More pre-season predictions of a very active Atlantic hurricane season

By: Dr. Jeff Masters , 3:02 PM GMT on July 12, 2010

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Hello again, it's Jeff Masters back again after a week away. Well, the past week was a wicked hot time to be in New England, where I was vacationing, and I certainly didn't expect to see 98° temperatures in Maine like I experienced! Fortunately, it's not hard to find cold water to plunge into in New England. Thankfully, the tropics were relatively quiet during my week away, and remain so today. There are no threat areas in the Atlantic to discuss at present, and none of the reliable computer models is forecasting tropical cyclone development over the next seven days. The NOGAPS model does show a strong tropical disturbance developing near the waters offshore of Nicaragua and Honduras this weekend, though. With not much to discuss in the present-day tropics, let's take a look at more pre-season predictions of the coming Atlantic hurricane season.

2010 Atlantic hurricane season forecast from Penn State
Dr. Michael Mann and graduate student Michael Kozar of Penn State University (PSU) issued their 2010 Atlantic hurricane season forecast on May 28. Their forecast utilizes a statistical model to predict storm counts, based on historical activity. Their model is predicting 19 to 28 named storms in the Atlantic, with a best estimate of 23 storms. The forecast assumes that record warm SSTs will continue in the Atlantic Main Development Region for hurricanes. Dr. Mann has issued two previous forecasts, in 2007 and 2009. The 2007 forecast was perfect--15 storms were predicted, and 15 storms occurred. The 2009 forecast called for 11.5 named storms, and 9 occurred (the 2009 forecast also contained the caveat that if a strong El Niño event occurred, only 9.5 named storms were expected; a strong El Niño did indeed occur.) So, the 2009 forecast also did well.


2010 Atlantic hurricane season forecast from the UK GloSea model
A major new player in the seasonal Atlantic hurricane season forecast game is here--the UK Met Office, which issued its first Atlantic hurricane season forecast in 2007. The UK Met Office is the United Kingdom's version of our National Weather Service. Their 2010 Atlantic hurricane season forecast calls for 20 named storms, with a 70% chance the number will range between 13 and 27. They predict an ACE index of 204, which is about double the average ACE index.

I have high hopes for the UK Met Office forecast, since it is based on a promising new method--running a dynamical computer model of the global atmosphere-ocean system. The CSU forecast from Phil Klotzbach is based on statistical patterns of hurricane activity observed from past years. These statistical techniques do not work very well when the atmosphere behaves in ways it has not behaved in the past. The UK Met Office forecast avoids this problem by using a global computer forecast model--the GloSea model (short for GLObal SEAsonal model). GloSea is based on the HadGEM3 model--one of the leading climate models used to formulate the influential UN Intergovernmental Panel on Climate Change (IPCC) report. GloSea subdivides the atmosphere into a 3-dimensional grid 0.86° in longitude, 0.56° in latitude (about 62 km), and up to 85 levels in the vertical. This atmospheric model is coupled to an ocean model of even higher resolution. The initial state of the atmosphere and ocean as of June 1, 2010 were fed into the model, and the mathematical equations governing the motions of the atmosphere and ocean were solved at each grid point every few minutes, progressing out in time until the end of November (yes, this takes a colossal amount of computer power!) It's well-known that slight errors in specifying the initial state of the atmosphere can cause large errors in the forecast. This "sensitivity to initial conditions" is taken into account by making many model runs, each with a slight variation in the starting conditions which reflect the uncertainty in the initial state. This generates an "ensemble" of forecasts and the final forecast is created by analyzing all the member forecasts of this ensemble. Forty-two ensemble members were generated for this year's UK Met Office forecast. The researchers counted how many tropical storms formed during the six months the model ran to arrive at their forecast of twenty named storms for the remainder of this hurricane season. Of course, the exact timing and location of these twenty storms are bound to differ from what the model predicts, since one cannot make accurate forecasts of this nature so far in advance.

The grid used by GloSea is fine enough to see hurricanes form, but is too coarse to properly handle important features of these storms. This lack of resolution results in the model not generating the right number of storms. This discrepancy is corrected by looking back at time for the years 1989-2002, and coming up with correction factors (i.e., "fudge" factors) that give a reasonable forecast.

The future of seasonal hurricane forecasts using global dynamical computer models is bright. Their first three forecasts have been good. Last year the Met Office forecast was for 6 named storms and an ACE index of 60. The actual number of storms was 9, and the ACE index was 53. Their 2008 forecast called for 15 named storms, and 15 were observed. Their 2007 forecast called for 10 named storms in July - November, and 13 formed. A group using the European Center for Medium Range Weather Forecasting (ECWMF) model is also experimenting with some promising techniques using that model. Models like the GloSea and ECMWF will only get better as increased computer power and better understanding of the atmosphere are incorporated, necessitating less use of "fudge" factors based on historical hurricane patterns. If human-caused climate change amplifies in coming decades, statistical seasonal hurricane forecasts like the CSU's may be limited in how much they can be improved, since the atmosphere may move into new patterns very unlike what we've seen in the past 100 years. It is my expectation that ten years from now, seasonal hurricane forecasts based on global computer models such as the UK Met Office's GloSea will regularly out-perform the statistical forecasts issued by CSU.

