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

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

Share this Blog
6
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 544 - 494

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35Blog Index

Quoting Hurrykane:
Updated shear forecast



By the time the jet stream gets to that point 93L will be gone anyway.
Member Since: Posts: Comments:
Quoting reedzone:
Where the so called high wind shear? It even cleared out near Texas on the newest update.. 5-10 knots in it's path.






Look at the flow of the shear. Throughout the entire life time of this system, it has been encountering upper level winds going in the same direction as the system which are favorable for a system. But now that its changing direction in motion, its encountering upper level winds around 15 kts from the southeast. This goes against the motion of the system.
Member Since: Posts: Comments:
At the very least 93L will allow the HHs to practice for the rest of the season.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting reedzone:
Where the so called high wind shear? It even cleared out near Texas on the newest update.. 5-10 knots in it's path.






I think what he's hinting at is that the subtropical jet stream located between the latitudes of 93L and our Caribbean AOI is forecast to move north a little.

However, by the time the stream moves north to have an extremely disruptive impact, 93L will already have made landfall at whatever intensity in the western gulf.
Member Since: Posts: Comments:
Quoting eyestalker:
POLL" What % chance do you give 93L of becoming a named storm?


50% chance

- low wind shear
- warm GOM temps
- already blew up some new bursts of convection right when it hit the waters.
- vorticity has also increased some per the latest update on CIMMS

I see no reason for this to fizzle out. 93L should be with us for couple more days.
Member Since: Posts: Comments:
Quoting cchsweatherman:


Keep in mind the convective burst came as a result of the normal diurnal processes and instability over Florida. Once it enters the Gulf of Mexico, not only will it lose this energy source, but it will be meeting 10-15 kt wind shear which would be the highest shear it has faced its entire life time. For such a small system, any increase in shear could be crippling to it. No surface observations show a surface circulation in association with this system either.
So, Your not giving it much of a chance?
Member Since: Posts: Comments:
Tornado on the ground here in MA, dont see that everyday

057 
WWUS51 KBOX 012036
SVSBOX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE TAUNTON MA
436 PM EDT WED JUN 1 2011

CTC003-013-015-MAC013-015-027-012115-
/O.CON.KBOX.TO.W.0004.000000T0000Z-110601T2115Z/
HARTFORD CT-TOLLAND CT-WINDHAM CT-WORCESTER MA-HAMPSHIRE MA-
HAMPDEN MA-
436 PM EDT WED JUN 1 2011

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 515 PM EDT FOR EASTERN
HAMPDEN...EXTREME SOUTHEASTERN HAMPSHIRE...SOUTHWESTERN WORCESTER...
NORTH CENTRAL WINDHAM...NORTHERN TOLLAND AND EXTREME NORTHEASTERN
HARTFORD COUNTIES...

AT 431 PM EDT...LOCAL LAW ENFORCEMENT REPORTED A TORNADO IN 
WESTFIELD IN THE SHAKER ROAD AREA. AT 435 PM A TORNADO WAS REPORTED 
BY AMATEUR RADIO OPERATORS HALF A MILE FROM MAIN STREET IN 
SPRINGFIELD HEADING TOWARD DOWNTOWN SPRINGFIELD. THIS IS A VERY 
DANGEROUS SITUATION.  THIS TORNADO WAS LOCATED NEAR 
SPRINGFIELD...MOVING EAST AT 40 MPH.

OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
LUDLOW...WILBRAHAM...HAMPDEN...PALMER...MONSON... WALES...BRIMFIELD...
WARREN...HOLLAND...BROOKFIELD AND STURBRIDGE

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF YOU ARE CAUGHT OUTSIDE...SEEK SHELTER IN A NEARBY REINFORCED
BUILDING. AS A LAST RESORT...SEEK SHELTER IN A CULVERT...DITCH OR LOW
SPOT AND COVER YOUR HEAD WITH YOUR HANDS.

