CSU predicts a very active hurricane season: 16 storms, 9 hurricanes
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
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Atlantic Tropical Invest 93L: a residual MCV from a Midwest MCS?
I agree that its still quite off from becoming a tropical depression at this time, but I have seen progress towards it.
A couple of models are picking up on it and 93L's speed could change the game a bit. The AOI could find itself in a quite favorable environment should 93L book down to MEX to help with venting.
Hey there
All is well ( so far ) in this neck of the woods and I have been just fine. As always, I am ready LOL.
Neutral ENSO conditions portend potential trouble through the Caribbean. Recurvature tends to come later than with La Nina conditions and instead of systems turning just NE of the Islands I expect to see more of a threat to the Central and Western Caribbean this year.
Time will tell.
AF309 has flown out to the Gulf twice today. On the first run looks there was 4 dropsondes, but only could see one. Then they went out there this evening. Gives a good look at the shear it's about to run into.
Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KNHC)
Transmitted: 1st day of the month at 23:45Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 309)
Mission: Non-Tasked Mission, possibly not tropical (flight in the North Atlantic basin)
Mission Identifier: 110601223009309 (2 digit year/2 digit month/2 digit day/6 digit mission start time/Last 3 digits of aircraft tail number)
Date Mission Started: June 1st in '11
Time Mission Started: 22:30:09Z
Observation Number: 03
Part A...
Date: Near the closest hour of 23Z on the 1st day of the month
Highest Mandatory Level For Which Wind Was Reported: 500mb
Coordinates: 27.7N 89.4W (View map)
Location: 162 miles (261 km) to the SSE (166) from New Orleans, LA, USA.
Marsden Square: 081 (About)
Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1018mb (30.06 inHg) Sea Level (Surface) 27.8C (82.0F) 23.2C (73.8F) 35 (from the NE) 5 knots (6 mph)
1000mb 155m (509 ft) 28.2C (82.8F) Approximately 15C (59F) 40 (from the NE) 8 knots (9 mph)
925mb 844m (2,769 ft) 24.6C (76.3F) Approximately 14C (57F) 50 (from the NE) 20 knots (23 mph)
850mb 1,577m (5,174 ft) 17.8C (64.0F) 12.9C (55.2F) 60 (from the ENE) 18 knots (21 mph)
700mb 3,208m (10,525 ft) 8.2C (46.8F) Approximately 0C (32F) 70 (from the ENE) 29 knots (33 mph)
500mb 5,900m (19,357 ft) -9.5C (14.9F) Approximately -26C (-15F) 55 (from the NE) 16 knots (18 mph)
Hey guys.Here is a great closeup of where the low is. You can see how the clouds curve.
You joined yesterday eh ??. So what was the handle before then ?
:)
Invest 93AL Floater - Rainbow Color Infrared Loop
are you JFV?
Looks like Ghost Rider in the Caribbean almost.
UMMM, one ?? LOL
Post a few toons and we'll know for sure...How are you???
back tomorrow.
Good night.
MS,,u have the conn.
A Mesoscale Convective System (MCS) can turn tropical..
Lastly, a mesoscale convective system or MCS can sometimes be the cause of tropical cyclone development. These organized clusters of storms can move off a continental landmass and drift over warm waters. If they already contain a small vortex in the cluster, this may make to region even more favorable for tropical cyclone development.
Not trying to validate anything..just observations~ As for the chemtrails it's overall been sparse til these fires start closing I-95. This last round was different. It's been critical one county north of me..Volusia. 95 closings & all..not much for chemtrails though. Then this MCS a bit stronger than models anticipated or so small they are having issues seeing shows up.. We got chemtrailed heavy early this morning right off the east coast. I have a friend that wolk up beach side early & noticed it all. Called me to rant to someone that will listen about the weather~ Commented it was intense. Wanted to blame the haze that set in on it even. Saw that roll in across the ocean, but I thought the haze smelled like smoke & colored the sunlight like smoke. For what little moisture it was working with, rain couldn't have targeted the area with the most fires along major roads better.
I am avoiding that for as long as I can.
I am trying plenty to rehab w/o surgery.
you got mail
I'm great...finally sold my lot (at a huge loss) in Pass Christian, which will hopefully let me get on with my life and quit dwelling on how much I miss Mississippi...How are you???
SunshineStateCarnage
RingOfDestruction
hurricane2011
NHC2011
CubanTropical
DOOM4MIAMI
GoldCoast2011
Winds in the area also suggest the circulation continues to tighten and become slowly better organized.
NWSNorman NWS Norman
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I'll be taking the kids to hang out on Ship Island pretty soon...The Beau Rivage has had some pretty nice rates lately and I love their buffet...But, we'll probably end up staying in Gulfport to be closer to the ferry...
i this wanted too make sure my good sir
Thats a decent drop in pressure. Visible organisation should soon follow suite. As well as a possible upgrade from the nhc o invest by tomorrow. If they acknowledge the pressure drop.
What's the purpose? To seed the clouds to rain? Possibly poison us in the process to some extent, or something more?
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