Average hurricane season foreseen by CSU, but TSR predicts an active season

By: Dr. Jeff Masters , 5:01 PM GMT on April 07, 2009

Share this Blog
2
+

A near-average Atlantic hurricane season is on tap for 2009, according to the latest seasonal forecast issued today by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The Klotzbach/Gray team is calling for 12 named storms, 6 hurricanes, and 2 intense hurricanes. An average season has 10-11 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is a step down from their December forecast, which called for 14 named storms, 7 hurricanes, and 3 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (32% chance, 31% chance is average) and the Gulf Coast (31% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.

The forecasters cited several reasons for reducing their forecast from an active season to an average season:

1) Sea surface temperature (SST) anomalies in the tropical Atlantic have cooled considerably since December. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Part of the reason for the substantial cooling since December is because a stronger than average Bermuda-Azores High drove strong trade winds. These strong winds acted to evaporate more water from the ocean, cooling it. Higher winds also increase the mixing of cool waters to the surface from below. However, in March, the Bermuda-Azores High weakened. The resulting weaker trade winds may allow SSTs to warm to above average levels by the coming hurricane season, if this weaker Bermuda-Azores High persists.

2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. The CSU team expects current weak La Niña conditions to transition to neutral and perhaps weak El Niño conditions (50% chance) by this year's hurricane season. April and May are typically the months when the atmosphere will swing between El Niño and La Niña, which makes any seasonal forecasts of hurricane activity during April low-skill. The current computer models used to predict El Niño (Figure 1) mostly favor neutral conditions for the coming hurricane season. These models are primarily based on statistical methods that observe how previous El Niño events have evolved. Three of the newer computer-intensive dynamical models (similar to the GFS model we use to make weather forecasts) do predict an El Niño event by hurricane season. The reliability of all of these models is poor.


Figure 1. Computer model forecasts of El Niño/La Niña made in March. The forecasts that go above the red line at +0.5°C denote El Niño conditions; -0.5°C to +0.5°C denote neutral conditions, and below-0.5°C denote La Niña conditions. Three computer models predict El Niño conditions for hurricane season (ASO, August-September-October). However, most of the models predict neutral conditions. Image credit: Columbia University's IRI.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar in April to what we are seeing this year. Those five years were 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1985, which had Category 3 Gloria in New England and Category 3 Elena in the Gulf of Mexico; 1976, which had Category 1 Hurricane Belle in New England; 1968, which had Category 1 Hurricane Gladys north of Tampa; and 1951, which had only one landfalling hurricane, Category 3 Hurricane Charlie in Mexico. The mean activity for these five years was 11 named storms, 7 hurricanes, and 3 intense hurricanes.

How accurate are the April forecasts?
This year's April forecast uses the same formula as last year's April forecast, which did quite well predicting the 2008 hurricane season. Last year's forecast included the statement, "These real-time operational early April forecasts have not shown forecast skill over climatology" during the 13-year period 1995-2007. Unfortunately, this year's forecast neglects to mention this fact. In fact, when looking at Excel spreadsheet of their forecast errors (expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) their April forecasts have had negative skill between 1995-2008. In other words, you would have been better off using climatology than believing their April forecasts.

2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2009 Atlantic hurricane season forecast yesterday, but they are calling for an active year: 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 63% chance of an above-average hurricane season, 24% chance of a near-normal season, and only a 13% chance of a below normal season. They give a 63% chance that 2009 will rank in the top third of most active hurricane seasons on record. The April 2009 TSR forecast is virtually identical to their December 2008 forecast, and is also quite close to their April 2008 forecast made for the 2008 hurricane season.

I like how TSR puts their skill level right next to the forecast numbers: 11% skill above chance at forecasting the number of named storms, 9% skill for hurricanes, and 7% skill for intense hurricanes. That's not much better than flipping a coin, but is better than the negative forecast skill of the Klotzbach/Gray April forecasts.

TSR projects that 4.8 named storms will hit the U.S., with 2.1 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 10-15% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.4 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites one main factor for their forecast of an active season: slower than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.4 meters per second (about 1 mph) slower than average in this region, which would create greater spin for developing storms, and allow the oceans to heat up due to reduced evaporational cooling. TSR forecasts that SSTs will be near average in the MDR during hurricane season, and will not have an enhancing or suppressing effect on hurricane activity.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and TSR (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 61 - 11

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8Blog Index

Hey Patrap.

Read the article.

My reaction to it?

Wuh?

What lightning are they talking about? Worldwide? Within a developing storm? They mention lightning sensors...that paragraph is the one that makes the whole article a "wuh?" for me.

Sounds like those two guys are sniffing around for a grant.
Member Since: Posts: Comments:
Thanks washingaway for posting that really cool animation.