2010 Atlantic hurricane season forecast from Florida State University
Last year, another group using dynamical computer forecast models entered the seasonal hurricane prediction fray. A group at Florida State University led by Dr. Tim LaRow introduced a new model called COAPS, which is funded by a 5-year, $6.2 million grant from NOAA. This year, the COAPS model is calling for 17 named storms and 10 hurricanes. Last year's prediction by the COAPS model was for 8 named storms and 4 hurricanes, which was very close to the observed 9 named storms and 3 hurricanes.

Summary of 2010 Atlantic hurricane season forecasts
Here are the number of named storms, hurricanes, and intense hurricanes predicted by the various forecasters:

23 named storms: PSU statistical model
20 named storms: UKMET GloSea dynamical model
18.5 named storms, 11 hurricanes, 5 major hurricanes: NOAA hybrid statistical/dynamical model technique
18 named storms, 10 hurricanes, 5 intense hurricanes: CSU statistical model (Phil Klotzbach/Bill Gray)
17.7 named storms, 9.5 hurricanes, 4.4 intense hurricanes: Tropical Storm Risk (TSR), hybrid statistical/dynamical model technique
17 named storms, 10 hurricanes: FSU dynamical model
10 named storms, 6 hurricanes, 2 intense hurricanes: climatology

Only four hurricane seasons since 1851 have had as many as nineteen named storms, so 5 out of 6 of these pre-season forecasts are calling for a top-five busiest season in history. One thing is for sure, though--this year won't be able to compete with the Hurricane Season of 2005 for early season activity--that year already had five named storm by this point in the season, including two major hurricanes (Dennis and Emily.)

Tropical Storm Conson threatens the Philippines
Weather456 has an interesting post on why the Western Pacific typhoon season has been exceptionally inactive this year. It looks like we'll have out first typhoon of the Western Pacific season later today, since Tropical Storm Conson appears poised to undergo rapid intensification, and should strike the main Philippine island of Luzon as a Category 1 or 2 typhoon.

Next post
I'll have an update Wednesday.

Jeff Masters

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Quoting KoritheMan:


It's been over a year since I last saw that map, and unfortunately, I can't find it anymore. But I do recall them being over -2.5C, by a fairly comfortable margin.
Interesting. I didn't find any map or graph from that time period either.
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Quoting fatlady99:


Thanks for that link. I've been looking for a good cheeeeeep weather radio. If past experience is any indicator, we'll probably loose power (and internet and wah...WU) a few time this summer. Any suggestions?


I was fortunate enough to be able to get a generator. That reminds me I need to go put some oil and gas in it and check to make sure it is working.
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Very well defined AEW about to emerge. If it weren't for the unfavorable SAL I would definitely be monitoring this one closely.



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Quoting ElConando:



A good time in this lull to remind people to everyone in Hurricane prone areas to stock up on essentials. Batteries, bottled water, flashlights etc.

A detailed list on NHC site is here and will be on my blog on here.


Thanks for that link. I've been looking for a good cheeeeeep weather radio. If past experience is any indicator, we'll probably loose power (and internet and wah...WU) a few time this summer. Any suggestions?
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Quoting MiamiHurricanes09:
It's possible that it could have been an anomaly because many other strong La Niña season's had lesser activity than let's say a weak La Niña or neutral season. But the 1+2 region (along the South America coast) doesn't really have a big effect on the Atlantic. Do you know what where the numbers in the 3.4 region?


It's been over a year since I last saw that map, and unfortunately, I can't find it anymore. But I do recall them being over -2.5C, by a fairly comfortable margin.
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Quoting severstorm:
Evening all, i just watch them put new cap on and i dont see any oil leaking from new cap. Fingers crossed


With our luck it means it blew out underneath the seabed...
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Quoting KoritheMan:


While I've heard this theory postulated before, I'm not quite sure it's official? For example, 1988 obviously had a very potent La Nina event. I recall seeing a map where SST anomalies were as much as 5C below normal across much of the equatorial Pacific, particularly along the coast of South America. And that year didn't see any appreciable increase in vertical shear relative to normal.

Or maybe '88 was an anomaly...
It's possible that it could have been an anomaly because many other strong La Niña season's had lesser activity than let's say a weak La Niña or neutral season. But the 1+2 region (along the South America coast) doesn't really have a big effect on the Atlantic. Do you know what where the numbers in the 3.4 region?
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Tazmanian:
hey IKE and 09 look at this





That sucks.

