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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1. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A BROAD AREA OF LOW
PRESSURE ARE GRADUALLY BECOMING BETTER ORGANIZED A COUPLE HUNDRED
MILES SOUTH-SOUTHWEST OF THE GULF OF TEHUANTEPEC. ENVIRONMENTAL
CONDITIONS ARE CONDUCIVE FOR ADDITIONAL DEVELOPMENT OF THIS SYSTEM
OVER THE NEXT COUPLE OF DAYS AS IT MOVES WEST-NORTHWESTWARD AT
ABOUT 10 MPH. THERE IS A MEDIUM CHANCE...30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Member Since: Posts: Comments:
363. IKE
12Z ECMWF
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do i smell a smell i think i smell JFV
Member Since: May 21, 2006 Posts: 5091 Comments: 114919
Quoting Baltimorebirds:
May you post the shear maps of that region please.Much appreciated thanks.


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Regarding the Bahamian thunderstorm complex, its nothing special. Just your run-of-the-mill thunderstorms caused by the presence of an upper level low to the east and diffluent flow aloft. Nothing will come from this thunderstorm cluster since conditions aren't favorable with relatively high wind shear and little happening in the lower levels. I would expect this activity to fall apart in the next six hours.
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Tropical Storm Conson - Joint Typhoon Warning Center Advisory #5
11am EDT
Graphics Update


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Here's Turks' latest report for Wunderground, BTW:

Providenciales, Turks Islands
Local Time: 3:09 PM EDT (GMT -04) Your time: 3:09 PM EDT (GMT -04)
Lat/Lon: 21.8° N 72.3° W (Google Map)


Current Conditions


Providenciales, TI (Airport)
Updated: 1 hr 9 min 35 sec ago
73 °F / 23 °C
Thunderstorm
Humidity: 88%
Dew Point: 70 °F / 21 °C
Wind: 7 mph / 11 km/h / 3.1 m/s from the East
Pressure: 30.05 in / 1018 hPa (Rising)
Visibility: 5.0 miles / 8.0 kilometers
UV: 9 out of 16
Clouds: Scattered Clouds 1000 ft / 304 m
Mostly Cloudy 8000 ft / 2438 m
(Above Ground Level)
Elevation: 13 ft / 4 m


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You know, speaking of forecast numbers for the season, didn't we do a blog forecast on ossqss' blog? Wonder what our WunderBloggers' 2010 forecast average is for NS and hurricanes?
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Quoting btwntx08:

alot of ppl did including me but hes still here


We got one last night and we will get this one. Give it time.
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14 years ago today. Hurricane Bertha hit South Carolina as a Category 2 hurricane. Bertha killed 12 and caused $270 million of damage.
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2010 Hurricane Preparation


With the Lil break in the 2010 action and the meat of the season to come still,
Now is a good time to buff up ones action plan for a Storm.


Hurricane Preparation is a Family oriented project that can and should include every member for input.


Also,review ones evac plan and destination too.

Time spent wisely now will save one from stress then, and that can affect ones capability to make sound and timely decisions when it counts.
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344. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15648
343. xcool
Current wave not to bad
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting will45:


they dont have to be on. if enuff flag him he will be gone. Enuff said


And to do it using the "name" of a local TV station.

Someone should drop them a letter...
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339. xcool
CV storm july 17 or july 25 imo
Member Since: September 26, 2009 Posts: 2 Comments: 15648
.
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I just counted about 20-30 posts on a blog personality, when we could be talking about the Bahama Blob....



An uncle of mine was supposed to fly in from Mayguana, which is the island right on the edge of the blue/green inside the blob, but he didn't get on the flight.

So, still no first-hand info on what's kickin... CRS should be around soon, though, with reports from T&C....
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Quoting HadesGodWyvern:
Japan Meteorological Agency
Tropical Cyclone Advisory #7
SEVERE TROPICAL STORM CONSON (T1002)
3:00 AM JST July 13 2010
============================

SUBJECT: Category Two Typhoon In Seas East Of The Philippines

At 18:00 PM UTC, Severe Tropical Storm Conson (975 hPa) located at 14.3N 126.5E has 10 minute sustained winds of 60 knots with gusts of 85 knots. The cyclone is reported as moving west at 11 knots.

Storm Force Winds
=================
60 NM from the center

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

Forecast and Intensity
========================
24 HRS: 15.5N 123.1E - 75 knots (CAT 3/Strong Typhoon)
48 HRS: 17.4N 119.5E - 75 knots (CAT 3/Strong Typhoon)
72 HRS: 19.6N 115.5E - 80 knots (CAT 3/Strong Typhoon)


You are posting Western Pacific advisories, all is right with the world.
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331. xcool
StormW i think so lol
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting Baltimorebirds:
The u.k has been doing a good job over the years in my opinion.


Outstanding in my opinion, closer then any other forecasts I've seen.
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329. xcool
my new forecast 13 names storms lmao
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting btwntx08:

idk maybe admin isnt on right now but when they do he'll be gone again


they dont have to be on. if enuff flag him he will be gone. Enuff said
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323. xcool
u.k veryyy good job 2009 forecast
Member Since: September 26, 2009 Posts: 2 Comments: 15648
322. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #7
SEVERE TROPICAL STORM CONSON (T1002)
3:00 AM JST July 13 2010
============================

SUBJECT: Category Two Typhoon In Seas East Of The Philippines

At 18:00 PM UTC, Severe Tropical Storm Conson (975 hPa) located at 14.3N 126.5E has 10 minute sustained winds of 60 knots with gusts of 85 knots. The cyclone is reported as moving west at 11 knots.

Storm Force Winds
=================
60 NM from the center

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

Forecast and Intensity
========================
24 HRS: 15.5N 123.1E - 75 knots (CAT 3/Strong Typhoon)
48 HRS: 17.4N 119.5E - 75 knots (CAT 3/Strong Typhoon)
72 HRS: 19.6N 115.5E - 80 knots (CAT 3/Strong Typhoon)
Member Since: May 24, 2006 Posts: 50 Comments: 45212
about td2 even masters didnt recognise that system.those waves out there are still not doing anything no suprise with dusty air. dud season ahead!
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Bastardi said last 10 days of month things will pick up.
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317. xcool
btwntx08 not good forecast.lol
Member Since: September 26, 2009 Posts: 2 Comments: 15648
315. xcool
7544 check accuweather..com
Member Since: September 26, 2009 Posts: 2 Comments: 15648

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.