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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Quoting pressureman:
Well the easterly currents above the system are much to strong for it to get to get it together...it will likely disipate as it moves further out into the GOM...Like i said may be a small rain maker for the lower texas coast on friday...


We'll wait and see. It might not strengthen, but if it doesn't it certainly won't have been due to strong easterly currents.
Member Since: August 10, 2010 Posts: 2 Comments: 1970
Union at Maine Street some kind of heavy water leak with people trapped inside...per Hampden County Police
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Quoting louisianaboy444:


We are thousands of miles away i'm pretty sure local authorities in the area are keeping their citizens more than informed

incorrect answer
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Member Since: July 3, 2005 Posts: 415 Comments: 125736
Tornado on the ground in Chicopee Ma
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18z GFS going more aggressive than the 12z run. Helluva trough trying to pick it up, 132 hours:

Member Since: September 2, 2009 Posts: 130 Comments: 21032
Holy Moly, Massachusetts!!

Three (plus) tornadoes on the ground in western MA, during the evening commute!

Live streaming broadcast here:
http://www.necn.com/pages/necn_streampage


Watch Providence RI and the middle of Maine too.
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Well the easterly currents above the system are much to strong for it to get to get it together...it will likely disipate as it moves further out into the GOM...Like i said may be a small rain maker for the lower texas coast on friday...
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Live Radio Feed of Police Radio
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Police reporting live right now another touchdown in the North end of city. This is crazy
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SEARCH & RESCUE
06/01/11 17:47 (SPRINGFIELD - ) MULTIPLE BLDGS WITH EXTENSIVE DAMAGE. ONGOING SEARCHES. [MAS001]
TECHNICAL RESCUE
06/01/11 17:40 (WEST SPRINGFIELD - ) COLLAPSE OF 2 STY BLDG. ACTIVE S&R REQUEST MUTUAL-AID. [MAS052]
SEARCH & RESCUE
06/01/11 17:20 (SPRINGFIELD - ) EXTENSIVE DAMAGE FROM POSSIBLE TORNADO STRIKE. BLDGS DAMAGED & INJURIES REPORTED. UNKNOWN ENTRAPS. [MAS001]
TRAUMA ALERT
06/01/11 17:17 (AGAWAM - ) PERSON HIT BY LIGHTNING ADVANCED LIFE SUPPORT REQ. [MAS125]
SPECIAL
06/01/11 17:13 (SPRINGFIELD - ) POLICE DEPARTMENT HAS ESTABLISHED COMMAND POST AT 50 MAPLE, REQUEST FIRE DEPARTMENT. 911 PHONES DOWN IN AREAS [MAS017]
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Quoting TropicalAnalystwx13:


Yup.

thanks for the map seems to be moving in stronger too only time i talk politics is a day before i vote until then dont care
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Looks like DMIN is taking it's effect on 93L, convection is starting to fade a bit. Kind of expected this, should see new burst later tonight.
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Quoting HarryMc:

Having another one develop over Springfield at the same place as the first one is totally bizarre. NWS just issued second warning for the SECOND tornado at the same location.


Crazy weather.
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TECHNICAL RESCUE
06/01/11 17:40 (WEST SPRINGFIELD - ) COLLAPSE OF 2 STY BLDG. ACTIVE S&R REQUEST MUTUAL-AID. [MAS052]
SEARCH & RESCUE
06/01/11 17:20 (SPRINGFIELD - ) EXTENSIVE DAMAGE FROM POSSIBLE TORNADO STRIKE. BLDGS DAMAGED & INJURIES REPORTED. UNKNOWN ENTRAPS. [MAS001]
TRAUMA ALERT
06/01/11 17:17 (AGAWAM - ) PERSON HIT BY LIGHTNING ADVANCED LIFE SUPPORT REQ. [MAS125]
SPECIAL
06/01/11 17:13 (SPRINGFIELD - ) POLICE DEPARTMENT HAS ESTABLISHED COMMAND POST AT 50 MAPLE, REQUEST FIRE DEPARTMENT. 911 PHONES DOWN IN AREAS [MAS017]
TRAFFIC ADVISORY
06/01/11 16:59 (AGAWAM - ) EXTENSIVE DAMAGE WITH TREES & WIRES DOWN. DRIVING IN AREA DISCOURAGED. [MAS052]
Listen Live
Link
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Another tornado is hitting and people are still talking politics! It's flag time.
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Quoting islander101010:
mojo got to be pulsing in the carib.


