Early 2011 Atlantic Hurricane Season Forecasts

By: Dr. Jeff Masters , 6:22 AM GMT on April 07, 2011

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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.

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1684. Xandra
Quoting Neapolitan:

The good news: it was just updated to a 6.6.

The bad news: the quake was actually centered inland roughly midway between Sendai and Tokyo, and located at a fairly shallow 13.1km.

According to Kyodo, external power is "no longer available" at the Fukushima plant, so water injection has ceased. Uh-oh...

The good, the bad and the ugly! ;)
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Quoting Xandra:
Japan, magnitude 7.1

The good news: it was just updated to a 6.6.

The bad news: the quake was actually centered inland roughly midway between Sendai and Tokyo, and located at a fairly shallow 6.2 miles.

According to Kyodo, external power is "no longer available" at the Fukushima plant, so water injection has ceased. Uh-oh...
Member Since: November 8, 2009 Posts: 4 Comments: 13509
1682. Xandra
Japan, magnitude 7.1

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1681. Ylee
All tornado warnings have now expired, and there are just a couple of severe Tstorm warnings left in Texas....
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Quoting SeALWx:


Nothing at all huh? Looks like somebody needs to call mommy cause the bad man on the internet is being mean.

Go ahead...flag this one too. Oh and it is swweeet to hear the GW crowd cry altered data. Oh the IRONY.


Oh great.. the zingers are back.

Seriously, go back through the blog and compare the zinger posts with the posts by people that are respected and that quote facts (on either side), the worse the argument and the less intelligent the poster, the greater the use of zingers.

I always hear George Costanza's voice after these. "It's a zinger, Jerry. He got with me with the zinger. I was right there, and then he brought out the zinger!"

Jerry: "I do think you're right. You have been zung, George."

George: "Yep, got me with the zinger. What can you do?"
Member Since: June 5, 2006 Posts: 0 Comments: 1220
TEPCO revises tsunami height to 15 meters.

Japan Times
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Powerful winds and some pretty heavy rain came through North Crowley, TX (SW Tarrant Count)about 30 minutes ago; some residual thunderstorm activity but looks like most of the action is just south about 10 miles in the area between Crowley and Alvarado along I-35 with it moving into Ellis County. We got some hail, not a lot, probably pea-sized at best. Winds though, were pretty powerful.
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1677. SeALWx
Go ahead admin. Delete all these posts and drop the ban hammer. I know I'm in the lions den here, but AGW is fraud science at this point. It might be happening, fair enough. But the science is WRONGLY conducted and untruthfully portrayed.
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TORNADO WARNING SAN ANGELO TX - KSJT 1225 AM CDT MON APR 11 2011
TORNADO WARNING FORT WORTH TX - KFWD 1225 AM CDT MON APR 11 2011
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Quoting SeALWx:
Okay if you just gonna take random graphs out of context, whatever...I'll just go ad hom and say that you're an idiot. My opinion carries just as much weight as your context-less arguments of validity.

Just like was testified in front of the house sub-commitee: smoke screens, misinformation, out-of-context arguments, and a general thought process of "I know I'm right and I'll make data to prove it." While giving no respect to even read others concerns about your data handling.

GDIAF

And I'll simply flag your comment for the ad hom.

I'm just trying to point out that this website is clearly altering data. I could honestly care less about your paleoclimate issues, it does nothing to disprove we are presently warming. nothing at all. night
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1673. xcool





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OKLAHOMA/ARKANSAS

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Quoting SeALWx:
Right Wing Hocus Pocus

I'm not going to bother reading through the many hours worth of text, but just looking at some of the graphs, I couldn't help but laugh:










comical at best. It's obvious he took graph charts and then added his own temp scales to the left side because of the different font and color. GEE, I WONDER WHY.

Not only that, but it doesn't even make sense. If you look at the graph and find the 0c anomaly line, its well above all the data. so where did he come up with the average? CLEARLY it was not determined using the data on the graph, or else the lines would reflect that. For all we know, he could of just created that line out of thin air.

How ironic is it that this man is trying to prove scientists are messing with the data, when clearly he is doing exactly that.




I also always find it ironic that people believe in what one website on the internet tells them over what all the scientists say.

Once again, let me know when you deniers can show me the earth is cooling. or how humans have zero effect.
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TEXAS

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1668. SeALWx
“The legitimate questions that have been raised about the processes used to generate climate change science and policy have thus far been cast aside. The reluctance to engage in conversations with people who have doubts or question the veracity of climate science is at the heart of the wrong doing that undermines trust in climate change science.”

