CSU predicts a very active hurricane season: 16 storms, 9 hurricanes

By: Dr. Jeff Masters , 4:30 PM GMT on June 01, 2011

A very active Atlantic hurricane season is on tap for 2011, according to the seasonal hurricane forecast issued June 1 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 166% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is identical to their April forecast. The forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 61% (42% is average.)

The forecasters cited four main reasons for an active season:

1) Neutral to weak La Niña conditions are expected during the most active portion of this year's hurricane season (August-October). This should lead to average to below average levels of vertical wind shear.

2) Above average May sea surface temperatures in the tropical Atlantic.

3) Below average surface pressures during May in the tropical Atlantic.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to weak La Niña conditions in the equatorial Eastern Pacific, and above-average tropical Atlantic and far north Atlantic SSTs during April - May. Those five years were 2008, which featured Hurricane Ike and Hurricane Gustav; 1996, which had two hurricanes that hit North Carolina, Fran and Bertha; 1989, which featured Category 5 Hurricane Hugo; 1981, a very average year with 12 named storms, 7 hurricanes, and 3 intense hurricanes; and 1951, a year that featured 6 major hurricanes. The mean activity for these five years was 12 named storms, 8 hurricanes, and 4 intense hurricanes.

How accurate are the June forecasts?
The June forecasts by the CSU team between 1998 and 2009 had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes cause 80% - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses a brand new formula never tried before, so there is no way to evaluate its performance. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.41 to 0.62 for their June forecasts made between 1984 and 2010, which is respectable.

Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

Figure 2. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2001-2010, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2001 - 2010 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

TSR predicts 25% more activity than normal
Expect the Atlantic hurricane season to be about 25% more active than usual, the British private forecasting firm Tropical Storm Risk, Inc. (TSR) said in their pre-season forecast issued on May 24. TSR calls for 14.2 named storms, 7.6 hurricanes, 3.6 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 124, which is 22% above average. Their May 24 forecast numbers are very close to their previous forecast issued in April. TSR predicts a moderate 55% chance that activity will rank in the top 1/3 of years historically, and a 59% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 16-25% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.

TSR projects that 4.4 named storms will hit the U.S., with 1.9 of these being hurricanes. The averages from the 1950-2010 climatology are 3.1 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 7 - 11% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.3 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their forecast of an active season:

1) Their model predicts that sea surface temperatures will be 0.11°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. They define this as the area between 10°N and 20°N, between the coast of Africa and Lesser Antilles Islands (20°W and 60°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)

2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 0.19 meters per second (about 0.4 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.

FSU predicts a very active hurricane season: 17 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their third annual Atlantic hurricane season forecast today. This year's forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE) of 163. They cite warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation as the major factors influencing their forecast.

Other seasonal forecasts
The UK Met Office's Glosea4 model is predicting a moderately more active season than normal, with 13 named storms and a ACE index of 151. The Cuba Institute of Meteorology is calling for 13 named storms and 7 hurricanes. NOAA predicts 15 named storms, 8 hurricanes, and 4.5 intense hurricanes. Pennsylvania State University predicts 16 named storms.

A surprise tropical disturbance for Florida
The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure and winds have leveled out at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds peaked at 19 mph, gusting to 22 mph, at 10:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. A Windsat pass this morning did not show a closed circulation, and I doubt 93L has enough time to develop into a tropical depression before landfall in Florida. The coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph this afternoon, though.

Figure 3. Afternoon radar image of 93L from the Melbourne, Florida radar.

Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico. The Hurricane Hunters are on call to fly into 93L Thursday afternoon at 2pm EDT, if necessary.

Central Caribbean disturbance
Moisture and heavy thunderstorm activity continues to slowly increase in the region between Central America and Jamaica, and wind shear is falling. With wind shear now 20 - 30 knots, we can expect this disturbance to show increased organization today, and recent satellite images show the beginnings of a surface circulation trying to get going about 100 miles off the coast of Northeast Nicaragua. All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them Thursday through Saturday this week.

Figure 4. Satellite image of the Central Caribbean disturbance.

Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, tomorrow (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. Welcome to the hurricane season of 2011!

Jeff Masters

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But keep something in mind guys convective maxiumum for land is actually during the afternoon so the time period that it is crossing Florida might actually help it sustain convection which might get the system stay in tact...Also in past experiences you have to watch systems like this...especially when they are small and near the coastline...those systems have a tendency to wind up pretty quickly
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Poll time: What will happen to 93L most likely;

B)Tropical storm

C)Stay a Depression

D) Just die over Florida.