Yup.

Member Since: July 6, 2010 Posts: 109 Comments: 30297
Quoting HarryMc:

Having another one develop over Springfield at the same place as the first one is totally bizarre. NWS just issued second warning for the SECOND tornado at the same location.


Luckily the 2nd one looks to be north of Springfield.
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Quoting HarryMc:

Having another one develop over Springfield at the same place as the first one is totally bizarre. NWS just issued second warning for the SECOND tornado at the same location.


And how
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Quoting breald:
Tornadoes breaking out all over Central MA. Springfield,and Worcester all have had tornadoes that touched down. What a crazy outbreak

Having another one develop over Springfield at the same place as the first one is totally bizarre. NWS just issued second warning for the SECOND tornado at the same location.
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i agree.
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Quoting Ameister12:
Incredible video of the tornado in Springfield.

Watch the Connecticut River.


Thats one scary looking tornado.
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Quoting pressureman:
the easterly winds above the system guiding it along are just much to strong for this thing to anything...also check out the dry air also in the GOM..


Winds don't guide a system, steering currents do. These currents don't cause damage to the system. It isn't having trouble firing up convection, and dry air doesn't always mean a storm can't form.
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Quoting eyestalker:
As for the born-again Christian thing, I just did some research and read that Rick Scott is and always was Methodist (he was raised in a Methodist home) though had a brief bout with Presbyterianism, it doesn't say he ever has strayed from Christianity.

He has also been quite vocal in his opposition to the mosque at Ground Zero. Overall he's a good solid Christian man and reedzone, yes, progressives have been trying to eliminate Christianity from America for decades, and it's a terrible thing.

Me? I don't really believe in God, but my girlfriend is Catholic and with Christianity you get good morals and viewpoints on life, whereas within religions such as Islam you get sexist, racist, homophobic pig bigots that spend their lives hating and disdaining and oppressing women. It's a shame that such filth still exists in the world.


Quoting reedzone:
I'm an Obama hater :P .. no seriously, should be impeached for the things he has done, in my opinion. But that's my opinion... ok back to the weather..


Please get back to weather.
Member Since: July 6, 2010 Posts: 109 Comments: 30297
Quoting MrstormX:


Holy Crap
Ditto.
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The official final death toll for the Joplin tornado is 134, with all unidentified remains and missing accounted for. (The toll is subject to rise only if any of the 900 injured do not survive.)

The U.S. tornado death toll for 2011 is officially 513.
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Tornadoes breaking out all over Central MA. Springfield,and Worcester all have had tornadoes that touched down. What a crazy outbreak
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"askamos" ????

my gut hurts from laughing.

And I didn't know debris ball was a ferret, just thought it was one damn-ugly kitten.
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Quoting Ameister12:
Incredible video of the tornado in Springfield.


Holy Crap
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Brand New Tornado Warning for storm just confirmed over Springfield, MA. Injury reports just coming in from some MA towns.
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I agree with the CIMSS thing, but it's not the only shear chart that exists. This chart proved itself to be very accurate last year. This at least gives some evidence for the people saying high shear. Maybe they aren't just making up numbers.
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the easterly winds above the system guiding it along are just much to strong for this thing to anything...also check out the dry air also in the GOM..
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mojo got to be pulsing in the carib.
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Surprised no death reports yet from that tornado...
Member Since: May 27, 2009 Posts: 0 Comments: 4355
Incredible video of the tornado in Springfield.

Watch the Connecticut River.
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Quoting PrivateIdaho:
....just what Florida needs....more Yankees.


And more askamos, and more Californians, and more Hawaiians. Even though I was originally born in New York and moved here when I was only 4, I'm starting to get a tad bit tired of all the mass migration. I understand the reasoning for them moving here but we still need some break. I'd rather discuss tropics now.
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789. newenglader

To EMBED a Utube here,,use the "Old Embed Codes"..then post directly in the comment box,,bypassing the image Button,,then post
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That tornado in Springfield had liberal views.
Booo!

(As far as destruction of property was concerned.)
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Quoting FLdewey:

I'm sorry you missed the news... but vorticity passed away over the winter.

Although it won't fill the void in my heart, I bought a new ferret named "Debris Ball" to help me move on.

RIP vorticity.
Wow, mid-season form already!
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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.