“The committee should understand that the IPCC presents one version of climate change science generated by an establishment that has evolved to largely reflect a particular point of view…this point of view attempts to dismiss information that questions the belief that greenhouse gases are the dominant cause of observed climate change.”

Link
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1667. SeALWx
Hocus Pocus
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HEADS UP ST LOUIS


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Quoting SeALWx:
nope. Wrong again. You brought up ice in your straw man argument against paleoclimatology 'irregularities'.
I said if you don't trust the scientists, you can look for yourself in the arctic or antarctic. I was wrong that the antarctic showed warming. But Tampa was equally wrong that t showed cooling.



In any case, the globe is still warming humans are still contributing. Let me know when ya'll find something of interest to suggest other wise.
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Quoting SeALWx:
It's the lying by climatologists that I'm concerned about, which has been steadily increasing over recent decades.


I don't even know what to say.
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TEXAS

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1661. Levi32
Quoting DDR:



Interesting how it differs from the new CFS.
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1660. SeALWx
Quoting KoritheMan:


Any climatologist worth their salt understands what I said. It's the arctic sea ice extent we're concerned about, which has been steadily declining over recent decades.
It's the lying by climatologists that I'm concerned about, which has been steadily increasing over recent decades.
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1659. DDR

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1658. SeALWx
Quoting TomTaylor:
Tampa brought it up with the record extent of antarctic sea ice levels post. I countered.

If you want to look at the climatic avg, t doesn't show any significant trends, unlike Tampa claimed.
nope. Wrong again. You brought up ice in your straw man argument against paleoclimatology 'irregularities'.
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Quoting SeALWx:
I'm sure you guys can get somebody to jockey that data around for ya though. At least by the time IPCC meets again.
Thas nice, make your predictions all you want, the point stands that the antarctic sea ice shows no significant trends.
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Quoting SeALWx:


Don't like the data...just throw it out.

Looks like Briffa and Mann and Schmidt have taught you all well!


Any climatologist worth their salt understands what I said. It's the arctic sea ice extent we're concerned about, which has been steadily declining over recent decades.
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Quoting SeALWx:


You don't really wanna hear the weather isn't climate talk right now do ya? You guys like saving that one for blizzards and cold snaps, right?
Tampa brought it up with the record extent of antarctic sea ice levels post. I countered.

If you want to look at the climatic avg, t doesn't show any significant trends, unlike Tampa claimed.
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1654. SeALWx
Quoting TomTaylor:
the antarctic isn't showing significant loss or addition.

It's in no bodies favor.
I'm sure you guys can get somebody to jockey that data around for ya though. At least by the time IPCC meets again.
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1653. xcool
tampa you goting mall sir thanks :)
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1652. DDR
Thanks
I'm expecting above average rainfall for this month,almost at the average already,it should be double or even triple the monthly average by April 30th.
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1651. SeALWx
Quoting TomTaylor:
Yea try and find an updated link.

Unlike your link, my link is up to date and shows that in the last year sea ice has been dropping. Yet your link stops the graph at mid 2010, ironically that's right when my graph begins to plummet.

Coincidence?..


You don't really wanna hear the weather isn't climate talk right now do ya? You guys like saving that one for blizzards and cold snaps, right?
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.
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Quoting SeALWx:


Don't like the data...just throw it out.

Looks like Briffa and Mann and Schmidt have taught you all well!
the antarctic isn't showing significant loss or addition.

It's in no bodies favor.
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Quoting SeALWx:


Don't like the data...just throw it out.

Looks like Briffa and Mann and Schmidt have taught you all well!


Does not fit the agenda.....or if the glove does not fit you must acquit.
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Quoting TampaSpin:
Antarctic ice is at a record high and growing at the %u2018steepest slope ever
Yea try and find an updated link.

Unlike your link, my link is up to date and shows that in the last year sea ice has been dropping. Yet your link stops the graph at mid 2010, ironically that's right when my graph begins to plummet.

Coincidence?..
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1646. SeALWx
Quoting KoritheMan:


Antarctic sea ice is largely irrelevant insofar as impacts to global climate are concerned.


Don't like the data...just throw it out.