1. Lower shear
2. No snow for us southerners. After having snow two years in a row I was just starting to get used to it. Oh well.. (I know you northerners think I'm outta my mind..)
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting MiamiHurricanes09:
Yes it's the Equatorial Pacific SSTs. Obviously we are in a La Niña with with the Niña 3.4 region acquiring SSTs below -0.5˚C. All I've got to say is, if this continues watch out! BUT if those SSTs get below -2.5˚C activity will begin to die down as a too strong La Niña starts to raise shear.


While I've heard this theory postulated before, I'm not quite sure it's official? For example, 1988 obviously had a very potent La Nina event. I recall seeing a map where SST anomalies were as much as 5C below normal across much of the equatorial Pacific, particularly along the coast of South America. And that year didn't see any appreciable increase in vertical shear relative to normal.

Or maybe '88 was an anomaly...
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Quoting IKE:
Climatology wins in 2010 in the ATL....



I mean sure, if you call a sub 950mb system in June climatological.. :P

I totally agree for the first half of July, but it'll probably be above average the rest of the time. Just 1 named storm in the second half of July and we are above average.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
History lesson and what is possible post landfall. Central Texans should not ignore Mexican land falling systems. Can't image what toll would be in modern times with the current populations.

From USGS - 1921 - Thrall Flood - A tropical storm formed in the Bay of Campeche the morning of Sept 6, 1921 - made hurricane intensity that afternoon - made landfall near Vera Cruz the early morning of Sept 7 - veered right and fell below depression intensity just as it crossed the Rio Grande at Rio Grande City the night of the 7th - Light rain began falling in San Antonio the 8th, which became a deluge the evening of the 9th, with totals to 18 in. in the northern part of San Antonio.

The 18 in. in northern Bexar County the evening of Sept 9, 1921, created a flood wave through downtown San Antonio 12 ft deep - The flow passed down Olmos and Apache Creeks into the San Antonio River - People caught downtown tried to evacuate vertically to upper floors - 51 didn't make it and drowned as the flood wave peaked near 1:30 AM -

Water was 4 to 5 ft deep in the current St. Marys Church and the Gunter Hotel. Olmos Dam was completed in 1928 as a flood-retention dam to protect downtown San Antonio as a direct result.

Thrall rainfall - 23.4 in. during 6 hrs/31.8 in. during 12 hrs/36.4 in. during 18 hrs/38.2 in. during 24 hrs at a U.S. Weather Bureau station at Thrall is still the national official 24-hr rainfall record ending at 7 AM Sept 10, 1921 - The storm total was 39.7 in. during 36 hrs - With 215 drownings statewide, this was the deadliest flood in Texas history.

Eighty-seven people drowned in and near Taylor and 93 in Williamson County. The confluence of the San Gabriel River and Brushy Creek was 10 mi wide. Not an El Nino or a La Nina year.



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Quoting Tazmanian:
hey IKE and 09 look at this



Yes it's the Equatorial Pacific SSTs. Obviously we are in a La Niña with with the Niña 3.4 region acquiring SSTs below -0.5˚C. All I've got to say is, if this continues watch out! BUT if those SSTs get below -2.5˚C activity will begin to die down as a too strong La Niña starts to raise shear.
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This is a good vid!!!



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hey IKE and 09 look at this


Quoting Tazmanian:
oh my by looking at this we may be heading in too a mod too strong La Nina La Nina may be come vary strong come winter if this keeps going

The latest weekly SST departures are:


Ni�o 4 -0.4�C
Ni�o 3.4 -0.8�C
Ni�o 3 -1.0�C
Ni�o1 2 -1.3�C

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Quoting HurricaneKatrina:


Within a month or so those ssts will be above 80 F. Anything going up there will be a major event.

Any TC that ventures quickly enough northward will create a MAJOR problem for the Mid-Atlantic, North East and New England.
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we have to go through another week without something to track this is depressing half of the blog will need zoloft
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O Romeo Romeo, wherefore art thou Romeo?
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Quoting CBS4:
Levi, where art thou?
Thou Levi has work.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting plywoodstatenative:
it seems as if the african wave train is firing on all barrels so to speak. However the issue becomes the fact that the Tropical Atlantic is not ready as we can all see by the fact that when the very impressive looking waves over the African continent hit the waters of the Atlantic they basically die until reaching the waters of the Caribbean. So until the Cape Verde season truly starts, and we see storms forming in that region of the Tropics, all we can focus on is when or if that wave that rolled off of Africa comes into the nexus of the Caribbean. Only then we can see if the "land-cane" can form into anything else other than a wave.
I reckon Cape Verde season will be starting in a weeks time. Below is the GFS 18z 200mb forecast and just look at those easterlies in the eastern Atlantic, since they flow with the trade winds shear will be very favorable for development. You match that up with a negative NAO, above average SSTs, and low SAL you are just going to get an explosion of activity.

