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: 361 - 311

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

361. caribbeantracker01
11:53 PM GMT on April 16, 2009
Quoting futuremet:
it looks to be warming up some what
Member Since: May 21, 2008 Posts: 0 Comments: 556
360. TampaSpin
2:29 PM GMT on April 10, 2009
For those needing i have posted live coverage of the Masters on my WebSite! Coverage starts at 10:35!

http://tampaspinsweather.webs.com/apps/forums/topics/show/595432-live-masters-coverage-
Member Since: September 2, 2007 Posts: 179 Comments: 20448
359. TampaSpin
1:56 PM GMT on April 10, 2009
Very Strong Low!

Member Since: September 2, 2007 Posts: 179 Comments: 20448
358. TampaSpin
1:53 PM GMT on April 10, 2009
Quoting Tazmanian:
do i smell wishcasters on the blog this AM or do i semll trolls


Taz you already got your Troll sniffer going....LOL
Member Since: September 2, 2007 Posts: 179 Comments: 20448
357. Tazmanian
1:33 PM GMT on April 10, 2009
The eruption of Redoubt continues, and the volcano remains at aviation color code ORANGE and alert level WATCH.

Seismicity continues to be elevated, with many small, discrete earthquakes occurring. Satellite images continue to be obscured by clouds. No ash emissions are visible in NWS radar.

A magnitude 5.1 earthquake, located 175 miles NNW of Anchorage, occurred yesterday at 9:50 PM AKDT and shows up strongly on the Redoubt seismic network
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
356. Tazmanian
1:27 PM GMT on April 10, 2009
do i smell wishcasters on the blog this AM or do i semll trolls
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
355. nrtiwlnvragn
12:52 PM GMT on April 10, 2009
2008 National Hurricane Center Forecast Verification Report
Member Since: September 23, 2005 Posts: 15 Comments: 11342
354. Ossqss
12:50 PM GMT on April 10, 2009
Looks like today has an interesting bag of tricks for the US
Member Since: June 12, 2005 Posts: 6 Comments: 8188
350. Ossqss
11:35 AM GMT on April 10, 2009
Quoting Patrap:



No,..but thats me in the foreground next to the Saturn 5 at JSC in Houston last April.


And they wouldnt give me the Keys to this one either..





Nice pics. It's amazing how large that ship actually is.

Things are shakin on the west coast today, from Baja to Central Alaska.
Magnitude Location Time
4.1 Off the coast of Oregon 4 hours ago Map
4.2 Off the coast of Oregon Yesterday
Member Since: June 12, 2005 Posts: 6 Comments: 8188
349. HadesGodWyvern (Mod)
7:29 AM GMT on April 10, 2009


looks like a possible cyclone for West Bengal region
Member Since: May 24, 2006 Posts: 52 Comments: 46908
348. HadesGodWyvern (Mod)
7:02 AM GMT on April 10, 2009
Mauritius Meteorological Services
Tropical Cyclone Warning Number TWENTY-FIVE
TEMPETE TROPICALE MODEREE JADE
10:00 AM Réunion April 10 2009
=================================

At 6:00 AM UTC, Moderate Tropical Storm Jade (991 hPa) located at 23.7S 52.3E has 10 minute sustained winds of 40 knots with gusts of 60 knots. The storm is reported as moving east-southeast at 9 knots

Dvorak Intensity: T3.0

Gale-Force Winds
=================
40 NM radius from the center, extending up to 90 NM in the southeastern semi-circle

Near Gale-Force Winds
=======================
80 NM radius from the center extending up to 130 NM in the northeastern quadrant and 200 NM in the southeastern quadrant and 100 NM in the southwestern quadrant

Forecast and Intensity
======================
12 HRS: 25.1S 53.9E - 40 knots (Tempête Tropicale Moderée)
24 HRS: 28.5S 56.3E - 40 knots (Devenant EXTRATROPICAL)
48 HRS: 36.9S 59.3E - 50 knots (Depression EXTRATROPICAL)
72 HRS: 47.5S 71.0E - 40 knots (Depression EXTRATROPICAL)

