Genesis of New Atlantic Tropical Cyclones: Which Model Should You Trust?

By: Dr. Jeff Masters , 3:29 PM GMT on August 29, 2013

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It's been a remarkably quiet late August in the Atlantic for hurricanes, with nary an "Invest", and precious few yellow 10% probability circles on NHC's Tropical Weather Outlook. When will this remarkable hurricane drought come to an end? The computer models we use to track hurricanes have conflicting ideas about this. Which model should we believe, and how far into the future can these models successfully predict genesis events of new tropical depressions in the Atlantic? Some answers come in a 2013 paper by a group of scientists led by Florida State's Daniel Halperin, just accepted for publication in the journal Weather and Forecasting, "An evaluation of tropical cyclone genesis forecasts from global numerical models." It turns out that two of the three most reliable models for predicting the genesis of tropical cyclones up to four days in advance are also the our top-performing models for predicting hurricane tracks: the American GFS model and the European ECMWF model. The UKMET model is also quite good at predicting tropical cyclone genesis events. The Canadian GEM model and the Navy NOGAPS model (now succeeded by the Navy NAVGEM model) do less well. When two or more models make the same genesis forecast, the odds of the event actually occurring are increased considerably. The models have improved greatly in making genesis forecasts in recent years; back in 2007, when our top three models made a 4-day genesis forecast, these verified only 17 - 28% of the time. By 2011, the hit rate had increased to 45 - 50%. However, the models still miss most genesis events. In 2011, the probability of detection of a tropical cyclone genesis event was only 8% - 23%, meaning that 77 - 92% of time, a tropical depression or tropical storm formed without the model predicting that it would form. The best model to use for looking at Atlantic tropical cyclone genesis in 2011 was the UKMET model, which combined a relatively high probability of detection rate with a low false alarm rate.


Figure 1. The probability of making a correct tropical cyclone genesis forecast for all forecast hours (06 to 96) by model, for the period 2004 - 2011. In 2011, three models--the GFS, UKMET, and European--made genesis forecasts that were correct 45 - 50% of the time. The Canadian GEM model and the Navy NOGAPS model did less well. Data taken from Halperin et al., 2013, "An evaluation of tropical cyclone genesis forecasts from global numerical models." Weather and Forecasting, doi: http://dx.doi.org/10.1175/WAF-D-13-00008.1

The paper looked at 135 Atlantic genesis events over the period 2004 - 2011, as predicted by five global computer weather forecast models: the GFS, ECMWF, UKMET, NOGAPS, and Canadian GEM. The regional GFDL and HWRF hurricane models were not considered, as they use output from the GFS model to drive them, and are not good at making genesis forecasts. The study only looked at forecasts made up to four days in advance. While there have been cases where I've seen genesis predictions made 7 - 10 days in advance come true, these are rare, and the "hit" rate of successful genesis forecasts even four days in advance is low. In the paper, a "hit" was defined as a forecast that successfully predicted genesis within 24 hours and 345 miles of the observed time and location. A "false alarm" occurred when the model predicted a storm that never developed. The other categories considered were "late genesis" events where a storm formed more than 24 hours before it was predicted to, and "early genesis", where a storm formed more than 24 hours after it was predicted to. Here are some details on each model's ability to make Atlantic tropical cyclone genesis forecasts:

European ECMWF model: The model is reluctant to predict genesis, and misses many genesis events (it had only an 8% probability of detection in 2011.) However, when it does predict genesis, it usually happens, with only a 16% false alarm percentage in 2011. The European model exhibits preferred regions of genesis, with over 60% of its genesis forecasts occurring in the MDR: 10-20°N, 60-20°W. Although the ECMWF misses many tropical cyclone genesis events in the Gulf of Mexico (as do the other models), when it does forecast genesis there, it almost always occurs. The model was highly prone to making late genesis forecasts.

American GFS model: The GFS model improved substantially in its genesis forecasts beginning in 2010, most likely due to a major model upgrade in 2010. The GFS is more aggressive at predicting genesis than the European model, and is less likely to miss a genesis event (22% probability of detection in 2011.) However, the incidence of false alarms was 32% in 2011, double what the European model had. Like the European model, the GFS exhibits preferred regions of genesis, with nearly 60% of its genesis forecasts occurring in the MDR: 10-20°N, 60-20°W.