E) Stay an invest and never develop into anything.
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WHXX04 KWBC 011737












0 30.3 78.9 240./21.0

6 29.2 80.8 241./20.1

12 28.2 83.3 248./23.4


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Wow, two invests. I should have been here earlier.

Hey, everybody!
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290. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15743
Surface observations indicate that 93L's surface circulation is near the Volusia/Brevard county line. The pressure in the area is near 1018mb and winds below 5 knots. The stronger winds and lower pressures are located further west, southwest, and northeast where stronger thunderstorms are present.

However, telling by latest satellite imagery, it appears the system's circulation has moved further west since these surface observations were reported.

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Plenty of precipitable Water where 93L will be emerging, especially in comparison to the rest of the GOM.

Member Since: May 27, 2009 Posts: 0 Comments: 4454
Since today is the first day of the season. Anyone aware of some changes to the wind mitigation system for home owners insurance in Florida that supposedly started today ???
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So whats the chance of me seeing a tornado in new york now ya'll.
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WHXX01 KWBC 011824




1824 UTC WED JUN 1 2011





DISTURBANCE INVEST (AL932011) 20110601 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

110601 1800 110602 0600 110602 1800 110603 0600


BAMS 29.1N 80.2W 27.9N 84.0W 27.2N 88.2W 26.9N 92.4W

BAMD 29.1N 80.2W 28.3N 82.8W 27.6N 85.3W 27.2N 87.8W

BAMM 29.1N 80.2W 28.0N 83.8W 27.1N 87.6W 26.6N 91.4W

LBAR 29.1N 80.2W 28.0N 83.3W 27.4N 86.6W 27.1N 89.8W



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

110603 1800 110604 1800 110605 1800 110606 1800


BAMS 28.1N 96.2W 31.9N 101.0W 35.3N 102.7W 38.3N 101.7W

BAMD 27.4N 91.0W 29.5N 96.4W 30.1N 99.0W 30.1N 98.8W

BAMM 27.0N 95.1W 28.7N 100.3W 29.8N 103.7W 30.6N 104.6W

LBAR 27.1N 93.1W 28.0N 98.5W 27.7N 101.5W 25.7N 101.6W





LATM12 = 31.1N LONM12 = 76.2W DIRM12 = 240DEG SPDM12 = 21KT

LATM24 = 33.7N LONM24 = 72.1W



RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



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283. xcool
. shadoclown45 .mmm soo good TACOSss hehe
Member Since: September 26, 2009 Posts: 2 Comments: 15743
We had some rain earlier now poof!

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281. xcool
wunderkidcayman ;lol
Member Since: September 26, 2009 Posts: 2 Comments: 15743
Quoting xcool:

93L HEAD to into Mexicoooo

For The TACOS!!!
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Member Since: January 30, 2010 Posts: 0 Comments: 3259
Perfect hurricane song :)
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Things are certainly getting interesting!
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Quoting xcool:


lol well we know it going to have a west component but its not going to be dead west or south so WNW-NW
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Quoting PrivateIdaho:
He works in the "Beyond" department.

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Heavy cloud cover, grey skies, drizzling at the moment. Not a happy day in JA. :-(
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awakening from my slumber... nice to see the same faces around here.
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curious to see how 93l does after it crosses over Florida

Convective energy is there

Wind Sheer is dropping (and also dropping for the SW Caribbean area)

SSTs are there

Now we just got to see how well it can keep together after crossing Florida. Time may also be working against it, depending on where it decides to come ashore
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12Z TWO 93L downgraded 20

by the way we should see 94L very soon
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268. xcool

93L HEAD to into Mexicoooo
Member Since: September 26, 2009 Posts: 2 Comments: 15743
Member Since: July 3, 2005 Posts: 452 Comments: 144123
Quoting RitaEvac:
I see a dinosaur where the loop current is

Oh yeah, you are right!
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Member Since: July 3, 2005 Posts: 452 Comments: 144123
Quoting Grothar:
Anyone remember this one that just wouldn't go away. Bought a roundtrip ticket.