Additional Information
======================
The system has re-intensified over last night with convective activity located less than 0.5 degree from the estimated center. Quikscat data 0318z shows a very well defined low level circulation center with winds reaching 35/40 knots (not contaminated by rain). Despite the persistent westerly wind shear. It seems the system has re-intensified thanks to the excellent poleward upper level divergence (polar jetstream). The system should begin its extratropical transition within the next 24 hours.

Jade should accelerate southeastwards and begin to evacuate towards the extratropical latitudes. Winds extension is calbrated thanks to recent satellite data.
Member Since: May 24, 2006 Posts: 52 Comments: 46908
347. Patrap
3:46 AM GMT on April 10, 2009
Quoting Ossqss:

Patrap, is that you on the far right? :)



No,..but thats me in the foreground next to the Saturn 5 at JSC in Houston last April.


And they wouldnt give me the Keys to this one either..



Member Since: July 3, 2005 Posts: 428 Comments: 129832
345. Ossqss
2:45 AM GMT on April 10, 2009
Quoting Patrap:
50th Anniversary of the Mercury 7




Patrap, is that you on the far right? :)
Member Since: June 12, 2005 Posts: 6 Comments: 8188
343. Patrap
2:28 AM GMT on April 10, 2009
50th Anniversary of the Mercury 7



Member Since: July 3, 2005 Posts: 428 Comments: 129832
342. hahaguy
2:25 AM GMT on April 10, 2009
Quoting StSimonsIslandGAGuy:
I think that 1940 record for the latest freeze is doubtful, especially since the earliest freeze in Daytona Beach was also in 1940, and is recorded as 26--on November 16. There's just no way it could be that cold down there so early!

I agree with you on that
Member Since: August 12, 2007 Posts: 2 Comments: 2838
339. hahaguy
2:19 AM GMT on April 10, 2009
Quoting StSimonsIslandGAGuy:
There was a very strong March cold wave in 1980. I remember we had snow flurries all day on March 2, 1980.


That's 5 years to early for me lol.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
336. hahaguy
2:12 AM GMT on April 10, 2009
Quoting StSimonsIslandGAGuy:
The same thing is true in Melbourne, monthly record low in February of 27 and for March, 25.

That is very odd.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
333. hahaguy
2:03 AM GMT on April 10, 2009
Quoting Ossqss:
My bad on a weather blog, couldn't resist.

6-1


6-1 even better LOL.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
332. Ossqss
2:01 AM GMT on April 10, 2009
My bad on a weather blog, couldn't resist.

6-1
Member Since: June 12, 2005 Posts: 6 Comments: 8188
331. hahaguy
1:56 AM GMT on April 10, 2009
Quoting Ossqss:


It sure got all the way to 40 in Bradenton. Sneaky cold is right!

PS 5-1 pens


How did I know you were going to sneak in the pens score lol. It got to 46 in Port St. Lucie. It's not suppose to be cold in april here lol.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
330. Ossqss
1:53 AM GMT on April 10, 2009
Quoting hahaguy:
South Florida gets sneakingly cold.


It sure got all the way to 40 in Bradenton. Sneaky cold is right!

PS 5-1 pens
Member Since: June 12, 2005 Posts: 6 Comments: 8188
329. hahaguy
1:48 AM GMT on April 10, 2009
South Florida gets sneakingly cold.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
327. Ossqss
1:40 AM GMT on April 10, 2009
What are the possibilities of a slow start with very few storms in the firt two months, and with the ones that develope being strong due to the built up energy. Then a swarm of storms over the 6 weeks that surround the peak and then a subsequent slow period with stronger storms towards the end for the same reasons referenced in the beginning. My view is based upon a transitoning environment from La to El and due to the rain in the Sahara and the potential dust intervention and a bit of a shift in the anchored high in the Atlantic. Not to menton the lower than normal SST's we are thinking about currently. I will not venture into the realm of the possible Volcanic impact or the GM storm items from the last post. Bottom line, until December, we are all guessing.