UKMET model: The UKMET is more aggressive at predicting genesis than the European model, and is less likely to miss a genesis event (20% probability of detection in 2011.) The incidence of false alarms was 18% in 2011, similar to what the European model had. Like the European and GFS models, the UKMET exhibits preferred regions of genesis, with more than 67% of its genesis forecasts occurring in the MDR: 10-20°N, 60-20°W. The model was prone to making late genesis forecasts.

Canadian GEM model: The Canadian model was the least likely to miss a formation event, with a 23% probability of detection in 2011. False alarms have been a major issue, though, and the Canadian model generated the second highest number of bogus genesis events of any of the five models evaluated (42% of all its genesis forecasts in 2011 were false alarms.) The Canadian model does not seem to have a preferred region of genesis—all types of genesis events occur across the entire basin. The model performs best over the main development region (MDR; 10-20°N, 60-20°W), Caribbean Sea, and Gulf of Mexico (GOM).

Navy NOGAPS model: This model was retired in 2012, but we may be able to assume that its successor, the NAVGEM model, will have some of the same characteristics. False Alarms have been a major issue, and the NOGAPS model generated the highest number of bogus genesis events of any of the five models evaluated (60% of all its genesis forecasts in 2011 were false alarms.) The model also had a low probability of detection, just 9%. NOGAPS model does not seem to have a preferred region of genesis—all types of genesis events occur across the entire basin. Despite the high levels of hurricane activity in 2004 and 2005, the NOGAPS model failed to successfully forecast any genesis events those years.

Sources of Model Data
You can view 7-day ECMWF and 16-day GFS forecasts on wunderground's wundermap with the model layer turned on.
Longer ten-day ECMWF forecasts are available from the ECMWF web site.
FSU's experimental hurricane forecast page (CMC, ECMWF, GFDL, GFS, HWRF, and NAVGEM models)
NOAA's HFIP model comparison page (GFS, ECMWF, FIM, FIM9, UKMET, and CMC models.)
Experimental HFIP models

Very Quiet in the Atlantic
A tropical wave that came off the coast of Africa on Sunday is midway between Africa and the Lesser Antilles Islands. This disturbance is moving westward at 15 mph, has a modest amount of spin, but only a limited amount of heavy thunderstorm activity. In their 8 am EDT Thursday Tropical Weather Outlook, NHC left the 5-day odds of formation of this disturbance at 20%, but increased the 2-day odds of formation to 10%. Wind shear is a moderate 10 - 20 knots over the system, but there is an area of dry air and dust from the Saharan Air Layer (SAL) to the north and west that is interfering with development. With the exception of the NAVGEM model, there is little support from the models for developing the disturbance during the next five days. The wave could spread heavy rains and gusty winds to the Lesser Antilles Islands on Sunday and Monday.

A tropical wave expected to emerge from the coast of Africa on Friday and track over the Cape Verde Islands is also showing little support for development from the models. This wave is expected to take a northwesterly track, and would likely not be able to make the long trek across the Atlantic to threaten North America or the Caribbean Islands. In their 8 am EDT Thursday Tropical Weather Outlook, NHC put the 5-day odds of development at 20%.

Wunderblogger Lee Grenci has an excellent new post, "Atlantic Hurricane Season: The Saharan Air Layer and Vertical Wind Shear".

California's Rim Fire Now 6th Largest in State History, and is 30% Controlled
California's massive Rim Fire in Yosemite National Park continues to grow, but an army of over 4,000 firefighters are making headway against the blaze, and had attained 30% containment of the fire as of 9:20 am EDT on Thursday. According to Inciweb, fire has burned over 192,700 acres. This moves the fire into 6th place for largest fire in state history, according to statistics tabulated by wunderground's weather historian, Christopher C. Burt in his latest post, "The Worst Wild Fires in U.S. History". The Rim Fire will have difficultly surpassing California's largest fire on record--the Cedar Fire in San Diego County of October 2003. That fire burned 273,246 acres (430 square miles). California has had its driest year-to-date period, so it is no surprise that the state is experiencing an unusually large fire this summer.


Video 1. Time-lapse photography shows various perspectives of the 2013 Rim Fire, as viewed from Yosemite National Park. The first part of this video is from the Crane Flat Helibase. The fire is currently burning in wilderness and is not immediately threatening visitors or employees. The second half of the video is from Glacier Point, showing Yosemite Valley, and how little the smoke from the fire has impacted the Valley.

