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

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

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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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seems like weve been having a vicious cycle for the past 3 days with pre-94L, it fires convection during the day then it all gets pulled off by the Jet(somewhat), and the Atlantic Ridge that is nosed in causing the convection to run away from the low pressure and the circulation that is attempting to form. the storm just gets stripped of convection, and then its left to restart the cycle the next morning.
if the cycle continues we may never see a storm out of this
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Quoting PcolaDan:


Saw this just a little bit ago too. Can you imagine the people in the cars on the bridge and then the highway - "WHAT THE *@&$%^^@# WAS THAT??????"

Looked like they came through it okay though.
i sincerely hope the cars stayed On the bridge!

feels like heavier populated areas are seeing tornadoes at a higher incidence rate this year, and at a proportion greater than general population sprawl. i might just be sensitive to it with the high deaths so far, and one swooping right through N Minneapolis neighborhoods last month.
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1342. Patrap
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okay, so second to last.



Link
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Dean, because you did mine, (thanks!) I will return the favor.
1. better chance B, but can't rule out A
2. A
3. Not expecting it to, but if it does.. A or B
4. B
5. A
6. B (we will = 2005 for month of JUNE only)
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Quoting Minnemike:
wow!! it's incredible to see the feeding inflow so well defined by the presence of water.. yet it's so different from what i usually see as water spouts. that is some unique and valuable footage.


Most waterspouts actually don't form from supercells and are classified as non-tornadic

Waterspout
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Thanks guys.
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Quoting Minnemike:
wow!! it's incredible to see the feeding inflow so well defined by the presence of water.. yet it's so different from what i usually see as water spouts. that is some unique and valuable footage.


Saw this just a little bit ago too. Can you imagine the people in the cars on the bridge and then the highway - "WHAT THE *@&$%^^@# WAS THAT??????"

Looked like they came through it okay though.
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from the looks of it 93L's convection is all off mostly to the west, it needs to get it's surface circulation up and operational, and wrap that convection around it if it wants to stand any chance.
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Quoting stillwaiting:
awsome,make thay unbelievable video of springfield,mass tornado from today
Link
wow!! it's incredible to see the feeding inflow so well defined by the presence of water.. yet it's so different from what i usually see as water spouts. that is some unique and valuable footage.
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1334. 7544
carib is really blowing up at this hour hmmm
no wonder why the cmc went wild lol
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Poll Time #2 Of Hurricane Season 2011:
Question #1~

Do you think 93L Will Develop?
(A) Yes
(B) No
(C) I Don't Know

Question 2~
Do you think Pre-94L Will Develop?
(A) Yes
(B) No
(C) I Don't Know

Question 3~
If yes to Question one, What will 93L's Strength Be?
(A) Tropical Depression
(B) Weak Tropical Storm(40 to 45 MPH)
(C) Moderate Tropical Storm(50 to 60 MPH)
(D) Strong Tropical Storm(65 MPH to 70 MPH)
(E) A Hurricane
(F) It Won't Form

Question 4~
If Yes to Question two, What will 94L's Strength Be?
(A) Tropical Depression
(B) (Weak to Moderate) Tropical Storm(40 to 60 MPH)
(C) Strong Tropical Storm(65 to 70 MPH)
(D) Category 1 Hurricane
(E) Category 2 Hurricane
(F) Major Hurricane

Question 5~
Do you think we will see three or more storms in June and July?
(A) Yes, 4 Storms
(B) Yes, 5 Storms
(C) Yes, 6 Storms
(D) Yes
(E) No, 2 Storm
(F) No, 1 Storm
(G) No Storms

Question 6~
Do you think we will have Arlene, Bret, And Cindy by the End of June?(Im Asking this question because we have 93L, Future-94L, and the GFS, NOGAPS, and CMC are calling for a storm to form NE of Puerto Rico)
(A) Only Arlene
(B) Arlene and Bret
(C) Arlene, Bret, and Cindy
(D) We will see Don
(E) We wont get Arlene
(F) I Don't Know

My Thought are C, A, A(If i were to say yes because i don't know if it will form or not), B, D, B...

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Quoting Speeky:
I heard that there is a new EF-5 Tornado.

The one that struck El Reno is now EF-5

is this true?



yes
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Quoting stillwaiting:
awsome,make thay unbelievable video of springfield,mass tornado from today
Link


That one passed 7 mi. north of where my sister lives. She said a friend's car was totalled. The Raleigh nader last month missed me by only 30 miles or so.
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1329. Patrap
NDBC Buoys
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1328. xcool
rip 93L LOL
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Quoting Kristina40:
Who has a link to the map that has buoy readings? I think it's a NOAA link but I can't remember and I've lost it in my favorites. GRRRRR
Link
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1326. Speeky
I heard that there is a new EF-5 Tornado.