I noticed that it's a forecast...way cool. You are correct in saying that this new thing [I've never seen it before, anywhere] will have an impact in this blog when hurricane season comes around.

Once again...many thanks!
Member Since: Posts: Comments:

Lightning Warns of Hurricanes' Most Intense Moments?

John Roach
for National Geographic News
April 6, 2009

Lightning may help improve hurricane forecasts by signaling when the storms are about to reach peak intensity, according to a new study.

Current satellite and radar technologies can fairly accurately predict a storm's path, but when and how much a storm will intensify are harder to pin down.
Member Since: July 3, 2005 Posts: 426 Comments: 128871
2007 Could have been worst than 2008. It was all thanks to that unusual strong subtropical ridge
Member Since: Posts: Comments:


Technical Attachment

AN OVERVIEW OF NHC PREDICTION MODELS

Bernard N. Meisner
Scientific Services Division
National Weather Service Southern Region

Introduction

Storm Track Guidance Models
HURRAN | CLIPER | NHC98 | BAM | LBAR | GHM (GFDL) | GFS (formerly AVN) | NOGAPS | GUNS, GUNA and CONU Ensembles
Relative Skill of the Statistical | Numerical Guidance Models

Storm Intensity Guidance Models
SHIFOR | SHIPS | GHM (GFDL)
Relative Skill of the Intensity Guidance Models

Forecast Verification

Storm Surge Guidance Model
SLOSH
Member Since: July 3, 2005 Posts: 426 Comments: 128871
Quoting CybrTeddy:
I declare it preseason Hurricane forecasting time!
Alright. A few questions, please answer if you wish.
1) When will Ana Form? (my vote 5-28-09)
2) How many storms will there me (my vote 15)
3) How many Hurricanes and Majors do we get? (5/2)
4) What place is most at risk this year? (My vote, Caribbean or East coast)
5) In an off chance, will we see a Category 5 this year? (My vote, possibly and if there is I hope its a fish, and someone was bound to ask the question :D)

I think this years going to prove similar to 2007.


OK, I'll bite.

1- 6-27 first storm
2- 13 total
3- 9 and 4 ( 2 big boyz at the same time )Try that on.
4- Yucatan and the Carolina's
5- 2 Cat 5 storms, one fish and one Yucatan

I believe we will see the Burmuda High in an unusual position this year. Slightly east of its normal position. Back to work. L8R
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Cybr, you forgot one.

6.) When does the CMC forecast the first apocalyptocane?
Member Since: August 23, 2008 Posts: 7 Comments: 5300
I declare it preseason Hurricane forecasting time!
Alright. A few questions, please answer if you wish.
1) When will Ana Form? (my vote 5-28-09)
2) How many storms will there me (my vote 15)
3) How many Hurricanes and Majors do we get? (5/2)
4) What place is most at risk this year? (My vote, Caribbean or East coast)
5) In an off chance, will we see a Category 5 this year? (My vote, possibly and if there is I hope its a fish, and someone was bound to ask the question :D)

I think this years going to prove similar to 2007.
Member Since: July 8, 2005 Posts: 259 Comments: 24251
Quoting CybrTeddy:
I think the TSR's the more accurate one in my opinion.
they got 2008 pretty close.


It's certainly closer to the real average of this period.

And I guess with these forecasts, the hurricane preseason begins in earnest...
Member Since: August 23, 2008 Posts: 7 Comments: 5300
LOL it is very humid out there

Member Since: Posts: Comments:
Quoting CybrTeddy:
I think the TSR's the more accurate one in my opinion.
they got 2008 pretty close.


Ive found them to have better information
Member Since: August 12, 2007 Posts: 2 Comments: 2838
Hillbilly Beachbum

that has a nice ring to it...
Member Since: Posts: Comments:
Well,if not for accuracy,at least it gets some hurricane talk going.
Member Since: Posts: Comments:
I think the TSR's the more accurate one in my opinion.
they got 2008 pretty close.
Member Since: July 8, 2005 Posts: 259 Comments: 24251
"flips coin"
Member Since: Posts: Comments:
All I know is that on June 2, I'm headed south for month of fun. I will be 2 blocks from the gulf. I'm hoping that the season starts out slow. I do not want my Hillbilly Beachbum vacation ruined! Almost finished sprucing up the "vintage" trailer I bought and the reservation is made. Vintage sounds so much better than the word old. he he...
Member Since: Posts: Comments:


Watch in HD. These are updated every 6 hrs. Will be nice to have during hurricane season.
Member Since: Posts: Comments:
I don't get it. If the Klotzbach/Gray team's skill at predictions is less than zero, why the heck do they put it out and why does anyone care???? Oh yeah, I'll bet they get some serious funding from somewhere to put out a "less than zero skill" prediction. Heck, fund me, I can do just as well with a coin.
Member Since: Posts: Comments:

The National Hurricane Conference Participating Organizations.