Jeff Masters

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Member Since: Posts: Comments:
Quoting 70. IKE:
12Z GFS.....snooze......snore.....season is a bust?
it will be a bust if we don't get something by the 20th of sept

by then we will only have close to home to watch
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Quoting 72. CaneHunter031472:


Oh. Yeah I was wondering about that as well. Maybe later I guess. But we're doing a great job remembering anyway.


Absolutely! I was scared hundreds of miles away. I remember Charley very well, saw it all firsthand (the next day). I can only imagine a city of 600,000+ being 80% flooded and a 28ft surge along the Gulf Coast. Remember, it's the power of water that usually has the worst outcomes.
Member Since: January 1, 2008 Posts: 0 Comments: 3839
its look like a tropical storm to me
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Quoting 56. Grothar:


So does that mean you are going to apologize tomorrow, for the things you said today? :)


It's all I do it seems
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Quoting 71. Patrap:
Don't worry over spilled milk Scott.

This day here in NOLA is one of reflection, peace, and remembrance,

I'm purty thick skinned to a degree and I was dealing with some personal feelings on yesterday as this time of year always brings feelings passion, fear, sorrow and personal grief.

I am Human and dont always deal with it in a manner becoming someone my age.

So we forge ahead, never forgetting the past, learning from it, and moving on to serve others the best we know how.


You are not alone Pat. We might not always agree, but Hurricanes don't take sides and hurt everyone equally so I share your feelings and reflect with you about that terrble day in history. I also thank God because my family and I made it. We lost everything, but we came out alive therefore we lost nothing.
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Quoting 69. HurricaneHunterJoe:
Thank you Dr Masters for those statistics on the models.

Good Morning Class!

It's a beautiful muggy day on America's Left Coast.

Anything going on in the Tropical Atlantic?


Nope not a thing as of right now and I for one like it that way :o) Just Saying


Taco :o)
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Does the UKMET produce maps like the GFS/CMC/EURO/etc? Just curious.
Member Since: January 1, 2008 Posts: 0 Comments: 3839
Quoting 37. StormTrackerScott:
Dear Blog, I just wanted to say sorry for all of the political bashing and GW post yesterday. I got out of hand and made some mad on here and that wasn't my intention but when you own 2 businesses and you see how the small business guy gets screwed then you will understand. With that said me being in a terrible mood has no place on this blog. Again sorry folks and especially sorry to Patrap as I feel I might have disrespected him yesterday.






He can take it. He's a sport.
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Great post Patrap!
Member Since: August 19, 2006 Posts: 13 Comments: 17405
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Quoting 61. CaneHunter031472:


Pat made a few comments earlier. I have tons of pictures as well. What can i say. I just hope it never happens again. Biloxi looked like an atom bomb went off right in the middle of it. The aftermath, that's what was sad. When it hits you that two houses down your own those black markings spray painted on your neighbor's house mean that your neighbor was killed and burried under that rubble. I just hope I never go thorugh that again. By the way Red cross, Salvation Army, National Guard. I remember and thank you for keeping us fed and clothed during that awful time. God bless you all.


Sorry I hit the wrong button. I meant to +
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Quoting 67. GatorWX:


I meant from the DR. I posted too, but with all the loooong range models floating around and the general lack of fruition, I guess it's suitable.


Oh. Yeah I was wondering about that as well. Maybe later I guess. But we're doing a great job remembering anyway.
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Don't worry over spilled milk Scott.

This day here in NOLA is one of reflection, peace, and remembrance,

I'm purty thick skinned to a degree and I was dealing with some personal feelings yesterday as this time of year always brings strong feelings of passion, fear, sorrow and personal grief.

I am Human and dont always deal with it in a manner becoming someone my age.

So we forge ahead, never forgetting the past, learning from it, and moving on to serve others the best we know how.
Member Since: Posts: Comments:
70. IKE
12Z GFS.....snooze......snore.....season is a bust?
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Thank you Dr Masters for those statistics on the models.

Good Morning Class!

It's a beautiful muggy day on America's Left Coast.

Anything going on in the Tropical Atlantic?
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Quoting 61. CaneHunter031472:


Pat made a few comments earlier. I have tons of pictures as well. What can i say. I just hope it never happens again. Biloxi looked like an atom bomb went off right in the middle of it. The aftermath, that's what was sad. When it hits you that two houses down your own those black markings spray painted on your neighbor's house mean that your neighbor was killed and burried under that rubble. I just hope I never go thorugh that again. By the way Red cross, Salvation Army, National Guard. I remember and thank you for keeping us fed and clothed during that awful time. God bless you all.


