Average hurricane season foreseen by CSU, NOAA, and TSR
A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued June 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 11 named storms, 5 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 88% 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 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their April forecast, which called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (28% chance, 31% chance is average) and the Gulf Coast (28% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.
The forecasters cited several reasons for an average season:
1) Sea surface temperature (SST) anomalies in the tropical Atlantic are quite cool. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Substantial cooling began in November 2008 (Figure 1), primarily due to a stronger than average Bermuda-Azores High that drove strong trade winds. These strong winds increased the mixing of cool waters to the surface from below, and caused increased evaporational cooling.
2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. This occurs because El Niño conditions bring higher wind shear over the tropical Atlantic. The CSU team expects the current neutral conditions may transition to El Niño conditions (70% chance) by this year's hurricane season. I discussed the possibility of a El Niño conditions developing this year in a blog posted Friday.
Figure 1. Change in Sea Surface Temperature anomaly between November 2008 and 2009. Most of the Atlantic has cooled significantly, relative to normal, over the past 7 months. Image credit: NOAA/ESRL.
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 slightly warm ENSO conditions, slightly below-average tropical Atlantic SSTs, and above-average far North Atlantic SSTs during April-May. Those five years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1965, which had Category 3 Betsy that hit New Orleans; 1960, which had two Category 5 hurricanes, Ethyl and Donna; and 1959, which had Category 3 Hurricane Gracie, which hit South Carolina. The mean activity for these five years was 10 named storms, 6 hurricanes, and 2 intense hurricanes, almost the same as the 2009 CSU forecast.
How accurate are the June forecasts?
The June forecasts by the CSU team have historically offered a skill of 20 - 30% higher than a "no-skill" forecast using climatology (Figure 2). 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. This year's June forecast uses the same formula as last year's June forecast, which did quite well predicting the 2008 hurricane season (prediction: 15 named storms, 8 hurricanes, 4 intense hurricanes; observed: 16 named storms, 8 hurricanes, 5 intense hurricanes). An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.44 to 0.58 for their June forecasts, which is respectable.
Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.
NOAA's 2009 hurricane season forecast
The National Oceanic and Atmospheric Administration (NOAA), issued its 2009 Atlantic hurricane season forecast on May 21. NOAA anticipates that an average season it most likely, giving a 50% chance of a near-normal season, 25% chance of an above-normal season, and a 25% chance of a below-normal season. They give a 70% chance that there will be 9 - 14 named storms, 4 - 7 hurricanes, 1 - 3 major hurricanes, and an Accumulated Cyclone Energy (ACE) in the 65% - 130% of normal range. The forecasters cited the following main factors that will influence the coming season:
1) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO).
2) There will either be an El Niño event or neutral conditions in the Equatorial Eastern Pacific. An El Niño event should act to reduce Atlantic hurricane activity. However, our skill at predicting an Niño in late May/early June is poor, so there is high uncertainty about how active the coming hurricane season will be.
3) Cooler-than-average SSTs are currently present in the eastern tropical Atlantic. These cool SSTs are forecast to persist through into August-September-October (ASO). ASO SSTs in the eastern tropical Atlantic have not been below average since 1997. Cooler SSTs in that region are typically associated with a reduction in Atlantic hurricane activity.
Thus, they expect that even though we are in an active hurricane period, the presence of an El Niño or cool SSTs in the eastern Atlantic could easily suppress activity, making a near-average season the most likely possibility. They note that two promising computer models, the NOAA CFS model and the European Center for Medium-Range Weather Forecasts (ECMWF) Global Climate Model System 3, both forecast the possibility of a below-average hurricane season.
2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) has joined the ranks of NOAA and Colorado State University in calling for near-average activity. The latest TSR forecast issued June 4 calls for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are close to the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes, and are sharp reduction from their April forecast of 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 50% chance that this season will be in the bottom 1/3 of years historically, and a 40% chance that U.S. landfalling activity will be in the lowest 1/3 of years historically. TSR gives a 32% chance of a near-normal season, and a 17% chance of a below normal season. TSR rates their skill level as 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.