The one that struck El Reno is now EF-5

is this true?
Member Since: April 10, 2009 Posts: 1 Comments: 305
Quoting Kristina40:
Who has a link to the map that has buoy readings? I think it's a NOAA link but I can't remember and I've lost it in my favorites. GRRRRR


http://www.ndbc.noaa.gov/
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For the first time in the past few days, surface observations are indicating that a low level circulation is indeed in the process of forming in the SW Caribbean about 50 or so miles off the Central Nicaraguan coastline. Finally getting southerly winds coming from the eastern portion of the system northwest of Colombia. This in combination with the northerly winds reported along the Nicaraguan coastline all day indicate turning occurring at the surface.
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1323. Patrap
NEXRAD Radar
Mobile, Base Reflectivity 0.50 Degree Elevation Range 248 NMI

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Who has a link to the map that has buoy readings? I think it's a NOAA link but I can't remember and I've lost it in my favorites. GRRRRR
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Quoting BahaHurican:


Whoa.... kewl stuff! Two yellows on the FIRST day of the season.... lol


Any rain today at Nassau? Here in PR,we continue to get plenty of rain and it looks like things will continue that way for the next few days.

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Quoting hurricane23:


To add to this 2008 was an active season and also followed the peak of a La Nina episode. However, the year with the second largest outbreak ever, 1974, had 7 total tropical cyclones and 4 hybrid-type subtropical cyclones. Of the 7 tropical cyclones, 4 were hurricanes and no major (Cat 3+) hurricanes occurred. 1974 also followed a strong La Nina...in fact peaking stronger than the than the episodes of winter 2007/ 2008 and winter 2010/2011. While evidence suggests the season following the peak of a La Nina may result in both increased tornado activity across the Midwest and Ohio Valley and a more active hurricane season, 1974 stands out as a rather "quiet" hurricane season. The presence of so many subtropical storms also suggests wind shear was higher than normal during the summer...which is not a La Nina trait. There is the possibility another longer-term cycle was at play, tied to salinity cycles in the North Atlantic and rainfall across northwest Africa (which was bone dry during the 1970s). Those cycles have reversed, allowing increased rainfall in northwest Africa (providing more of the tropical weather disturbances responsible for tropical cyclone formations in the deep tropics).

Adrian


Actually, it was a quite active season with 20 Tropical Cyclones forming...when you think about it a lot of those might have been named to this day because of the lack of technology in 1974.
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1317. Patrap
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awsome,make thay unbelievable video of springfield,mass tornado from today
Link
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Quoting BahaHurican:
Hey, zoo. We actually got rain for most of the first part of the day!!!! Plus continued easterlies kept the rest of the day cool... great stuff if you can get it... the fact that it rained here at all today is proof that the atmosphere is moistening. I wouldn't mind another couple of mornings with some early morning showers...


Hi Baha -- nice to see you. Well if its raining there it should rain here pretty soon. Not like we are all that far apart. Sounds like a beautiful day.
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1311. Grothar
Quoting HotBreeze:
Hi Groth.


Que bola?
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Quoting CosmicEvents:
I'm catching up pages back(there's all kinds of drama it looks like I'm wading into)....but I second that opinion.
I'm surprised a recall campaign hasn't been mentioned against this Scott character. Oh well, onto the drama....


Greetings, Cos. Actually there is a grass roots movement.


Link
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1307. afj3
Who is JFV?
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1305. Grothar
Quoting Bitmap7:


This is the one I have.


I don't think you can post those directly anymore. I will give you a link to all of them.

Link
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Quoting Tazmanian:
i smell JFV on the blogs


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It's seriously crazy to see the 2005 names again. Can't believe it's already been 6 years...
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Whoa.... kewl stuff! Two yellows on the FIRST day of the season.... lol
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Quoting DontAnnoyMe:
What's going on in here? Any blobs spun up to Cat 5s yet?


DOOMCON was not elevated, so I think the crisis has been averted.
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Quoting Chicklit:


rofl
That egghead is currently the most hated man in Florida. Evil I tell ya.
We get a hurricane in Florida and his policy will probably be 'survival of the fittest.'
If you're on the losing end then you deserve to be.
Yup that's our gov.
I'm catching up pages back(there's all kinds of drama it looks like I'm wading into)....but I second that opinion.
I'm surprised a recall campaign hasn't been mentioned against this Scott character. Oh well, onto the drama....
Member Since: August 3, 2005 Posts: 10 Comments: 5535
1298. Grothar
Quoting Bitmap7:


It gets more intense than that in the longer run at the nhc site. The UKmet is onboard with development also.
Link


I just posted that. LOL It is scary to think someone is thinking of the same thing as I. It appears most of the models are coming into agreement about development.
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1297. Bitmap7
Quoting Grothar:
Here is the UKMET



This is the one I have.
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Quoting PcolaDan:


WHERE, WHERE?????



Right there -->
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Quoting washingtonian115:
Well i'm off for tonight.Good-bye everyone.Have a nice evening.


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