An Active Atlantic Hurricane Season Still Predicted by NOAA, CSU, and TSR

By: Dr. Jeff Masters , 4:07 PM GMT on August 09, 2013

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As we stand on the cusp of the peak part of hurricane season, all of the major groups that perform long-range seasonal hurricane forecasts are still calling for an active 2013 Atlantic hurricane season. NOAA forecasts an above-normal and possibly very active Atlantic hurricane season in 2013, in their August 8 outlook. They give a 70% chance of an above-normal season, a 25% chance of an near-normal season, and 5% chance of a below-normal season. They predict a 70% chance that there will be 13 - 19 named storms, 6 - 9 hurricanes, and 3 - 5 major hurricanes, with an Accumulated Cyclone Energy (ACE) 120% - 190% of the median. If we take the midpoint of these numbers, NOAA is calling for 16 named storms, 7.5 hurricanes, 4 major hurricanes, and an ACE index 155% of normal. This is well above the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2012 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median.


Figure 1. Tropical Storm Dorian on July 25, 2013, when the storm reached peak intensity--sustained winds of 60 mph. Formation of early-season tropical storms like Chantal and Dorian in June and July in the deep tropics is usually a harbinger of an active Atlantic hurricane season. Image credit: NASA.

NOAA cites five main reasons to expect an active remainder of hurricane season:

1) Sea Surface Temperatures (SSTs) are above average in the Main Development Region (MDR) for hurricanes, from the coast of Africa to the Caribbean. As of August 9, SST were 0.4°C (0.8°F) above average.
2) Trade winds are weaker than average across the MDR, which has caused the African Monsoon to grow wetter and stronger, the amount of spin over the MDR to increase, and the amount of vertical wind shear to decrease.
3) No El Niño event is present or expected this fall.
4) There have been two early-season tropical storms in the deep tropics (Tropical Storms Chantal and Dorian), which is generally a harbinger of an above-normal season.
5) We are in an active hurricane period that began in 1995.

Colorado State predicts a much above-average hurricane season
A much above-average Atlantic hurricane season is on tap for 2013, according to the seasonal hurricane forecast issued August 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 18 named storms, 8 hurricanes, and 3 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 142. The forecast calls for an above-average chance of a major hurricane hitting the U.S., both along the East Coast (40% chance, 31% chance is average) and the Gulf Coast (40% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also above average, at 53% (42% is average.)

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: cool neutral ENSO conditions and slightly above-average tropical Atlantic sea surface temperatures. Those five years were 2008, a very active year with 16 named storms and 4 major hurricanes--Gustav, Ike, Paloma, and Omar; 2007, an active year with 15 named storms and two Category 5 storms--Dean and Felix; 1996, an above average year with 13 named storms and 6 major hurricanes--Edouard, Hortense, Fran, Bertha, Isidore, and Lili; 1966, an average year with 11 named storms and 3 major hurricanes--Inez, Alma, and Faith; and 1952, a below average year with 7 named storms and 3 major hurricanes. The average activity during these five analogue years was 12.4 named storms, 7.2 hurricanes, and 3.8 major hurricanes.

TSR predicts an above-average hurricane season: 14.8 named storms
The August 6 forecast for the 2013 Atlantic hurricane season made by British private forecasting firm Tropical Storm Risk, Inc. (TSR) calls for an active season with 14.8 named storms, 6.9 hurricanes, 3 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 121. The long-term averages for the past 63 years are 11 named storms, 6 hurricanes, 3 intense hurricanes, and an ACE of 103. TSR rates their skill level as good for these August forecasts--47% - 59% higher than a "no-skill" forecast made using climatology. TSR predicts a 58% chance that U.S. land falling activity will be above average, a 26% chance it will be near average, and a 16% chance it will be below average. They project that 4 named storms will hit the U.S., with 1.8 of these being hurricanes. The averages from the 1950-2012 climatology are 3.1 named storms and 1.4 hurricanes. They rate their skill at making these August forecasts for U.S. landfalls just 9% - 18% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.4 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR's two predictors for their statistical model are the forecast July - September trade wind speed over the Caribbean and tropical North Atlantic, and the forecast August - September 2013 sea surface temperatures in the tropical North Atlantic. Their model is calling for warmer than average SSTs and near average trade winds during these periods, and both of these factors should act to increase hurricane and tropical storm activity.


Figure 2. 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 3. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2003-2012, 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 2003 - 2012 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.