International Association of Emergency Managers
International Code Council
LSU Hurricane Center
National Emergency Management Association
National Storm Shelter Association

Next of Kin Registry (NOKR)
National Oceanic and Atmospheric Administration
Member Since: July 3, 2005 Posts: 426 Comments: 128871
40. IKE
Quoting tornadofan:


It is good to see hurricane conversations though...


Yup...

54 days...
9 hours...
5 minutes and it starts....
Member Since: Posts: Comments:
Schedule for the 2009 National Hurricane Conference

Schedule and Workshop list

Member Since: July 3, 2005 Posts: 426 Comments: 128871

From CSU today...It will be interesting to see how things evolve in the comings months.

Member Since: May 14, 2006 Posts: 8 Comments: 13807
No mention of African dust? Does anyone have a sat. link?
Member Since: Posts: Comments:
Quoting IKE:


LOL...one minute...


It is good to see hurricane conversations though...
Member Since: Posts: Comments:
Member Since: Posts: Comments:
34. IKE
Quoting tornadofan:
How long until someone says, "It only takes one storm"?


LOL...one minute...
Member Since: Posts: Comments:
Mauritius Meteorological Services
Tropical Cyclone Warning Number FIFTEEN
TEMPETE TROPICALE MODEREE JADE
22:00 PM Réunion April 7 2009
=================================

At 18:00 PM UTC, Moderate Tropical Storm Jade (994 hPa) located at 20.8S 49.1E has 10 minute sustained winds of 40 knots with gusts of 60 knots. The storm is reported as moving south at 8 knots.

Dvorak Intensity: T3.0

Gale-Force Winds
=====================
100 NM radius from the center within the eastern semi-circle and up to 30 NM in the southwestern quadrant

Near Gale-Force Winds
=======================
190 NM radius from the center within the eastern semi-circle, extending up to 250 NM in the southeastern quadrant

Forecast and Intensity
======================
12 HRS: 21.8S 48.7E - 45 knots (Tempête Tropicale Moderée)
24 HRS: 22.5S 48.3E - 40 knots (Tempête Tropicale Moderée)
48 HRS: 24.1S 48.1E - 35 knots (Tempête Tropicale Moderée)
72 HRS: 25.4S 49.7E - 30 knots (DEPRESSION Tropicale)

Additional Information
======================
After a few hours where it was almost impossible to provide a dvorak analysis over the system but where it was showing some gale force winds over a large area within the eastern semi-circle. (CF. today's Quikscat and ASCAT Passes), a nice curved band has maintained since 1500z in the eastern semi-circle. At 1800z, the system shows a white band at 0.50 on a LOG10 spiral, that gives a DT at 3.0. The system still tracks southward over the last hours under the steering influence of the mid level subtropical ridge located in the east. The southward track is expected to slow down tomorrow as the subtropical highs rebuilds temporarily south to Madagascar. As the system is back over quite warm water, strengthening is on the way. However, due to the proximity of land and a gradual deterioration of the environmental conditions, intensification should be limited (gradually stronger northwesterly to westerly shear).
Member Since: May 24, 2006 Posts: 51 Comments: 45739
See CSU lowered there numbers for a few reasons sst's and possible weak nino developing.No matter what the predictions say one must always prepare as they do every season.Remember numbers predicted are not of any importance as the ones that hit land have the greatest impact.
Member Since: May 14, 2006 Posts: 8 Comments: 13807
my numbers up in my blog pretty well the same except iam expecting some subtropical activity early and late in the season
Member Since: Posts: Comments:
Quoting msphar:
Glad to see the Colo Team has reduced their prediction from Dec and glad to read the reasons why. Sol continues its reluctance to spot. 593 spotless days, likely to surpass the Cycle 9/10 transition by early this hurricane season. Now back to wait and see.


Spotless Days
Current Stretch: 12 days
2009 total: 84 days (87%)
Since 2004: 595 days
Typical Solar Min: 485 days
Member Since: June 12, 2005 Posts: 6 Comments: 8186
28. N3EG
My hurricane predictions: I flipped the same coin as last year, and it landed on the same side as last year, so therefore our hurricane season will be the same as last year. Note: Flipping coins is a game of chance, and should not be used for hurricane intensity predictions, picking lottery numbers, or determining the percentage of accuracy a QuikSCAT improves hurricane forecasting.
Member Since: April 23, 2005 Posts: 38 Comments: 234
Quoting jeffs713:
5. JRRP - If by "slightly similar" you mean "barely alike", yes. The only place that is even somewhat similar is the NE gulf having a cool spot, and the NW gulf having a slightly warm spot, but the degree of the anomaly is off for both. The North Pacific is completely different (this year has a huge warm spot in the central pacific), and even the equatorial eastern pacific looks drastically different.

