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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2814. xcool
you have to see video
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2812. xcool
hey jfv
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2809. xcool
ECMWF,shows 5%
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2808. xcool
joe b mad about wpac
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2807. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #19
TROPICAL STORM CONSON (T1002)
15:00 PM JST July 14 2010
============================

SUBJECT: Category One Typhoon In The South China Sea

At 6:00 AM UTC, Tropical Storm Conson (992 hPa) located at 15.3N 118.3E has 10 minute sustained winds of 45 knots with gusts of 65 knots. The cyclone is reported as moving west northwest at 15 knots.

Gale Force Winds
=================
100 NM from the center

Forecast and Intensity
========================
24 HRS: 17.2N 114.4E - 50 knots (CAT 2/Severe Tropical Storm)
48 HRS: 18.8N 111.5E - 60 knots (CAT 2/Severe Tropical Storm)
72 HRS: 20.4N 110.2E - 55 knots (CAT 2/Severe Tropical Storm)
Member Since: May 24, 2006 Posts: 48 Comments: 43639
96E also appears to be experiencing some easterly shear:



Notice the lack of upper-level outflow along the eastern semicircle.

This could slow development in the near-term, but not significantly. I wouldn't be surprised to see a tropical depression form tonight (as in, Wednesday night) or early Thursday morning.
Member Since: Posts: Comments:
Quoting btwntx08:
ahhh something in the epac nice i wanted something to track aleast


I know. It's nice.
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2802. xcool
lol
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting bappit:

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.


Ah. I hadn't thought of it that way before, admittedly. You make a good point.
Member Since: Posts: Comments:
what in the world are you talking about there is no limit on the Long. line only on the lat. line at 20-23N to me our fartest east AOI is the wave at 20E but our main areas of intrests are at 17W our Wave with little SAL affecting it onlt to the very northern parts next is the wave near 45-50W and the other is in the SW Caribbean



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Quoting xcool:
96e poof


96E will develop. Upper-level shear favors it.
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Quoting JLPR2:


That one is related to the one that slammed into Nicaragua right?


Aye.
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2796. JLPR2
Quoting KoritheMan:
Possible CDO developing with 96E:



That one is related to the one that slammed into Nicaragua right?
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2795. xcool
96e poof
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Possible CDO developing with 96E:

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2793. centex
I'M OUT.
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2792. xcool
i'm back
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2791. centex
Quoting xcool:


big waves
looking too far east. 45w is our limited AOI.
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Quoting xcool:
16 to 26 july active periods


active-how many TC's will form?
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2788. xcool


big waves
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2787. kramus
Quoting btwntx08:
bb in 20 min


blt in 5
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2785. JLPR2
Quoting xcool:
It's Never To Early for cv Storms


Yeah, if you have the right conditions a storm could form anywhere at any time.
eh...
nothing surprises me anymore. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2784. xcool
:)
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2782. xcool
Buttercup.lol
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2781. kramus
Great name for a 'B' storm: "Buttercup." I know, I know, it's a horse name. For once, humor me. There must be a woman out there somewhere named Buttercup.
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2780. xcool
btwntx08 he come back so looking out
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2779. centex
Quoting xcool:
centex ?
I guess I should go to bed.
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2778. xcool
It's Never To Early for cv Storms
Member Since: September 26, 2009 Posts: 2 Comments: 15603
I glanced at StormW's Blog and he said there was something he was keeping his eye on and that is usually pretty good information
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2775. xcool
centex ?
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2774. JLPR2
Quoting traumaboyy:
Stupid question, isn't it a little early in the season for African Storms?....night shift makes my brain soft but I thought the Cape Verde season was usually a bit later in the year.


yep, it usually runs from late August through September, I think...
Member Since: September 4, 2007 Posts: 7 Comments: 8459
2773. bappit
Quoting traumaboyy:
Stupid question, isn't it a little early in the season for African Storms?....night shift makes my brain soft but I thought the Cape Verde season was usually a bit later in the year.

Typically is. Insert Carly Simon lyrics here.
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2772. centex
40W a little more probable.
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2771. xcool
timed to call a d.r
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2770. bappit
What's happening with King TUTT?

Some shear to be reckoned with is out there.
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2768. xcool
he be back fast
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Stupid question, isn't it a little early in the season for African Storms?....night shift makes my brain soft but I thought the Cape Verde season was usually a bit later in the year.
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Quoting xcool:
jfv stop talked to you self




he be banned by AM this sent a note too Admin
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2765. xcool
jfv stop talked to you self
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2764. xcool
btwntx08 :)))
Member Since: September 26, 2009 Posts: 2 Comments: 15603

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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.