HEAVY RAINFALL MAY OBSCURE THIS TORNADO. TAKE COVER NOW! IF YOU WAIT
TO SEE OR HEAR IT COMING...IT MAY BE TOO LATE TO GET TO A SAFE PLACE.

&&

LAT...LON 4202 7262 4220 7263 4222 7205 4199 7203
TIME...MOT...LOC 2035Z 262DEG 33KT 4212 7254

$$


--

NWS Warnings Provided by AllisonHouse.com


Member Since: Posts: Comments:
Quoting NOLAInTheEye:
Just hit 99.1


Yeah it's cooking in the SE today. Crestview, FL is sitting at 100 degrees right now breaking their old record hi of 97! Not the kind of weather we need with the drought we're having, need 93L to turn more North and bring us some rain but doesn't look like it's going to happen.
Member Since: Posts: Comments:
Quoting CajunTexan:


Thanks, glad you enjoy them. Greetings to you as well. A couple of storms to watch aint bad for June 1st, huh?


That was a brilliant rhyme Cajun, just beautiful. Seems this season is going to be one full of surprises.
Member Since: Posts: Comments:
Quoting reedzone:


High wind shear?? Where?? I see a nice burst of convection where the new LLC may form in a matter of a couple hours. I see no dissipation anytime soon.

Will 93L lose some foward speed, and if so by how much? Wouldn't it help the disturbance be more vertically stacked if it did (I just remembered Colin of last year, he was going so fast he lost it and then regenerated once it slowed down)

Thanks in advance for any input.
Member Since: Posts: Comments:
Where the so called high wind shear? It even cleared out near Texas on the newest update.. 5-10 knots in it's path.




Member Since: Posts: Comments:
Wow, this is a very early start, in 09, we had to wait till june 25th to have a yellow circle...

As time passes, conditions and senarios are looking better for tc formation for both 93L and what will probably be 94L.

I say that there is a 85% chance of one of them forming and a 25% chance of both of them forming at some period over the next 3-7 days.
Member Since: Posts: Comments:
Quoting reedzone:


High wind shear?? Where?? I see a nice burst of convection where the new LLC may form in a matter of a couple hours. I see no dissipation anytime soon.


Keep in mind the convective burst came as a result of the normal diurnal processes and instability over Florida. Once it enters the Gulf of Mexico, not only will it lose this energy source, but it will be meeting 10-15 kt wind shear which would be the highest shear it has faced its entire life time. For such a small system, any increase in shear could be crippling to it. No surface observations show a surface circulation in association with this system either.
Member Since: Posts: Comments:
526. Skyepony (Mod)
This is the damage swath of the MCS that is now 93L.
Member Since: Posts: Comments:
This is my 3rd season on here. The one thing that is consistant with some models.....is that they are not consistant!
Member Since: Posts: Comments:
Quoting eyestalker:
POLL" What % chance do you give 93L of becoming a named storm?


60%
Member Since: Posts: Comments:
Quoting ajcamsmom2:
492. TropicalAnalystwx13 3:26 PM CDT on June 01, 2011

great job! thanks for taking the time to put your thoughts out here for us to think about...


Thanks, I'll probably end up making a better quality one tonight, and a lot neater.
Member Since: Posts: Comments:
http://www.compasscayman.com/caycompass/portal/Geor ge-Town-Webcam/
Member Since: Posts: Comments:
Is the skill in August for the prediction for the rest of the Hurricane Season, or is it for the whole season.
If it is for the whole season, and half the season has passed, then an improvement in skill of less that 50% is actually a decrease in skill for the second half of the season, right?

FYI I am under 93L's cloud shield, yellow area, and we are not getting any rain under here. The actuall convection is rather small.
Member Since: Posts: Comments:
Just hit 99.1
Member Since: Posts: Comments:


High wind shear?? Where?? I see a nice burst of convection where the new LLC may form in a matter of a couple hours. I see no dissipation anytime soon.
Member Since: Posts: Comments:
Quoting sammywammybamy:


Run the Loop:

Link

CMC (102 Hours / Curving From WNW to N) :



CMC ( 126 Hours / Heading Due North)



CMC ( 144 Hours / Heading NE)



Florida.