FSU predicts an above-average hurricane season: 15 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their fifth annual Atlantic hurricane season forecast on May 30, calling for a 70% probability of 12 - 17 named storms and 5 - 10 hurricanes. The mid-point forecast is for 15 named storms, 8 hurricanes, and an accumulated cyclone energy (ACE) of 135. The scientists use a numerical atmospheric model developed at COAPS to understand seasonal predictability of hurricane activity. The model is one of only a handful of numerical models in the world being used to study seasonal hurricane activity and is different from the statistical methods used by other seasonal hurricane forecasters such as Colorado State, TSR, and PSU (NOAA uses a hybrid statistical-dynamical model technique.) The FSU forecast has been one of the best ones over the past four years:

2009 prediction: 8 named storms, 4 hurricanes. Actual: 9 named storms, 3 hurricanes
2010 prediction: 17 named storms, 10 hurricanes. Actual: 19 named storms, 12 hurricanes
2011 prediction: 17 named storms, 9 hurricanes. Actual: 19 named storms, 7 hurricanes
2012 prediction: 13 named storms, 7 hurricanes. Actual: 19 named storms, 10 hurricanes

Penn State predicts an above-average hurricane season: 16 named storms
A statistical model by Penn State's Michael Mann and alumnus Michael Kozar is calling for an active Atlantic hurricane season with 16 named storms, plus or minus 4 storms. Their prediction was made using statistics of how past hurricane seasons have behaved in response to sea surface temperatures (SSTs), the El Niño/La Niña oscillation, the North Atlantic Oscillation (NAO), and other factors. The statistic model assumes that in 2013 the May 0.87°C above average temperatures in the MDR will persist throughout hurricane season, the El Niño phase will be neutral to slightly warm, and the North Atlantic Oscillation (NAO) will be near average.

The PSU team has been making Atlantic hurricane season forecasts since 2007, and these predictions have done pretty well, except for in 2012, when an expected El Niño did not materialize:

2007 prediction: 15 named storms, Actual: 15
2009 prediction: 12.5, named storms, Actual: 9
2010 prediction: 23 named storms, Actual: 19
2011 prediction: 16 named storms, Actual: 19
2012 prediction: 10.5 named storms, Actual: 19

UK Met Office predicts a slightly above-average hurricane season: 14 named storms
The UKMET office forecast for the 2013 Atlantic hurricane season, issued May 13, calls for slightly above normal activity, with 14 named storms, 9 hurricanes, and an ACE index of 130. In contrast to the statistical models relied upon by CSU, TSR, and NOAA, the UKMET model is done strictly using two dynamical global seasonal prediction systems: the Met Office GloSea5 system and ECMWF system 4. In 2012, the Met Office forecast was for 10 tropical storms and an ACE index of 90. The actual numbers were 19 named storms and an ACE index of 123.


Figure 4. Total 2013 Atlantic hurricane season activity as predicted by twelve different groups.

NOAA predicts a below-average Eastern Pacific hurricane season
NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 23, calls for a below-average season, with 11 - 16 named storms, 5 - 8 hurricanes, 1 - 4 major hurricanes, and an ACE index 60% - 105% of the median. The mid-point of these ranges gives us a forecast for 13.5 named storms, 6.5 hurricanes, and 2.5 major hurricanes, with an ACE index 82% of average. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes.

NOAA predicts a below-average Central Pacific hurricane season
NOAA's pre-season prediction for the Central Pacific hurricane season, issued on May 22, calls for a below-average season, with 1 - 3 tropical cyclones. An average season has 4 - 5 tropical cyclones, which include tropical depressions, tropical storms, and hurricanes. Hawaii is the primary land area affected by Central Pacific tropical cyclones.

West Pacific typhoon season forecast not available this year
Dr. Johnny Chan of the City University of Hong Kong usually issues a seasonal forecast of typhoon season in the Western Pacific, but did not do so in 2012 or 2013. An average typhoon season has 27 named storms and 17 typhoons. Typhoon seasons immediately following a La Niña year typically see higher levels of activity in the South China Sea, especially between months of May and July. Also, the jet stream tends to dip farther south than usual to the south of Japan, helping steer more tropical cyclones towards Japan and Korea.

