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 Stormchaser2007:
Im pretty surprised by how quiet the Atlantic has been so far this July.

Regardless, theres a pretty potent pattern shaping up in the MDR for the mid-later part of the month. This could cause the initiation of the Cape Verde season which could breed 2-3 storms before the month ends. This pattern should continue for a while and we could have a pretty active August and September and possibly even October.
We'll see what happens.

18z GFS 117 hours. Zero shear in the Central Atlantic:


Goes to show that the recipe for hurricanes isn't just hot water and low shear. It's hot water, low shear, and sustained convection far enough from the equator to get a spin. Strong inversion layers are just as preventative of cyclogenesis as wind shear and cold water. You gotta have CAPE.
Member Since: September 7, 2007 Posts: 1 Comments: 937
Quoting weathermanwannabe:
Well just about out for the evening. Most interesting thing in the tropical Atlantic for me right now is the very quick rise of the ITCZ in just a matter of 72 hours. On Friday, I was commenting on how low it had dipped, actually right around 5N, and the whole thing has risen right up to near 10N in some places over the past 24-48 hours; Mother Nature basically telling us that August and the CV season is right around the corner.......See everyone tommorow.

Or the people doing the interpretation decided to move it. :)
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Quoting MiamiHurricanes09:
1 maybe 2 what?


named storms by the end of July.
Member Since: July 6, 2010 Posts: 113 Comments: 31581
Quoting TropicalAnalystwx13:


yes.

Brief explanation concerning the S US El Nino Snow events.

The Sub-tropical Jet shot tons on moisture in all levels across the Southern USA. Several Arctic/Polar airmasses shot south, one straight from Siberia into the Southern US, in the states of TX, LA, MA, AL into FL, then decided to stuck around for 6-7 weeks.

Add areas of Low pressure shooting across the above mentioned states, viola', heavy winter snows.

A few examples, about 14" in Arlington, TX, 12" at the DFW TX AP, up to 5" in SE TX, LA, MS, AL and snow flurries as far south as Orlando, FL, including a few sleet pellets in Miami!
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Quoting beell:


What do you use?
Goat bones?
;)

From my 1962 copy (eleventh printing) of the Golden Nature Guide to Weather:

Machine forecasting as accurate as human forecasting, or more so, is now being done by electronic computers. The U.S. Joint Numberical Weather Prediction Unit began opeation of the first "electronic brain" for routine weather forecasting in 1955.

They might have been a little cheery in their assessment for the time. Odd that they don't mention goat bones.
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Quoting KoritheMan:


That, and a negative phase of the NAO (I think).


Yeah, I think so, too.
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Quoting Baltimorebirds:
I think we'll most likley have one,maybe 2.


I think we will have one, a good chance of two, and maybe three. :P
Member Since: July 6, 2010 Posts: 113 Comments: 31581
Quoting MiamiHurricanes09:
Consistency.


Aye.
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Quoting MiamiHurricanes09:
Basically yes.

La Niña: hot winter and hot summer.
El Niño: cold winter cold summer.


Yeah, that makes sense! 2007 was a record year, and 2008 and 2009 weren't that bad! I think it has something to do with the ridge. In 2007, we had a high sitting over Tennessee like a giant oven. Now, it's over like Georgia or something.
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Quoting cg2916:
Question!

Did the El Nino cause above-average snow for the south? If not, what did?


That, and a negative phase of the NAO (I think).
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Quoting Baltimorebirds:
I think we'll most likley have one,maybe 2.
1 maybe 2 what?
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Quoting StormW:


LOL!


Yeah, I want a Whopper, with no onions, lettuce, or heart attack, is that ok?
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Quoting cg2916:


Does the La Nina do the same in the summer, LOL. I'm dying here!
Basically yes.

La Niña: hot winter and hot summer.
El Niño: cold winter cold summer.
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Quoting MiamiHurricanes09:
Consistency.


Yup, shear-wise. I think the GFS has been downcasting the season a little bit. The ECMWF is on a roll, though!
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Quoting KoritheMan:


GFS has been forecasting this for awhile. Quite awhile.
Consistency.
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If they get this oil spill under control within a 100 days, I will consider the containment a success.
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Quoting MiamiHurricanes09:
El Niño's cause colder conditions in the winter, La Niña's do the opposite. So yes, the strong El Niño caused the cold winter this year.


Does the La Nina do the same in the summer, LOL. I'm dying here!
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Quoting IKE:
Keith Olbermann just asked a real good question...why didn't BP have this back on April 20th when this happened?


Yeah, shouldn't they have had a back-up plan in place. Of course, this is so massive it's hard to contain. At least if this happens again (hopefully it won't), we should.
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Quoting cg2916:
Question!

Did the El Nino cause above-average snow for the south? If not, what did?
El Niño's cause colder conditions in the winter, La Niña's do the opposite. So yes, the strong El Niño caused the cold winter this year.
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Quoting cg2916:
Question!

Did the El Nino cause above-average snow for the south? If not, what did?


yes.
Member Since: July 6, 2010 Posts: 113 Comments: 31581
Quoting Stormchaser2007:
Im pretty surprised by how quiet the Atlantic has been so far this July.

Regardless, theres a pretty potent pattern shaping up in the MDR for the mid-later part of the month. This could cause the initiation of the Cape Verde season which could breed 2-3 storms before the month ends. This pattern should continue for a while and we could have a pretty active August and September and possibly even October.
We'll see what happens.

18z GFS 117 hours. Zero shear in the Central Atlantic:


GFS has been forecasting this for awhile. Quite awhile.
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Quoting IKE:
Keith Olbermann just asked a real good question...why didn't BP have this back on April 20th when this happened?