I would still like to find data relating to cyclone frequency in a post Volcanic event senario around the globe. Someone had to study that and or researched it after the fact.

BTW, where are the blog stretching graphic police? ??? :)
Member Since: June 12, 2005 Posts: 6 Comments: 8188
326. KoritheMan
12:52 AM GMT on April 10, 2009
Quoting G35Wayne:
Looks like this will be another boring season


Fail.

It only takes one. Need I remind you of some below average years since 1979 that had some notable events?

1983: Alicia
1987: Emily
1991: Bob
1992: Andrew
1993: Emily
1994: Gordon
2002: Isidore and Lili

IIRC though, you were the guy who stated on numerous occasions throughout the last several months that you wanted a hurricane strike. Bearing that in mind, it isn't quite so surprising to hear you complain about what 2009 is going to be in terms of activity.

To begin with, neutral years are worse than La Nina years, at least in terms of United States landfalls (La Nina years are typically worse for the Caribbean and Central America, as evidenced in 1999, 2000, and 2007), so we aren't out of the woods in spite of La Nina's inevitable demise.

Furthermore, it only takes one. And certainly, CSU's April forecasts should be taken with a grain of salt. Pre-season forecasts mean next to nothing, and although the May forecasts are more accurate, they can still be quite erroneous and off the mark, as evidenced in 2005, when an average season was predicted.
Member Since: March 7, 2007 Posts: 602 Comments: 21302
325. hahaguy
12:45 AM GMT on April 10, 2009
Quoting CybrTeddy:
I rather have a La Nina than an ENSO Neutral
2005 and 2008 were Neutrals.


I knew i was wrong about 2005 lol.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
324. G35Wayne
12:39 AM GMT on April 10, 2009
Looks like this will be another boring season
323. CybrTeddy
12:37 AM GMT on April 10, 2009
I rather have a La Nina than an ENSO Neutral
2005 and 2008 were Neutrals.
Member Since: July 8, 2005 Posts: 259 Comments: 24574
322. hahaguy
11:56 PM GMT on April 09, 2009
Pat thanks for posting that that's really cool.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
321. Patrap
11:53 PM GMT on April 09, 2009
Earth Scan Laboratory GOES Night Time SST/SSH Composite Imagery and Animations

Member Since: July 3, 2005 Posts: 428 Comments: 129832
319. Cotillion
11:07 PM GMT on April 09, 2009
http://www.newscientist.com/article/dn16936-curved-laser-beams-could-help-tame-thunderclouds.html

'Curved laser beams could help tame thunderclouds.'

Lasers may have thousands of applications in every section of modern society, but all laser beams are fundamentally similar: single-coloured and straight.

Now, US physicists have helped to break that mould by creating the first curved laser beams. The feat could one day help guide lightning to the ground.

Optics researchers led by Pavel Polynkin at the University of Arizona in Tucson generated 35-femtosecond-long laser pulses from a standard titanium-sapphire system.

The straight laser pulses differ from standard lasers in that they cover a wide range of colour frequencies rather than a single colour. Each pulse then passes through a transparent "phase pattern" mask and a lens, which together divide the laser pulse into its constituent parts, rather like breaking a musical chord into its individual notes.

The intensity profile of a normal laser beam is symmetrical around a central intense region, but the mask and lens are specially designed to impose an unusual asymmetric intensity profile, creating a so-called Airy beam. On the right-hand side of the Airy beam there is one intense bright region, and there is a series of smaller, less intense regions to the left.

