myself.......YOU ARE WAY OUT OF LINE to suggest i was picking a fight.
Mom? You had the same mom as me? How is that possible?
Noooooooooo
I picked 13-7-4 about 3 months ago...and will stick with those numbers. I'm probably under what the totals will be.
Looks like an active season.
Sorry for what you're going through with your business.
It's always been this way on here when it gets active(lol...and it's not even active...yet). Best to just roll with the punches.
I was reading an article today on FoxNews.com about the oil spill. It said something in just two quick sentences that perked up my fuzz.
"In another troubling discovery, marine scientists said they have spotted a huge new plume of what they believe to be oil deep beneath the Gulf, stretching 22 miles from the leaking wellhead northeast toward Mobile Bay, Ala. They fear it could have resulted from using chemicals a mile below the surface to break up the oil."
A plume of oil 22 miles long flowing underwater North-East toward Mobile Bay, Ala?
First... it's flowing toward shallower water, so it is obviously moving upward toward the surface. It will surface eventually.
Secondly... how does this 22 mile long plume NOT get mentioned on the news for 2-weeks? I'm sure when it shows up on the surface in Mobile Bay, people will eventually notice.
Third... the fear is that this plume is a result of using dispersant 1-mile below the surface to break up the oil... however we KEEP DOING IT! They're still using the dispersant today.
Fourth... since this is moving into shallower water, eventually the plume will be less than 650 feet deep, which is perfect for upwelling by a passing hurricane.
I just thought that was an interesting "oh, by the way" add on to the leak story.
An Hebert Box (pronounced AY-bear, also known as Hebert's Box) is one of two regions of the tropical Atlantic Ocean that are useful as predictors of hurricanes that will strike South Florida, USA. They are named for former National Weather Service and National Hurricane Center forecaster Paul Hebert, who observed in the late 1970s that most strong hurricanes (characterized as those with winds exceeding 110 miles per hour (177 km/h)) which had struck South Florida since 1900 had also passed through one of these two small 335-mile-by-335-mile (517-km-by-517-km) square geographic regions.
Just didn't sound encouraging from watching CNN just now. I haven't given up.
That story broke this morning...
12–15, 7–9, 3–5
These are the 2010 NOAA numbers:
14-23, 8-14, 3-7
*Very weird to see such a large margin between numbers, for example, in the "Named storms" category there is a 9 name discrepancy, very interesting but yet weird.
lol, I can sense your sarcasm from here.
dont judge the blog by today Eric. This blog is very informative some us know what we are talking about and like everything you will find a plurality of opinions here and I applaud it. We can all agree that we are here because we are fascinated with storms and at its heart thats where the passion come from.
It was a 20-20 hindsight sort of thing...a met named Paul Hebert noticed that a large number of landfalling storms in Florida had passed through one of two boxes, one at 15° and 20° north latitude and 60° to 65° and the other at 15° and 20° north latitude and 80° to 85°...invariably someone in here mentions them and eveyone freks...the problem is that not ALL storms that pass throgh the boxes hit Florida...
Uh-huh...My buddy
Jerry!
(Hmmm, my mom is a dead-head...)
I have always said that you are a bright, intelligent and intuitive man...
LOL
I heard that on TV today.
Busted down on Bourbon St.,set-up..like a Bowling pin..
http://www.davidharrisons.com/agriculture/a_stock.htm
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And it was never subtropical at all. Even Jeff Masters said it was nontropical not just the NHC.
So did I during the press conference. That would not be good.
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