I meant from the DR. I posted too, but with all the loooong range models floating around and the general lack of fruition, I guess it's suitable.
Member Since: January 1, 2008 Posts: 0 Comments: 3839
Thanks Doc, I found it suprising that predicting the genesis in all models, is a lower % than I expected.
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.
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Quoting 56. Grothar:


So does that mean you are going to apologize tomorrow, for the things you said today? :)
that will be Saturdays activity

lol

good day to ya gro I take crazy pills they sometimes help
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La cuenca:





Mother mother ocean, I've heard you call.....
Member Since: January 1, 2008 Posts: 0 Comments: 3839
As for the lack of tropical activity this season, it MUST be "Global Warming".
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Quoting 54. GatorWX:
Nothing about Katrina, hmmm. That's strange.


Pat made a few comments earlier. I have tons of pictures as well. What can i say. I just hope it never happens again. Biloxi looked like an atom bomb went off right in the middle of it. The aftermath, that's what was sad. When it hits you that two houses down your own those black markings spray painted on your neighbor's house mean that your neighbor was killed and burried under that rubble. I just hope I never go thorugh that again. By the way Red cross, Salvation Army, National Guard. I remember and thank you for keeping us fed and clothed during that awful time. God bless you all.
Member Since: Posts: Comments:
Member Since: January 1, 2008 Posts: 0 Comments: 3839
Quoting 37. StormTrackerScott:
Dear Blog, I just wanted to say sorry for all of the political bashing and GW post yesterday. I got out of hand and made some mad on here and that wasn't my intention but when you own 2 businesses and you see how the small business guy gets screwed then you will understand. With that said me being in a terrible mood has no place on this blog. Again sorry folks and especially sorry to Patrap as I feel I might have disrespected him yesterday.



Scott, thanks. You know I get what it is you're saying. Empathy for other's situations is important, so hopefully you'll understand why some of us get worked up as well when people claim that the fields we have gone into (research and science based work) get trashed by claims of corruption due to government grants or straight out committing scientific fraud.

So let's move forward.
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144 hours
Member Since: August 19, 2006 Posts: 13 Comments: 17405
Quoting 46. StormTrackerScott:


Oh boy, you can't say anything without someone taking your post out of context.


yeah but at least ya said something that's all that's important

taz you took what comment 31 said too serious it was a joke lighten up will ya

and if you reporting just do it don't say when yer doing it that may be better for everyone all the way around
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Quoting 37. StormTrackerScott:
Dear Blog, I just wanted to say sorry for all of the political bashing and GW post yesterday. I got out of hand and made some mad on here and that wasn't my intention but when you own 2 businesses and you see how the small business guy gets screwed then you will understand. With that said me being in a terrible mood has no place on this blog. Again sorry folks and especially sorry to Patrap as I feel I might have disrespected him yesterday.



So does that mean you are going to apologize tomorrow, for the things you said today? :)
Member Since: July 17, 2009 Posts: 72 Comments: 28794
the blog sometimes..I declare..

It is always so simple, and so complicating, to accept an apology.
Member Since: August 19, 2006 Posts: 13 Comments: 17405
Nothing about Katrina, hmmm. That's strange.
Member Since: January 1, 2008 Posts: 0 Comments: 3839
Quoting 30. yoboi:
I wonder if they are really trying to change the hurricane names or is the a joke????




Link


yoboi, I think it's a serious effort on their part. I don't think it will ever happen. And in my personal opinion, it should not happen. We need less politics involved here, not more.
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Quoting 37. StormTrackerScott:
Dear Blog, I just wanted to say sorry for all of the political bashing and GW post yesterday. I got out of hand and made some mad on here and that wasn't my intention but when you own 2 businesses and you see how the small business guy gets screwed then you will understand. With that said me being in a terrible mood has no place on this blog. Again sorry folks and especially sorry to Patrap as I feel I might have disrespected him yesterday.


I think you'd be surprised. I'd be most people actively promoting climate science and pushing for political action to reduce its effects have empathy for your situation, and someone like you is right in line with who they are trying to help.