On my iPad, so can't see the loop. Thanks for the info!
Member Since: Posts: Comments:
I know that this is probably a question asked before, but I couldn't find it. What is the dark line on the hurricane sea temperature map at about 79 deg. F.?
Thanks!
Member Since: Posts: Comments:
Quoting MrstormX:
93L HWRF


10 kts away from a hurricane.
Member Since: Posts: Comments:
93L HWRF
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Houston/Galveston residents, here ya go:

http://webgis2.h-gac.com/evacviewer/
Member Since: Posts: Comments:
Well finally getting some much needed rain here in South Sound , Grand Cayman, hope it doesn't turn out to be more than we bargained for
Member Since: Posts: Comments:
aspectre "Since there is low-to-no Fujiwhara repulsion, can two Invests join together into a cyclone?
Is there any record of two having done so?"
453 Skyepony "That's when one blob consumes another.. we've seen that plenty."

Most blobs never become Invested. Specifically interested in Invest-to-Invest mergers:
Disturbance-to-Disturbance? Disturbance-to-Low? Low-to-Low? Invest-to-formerInvest?
Member Since: Posts: Comments:
Is there a high parked over the N Gulf Coast States?
Member Since: Posts: Comments:
505. Skyepony (Mod)
Quoting eyestalker:

I was referring to our basin. Absorption of the weaker system in our basin generally occurs with African waves. Examples would include Dennis in 05 which absorbed the front-running wave which happened to be weaker than the trailing wave on its heels, the one with the surface low -- and Alex, which absorbed at least one other tropical wave in the Caribbean.


Like what happened with Alex..I was agreeing it happens everywhere including the Caribbean. Didn't realize you were looking for names.
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
TROLL BE GONE




Nice image, Keep!
Member Since: July 23, 2010 Posts: 1 Comments: 12414
Quoting NRAamy:
STORMTOP!!!!! I MISS HIM!!!!!!

:)


Maybe someday your aim will improve...
Member Since: Posts: Comments:
already might get two tropical storms for the numbers game big bend area of fl. to be 94
Member Since: Posts: Comments:
Quoting P451:


Then it is to be discounted. BAM-D member is for Deep systems (Intense systems). If you are going to follow the BAM model suite you would use the BAM-S member (shallow or weak systems).

Oh, I know. I was just looking at lines on the map. BAM-S wouldn't be horrible (in terms of drought relief), but stays too far south to have the most impact on the worst drought areas.
Member Since: Posts: Comments:
Quoting Levi32:


Not too much, but it's on the edge. The system is fragile and not hanging on by much for now. These things can surprise you if they get going though, so we'll have to keep an eye on it.

Out 'til later.
Thanks
Member Since: Posts: Comments:
497. xcool


Member Since: Posts: Comments:
492. TropicalAnalystwx13 3:26 PM CDT on June 01, 2011

great job! thanks for taking the time to put your thoughts out here for us to think about...
Member Since: Posts: Comments:
Quoting RitaEvac:


Nope, hours. The dark greens/yellows/oranges for hours of soaking rain
IIRC, to "break" a drought, you need at least 1/2 to 2/3 of the rainfall deficit made up. Right now, IAH is about 12-13" under its normal, so we would need 6-8" of rain. Even with how severe our drought is, 6-8" in a single day would lead to flash flooding issues. Thats why I would love to see 3-4 days of 1-2" per day. Still gets the same total, still as a soaking rain, but without widespread flooding.
Member Since: Posts: Comments:
Quoting scott39:
Do you think there is too much shear, for it to close any time soon?


Not too much, but it's on the edge. The system is fragile and not hanging on by much for now. These things can surprise you if they get going though, so we'll have to keep an eye on it.

Out 'til later.
Member Since: Posts: Comments:

Viewing: 544 - 494

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35Blog Index

Top of Page

About

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

Local Weather

Overcast
52 °F
Overcast