Quiet in the Atlantic this weekend
There are no Atlantic threat areas to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming seven days. However, there are some indications that the atmosphere over the tropical Atlantic will become more conducive for tropical storm formation beginning around August 15. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, may move into the Atlantic then, increasing tropical storm formation odds. At the same time, the computer models are indicating an increase in moisture over the tropical Atlantic, due to a series of tropical waves expected to push off of the coast of Africa. There will also be several eastward-moving Convectively-Coupled Kelvin Waves (CCKWs) traversing the Atlantic during that period. These atmospheric disturbances have a great deal of upward-moving air, which helps strengthen the updrafts of tropical disturbances. Formation of the Eastern Pacific's Hurricane Gil and Henriette were aided by CCKWs. These same CCKWs will cross into the Atlantic and increase the odds of tropical storm formation during the period August 15 - 20.

Have a great weekend, everyone!

Jeff Masters

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The Etn model almost seems like the cyclogenesis run that the other FIMs use for start-points.

FIM seems to be out-running GFS all around.
Member Since: August 4, 2007 Posts: 0 Comments: 3282
2289. sar2401
Quoting Grothar:


The Swedes just like to brag.

Well, if you don't count Count Carl Gustaf von Rosen and his crazed Swedish pilots fighting for Biafra in the late 60's, the last war Sweden was in was 1814, when they invaded Norway, probably to protect their precious ligonberry supply, so they don't have a lot to brag about. :-)
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Convection redeveloping near Henriette's center.

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Quoting sar2401:

That cone is starting to move toward Vietnam also, which is pretty unusual. I hope it's not too bad in the Philippines, but they always seem to catch the worst of it from typhoons.




Tomorrow I feel there will be a bigger area of red.
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Quoting 2284. Siker:
The GEM and CMC both refer to the same model, just FYI.


Is that really so? I had no idea.
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2284. Siker
Quoting 2275. BaltimoreBrian:


There was another model that showed something similar I posted a couple hundred comments ago. It may have been the same model. Nope different one, I'll post it again. It's the GEM.

The GEM and CMC both refer to the same model, just FYI.
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Quoting 2275. BaltimoreBrian:


There was another model that showed something similar I posted a couple hundred comments ago. It may have been the same model. Nope different one, I'll post it again. It's the GEM.




The Navy Model also shows a system in the NW Caribbean a little slower arriving in the GOM but it is the same system developing.
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Quoting 2266. sar2401:

Oh, private helicopters. Good heavens, here we have private birds flying cocaine and Norway has ligonberry smugglers. I didn't mean to play down the role of Norway in NATO. They provide the main anti-submarine and mine hunting forces to the Northern Command of NATO. I just meant that, if an all-out ligonberry war developed, Norway's 57 aging F-16 fighters might have a difficult time against the Swedish Air Force's 130 or so JAS 39 Grippen fighters. :-)


Norway's looking better and better. No debt. Helipad in every backyard. Humanitarian attitude. And scrumptious ligonberry treats on every table.
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2281. sar2401
Quoting AussieStorm:


Well,,, I am worried as my Wife has all of her family there and we will be going there in just over 4 months. I know exactly where Utor will travel. The mountain range that is in it's path will hurt it a fair bit but will also cause flash flooding.


That cone is starting to move toward Vietnam also, which is pretty unusual. I hope it's not too bad in the Philippines, but they always seem to catch the worst of it from typhoons.
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2280. sar2401
Quoting Grothar:
To show you how serious it is. Here is a video of a Norwegian Navy ship attacking a Swedish ship. :)



Those Norwegians looked pretty deadly with that fire hose. I'm almost certain I saw one of those sailors with what looked like an itchy trigger finger on the 7.62mm machine gun though. :-)

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Eye continues to clear out.

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Quoting Civicane49:
Additional strengthening should occur for the next 12-18 hours over very warm waters before making landfall on Luzon. Restrengthening is expected once entering into the South China Sea.



Well,,, I am worried as my Wife has all of her family there and we will be going there in just over 4 months. I know exactly where Utor will travel. The mountain range that is in it's path will hurt it a fair bit but will also cause flash flooding.

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Quoting 2270. redwagon:
I wish there was commentary from the FIM developers to explain the three sets. Then there's that one extremely obscure experimental model Gro posts from time to time. Starts with Etn or something.