This far out, SSTs aren't much an indicator of activity, as shear trends and trade wind speed are both more important to how the season will shape up. (remember last year we had 2 eddies break off in the GOM, which is unusual, and the second broke off in July and fed both Gustav and Ike)


Yup...Those dreaded "warm pools" and the corresponding problem of rapid intensifation and sustinence for any potential Gulf storm..
Member Since: Posts: Comments:
Glad to see the Colo Team has reduced their prediction from Dec and glad to read the reasons why. Sol continues its reluctance to spot. 593 spotless days, likely to surpass the Cycle 9/10 transition by early this hurricane season. Now back to wait and see.
Member Since: Posts: Comments:
5. JRRP - If by "slightly similar" you mean "barely alike", yes. The only place that is even somewhat similar is the NE gulf having a cool spot, and the NW gulf having a slightly warm spot, but the degree of the anomaly is off for both. The North Pacific is completely different (this year has a huge warm spot in the central pacific), and even the equatorial eastern pacific looks drastically different.

This far out, SSTs aren't much an indicator of activity, as shear trends and trade wind speed are both more important to how the season will shape up. (remember last year we had 2 eddies break off in the GOM, which is unusual, and the second broke off in July and fed both Gustav and Ike)
Member Since: Posts: Comments:
TSR are calling for an average +AMO season (15/8/4) more or less...

Yep, wait and see. Be interesting to see come early June whether the CSU varies again.. as well as it'd be worth keeping on eye on the El Nino variations.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Afternoon.......Nothing new here (in terms of the early predictions from the pros) and what can change between now and the dead of summer...Will just have to see what sets up later in the year come June in terms of all of the relevent factors (SST's/Bermuda High/SAL values/Wind Shear, etc......)...We have always had a few surprises over the past several years during the season (TS Faye comes to mind from last year)so looking forward to see what Mother Nature may/may not (hopefully) unleash this coming Year............Thanks Dr. M..
Member Since: Posts: Comments:
Thanks for the update, Dr. Masters.

Hi all:

Everything is still go on my upcoming video presentation "Experience the Preparation for Hunting Hurricanes." The local fire dept. "is down" for the experiment where I will test my hurricane safety gear for me and my technology. We'll be collecting an interesting bit of data during the test. Right now, the fire dept. team knows what the psi of the water that comes down the hose is...but not the water's speed. I'll be able to provide them with that info during the tests.

In the meantime, I've released a new video called "American Rockhound in HD" which documents my other passion in life, rockhounding.

I anticipate another video release shortly that will be called "Turkey Hunt New Mexico" which will also be in HD.

Hopefully, many of you out there are having as much fun as I am these days. Cheers!
Member Since: Posts: Comments:
Quoting tornadofan:
How long until someone says, "It only takes one storm"?


Ummmm. I think you were the first

Back to work L8R and #20 I concur, just rollin the dice right now.
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Quoting tornadofan:
How long until someone says, "It only takes one storm"?


It only takes one. :)

In all seriousness, I don't give much credence to any pre-season forecast from any forecast group. I might start paying attention more once CSU's May forecast is released, since by that time, we may have a general idea of what the pattern will be like for the season.
Member Since: March 7, 2007 Posts: 587 Comments: 20880
Quoting Patrap:
We look mto the GOM and Carri bean for the early systems,for cyclogenesis.
Late May-June.

Not the Atlantic.



Yep, here are the POO's ( points of origin ) from 44-99 by month

Link
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Oh Boy, just in. Not good

Earthquake Details
Magnitude 5.6 (Preliminary magnitude — subject to revision)
Date-Time Tuesday, April 07, 2009 at 17:47:41 UTC
Region CENTRAL ITALY
Member Since: June 12, 2005 Posts: 6 Comments: 8186
We look mto the GOM and Carribean for the early systems,for cyclogenesis.
Late May-June.

Not the Atlantic.

Member Since: July 3, 2005 Posts: 426 Comments: 128871
Well nothing can survive 65kt shear.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
Atlantic Low Level
Visible and Infrared Winds
Member Since: July 3, 2005 Posts: 426 Comments: 128871
Cooperative Institute for Meteorological Satellite Studies
Space Science and Engineering Center / University of Wisconsin-Madison

Tropical Cyclones ...A Satellite Perspective


WAVETRAK - Northern Atlantic Sector
Member Since: July 3, 2005 Posts: 426 Comments: 128871
does anyone remember an approx time last yr when we started to see all those waves come off africa?
Member Since: Posts: Comments:

Viewing: 61 - 11

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8Blog Index

Top of Page

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.

Local Weather

Partly Cloudy
56 °F
Partly Cloudy