Looks like Briffa and Mann and Schmidt have taught you all well!
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1645. Skyepony (Mod)
Situation Update No. 1
On 11.04.2011 at 03:24 GMT+2

Wildfires scorched more than 230,000 acres in Texas on Sunday, roaring through a West Texas town, destroying an estimated 80 homes and buildings and critically injuring a firefighter. The Texas Forest Service reported more than 60,000 acres burned and 40 homes lost in one blaze that raced through West Texas and into the small mountain town of Fort Davis. The fire rushed across 20 miles in 90 minutes. Officials at the scene, however, estimated at least 100,000 acres in two counties had burned from the fire, which continued to grow Sunday evening. "I can only describe it as an ocean of black, with a few islands of yellow," State Representative Pete Gallego said. Flames "licked at the edges" of the town but did not burn their way through its center, sparing more buildings than expected, he said. But 17 to 20 homes were destroyed, and as many as 30 more buildings were burned, he said after visiting the town, including a more than 100-year-old historic wooden ranch home. Residents had worked overnight to save their homes and moved on to help their neighbors, he said. Hot spots still burned along the highway, and a glow from miles away was visible at night, he said.

"Even now, the flames in some places are 15 to 20 feet high," Gallego said. The town was without power Sunday evening. Gallego said many of the residents may not have been insured for fire. Presidio County Emergency Management Coordinator Gary Mitschke said it was the first fire to scare him in 13 years of fighting grass fires. The blaze crossed railroad tracks and state highways as it roared past Fort Davis, he said. Without a change in winds, which were keeping aircraft from helping firefighting efforts, the fire could burn for days or weeks, he said. "Frankly, it moved almost as quick as a truck," Mitschke said. "When you hear the word firestorm, this is what I imagine." A federal emergency management spokesman said a fire grant for the county had been approved Saturday and that the agency stood by to support as needed. Wildfires fed by dry, windy conditions have charred more than 270,000 acres in eight days across Texas, burning homes, killing livestock and drawing in crews and equipment from 25 states. Plants that thrived in wet weather turned to tinder under a cold, dry winter. Weeks of high winds and little moisture have made every spark dangerous. A Texas firefighter was in critical condition with severe burns Sunday afternoon after fighting an estimated 60,000-acre fire in the northern Panhandle.

The cause of the fire was under investigation, but it started in an isolated area near a natural gas plant and a few other industrial sites in an empty town called Masterson, said David Garrett, an emergency management spokesman for Moore County. "Kind of like a wide spot in the road that has a name," Garrett said. "The fire started in open country and stayed in open country." Two nearby communities were considered threatened but were not evacuated late Sunday afternoon, according to the forest service. A Midland County wildfire burned 40 homes and at least 15,000 acres, according to the service. Crews had stopped from crossing a highway a sprawling 71,000-acre fire that killed almost 170 head of cattle in Stonewall County, spokesman Lee McNeely said. Air tankers had dropped 60,000 gallons of retardant to help slow the blaze. Firefighters had most of the day to prepare for a cold front with gusting winds, McNeely said. High winds and dry conditions were expected to persist into the evening across West Texas, the National Weather Service warned. In Oklahoma, where Governor Mary Fallin has extended a 30-day state of emergency she declared on March 11, firefighters and helicopters on Sunday mopped up the smoldering remains of two fires that erupted Saturday. One wildfire in Cleveland in north central Oklahoma charred more than 1,500 acres and forced 350 people to evacuate while another struck near Granite in southwest Oklahoma, said Michelann Ooten, a spokeswoman for the state Office of Emergency Management.


Spain is burning too.
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1643. SeALWx
1632.

Hmmm...Removing evidence of the MWP and leading people to believe that the earth is warming so much that it has never been as hot as it will be isn't important to the AGW situation? Manipulating data sets to skew plots of temp trends isn't unacceptable behavior to the GW team huh? Looks to me like southern ice gains more in the winter than gets lost in the summer. Look at all those data points above zero!

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Quoting geepy86:

Link not working for me.



sorry fixed it
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why are my arrows not on the right storms?....some vortexs here.........
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.
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1639. geepy86
Quoting TampaSpin:
Antarctic ice is at a record high and growing at the ‘steepest slope ever’

Link not working for me.
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Quoting TampaSpin:
Antarctic ice is at a record high and growing at the ‘steepest slope ever’


Antarctic sea ice is largely irrelevant insofar as impacts to global climate are concerned.
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1637. Levi32
Quoting DDR:
Very informative blog Levi,thanks again
Looks like some rain for us here in the windward islands :D
BTW can you post the precip forecasts for the Atlantic basin TIA.


Sure.

ECMWF:



Japanese:



CFSv2 (a little drier, which is interesting):

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1635. DDR
Very informative blog Levi,thanks again
Looks like some rain for us here in the windward islands :D
BTW can you post the precip forecasts for the Atlantic basin TIA.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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