But just remember, policy that affects small business is different than science. Science is true regardless of whether or not someone likes the policy outcome based upon the science.
Member Since: September 28, 2002 Posts: 5 Comments: 3477
Quoting 33. MagicSpork:
This is also the 30th anniversary of Hurricane Alicia. I was on my grandmother's porch watching it all happen. This is about what my parents' back yard looked like:

I remember John Hope reporting on Alicia. She packed some punch fer a little gal..:)
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Quoting 40. Tazmanian:




dont start it plzs i have not dont a dran thing this AM post 31 was the one that started it and i this haveing too replay



Taz, calm down buddy, was only joshing you.Smile any day above ground is a good day!
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48. IKE
Hour 123....not much....not surprising.....


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Quoting yoboi:
I wonder if they are really trying to change the hurricane names or is the a joke????




Link


LOL that is SOOO funny! Great find!
Is there anything in the Atlantic or just that dry dry wave?
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Quoting 41. CarolinaHurricanes87:


Telling us to forgive you because, basically, you're a "business owner" and we're something along the lines of peasants, not capable of understanding the issues a business man like yourself deals with, isn't really the best way to go about it. If you think you get screwed by the system, how do you think people less fortunate than you feel?

Just my two cents.


Oh boy, you can't say anything without someone taking your post out of context.
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This is the Very Quiet in the Atlantic Year for Hurricanes!
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good read doc thanks for the lunch time update
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Daily accumulated precipitation in Taiwan due to TS Kong-Rey

Source

Twitter news by James Reynolds ‏@typhoonfury 5h
Top rainfall total out of Taiwan since midnight yesterday is 764mm at Shanshang in Tainan - http://cwb.gov.tw/V7e/observe/rainfall/hb_100.htm … #Kong-rey

764mm = 30 inches! Yosemite National Park sure would love to get at least some portion of it ...
Member Since: October 25, 2008 Posts: 73 Comments: 8220
Please everyone, can we focus on hurricanes and forecasts and take the AGW to a more appropiate forum? I'm sure there are plenty of blogs here to discuss it. We will never agree on AWG. not GW or climate change, but in the fact humans are causing it we'll never agree on that.
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Quoting 37. StormTrackerScott:
Dear Blog, I just wanted to say sorry for all of the political bashing and GW post yesterday. I got out of hand and made some mad on here and that wasn't my intention but when you own 2 businesses and you see how the small business guy gets screwed then you will understand. With that said me being in a terrible mood has no place on this blog. Again sorry folks and especially sorry to Patrap as I feel I might have disrespected him yesterday.



Telling us to forgive you because, basically, you're a "business owner" and we're something along the lines of peasants, not capable of understanding the issues a business man like yourself deals with, isn't really the best way to go about it. If you think you get screwed by the system, how do you think people less fortunate than you feel?

Just my two cents.

Edit to add: I feel kind of bad about this post because you clearly had the good intention of apologizing. Just don't think you realize how condescending you came off as in your apology...
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Quoting 35. BaltOCane:


and yet, you want everyone banned whenever they do something that isn't to your liking...

Officer Taz at it again.




dont start it plzs i have not dont a dran thing this AM post 31 was the one that started it and i this haveing too replay
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I always trust my yearly models.

2013 Atlantic Hurricane Season Update #2

The ending is focused on climate change, and the potential danger of ignoring the clear warning signs.

With 7 billion souls on board this ship, most of which are living hand to mouth, it's risky business what we're doing.

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Quoting 8. Ameister12:
Thanks Dr. Masters.

8 years ago today:
I can look at that and feel what I felt that Sunday morning when I got up to check the situation. Told my wife it wasn't too late to boogie but she felt ok riding it out. I said "ok, but you know we might die, right"? I felt I had to point it out in case she didn't get it. So lucky we were.
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Dear Blog, I just wanted to say sorry for all of the political bashing and GW post yesterday. I got out of hand and made some mad on here and that wasn't my intention but when you own 2 businesses and you see how the small business guy gets screwed then you will understand. With that said me being in a terrible mood has no place on this blog. Again sorry folks and especially sorry to Patrap as I feel I might have disrespected him yesterday.

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Lol Michael Lowry "Unfortunately I MEAN FORTUNATELY the Atlantic looks quiet at the moment."
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Quoting 34. Tazmanian:



reported i will do what evere i want unless the mods say other wises


and yet, you want everyone banned whenever they do something that isn't to your liking...

Officer Taz at it again.
Member Since: Posts: Comments:

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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