TSR projects that 3.2 named storms will hit the U.S., with 1.3 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 7 - 18% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 0.9 named storms, 0.4 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.
TSR cites two main factors for their reduced forecast: a large and unexpected cooling of sea surface temperatures in the tropical Atlantic, and warmer SSTs in the Equatorial Eastern Pacific (which might lead to an El Niño event that will bring high wind shear to the Atlantic). TSR expects faster than than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.83 meters per second (about 1.7 mph) faster than average in this region, which would create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling. TSR forecasts that SSTs will cool an additional 0.3°C compared to average over the MDR during hurricane season.
Air France crash
The Air France Flight 447 A330 aircraft that disappeared over the mid-Atlantic Ocean yesterday definitely crossed through a thunderstorm complex near the Equator, according to a detailed meteorological analysis by Tim Vasquez. He concludes that "the A330 would have been flying through significant turbulence and thunderstorm activity for about 75 miles (125 km), lasting about 12 minutes of flight time" but that "complexes identical to this one have probably been crossed hundreds of times over the years by other flights without serious incident". See also the excellent CIMSS satellite blog for more images and analysis of the weather during the flight.
Invest 92
NHC is tracking a storm near the Azores Islands (Invest 92L) that is probably the remnants of the core of an extratropical cyclone that closed off some warm air at the center. The system has developed some heavy thunderstorm activity near its center, making this a hybrid storm. However, with ocean temperatures near 62°F (16°C), this storm has little chance of becoming a named subtropical storm.
Jeff Masters
Reader Comments
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There is a trough running SW to NE through the BOC/GOM. Currently there is no associated low, but there is a little surface vorticity at the southern most end. There is some disorganized vorticity in the very upper levels. This trough should be moving NW over the next day or so.
Agreed...but my central point is that you still need the seed of an African wave to get a storm to form in August or September and railing end fronts are hard to come by then...
You did get me to go back and read the NHC forecast discussion for Andrew...which was cool...so thanks!
For those of you out there looking for some fascinating reading - albeit you know how the story turns out - check out the archived forecast discussion for Hurricane Andrew...
"LOWEST CENTRAL PRESSURE
NEAR 1015 MB AND MAXIMUM SUSTAINED WINDS AT 1500 FEET OF 54 KNOTS" Strong Pressure Gradient!
http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/andrew/tropdisc/
The GFS takes this into the north central gulf as an extratropical low when the front picks it up.
Some t-storms?......(ok, a large blob,...Lol)
bahahahaha
255 PM EDT TUE JUN 2 2009
AT THE SURFACE...BOTH THE GFS AND NAM DEVELOP A LOW IN THE NORTH CENTRAL GULF SOUTH OF
LOUISIANA WEDNESDAY AFTERNOON. THE GFS TRACKS A WEAKER LOW TO THE NORTHEAST AND INLAND OVER THE FLORIDA PANHANDLE THURSDAY MORNING.
THE NAM TRACKS THE LOW SLOWLY TO THE EAST ALONG OR JUST OFFSHORE THE LA COAST WEDNESDAY THROUGH THURSDAY. THE 00Z EURO SHOWS NO SUCH
FEATURE DEVELOPING. REGARDLESS OF HOW OR EVEN IF THIS LOW FORMS...ALL MODELS AGREE THAT DEEP LAYER MOISTURE WILL RETURN TO THE REGION.
Guess I missed the discussion....
-- EMC Cyclogenesis Tracking Page --
Model Cycle: 2009060218
18z NAM
12z NAM
NOLA Long Range Radar
LOL.....no doubt!
34 inches NE of downtown Houston IN ONE NIGHT
325 PM CDT Tuesday Jun 2 2009
Short term...
an area of scattered showers and thunderstorms associated with an
upper level trough located in the northwest Gulf continues to
advance northeast across southeast Louisiana. So have raised chance
of rain for all of forecast area tonight.
