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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Link
A magnitude earthquake 9.1 is 100 times bigger than a 7.1 magnitude earthquake on a seismogram, but is 1000 times stronger (energy release).
I posted a full list on my blog, for use as a reference during the season...
I saw that the other day. Very amusing, +100.
made it north of the equator
She's a lot prettier. Maybe I'm wrong.
It's 80.8 outside my window. High in the low 80's today.
What is ESPI ? Thanks
European Space Policy Institute!
...
It's ENSO Precipitation Index. Link
'82, '92, and '97 all being strong El Nino episodes.
It's figuring how strong ENSO is using precipitation anomaly & differences from the equator region over the Pacific & North of Australia. Here's more.
I wish this would update. It's the history of it plotted out. ESPI is blue. See how it usually dives right before ENSO goes up? This is another sign we will get hotter than neutral conditions. -1.9 is more on the extreme end. it was just -1.06 maybe 10 days ago..last time I looked over ENSO.
Could that dive be a sensing issue- some sort of artifact- or do they remove those. Is that data looked at at all or is it raw?
'The Earth sees about 760 thunderstorms every hour, scientists have calculated.
The figure, unveiled at the European Geosciences Union meeting in Vienna, is substantially lower than numbers that have been used for nearly a century.
The new research uses a global network of monitoring stations that detect the electromagnetic pulses produced by major bolts of lightning.
It confirms that thunderstorms are mainly a tropical phenomenon - and the Congo basin is the global hotspot.'
link
== PRELIMINARY EARTHQUAKE REPORT ==
Region: NORTH OF HONDURAS
Geographic coordinates: 17.218N, 85.090W
Magnitude: 5.8 Mw
Depth: 19 km
Universal Time (UTC): 7 Apr 2011 20:41:54
Time near the Epicenter: 7 Apr 2011 14:41:54
Local standard time in your area: 7 Apr 2011 15:41:54
Location with respect to nearby cities:
125 km (78 miles) W (260 degrees) of Swan Island
172 km (107 miles) NNE (32 degrees) of Trujillo, Colón, Honduras
181 km (113 miles) ENE (57 degrees) of Roatán, Islas de la Bahía, Honduras
242 km (150 miles) NE (48 degrees) of La Ceiba, Atlántida, Honduras
394 km (245 miles) E (89 degrees) of BELMOPAN, Belize
answered my own question- the data are subjected to a running two month mean to reduce variability.
El~ El Nino index & LI is the La Nina index~ I'm not sure which is which but they run really similar. I think EL is the usual manner ENSO is discussed with he 3 month average of region 3,4.
In that chart a 60 day average of ESPI is used. The -1.90 current is a 30 day average.
i would have to agree with you keeper
From the article:
"Thunderstorms cluster in the centre of continents in the tropics, with the Congo basin standing out.
"That's perhaps because it's drier there than in the Amazon, for example - thunderstorms seem to form more easily in drier conditions," Dr Price told BBC News."
It's interesting that the Congo basin sees more lightning than the Amazon, because as the article hints at, the Amazon receives much more rain.
I'm guessing the reason for greater lightning in the Congo is because the drier air in the Congo allows for greater heating allowing for greater lift & instability. Meanwhile, the Amazon is more uniformly moist, meaning more cloud cover and less opportunity for significant heating, like the Congo sees.
thats my guess
Here's a map of the global lightning strike density. view in another tab to enlarge
For example, try to move to things that won't slide easily against each other. They will move in spurts. Same concept here, except it has spanned the last 8 years because of the speed of the tectonic plates.
Regardless of sensationalist apocalyptic talk, the JTWC has released the best track data for 2010.
Our first estimates of the megaquake of Honshu, Nothern Japan Coast , at 5:46 UT on polar motion. According to the preliminary US Geological Survey and Harvard University seismic parameters used with Dahlen's dislocation model (1973), the principal axis of inertia
with highest moment of inertia (also called figure axis, closed to
symetry axis) was displaced by about 15 cm at the earth surface in the
direction 135° East (value confirmed by R. Gross, JPL, with another
model). The effect is larger than for Chili (February 2010) and Sumatra
(Dec. 2004) earthquakes (see below corresponding news). This could be
observed as a step in the so-called excitation function, deduced from
the determination of pole coordinates by space geodesy. But such a step
could be hardly discernible from common hydro-meteorological processes.
The oceanic angular momentum still lacking, only next months will tell
us wether something is detectable.
Modeled co-seismic shift of the main inertia pole since January 2004:
Modeled co-seismic shift of the rotation pole since January 2004:
http://hpiers.obspm.fr/eop-pc/index.php?index=new s
My advice is :
Take a look on Dr. Jeff Masters' WunderBlog Archived Entries
Link Link
Read through some days and get the feeling on how the blog behaves...
You will learn to identify bloggers, their attitudes and their likes...
Then, stay calm, be informative, be friendly with those who are friendly and avoid provocations
Are they really that desperate?
The rainy season has already started in the South Pacific, Costa Rica,around two weeks earlier than usual.
This year, we've had 4 thunderstorms in the first 7 days of April alone(really uncommon).
Looking forward 2011 Hurricane Season!
http://earthquake.usgs.gov/learn/topics/increase_ in_earthquakes.php
Troll caster: blog-member who concentrate on identifying and outing trolls.
http://earthquake.usgs.gov/learn/topics/increase_ in_earthquakes.php
I've never been on this blog during Presidential elections, but I can't imagine how it will be come 2012 when we still got a lot of blog members since it will still be hurricane season, but there won't be much to talk about hurricane wise since the season will be almost over, and the elections & campaign will be all over the media.
Recipe for disaster.
I'm jealous. Must be nice living there. And I've been watching the sat loops, southern central american has been getting quite a few thunderstorms in
I clicked on your link and it was a 404 page not found. Was this the article you were referring to?
http://earthquake.usgs.gov/learn/topics/increase_ in_earthquakes.php
If so, that article is 2 years old and I believe they have changed their thinking I don't have a direct link. Anybody?
Yeah it will be wacked, politics is so stupid, I may not vote at all next election. Our system has grown to the point where the hope of honest leadership that actually serves the people is all but completely hopeless. Ive trusted people too much for too long.
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