I dont think many people down here will forget Ivan The Terrible, for a loooong time...
Member Since: October 24, 2005 Posts: 0 Comments: 26997
263. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15743
Quoting DookiePBC:

Bed Bath and Beyond?
He works in the "Beyond" department.
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Anyone remember this one that just wouldn't go away. Bought a roundtrip ticket.

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Quoting Levi32:

That's a bit inconsistent with visible imagery.

I know, the only thing I can see that might support it is a faint line of showers on the radar out of MLB, however all three were close in their location. I did find it strange.
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I'm off to work. Later all.
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257. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15743
Quoting 7544:

hey levi you also metioned in your tidbit it may take that track the cmc is showing this am before the new run came out how do u feel on that path i know the intenisity is a bit much but good call on the path on your part so far the cmc shows it will the others follow . lloks like a 50 / 50 now thanks

The CMC doesn't usually lead the models to victory. Typically the ECMWF does that once it's locked on. Personally I think the UKMET has presented the best and most consistent solution so far with this system, and may end up winning the prize here. The CMC has been floppy at best, showing nothing one day and Cat 2 hurricanes the next, with a different track on each run.
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Quoting ajcamsmom2:
210. RitaEvac 1:28 PM CDT on June 01, 2011
Lets hope not, the squirrels ate the lead seal off the pipes coming out of my roof and I won't be having them repaired until the 16th...so, my hubby would have to climb up there and put a temporary seal until the roofers make it over...I can just see that now...NOT...I don't want my cute hubby taking a chance of falling off the roof and breaking his beautiful nose....

Reminds me of a song...
"Dont fall off the roof Dad
You'll make a hole in the Yard.
Mother's just planted Petunias,
The digging and sowing was hard.
If you must end it all dad,
Just take a walk in the Park,
And there you can jump in the lake dad,
But please do it long after dark.
Member Since: October 24, 2005 Posts: 0 Comments: 26997
Quoting caneswatch:

It's Canadian, do you think I would LOL
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Quoting Grothar:
Just got an E-mail from Allan Huffman. A number of us were having trouble posting images from his blog, which is very popular. It would not allow Remote linking. He said that the problem has been fixed and apologized. So, we shouldn't have too many of those little red X and black screens. His site is used quite often during the season since it contains all the best maps for tracking and all the models. No need to thank me.

Thanks for alerting him, Gro.
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Global models more aggressive with our Caribbean disturbance today.

Interested with what happens with 93L as well...
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I'm in Pinellas, just had that main would-be-pseudo-band move through. It was pretty weak but it gave a nice anomalous gust (40mph give or take 3-4 for about 15 seconds) and dropped the temp about 20f.
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Quoting Levi32:

It's weaker. Lets the low sit there for a long time doing nothing and not strengthening.

Day 7:

The other four models develop it into at least a TS with the UKMET and CMC going more than that. You think is a good consensus despite the lack of development by ECMWF or still we have to wait for more runs?
Member Since: April 29, 2009 Posts: 76 Comments: 16734

Where is JFV when you need him?

Bed Bath and Beyond?
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Quoting Levi32:

I will thank you anyway. That's a great inconvenience to be rid of.

I know I have seen you use them sometimes. I shall have try a few out to see if the problem is cleared. It you want, I can put you in touch with him. He always has very current info. I like his spaghetti string models.
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Quoting tropicfreak:

being cubantropical i think.


When will he ever learn....
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246. 7544
Quoting Levi32:
12z NOGAPS has a tropical storm moving ENE over eastern Cuba by Day 6. It would seem that model support is coming in stronger for development. The GFS, as usual, is the last one to come onboard. The ECMWF is still a little weak as well, but shows a tropical storm nonetheless.

hey levi you also metioned in your tidbit it may take that track the cmc is showing this am before the new run came out how do u feel on that path i know the intenisity is a bit much but good call on the path on your part so far the cmc shows it will the others follow . lloks like a 50 / 50 now thanks
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Quoting nrtiwlnvragn:

At 18Z NHC location is near 29N 80W. SAB and TAFB also.

AL 93 201106011745 10 DVTS CI 2900N 8020W 30 TAFB 1520 ///// T Pattern T more consistent with obs and ASCAT pass at

AL 93 201106011745 10 DVTS CI 2950N 8070W 25 SAB 1010 ///// T DT=0.0 BO CBND MET=1.0 PT=1.0 FTBO MET PA=40 NMI

That's a bit inconsistent with visible imagery.

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Quoting Grothar:


:P Sorry a bit of my Irish showed.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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