I asked the question about FIM yesterday. FIM7 & 8 are lower resolution, so less accurate than FIM9. FIM9 goes out 7 days, whereas 7 and 8 go out 14. Any more info than that and an expert will have to answer.
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2276. Grothar
Quoting 2266. sar2401:

Oh, private helicopters. Good heavens, here we have private birds flying cocaine and Norway has ligonberry smugglers. I didn't mean to play down the role of Norway in NATO. They provide the main anti-submarine and mine hunting forces to the Northern Command of NATO. I just meant that, if an all-out ligonberry war developed, Norway's 57 aging F-16 fighters might have a difficult time against the Swedish Air Force's 130 or so JAS 39 Grippen fighters. :-)


The Swedes just like to brag.
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Quoting 2263. TampaSpin:
The CMC MODEL has a Storm developing in the GULF OF MEXICO in about 7 days. The Navy Model also shows the same system in the NW Caribbean. Need to watch how this plays out.



There was another model that showed something similar I posted a couple hundred comments ago. It may have been the same model. Nope different one, I'll post it again. It's the GEM.

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2274. Grothar
Quoting 2270. redwagon:
I wish there was commentary from the FIM developers to explain the three sets. Then there's that one extremely obscure experimental model Gro posts from time to time. Starts with Etn or something.


I'm really not supposed to post that anymore. It is not for general publication. If I do it again, they are going to pull my library card.
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Quoting 2257. Grothar:
To show you how serious it is. Here is a video of a Norwegian Navy ship attacking a Swedish ship. :)

img src="">



They had brutal fleets back in the day.
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Quoting 2267. Birthmark:

I don't know him well enough to say (or at all). He certainly posts anti-science garbage on a fairly regular basis.


riiighhhttt....
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I wish there was commentary from the FIM developers to explain the three sets. Then there's that one extremely obscure experimental model Gro posts from time to time. Starts with Etn or something.
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2269. Gearsts
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Just a note: Hurricane Cleo, a strong cat.-2 storm made a direct hit on Miami and MiamiBeach on August 27th, 1964 with 110-MPH sustained winds and gusts to 135-MPH. Coconut palm trees were knocked down by the thousands and windows held together with masking tape were smashed to pieces. So get ready everyone. I think the show is about to begin.
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2266. sar2401
Quoting Grothar:


There is very little borders control between the two countries and many towns are half in Norway and half in Sweden. The Norwegians have become quite wealthy and many of them own their own helicopters and fly over and actually steal the tyttebaerer or Lingonberries that only grow in that particular part of Sweden. And by the way, Norway is one of the most important members of NATO and I have actually served on a number of NATO missions with a few of the bloggers on here. Also, I grew up there.

Oh, private helicopters. Good heavens, here we have private birds flying cocaine and Norway has ligonberry smugglers. I didn't mean to play down the role of Norway in NATO. They provide the main anti-submarine and mine hunting forces to the Northern Command of NATO. I just meant that, if an all-out ligonberry war developed, Norway's 57 aging F-16 fighters might have a difficult time against the Swedish Air Force's 130 or so JAS 39 Grippen fighters. :-)
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Good evening everyone

So....It's bad enough that I have to suffer through Aislin's incredible breakfast postings, now I have to go through this ridiculous sweet craving I've just developed. Thanks, Brian.

Lindy
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The CMC MODEL has a Storm developing in the GULF OF MEXICO in about 7 days. The Navy Model also shows the same system in the NW Caribbean. Need to watch how this plays out.

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So, Joe D'Aleo is "anti-science"?
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Quoting 2251. Birthmark:

Good gravy! There's more? lol

I think I'll pass until it comes out in peer-reviewed form. Blog rants that misuse science are a dime a dozen. I prefer real science, if it's all the same to you. :p

While others bring up Kool Aid I'll find some lingonberry gravy. Good Gravy indeed!

Five

Six

Ah, that's better. Another plate of meatballs with lingonberry gravy Birthmark?
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Is everything Dr. Masters puts up here "peer-reviewed"?

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Quoting 2239. unknowncomic:
BOC disturbance


more like Gulf of Honduras system
Member Since: June 13, 2009 Posts: 2 Comments: 12818
2257. Grothar
To show you how serious it is. Here is a video of a Norwegian Navy ship attacking a Swedish ship. :)

img src="">
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2255. Grothar
Quoting 2245. redwagon:
Birthmark: it's a little green melon-lookin berry but it acts like a little blue chalky round ting.


They're red.
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Quoting 2251. Birthmark:

Good gravy! There's more? lol

I think I'll pass until it comes out in peer-reviewed form. Blog rants that misuse science are a dime a dozen. I prefer real science, if it's all the same to you. :p


Here's his Bio.