Long term...
convective feedback problems in both the NAM and GFS models are
evident tonight and Wednesday as the upper trough continues to move
towards la and south MS. Still its reasonable to go with a higher
chance of rain on Wednesday. Based on anticipated rainfall and
cloudiness...have lower Wednesday high temperature forecast a few
degrees. Otherwise...have not made any other significant changes to
the forecast grids.
By Wednesday night the Gulf of Mexico upper level disturbance
moves east of our area...but another upper level trough moves
from the Southern Plains across the middle Gulf region Wednesday
night and Thursday, a weak cold front will move through the region
Thursday night which will bring some dry air to the region.
However...very warm temperatures are expected this weekend as the
air mass quickly modifies
Oh cool, our second GOM Blob in less than two weeks! At least this one is nice enough to come through the middle of the week and leave our weekend alone LOL!
That's right...."Nice" weekday Blob...Lol
Posted on Jun 02, 2009 04:35:34 PM | Dan Kanigan
The Atlantis Ferry Flight will depart Columbus Air Force Base in Mississippi at approximately 3:40 pm CDT and arrive at the Shuttle Landing Facility at NASA's Kennedy Space Center at approximately 6:30 pm EDT. Pilots will do a fly-by of the beach if weather permits.
Earlier this afternoon, a huge crowd of well-wishers gathered at Columbus to welcome Atlantis when it landed en route from San Antonio. The stop in Mississippi allowed refueling and a weather briefing before resuming the trip to Florida.
Stay tuned -- recap photos and videos are on the way after Atlantis lands at Kennedy Space Center!
En Route (151 miles down; 431 miles to go)
Scheduled Actual/Estimated
Departure 03:50PM CDT 03:37PM CDT
Arrival 06:42PM EDT 06:25PM EDT
Speed 325 kts 315 kts
Altitude 15000 feet descending 14900 feet
FlightAware
Yeah the rain figures to keep the water in my ditch long enough to hatch a good crop of tadpoles this year just like in 2005, hmmm, another wet spring in Florida and we remember how that turned out!
That's why I like the fact the tadpoles are going to hatch into a bunch of little mosquito eating frogs!
Sounds like a magazine: 'The Weekly Blob'.
Which will probably be the case on the Blog over the next four weeks......
My link isn't working but..
this song seems vastly appropriate for this season.
It looks like it is making a run at an annular hurricane
Those names are just not mentionable on most blogs...
I like this better...
http://www.youtube.com/watch?v=7iHS3rIwX8Q&feature=related
http://www.aoml.noaa.gov/phod/cyclone/data/at.html
Thats the link I use for TCHP and SSTs. It also has how deep the 26C level is, along with anomalies.
Ahh yes we end up naming them ourselves, they don't get official names unless the media gets hold of them and calls them "Storm of the Century" etc. Our chosen names are a bit shall we say umm less PG
This is the biggest I could find :)
Thanks! Can you explain what data goes into the TCHP to make it different than SST's? I would assume it hase something to do with energy, but what else besides temps affects energy?
The NASA 747 and Atlantis will land at the Shuttle Landing Facility Runway at KSC.
They are expecting a Beach Pass before the Final approach.
I believe the min for a sustained system is 150' depth on the 26.5 temp or it will cool the water off via upwelling and degrade. I will defer to the pros on that part.
Here is the link for you CDL Link
http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html
src="http://image.weather.com/images/maps/tropical/atl_sst_720x486.jpg" alt="" />
It is a combination of SST, depth of the 26c isotherm (how deep the waters are 26c), and I think current speed plays into it, too. (the faster the current, the more potential heat)
Anything 80+ on TCHP can lead to rapid intensification.
This year, SSTs are cooler, but the 26c isotherm is remarkably deep. Shows just how much the trades this spring mixed the water.
The Atlantis Ferry Flight will depart Columbus Air Force Base in Mississippi at approximately 3:40 pm CDT and arrive at the Shuttle Landing Facility at NASA's Kennedy Space Center at approximately 6:30 pm EDT. Pilots will do a fly-by of the beach if weather permits.
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