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 Grothar:



CANES!!!!!!


:P Sorry a bit of my Irish showed.
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Quoting WINDSMURF:


Where is JFV when you need him?


being cubantropical i think.
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Quoting tropicfreak:


No not yet, but could see an invest tagged later on this evening or early tomorrow morning.


NHC kinda speaks their intentions in the advisory in saying when upper level winds become more favorable Thursday & Friday. Look for an invest to be tagged on one of the next couple updates (10pm/2am).
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting alfabob:
Looks like the low level circulation is about half way over Florida now. I'm thinking just SW of Orlando.


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
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Quoting Tropicsweatherpr:
Anyone has the 12z Euro?


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

Day 7:

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Quoting caneswatch:


I'm in Palm Beach County. That's not a good sign.


Where is JFV when you need him?
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Quoting caneswatch:


It's Canadian, do you think I would LOL



CANES!!!!!!
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I see what appears to see a circulation forming with the AOI in the SW Carib around 14.5N/82W. Overall the circulation appears to cover a large area.
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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 their 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....


I'd just have to send him right on up there...my hubby is old, cute and active....lol...and I'd send him on up that ladder...soon
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Link
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Quoting tropicfreak:


Levi, do you see this Caribbean system being an east coast rider. I know it's a little too early, but is it possible?


Doubtful. The pattern is not amplified enough for a trough to dig in that deep over the eastern seaboard, not to mention that the big central U.S. high won't allow the trough to back that far west. If it gets pulled up, it will be sharply to the northeast and out to the middle of the sea.

I know the 12z GFS gets it close, but it waits longer than any other model to pull it up, and the high completely breaks down by that point, allowing a random trough to swing across. In my mind right now that is unlikely.
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233. xcool
caneswatch -lmaoo
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Quoting RitaEvac:
I see a dinosaur where the loop current is



That is just Barney returning from vacation at Disney.
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I'm really hoping 93L becomes a tropical system over the gulf..the most it will have time to become is a 40-45mph Tropical storm this would do wonders for the 1 in 10 year drought occurring over LA and East TX
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Does anyone has the 12z Euro?
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Quoting JRRP:

take it easy ... is just one run


I know, I know, i'm just watching it.
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Quoting caneswatch:


I'm in Palm Beach County. That's not a good sign.


I would not worry about it at this time. There is no developed system at this time. The models are going to flip all over the place. Far as we know the same model could show the potential system over Guadalajara Mexico tomorrow.
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Found another unamed storm from the '30s
Photobucket
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market crashingLink
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Hey 93L,

Here I ammmm,.............. Rocccck me like a hurricannnne
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Quoting Levi32:
Wow at the 12z Canadian. Cat 2 hurricane over Palm Beach at 180 hours:



Levi, do you see this Caribbean system being an east coast rider. I know it's a little too early, but is it possible?
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12Z TWO

DISORGANIZED CLOUDINESS AND SHOWERS OVER THE SOUTHWESTERN AND
WEST-CENTRAL CARIBBEAN SEA ARE ASSOCIATED WITH A BROAD SURFACE
TROUGH. SOME GRADUAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE ONCE
UPPER-LEVEL WINDS BECOME A LITTLE MORE CONDUCIVE LATE THURSDAY AND
FRIDAY. THERE IS A LOW CHANCE...10 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE AS IT MOVES LITTLE DURING THE NEXT 48
HOURS.

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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....
Member Since: March 15, 2008 Posts: 4 Comments: 2492
93L will be in gulf tonight
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220. JRRP
Quoting caneswatch:


I'm in Palm Beach County. That's not a good sign.

take it easy ... is just one run
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Perfect song for hurricane season :)
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Quoting caneswatch:


I'm in Palm Beach County. That's not a good sign.


Actually, it's a great sign. The landfall location of a storm shown that far out in any model is almost never the final landfall location XD
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Quoting Levi32:


Don't take that model seriously lol.


It's Canadian, do you think I would LOL
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Quoting caneswatch:


I'm in Palm Beach County. That's not a good sign.


Don't take that model seriously lol.
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Leaving Houston dry as usual
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93L has lost the surface cerculation that was following it . This should allow it to develop a new cerculation under the system so it should be more stacked.
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Quoting Levi32:
Wow at the 12z Canadian. Cat 2 hurricane over Palm Beach at 180 hours:



I'm in Palm Beach County. That's not a good sign.
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211. xcool
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93L thru a time machine, turns into hurricane and plows into the Sabine Pass of LA/TX

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208. xcool
Levi32 -haha
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Quoting DookiePBC:
Levi...so what you are saying is that there's a bit of uncertainty with the storm brewing in the Caribbean? ;-)

Nice update this morning by the way!!


There's always uncertainty before you even have a well-defined system to work with. Some things are becoming clearer, but we still have a long way to go. Step 1 is always to get the thing to develop in the first place.
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Here is all I could find that was traveling from NE to SW instead of the otherway around.

Photobucket
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Levi...so what you are saying is that there's a bit of uncertainty with the storm brewing in the Caribbean?
;-)

Nice update this morning by the way!!
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Quoting xcool:
Levi32 = come on now you know cmc forecastmodel like to flip-flopping lol


I never spoke of its validity lol. It's just always "wow" when looking at that model. Worst-case scenarios are like that, you know.
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Circulation very evident on the Caribbean disturbance.

Caribbean Rainbow Loop
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201. xcool
Levi32 = come on now you know cmc forecastmodel like to flip-flopping lol
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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.

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INVEST, M,
AL, 93, 2011060118, , BEST, 0, 291N, 802W, 25, 1013, LO, 0, , 0, 0, 0, 0, 1017, 35, 45, 0, 0,
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198. afj3
Quoting Levi32:


Not yet. Watch for it at 0z.

Will do! I viewed the GFS 12z run with interest....
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AL 93 2011060118 BEST 0 291N 802W 25 1013 LO
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Quoting afj3:
I see the system off Nicaragua is getting NHC attention. Does it have Invest status?


No not yet, but could see an invest tagged later on this evening or early tomorrow morning.
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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.


Well dang, Grothar...."you tha man"...you go...a TY anyway :)
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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.

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