Joseph D' Aleo Chief Forecaster

Joseph D'Aleo is a partner at WeatherBELL and has been with the company since its inception. Mr. D'Aleo has a deep understanding of global oscillations and historical weather patterns. He uses an advanced statistical approach in applying this knowledge to weather and climate forecasting, specifically for the agriculture industry.

Mr. D'Aleo has over 30 years experience in professional meteorology. He was the first Director of Meteorology at the The Weather Channel. Mr. D'Aleo was Chief Meteorologist at WSI Corporation where he spent 17 years and created "Dr. Dewpoint" for WSI's popular Intellicast.com web site. He is a former college professor of Meteorology at Lyndon State College. He has authored and presented a number of papers as well as published a book focused on advanced applications enabled by new technologies and how research into ENSO and other atmospheric and oceanic phenomena has made skillful seasonal forecasts possible. Mr. D'Aleo has also authored many articles and made numerous presentations on the roles cycles in the sun and oceans have played in climate change.

Mr. D'Aleo is a Certified Consultant Meteorologist and was elected a Fellow of the American Meteorological Society (AMS). He has served as a member and chairman of the AMS Committee on Weather Analysis and Forecasting, and has co-chaired national conferences for both the AMS and the National Weather Association.

Joseph D'Aleo is a graduate of the University of Wisconsin and holds a Bachelors and Masters of Science.
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Looks like the GFS wants to bring the system back. Back-n-forth this model goes where it goes no one knows.

Member Since: June 30, 2013 Posts: 12 Comments: 9083
2252. sar2401
Quoting HurricaneHunterJoe:
All this talk of military maneuvers over ligonberries is going to make me want to watch Winds of War and War and Remembrance again!

LOL. I can just see the Swedish Air Defence Command now. "Forget those planes coming from Russia, we've got more ligonberry bogies coming in from the west.". :-)
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2250. Grothar
Quoting 2216. sar2401:

Gro, the Swedes have one of the best air defense systems in Europe, and it has quite a sizable air force. The Norwegians barely have enough helicopters to fly the Crown Prince around. I imagine the Swedes could protect their ligonberries if push came to shove. :-)


There is very little borders control between the two countries and many towns are half in Norway and half in Sweden. The Norwegians have become quite wealthy and many of them own their own helicopters and fly over and actually steal the tyttebaerer or Lingonberries that only grow in that particular part of Sweden. And by the way, Norway is one of the most important members of NATO and I have actually served on a number of NATO missions with a few of the bloggers on here. Also, I grew up there.
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2249. JLPR2
Seems there is something in the BOC around hour 135.

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Quoting 2219. Birthmark:

The real story in your post is that the "G" in "AGW" stands for "Global." Showing US temperature data to refute global warming is a bit like showing a state with a budget surplus and then claiming that that refutes the US deficit.



G stands for "Goober" go read the rest of it.
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2246. sar2401
Quoting mitchelace5:


Will the current SAL we have now dissipate in a few days?

No, it takes at least a week. All it takes is the right circumstances with high winds, either from convective systems or high pressure systems, and the SAL can get cranked right up again. Like everything else this season, weak storms are going to be affected by SAL. Stronger systems are more likely to shrug it off.
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Birthmark: it's a little green melon-lookin berry but it acts like a little blue chalky round ting.
Member Since: August 4, 2007 Posts: 0 Comments: 3282
All this talk of military maneuvers over ligonberries is going to make me want to watch Winds of War and War and Remembrance again!
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Quoting 2236. JLPR2:


Right now there isnt any new SAL emerging and the last burst is moving west just to the NW of the TW.


Seems like the positive MJO may be kicking in already.
Member Since: July 27, 2013 Posts: 0 Comments: 501
2242. sar2401
Quoting mitchelace5:
I know a positive MJO causes lift and instability in the atmosphere, and increases moisture supply to TWs. But what effect does it have on wind shear? Does the positive MJO weaken it?

A positive MJO has very little influence on wind shear. It does cause ascending air, making convection more likely, but all the other pieces, like low wind shear and high vertical instability have to be in place before storms really get going.
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Quoting 2238. seer2012:


8-11-13 @ 3:00 utc. It looks like p22l has more go than p20l.
That one looks massive, could be a large system.
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Quoting 2236. JLPR2:


Right now there isnt any new SAL emerging and the last burst is moving west just to the NW of the TW.


Will the current SAL we have now dissipate in a few days?
Member Since: July 27, 2013 Posts: 0 Comments: 501

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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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