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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2764. xcool
btwntx08 :)))
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2761. xcool
btwntx08 wind shear to high
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2760. centex
Quoting LawStudent:
Cent, come on now, man, plz behave yourself, JP is not picking on you.
I'm just giving him his due. Not giving in, I'm right not always but more than him. No serious entry here but not caving in.
Member Since: Posts: Comments:
2759. xcool
lolol
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2757. JLPR2
Quoting bappit:

I think Levi would agree with Centex on that statement.


they miss each other? o.O?
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2755. bappit
Quoting JLPR2:
Looks like Centex is lonely LOL!
He misses Levi to argue with, sorry buddy, I'm not in the mood to argue with you.

I think Levi would agree with Centex on that statement.
Member Since: Posts: Comments:
2753. xcool
cia here haha
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2752. bappit
Quoting KoritheMan:
2687.

You didn't explicitly, but you certainly implied as much. Anyway, I'll mail you. Let's keep this blog clean!

Actually, I think Seastep's riff on the flying spaghetti monster does have a connection to some meteorological comments posted on the blog.

I see comments that invoke a teleological reasoning to explain what is happening weather-wise. Sometimes it comes up in a purely casual way as in "this system just won't give up." On the other hand, one frequent blogger, at least, uses it in a highly conscious way hinting at an underlying belief about intelligent design.

Teleological reasoning has been generally discredited in academia. The idea of final causes was big with Aristotle in his version of "hard" science and with Hegel in his version of social science. On the other hand, according to my friendly Wikipedia (look up teleology) it has been quite difficult for research biologists to completely eliminate turns of phrase with a teleological slant from their discussions. At least that situation does not seem to apply to serious meteorological research.
Member Since: Posts: Comments:
2751. xcool
iknowww
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting btwntx08:
wow 4 handles in a day geez




thats not right
Member Since: Posts: Comments:
2749. JLPR2
Quoting CybrTeddy:
Don't fight to hard gang.


What are you talking about, its all peace and love here. XD LOL!
Member Since: September 4, 2007 Posts: 7 Comments: 8459
So how are they doing on that oil thingy out there?
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.
Member Since: Posts: Comments:
2744. JLPR2
Quoting wunderkidcayman:
Atlantic Tropical Weather Discussion
--------------------------------------------------------------------------------


000
AXNT20 KNHC 140535
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED JUL 14 2010

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC...

...TROPICAL WAVES...

TROPICAL WAVE HUGS THE AFRICAN COAST ALONG 17W S OF 22N MOVING W
15-20 KT. SATELLITE IMAGERY INDICATES A BROAD AREA OF CYCLONIC
FLOW IN THE VICINITY OF THE WAVE AXIS. SURFACE WIND OBSERVATIONS
FROM DAKAR SENEGAL WENT FROM NWLY TO ELY AROUND 33O UTC
INDICATING THE PASSAGE OF THE WAVE. A SURGE OF MOISTURE NEAR THE
WAVE AXIS IS ALSO PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-14N
BETWEEN 17W-22W.

nothing about SAL affecting it



The northern tip of the wave is under SAL
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2743. xcool
16 to 26 july active periods
Member Since: September 26, 2009 Posts: 2 Comments: 15603
ugh
Member Since: Posts: Comments:
2736. xcool
CMC SHOWS 000%
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Don't fight to hard gang.
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2734. xcool
SpaceNeedle YEP I'M LOLOL YOU I;M JOKE
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2733. JLPR2
Quoting xcool:



HA


That's interesting and waaay south. :O
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2730. centex
Quoting JLPR2:
Looks like Centex is lonely LOL!
He misses Levi to argue with, sorry buddy, I'm not in the mood to argue with you.
You could not be more right on that point. Hate too admit it.
Member Since: Posts: Comments:
2729. JLPR2
Quoting skkippboo:


We definitely don't need anymore systems here in S. Tex this year, or anywhere for that matter. Our floodway is still filling with water from the runoff from Alex and TD2. Skeeter are still awful too.


Neither Mexico or South Texas needs another storm for awhile, Td's tend to get downplayed but they can dump lots of rains, which get deadly.
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2728. xcool
LMAO
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting centex:
Not much unless you don't live in S. TX.


We definitely don't need anymore systems here in S. Tex this year, or anywhere for that matter. Our floodway is still filling with water from the runoff from Alex and TD2. Skeeter are still awful too.
Member Since: Posts: Comments:
2726. JLPR2
Looks like Centex is lonely LOL!
He misses Levi to argue with, sorry buddy, I'm not in the mood to argue with you.
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2725. xcool



HA
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2724. bappit
Quoting JLPR2:


Not sure if that's a wow but so far its sustaining itself.

Can't get no ... CV action.
And I try and I try and I try and I try.

But he can't be a met cause he don't forecast like me.
Member Since: Posts: Comments:
2723. xcool
HEY JFV
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Atlantic Tropical Weather Discussion
--------------------------------------------------------------------------------


000
AXNT20 KNHC 140535
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED JUL 14 2010

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC...

...TROPICAL WAVES...

TROPICAL WAVE HUGS THE AFRICAN COAST ALONG 17W S OF 22N MOVING W
15-20 KT. SATELLITE IMAGERY INDICATES A BROAD AREA OF CYCLONIC
FLOW IN THE VICINITY OF THE WAVE AXIS. SURFACE WIND OBSERVATIONS
FROM DAKAR SENEGAL WENT FROM NWLY TO ELY AROUND 33O UTC
INDICATING THE PASSAGE OF THE WAVE. A SURGE OF MOISTURE NEAR THE
WAVE AXIS IS ALSO PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-14N
BETWEEN 17W-22W.

nothing about SAL affecting it

Member Since: Posts: Comments:
2716. bappit
Quoting JLPR2:
Dry Air:

One of those dry blobs looks like Flipper.
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2715. xcool
JLPR2 .meaning wave look good
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2714. JLPR2
Quoting centex:
LOL, your out of touch. Don't you follow the news? I thing you live elsewhere and don't care.


What are you talking about?
Member Since: September 4, 2007 Posts: 7 Comments: 8459

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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.