GFS 18z 120 hours
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Evening all, i just watch them put new cap on and i dont see any oil leaking from new cap. Fingers crossed
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Off topic, but is there anyone here that can comment on the latest about the oil leak? I am watching feeds and I don't see any oil...could the cap actually be working this time?
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Quoting ElConando:
Hope for another week of calm.


I 2nd that..every week, day, hour that goes by without a storm brings us closer to the end of another season. Don't need any storms in any way shape or form..but I do see some that get their ya ya's out on that stuff...
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It's quiet in the Atlantic, but not Severe Weather-wise:
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JLPR, I would rather get your take on what I have written.
Member Since: November 15, 2005 Posts: 16 Comments: 4189
Quoting HurricaneKatrina:


Within a month or so those ssts will be above 80 F. Anything going up there will be a major event.
Why should we trust what you have to say? Your name suggests that you have a familial relationship in these things.
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884. xcool
MiamiHurrican lol
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883. JLPR2
Well, I will go away earlier today. :P
Nite everyone!

Quiet day in the Atl =)
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it seems as if the african wave train is firing on all barrels so to speak. However the issue becomes the fact that the Tropical Atlantic is not ready as we can all see by the fact that when the very impressive looking waves over the African continent hit the waters of the Atlantic they basically die until reaching the waters of the Caribbean. So until the Cape Verde season truly starts, and we see storms forming in that region of the Tropics, all we can focus on is when or if that wave that rolled off of Africa comes into the nexus of the Caribbean. Only then we can see if the "land-cane" can form into anything else other than a wave.
Member Since: November 15, 2005 Posts: 16 Comments: 4189
Quoting xcool:
Of course, the model with the SW Caribbean fetish develops yet another system there. I mean if every single system the NOGAPS develops in the SW Caribbean verifies we would be by the Chinese alphabet.
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Quoting KoritheMan:


While you're correct for the most part, there are exceptions. For example, my Firefox spellchecker depicts the word "millennia" as an invalid word, even though it obviously isn't.

tl:dr; spellcheckers aren't always accurate.
plus, there was a reason I posted that.
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879. xcool
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Quoting beell:


What do you use?
Goat bones?
;)
I have never tried that but it may be promising...I like to stick with a little eye of newt :)
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Quoting hunkerdown:
thats because its hostile out there...the fish are fighting fish, the birds are fighting each other, heck, the fish are fighting the birds. Its a veritable cornucopia of hostility out there.
ROFL.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting KoritheMan:


While you're correct for the most part, there are exceptions. For example, my Firefox spellchecker depicts the word "millennia" as an invalid word, even though it obviously isn't.

tl:dr; spellcheckers aren't always accurate.
It does the same thing to me with "cyclogenesis", and "forecasted".
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting KoritheMan:


While you're correct for the most part, there are exceptions. For example, my Firefox spellchecker depicts the word "millennia" as an invalid word, even though it obviously isn't.
true that would not fall under the heading of blatantly misspelling...
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874. beell
Quoting hunkerdown:
thank you mr modelcaster :P


What do you use?
Goat bones?
;)
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A good time in this lull to remind people to everyone in Hurricane prone areas to stock up on essentials. Batteries, bottled water, flashlights etc.

A detailed list on NHC site is here and will be on my blog on here.
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Quoting hunkerdown:
its really sad when people post comments and continue to blatantly misspell words...the darn blog has spell check people. You know, that little red line under the word means its spelled wrong. Its even dummy proof, all yo have to do is right click on the misspelled word and it will GIVE you the correct spelling...suicidal.


While you're correct for the most part, there are exceptions. For example, my Firefox spellchecker depicts the word "millennia" as an invalid word, even though it obviously isn't.

tl:dr; spellcheckers aren't always accurate.
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its really sad when people post comments and continue to blatantly misspell words...the darn blog has spell check people. You know, that little red line under the word means its spelled wrong. Its even dummy proof, all you have to do is right click on the misspelled word and it will GIVE you the correct spelling...suicidal.
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Quoting Relix:
How's our African wave doing?


She has got friends behind her....

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You know I have seen you write a bunch of crap all day with no knowledge . Do you have a degree? Others have said it before me...get off this blog!





You>
scott that is what im trying to get the rest in here to understand...well said the tropics are hostile right now no development until the first or middle part of august...everyone needs to take a breather..
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Good evening all. Looks like it's all quiet on the Atlantic front.
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Quoting MiamiHurricanes09:
Lotsa nothin' except for the lotsa convection in the ITCZ.

thats because its hostile out there...the fish are fighting fish, the birds are fighting each other, heck, the fish are fighting the birds. Its a veritable cornucopia of hostility out there.
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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.