As the pulse moves away from the lens, energy flows between the different intensity regions. Because of the underlying asymmetry, the beam bends around 5 millimetres to the right over its 60-centimetre measured length. That's not enough to send the beams around sharp corners, but they could be guided around objects, such as cells, in microscopic applications.

There is such an intense concentration of electromagnetic energy in the strong curving peak of the pulse that it ionises the air as it travels, leaving a plasma arc in its wake. Team member Demetrios Christodoulides of the University of Central Florida in Orlando says those plasma arcs can help in analytical procedures.

"The emissions generated during the process are indicative of the gas composition [that the plasma is travelling through]," he says.

Previously, straight plasma channels have been used to produce those emissions, but all the emissions are projected forwards onto the same spot. Since the forward direction constantly changes for the arc, however, the emissions would arrive at different points on a detector. "Now, because the emissions are from a curved plasma pattern, you can pinpoint precisely where in the gas they came from," Christodoulides says.

But Jerome Kasparian at the University of Geneva in Switzerland, who was not involved in the study, thinks plasma channels produced by laser pulses could perform a more spectacular function on a larger scale.

Kasparian and Jean-Pierre Wolf, also at Geneva, are attempting to use plasma channels to control lightning strikes by firing laser pulses into thunderclouds.

In 2004, Kasparian and Wolf took their plasma channel-generating laser equipment into thunderstorms in New Mexico. They fired straight laser pulses into the thunderclouds 10 times every second, hoping that the high energy plasma channels that form in the laser pulse's wake would trigger lightning strikes, which would then travel along the plasma channels down to the ground, like a train running along railway tracks (Optics Express, DOI: 10.1364/OE.16.005757).

"We didn't detect triggered lightning but we did detect electric activity synchronised with the laser pulses," says Kasparian. He thinks the plasma was too low in energy to trigger full lightning strikes, but the researchers think they can solve that problem with modifications to the system.

Kasparian says that in future, Christodoulides's team's work could be combined with his to help aim the laser pulses and plasma channels at specific targets, such as clouds, although he points out that the laser pulses can also be guided using mirrors. "But it would be fun to see curved lightning discharges," he says.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
318. Tejano72
11:05 PM GMT on April 09, 2009
Here's a climatology question: Is the First Lady sleeveless due to global warming?
317. ajcamsmom2
10:59 PM GMT on April 09, 2009
We had two cases of MRE's left from Katrina that we just tossed...I had held on them, just in case...
Member Since: March 15, 2008 Posts: 4 Comments: 2492
316. Patrap
10:50 PM GMT on April 09, 2009
Stock up on MRE's and Heater Meals now..

Avoid the Line when a Strike does come.

Member Since: July 3, 2005 Posts: 428 Comments: 129832
315. Tejano72
10:48 PM GMT on April 09, 2009
We have dangerous particulate levels today...

Link
314. Tejano72
10:41 PM GMT on April 09, 2009
Volcanic ash, resumption of Chinas Factory production, widespread demolition of failed properties globally to reduce property tax, burning of trash to produce energy, etc. have increased global atmospheric particulates, which have resulted in a decrease in surface warming, hence an average or slightly below average Spring in the northern hemisphere globallly. Fortunately, the administrations' new EPA pick plans to fire confetti into the atmosphere to further cool things down. And you thought you had breathing problems now. PS> We are having severe wildfires, 6 counties here under partial or full evacuations with 6-7% humidity and 35 mph winds with gusts to 51. Smoke, dust and wind. Hack! Cough!
313. ajcamsmom2
10:33 PM GMT on April 09, 2009
We don't get hurricane supplies anymore...we just leave...
Member Since: March 15, 2008 Posts: 4 Comments: 2492
311. Patrap
10:17 PM GMT on April 09, 2009


NEXRAD Radar
Wichita, Base Reflectivity 0.50 Degree Elevation Range 124 NMI
Member Since: July 3, 2005 Posts: 428 Comments: 129832

Viewing: 361 - 311

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

Overcast
26 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron