Early 2011 Atlantic Hurricane Season Forecasts
Hi everybody, this is Dr. Rob Carver filling in for Dr. Masters.
A continuation of the pattern of much above-average Atlantic hurricane activity we've seen since 1995 is on tap for 2011, according to the latest seasonal forecast issued April 6 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). They are calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes. An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is nearly identical to their forecast made in December, which called for 17 named storms, 9 hurricanes, and 5 intense hurricanes. Only six seasons since 1851 have had as many as 17 named storms; 19 seasons have had 9 or more hurricanes. The 2011 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 Caribbean is forecast to have a 61% chance of seeing at least one major hurricane (42% is average.) Five years with similar pre-season November atmospheric and oceanic conditions were selected as "analogue" years that the 2011 hurricane season may resemble: 2008, 1999, 1996, 1955, and 2006. The first four years listed all had neutral to La Niña SST's during hurricane season, while 2006 had El Niño SST's. The average activity for these years was 12.6 named storms, 7.8 hurricanes, and 4.8 major hurricanes.
This year, the forecasters have introduced a new statistical model for their April forecasts. There are four components in this model:
1. Average sea-level pressure in March around the Azores in the subtropical Atlantic.
2. The average of January through March sea-surface temperatures (SST's) in the tropical Atlantic off the coast of Africa.
3. Average sea-level pressure in February and March for the southern tropical Pacific ocean west of South America.
4. Forecasts of September's SST in the tropical Pacific using a dynamical model from the European Centre for Medium-Range Weather Forecasts (ECMWF)
The first two components are loosely linked together. Statistical studies have shown that a weaker subtropical high near the Azores, combined with warmer SST's off the coast of Africa in March are associated with weak winds near the surface and aloft from August to October. This decrease in wind speeds reduces wind shear which can disrupt forming storms. These March conditions also are associated with warmer SST's in August to October, which is also favorable for more tropical storms. For this forecast, the first component is strongly favorable for increased hurricane activity, while the second component is weakly negative.
The last two components represent the changes in sea-surface temperature and sea-level pressure that are the El Niño-Southern Oscillation (ENSO). Briefly speaking, El Niño conditions (warm sea-surface temperatures) are not favorable for Atlantic hurricanes. For more info on ENSO and hurricanes, Jeff has this article.
Using the ECMWF model as guidance (see Figure 1), the CSU group believes that SST's in the tropical Pacific will be neutral (less than 0.5°C from normal). This would have a small negative effect on hurricane activity. However, the tropical Pacific sea-level pressure shows that the atmosphere looks like a La Niña event is still going on. This is strongly favorable for Atlantic hurricane activity in the CSU group's model.
Figure 1. Forecasts of El Niño conditions by 20 computer models, made in March 2011. The ECMWF forecast used by the CSU group is represented by the dark orange square. The forecasts for August-September-October (ASO) show that 5 models predict El Niño conditions, 7 predict neutral conditions, and 5 predict a weak to moderate La Niña. El Niño conditions are defined as occurring when sea surface temperatures in the Equatorial Pacific off the coast of South America ( the "Niño 3.4 region) rise to 0.5°C above average (top red line). La Niña conditions occur when SSTs in this region fall to 0.5°C below average. Image credit: Columbia University.
How accurate are the April forecasts? While the formulas used by CSU do well in making hindcasts--correctly modeling the behavior of past hurricane seasons--their April hurricane season forecasts have had no skill in predicting the future. This year's April forecast is using a new system and has not yet produced a verified forecast. The scheme used in the past three years successfully predicted active hurricane seasons for 2008 and 2010, but failed to properly predict the relatively quiet 2009 hurricane season. A different formula was used prior to 2008, and the April forecasts using that formula showed no skill over a simple forecast using climatology. CSU maintains an Excel spreadsheet of their forecast errors ( expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) for their their April forecasts. For now, these April forecasts should simply be viewed as an interesting research effort that has the potential to make skillful forecasts. The next CSU forecast, due by June 1, is the one worth paying attention to. Their early June forecasts have shown considerable skill over the years.
Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and Tropical Storm Risk, Inc. (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. 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.
2011 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2011 Atlantic hurricane season forecast on April 5. They are also calling for a very active year: 14. 2 named storms, 7.5 hurricanes, and 3.6 intense hurricanes. We would round that to 14 named storms, 8 hurricanes, and 4 intense hurricanes. This compares to their forecast issued in December of 15.6 named storms, 8.4 hurricanes, and intense hurricanes. TSR predicts a 55% chance of an above-average hurricane season, 28% chance of a near-normal season, and only a 17% chance of a below normal season. TSR bases their April forecast on predictions that sea surface temperatures this fall in the tropical Atlantic will be above about 0.08°C above average, and trade wind speeds will be about 0.2 m/s slower than average. The decrease in the trade wind speeds is favorable for enhanced hurricane activity, while the forecast SST's are expected to be neutral for hurricane activity.
TSR puts their skill level right next to the forecast numbers: 13% skill above chance at forecasting the number of named storms, 11% skill for hurricanes, and 10% skill for intense hurricanes. That's not much skill, and really, we have to wait until the June 1 forecasts by CSU, NOAA, and TSR to get a forecast with reasonable skill.
Rob's critiques of the April forecasts
I have to note that Jeff and I wrote this article together. He wrote the general framework before the forecasts were issued, while I wrote the details based on the actual forecasts. So the preceding text is a joint production. However, I have a few observations to make that are my responsibility alone.
First, I am disappointed that the CSU group has changed forecast models only after three seasonal forecasts. This makes it very difficult to assess the skill of the current forecast using past performance. This is very important for forecast users, and they do it everyday. For example, I tend to discount a forecast of rain if it comes from a source that over-forecasts rain (The boy who cried wolf problem).
In the documentation that came with the April forecast, the CSU group argue that the hindcasts show the new forecast model has skill. However, I think hindcasts are a poor substitute for real forecasts in understanding the skill of a statistical forecast model, like that of the CSU's group. As Jeff noted, the previous forecast model did well with the hindcasts and yet had mixed results with the actual forecasts. This does not give me confidence that the new forecast model will be superior to the previous model.
From a philosophical viewpoint, I am inherently cautious about statistical forecast models like the one used by the CSU group. Essentially, they look at what happened in the past and use that to predict the future. However, for making forecasts, we assume that the relationships in space and time between the predictors (such as the average March sea-level pressure around the Azores) and the predictands (Atlantic hurricane activity) does not change as we move forward in time. In a world with climate change, that's a tricky assumption to make.
In any event, it is customary in the meteorological community to continue running older forecast guidance models after the introduction of newer models. This allows forecasters and forecast users to leverage their knowledge of the forecast skill of the older model and gain insight into the forecast skill of the new model. The CSU group really should have included the forecast from the previous statistical forecast system in this forecast.
I am uneasy with some of the methodology choices made in implementing the forecast model. Data for the first three predictors was obtained from the Climate Forecast System Reanalysis (CFSR), NOAA's newest and most advanced reanalysis product. However, CFSR data for 2010 and 2011 has not been released yet, so the CSU group used NCEP/NCAR Reanalysis (NNR), NOAA's first-generation reanalysis, to fill in the gaps. Due to differences in design, resolution, etc., CFSR and NNR can have different depictions of the state of the atmosphere. So using NNR's March 2011 average SLP instead of CFSR's could alter the forecast in unexpected ways. It would be interesting to see how CFSR's 2010-2011 data changes the results.
In any event, we will have to wait and see what the Atlantic hurricane season of 2011 brings.
Reader Comments
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...SEVERE THUNDERSTORM WATCH 112 IN EFFECT UNTIL 7 PM EDT THIS
EVENING...
THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN KENTUCKY.
.DAY ONE...THIS AFTERNOON AND TONIGHT.
THERE IS A CHANCE FOR THUNDERSTORMS TODAY AND TONIGHT. SOME STORMS THIS AFTERNOON AND EVENING COULD BECOME SEVERE WITH DAMAGING WINDS AND LARGE HAIL THE PRIMARY THREAT. AN ISOLATED TORNADO IS ALSO POSSIBLE. THE THREAT OF FLASH FLOODING IS ALSO POSSIBLE TODAY WHERE STORMS REPEATEDLY MOVE OVER THE SAME AREA.
.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.
THUNDERSTORMS ARE ALSO POSSIBLE SATURDAY NIGHT AND SUNDAY NIGHT THROUGH MONDAY NIGHT. THERE IS ALSO A SLIGHT CHANCE FOR THUNDERSTORMS THURSDAY AND THURSDAY NIGHT.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING TO REPORT ANY INSTANCES OF WIND DAMAGE... LARGE HAIL...SIGNIFICANT FLOODING...FUNNEL CLOUDS OR TORNADOES TO THE NATIONAL WEATHER SERVICE.
$$
:)
Click for probabilities and text.
April 9, 2011
No problemo.
:)
Seems like they're looking for mid-afternoon storm initiation up there tomorrow but not impossible for Chi-land to be under moderate risk before 0600 CST 4/10, when today becomes tomorrow for SPC.
000
NWUS53 KJKL 091850
LSRJKL
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JACKSON KY
250 PM EDT SAT APR 09 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1152 AM TSTM WND DMG BOWEN 37.84N 83.77W
04/09/2011 POWELL KY FIRE DEPT/RESCUE
UNCONFIRMED TORNADO DAMAGE. SEVERAL TREES DOWN AND STRUCTURES DAMAGED. MANY ROADS BLOCKED BY TREES.
SVSJKL
SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSON KY
245 PM EDT SAT APR 9 2011
KYC071-115-153-175-091900-
/O.CON.KJKL.TO.W.0017.000000T0000Z-110409T1900Z/
MORGAN KY-JOHNSON KY-MAGOFFIN KY-FLOYD KY-
245 PM EDT SAT APR 9 2011
...A TORNADO WARNING REMAINS IN EFFECT FOR EXTREME NORTH CENTRAL FLOYD...NORTH CENTRAL MAGOFFIN... JOHNSON AND EAST CENTRAL MORGAN COUNTIES UNTIL 300 PM EDT...
AT 242 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE SQUALL LINE CAPABLE OF PRODUCING DAMAGING STRAIGHT LINE WINDS AND BRIEF RAIN-WRAPPED TORNADOES. THIS DANGEROUS STORM WAS LOCATED NEAR OIL SPRINGS...OR 8 MILES NORTHEAST OF SALYERSVILLE...MOVING EAST AT 50 MPH.
LOCATIONS IMPACTED INCLUDE...PAINTSVILLE...DOBSON...FLATGAP...BARNETT S CREEK...LEANDER...PATRICK...DENVER...WINIFRED...ST AFFORDSVILLE...FITZ...KERZ...BLAIR...COLLISTA...SI P...CHANDLERVILLE...GALEN...EAST POINT... WITTENSVILLE... STAMBAUGH AND HAGERHILL.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT YOURSELF FROM FLYING DEBRIS.
&&
LAT...LON 3773 8307 3793 8304 3798 8286 3797 8282
3794 8279 3793 8276 3792 8274 3772 8273
TIME...MOT...LOC 1845Z 268DEG 43KT 3782 8291
303 PM EDT SAT APR 9 2011
VAC191-091930-
/O.CON.KMRX.TO.W.0013.000000T0000Z-110409T1930Z/
WASHINGTON VA-
303 PM EDT SAT APR 9 2011
...A TORNADO WARNING REMAINS IN EFFECT UNTIL 330 PM EDT FOR WASHINGTON COUNTY...AT 259 PM EDT... NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO INDICATE A TORNADO. THIS TORNADO WAS LOCATED NEAR GLADE SPRING...OR 6 MILES SOUTH OF SALTVILLE...MOVING EAST AT 40 MPH.
KYC051-121-091915-
/O.CON.KJKL.TO.W.0018.000000T0000Z-110409T1915Z/
CLAY KY-KNOX KY-
300 PM EDT SAT APR 9 2011
...A TORNADO WARNING REMAINS IN EFFECT FOR NORTH CENTRAL KNOX AND SOUTH CENTRAL CLAY COUNTIES UNTIL 315 PM EDT...
AT 259 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR GIBBS...OR 10 MILES NORTH OF BARBOURVILLE...MOVING EAST AT 45 MPH.
LOCATIONS IMPACTED INCLUDE...SPRULE...COTTONGIN...WOOLLUM...HAVEN...F OUNT...CAN NON...JONSEE... GREEN ROAD...GIRDLER AND HINKLE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.
Lookin at the world..
Las Vegas officials say a lack of rain and little snowpack may lead them to declare a water emergency. The city this week imposed water restrictions that limit residents to one hour of outdoor watering per week. The restrictions could be upgraded to an all-out ban on outdoor watering by next week. State hydrologists tell the Las Vegas Optic the northern New Mexico town is in a particularly bad spot because it gets 90 percent of its water supply from the Gallinas River which is well below normal this year.
Very unusual sandstorm struck Bicske, Fejér County, Hungary on Saturday. A desert like sandstorm several animals drowned, the traffic had to be stopped in the area. The visibility was 2-5 feet in the county. The whole country was a hurricane-like storm winds, which caused significant damage.
Most likely NAO went Positive..I'd 1/2 expect it to stay higher for a few weeks.
The last section, to Orca, was very well written. (as you usually do)
Simple, concise, understandable. Especially the point that every molecule is a heat-storing device. For a while...
Good post.
yep seems right
yes explanation about a couple of things
I love those "higher concern areas" by Accuweather. We don't need Accuweather to tell that, we could just check the NOAA tropical cyclone climatology since those are always the biggest concern areas :)
notice the area of disturb weather?? early start for the eastern pacific?
Not drastically different from historical...
June:
July:
August:
September:
October:
Pretty hot here in Central Florida too! Had a high of 91 here!
I love this though, personally :)
+1
Interesting quake of 4.9 inside the Tokyo bay area,doesn't seem to be connected to the other bigger one to the south earlier but this area has been a bit too quiet compared to the northern coasts and might be about to do a bit of catching up. not even a major rattle by Japan standards but oak trees grow from acorns.
I think that although it is a healthy thing for people to comment on just about anything, people also should not criticise what they do not wish to understand. Learning is easy but you have to want to do it.
This is pretty much right on the eastern edge of the subduction zone where the Eurasian plate rides over the Philippine plate (as opposed to the Pacific plate for the 9.0)
(on the 9.0, I've read some expert commentary suggesting that that quake actually increased strain in the Tokyo area.)
WTO
Uh-oh, appears like this is the season for us in South Florida...well as long as it's no catastrophe.
1094, Interesting:-
If you hit a large ceramic tile with a hammer and push one of the edges/sides of it the pieces don't behave like they were one tile any more.
Based on this idea, if you push a lot of the north eastern japan coast in a lifting and sightly westerly direction by up to 30 meters/100 feet then it seem to follow that you will get a tearing effect in a west to easterly direction around Tokyo.
Only from a simplistic point of view but the Tokyo area must be heavily strained at the junction with the Philippine plate now.
Don't worry; the next--or should I say upcoming--Tokai earthquake will relieve all that strain almost at once. If that goes as many seismologists believe it will, the damage and deaths will be perhaps three or four times worse than that caused by last month's monster--and that doesn't include the five nuclear reactor sites directly in harm's way.
684: 8.3
887: 8.5 (203 years)
1096: 8.4 (209)
1361: 8.5 (265)
1498: 8.4 (137)
1605: 7.9 (107)
1707: 8.4 (102)
1854: 8.4 (147)
20??: 8.? (157 and counting)
So: anytime between now and 2115, and with a magnitude in the range 7.9 to 8.5 (that is, between 1/44th and 1/5th as strong as last month's quake, but far closer to one of the world's most crowded population centers).
The beginning?
WFUS53 KOAX 092339
TOROAX
IAC133-100030-
/O.NEW.KOAX.TO.W.0009.110409T2339Z-110410T0030Z/
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
639 PM CDT SAT APR 9 2011
THE NATIONAL WEATHER SERVICE IN OMAHA HAS ISSUED A
* TORNADO WARNING FOR...
WESTERN MONONA COUNTY IN WEST CENTRAL IOWA...
* UNTIL 730 PM CDT
* AT 633 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS
STORM WAS LOCATED NEAR WHITING...OR 30 MILES SOUTH OF SIOUX CITY...
AND MOVING SOUTHEAST AT 15 MPH.
* LOCATIONS IMPACTED INCLUDE...
WHITING...ONAWA...LEWIS AND CLARK STATE PARK...KENNEBEC...TURIN AND
CASTANA.
THE WARNED AREA INCLUDES INTERSTATE 29 IN IOWA BETWEEN MILE MARKERS
112 AND 120.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR
OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.
LAT...LON 4214 9591 4201 9585 4196 9600 4207 9627
4213 9623
TIME...MOT...LOC 2339Z 298DEG 13KT 4208 9619
NIETFELD
Viewing: 1051 - 1101
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