That's easy, they didn't plan on needing to do anything like this. Their plan was the blow out preventer they had in place. They did not execute the plan ... among other things.
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936. IKE
SYNOPSIS FOR CARIBBEAN SEA AND TROPICAL N ATLC FROM 07N TO 22N
BETWEEN 55W AND 65W
530 PM EDT MON JUL 12 2010

.SYNOPSIS...A TROPICAL WAVE ALONG 85W WILL MOVE ACROSS THE
YUCATAN PENINSULA TONIGHT. ANOTHER TROPICAL WAVE ALONG 47W WILL
APPROACH 55W LATE TUE INTO EARLY WED THEN WILL MOVE ACROSS THE
TROPICAL N ATLC WED ENTERING THE E CARIBBEAN EARLY THU THEN
MOVING THROUGH THE E CARIBBEAN THU AND FRI...AND ACROSS THE
CENTRAL CARIBBEAN SAT. A THIRD TROPICAL WAVE WILL APPROACH THE
TROPICAL N ATLC LATE SAT.


SYNOPSIS FOR THE GULF OF MEXICO
430 PM CDT MON JUL 12 2010

.SYNOPSIS...A RIDGE ALONG 25N WILL SHIFT N TO ALONG 27N TUE THEN
TO ALONG 29N THU AND FRI. THE RIDGE WILL RETREAT E AS WEAK LOW
PRES DEVELOPS OVER THE SW GULF WATERS.
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Quoting StormW:


Good...just got back from taking my boys to Burger King.


Should've bought me some. I love Burger King. :P
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Quoting StormW:


Good...just got back from taking my boys to Burger King.


Hold the pickles, hold the lettuce, special orders don't upset us....God, I am old!
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Member Since: July 6, 2010 Posts: 113 Comments: 31581
Question!

Did the El Nino cause above-average snow for the south? If not, what did?
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931. IKE
Quoting weathermanwannabe:


They are making it up as they go along.......See You Tommorow Ike....Good Night.


They didn't have a plan.

L8R.
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Quoting IKE:
Keith Olbermann just asked a real good question...why didn't BP have this back on April 20th when this happened?


They are making it up as they go along.......See You Tommorow Ike....Good Night.
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Quoting Dakster:


How many does the CMC predict?

They toned it down. See this link.

Prior to 2009, the CMC GEM had a tendency to over-forecast genesis of TCs. The recent changes to the model upper boundary are believed to decrease the false alarm ratio for TC genesis, particularly at day 3 and beyond in the forecast period.
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927. IKE
Keith Olbermann just asked a real good question...why didn't BP have this back on April 20th when this happened?
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pretty crazy to see these robots pulling wires and moving them in place

link to live feed

http://www.wkrg.com/gulf_oil_spill/spill_cam/
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for those of you too young to remember, a radio is sort of like an early iPod with data reception but no storage.

Weather Radios are they too old school? Power out for two weeks means no internet. Even our county library was out of power for awhile. Anyone here know anything about weather radios?
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Quoting bakers:
also global climate models indicate cooling over 75% of the globe in the next few years.


Global cooling??
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923. IKE
Quoting truecajun:
the new cap is on and so far so good. this one is said to be able to catch all of the oil leaking!!! now we just need the weather to stay quiet so they can finish the relief well.


I was just fixing to post this....Containment cap on BP well appears to be in place
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the new cap is on and so far so good. this one is said to be able to catch all of the oil leaking!!! now we just need the weather to stay quiet so they can finish the relief well.
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Quoting Tazmanian:
hey IKE and 09 look at this



also global climate models indicate cooling over 75% of the globe in the next few years.
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Well just about out for the evening. Most interesting thing in the tropical Atlantic for me right now is the very quick rise of the ITCZ in just a matter of 72 hours. On Friday, I was commenting on how low it had dipped, actually right around 5N, and the whole thing has risen right up to near 10N in some places over the past 24-48 hours; Mother Nature basically telling us that August and the CV season is right around the corner.......See everyone tommorow.
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CA is heading for a cold winter
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Quoting earthlydragonfly:


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.


gosh, yes, thanks! I try to get things done by June, but obviously am not that organized. have to get the dogs their health papers, too, in case we are forced to make a run for it! :(

But I'd still love to get a recommendation for a battery or hand crank powered radio, if anyone knows of one. Or see if y'all have an opinion of the red cross radios out there....
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Quoting Stormchaser2007:
Im pretty surprised by how quiet the Atlantic has been so far this July.

Regardless, theres a pretty potent pattern shaping up in the MDR for the mid-later part of the month. This could cause the initiation of the Cape Verde season which could breed 2-3 storms before the month ends. This pattern should continue for a while and we could have a pretty active August and September and possibly even October.
We'll see what happens.

18z GFS 117 hours. Zero shear:
Exactly what I was saying earlier with the dominant easterlies in the eastern Atlantic (post 891).
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I'm sorry but the prospect of benzene, methane, corexit/oil and associated chemicals being transported hundreds of miles inland by a violent hurricane is too horrifying for words. Being in north TX, I am contemplating moving to Idaho to escape the toxic blasts. I don't know how I'll afford it but it will be preferred over imminent sickness and death wrought by the military industrial complex in the Gulf.
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Im pretty surprised by how quiet the Atlantic has been so far this July.

Regardless, theres a pretty potent pattern shaping up in the MDR for the mid-later part of the month. This could cause the initiation of the Cape Verde season which could breed 2-3 storms before the month ends. This pattern should continue for a while and we could have a pretty active August and September and possibly even October.
We'll see what happens.

18z GFS 117 hours. Zero shear in the Central Atlantic:
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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