Bogus GFS Model Forecasts of Atlantic Tropical Cyclone Genesis

By: Dr. Jeff Masters , 3:49 PM GMT on June 13, 2014

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There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. However, the 00Z Friday run of the GFS model predicts that a low pressure area will develop over the Western Caribbean by Wednesday, and push northwards into the Gulf of Mexico and become a tropical storm late in the week. The GFS has been fixated on variations of this idea in all of its runs for the past five days--though the timing of when the predicted storm will form has bounced around from 5 - 11 days into the future. Should we be concerned? A 2013 study by a group of scientists led by Florida State's Daniel Halperin found that we have three models that can make decent forecasts of the genesis of new tropical cyclones in the Atlantic: the GFS, European (ECMWF), and UKMET models. The study only evaluated the model skill for forecasts out to four days in the future, and the forecast skill declined markedly for three- and four-day forecasts. In the current scenario, we are talking about forecasts made much further into the future, which are bound to be low-skill. In addition, the study found that the GFS model had a high incidence of false alarms for tropical cyclone genesis forecasts in the Caribbean (50%). The other two reliable models for predicting tropical cyclone genesis (European and UKMET) had no hint of a low pressure area developing in the Western Caribbean on Wednesday in their 00Z Friday runs. One additional model to consider: the 00Z Friday run of the NAVGEM model is supporting the GFS's idea of a low pressure area forming in the Western Caribbean by Wednesday. The predecessor to this model, the NOGAPS model, was evaluated in the Florida State study, but performed poorly in making tropical cyclone genesis forecasts. However, when two or more models make the same genesis forecast, the odds of the event actually occurring are increased considerably, the study found.


Figure 1. Friday the 13th, GFS style: The 00Z UTC Friday, June 13, 2014 forecast from the GFS model for nine days into the future shows a powerful tropical storm in the Gulf of Mexico. The purple colors indicate winds of 50 - 60 knots (57 - 69 mph.) But is it a bogus forecast? Very likely.


Figure 2. The 2004–11 GFS forecasts for tropical cyclone genesis, showing Hits (green triangle), False Alarms (red square), and Incorrect Timing (blue circle) event locations. Numbers in parentheses are the numbers of model-predicted events. The model made 46 forecasts that a tropical depression or tropical storm would form in the Caribbean (purple box) during this 8-year period. Fully 50% of these forecasts were False Alarms; 11% of the forecasts verified, but the timing was off by at least a day (IT events); and 39% of the genesis forecasts verified with the right timing. Noteworthy is the model's few False Alarms over the Gulf of Mexico: only 15% of the total. Image credit: Halperin et al., 2013, Weather and Forecasting, "An evaluation of tropical cyclone genesis forecasts from global numerical models."

We know that the GFS model gets in trouble when making predictions of heavy thunderstorm activity via a problem called "convective feedback." Basically, the model sometimes simulates that an unrealistically large area of thunderstorms will develop, destabilize the atmosphere, and cause an area of low pressure to form that will draw in more moisture and create more heavy thunderstorms. This vicious cycle can snowball out of control and generate a bogus low pressure area that can then modify the upper level winds, reduce the wind shear, and allow a tropical depression to form. This problem may be less of an issue in a new version of the GFS model scheduled to be released late this summer; NHC hurricane specialist Eric Blake tweeted on Tuesday a comparison of the old and new 1-week GFS model forecasts for the Western Caribbean made last Tuesday, showing that the upgraded GFS model was not creating nearly as strong of a low pressure system as the old GFS model. Arguing against any development in the Atlantic the remainder of June is the anticipated strengthening in the West-Central Pacific Ocean of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days. An active MJO in that part of the tropics tends to bring large-scale sinking motion to the tropical Atlantic and increased wind shear, which puts a damper on the chances of tropical storm formation in the Atlantic. The MJO is predicted to drift slowly eastwards into the Eastern Pacific by late June, which will tend to keep odds of tropical storm formation lower than average in the Atlantic into late June. All factors considered, I am inclined to give a 10% chance that the GFS model is correct in spinning up a tropical depression late in the week in the Western Caribbean.

Hurricane Cristina weakening
Hurricane Cristina is headed downhill after peaking as powerful Category 4 hurricane with 150 mph winds and a central pressure estimated at 935 mb at 11 am EDT Thursday, June 12, 2014. The double feature of Category 4 hurricanes Cristina and Amanda gives 2014 two of the five strongest hurricanes ever recorded in the Eastern Pacific so early in the year:

Top Five Strongest Early Season (May - June) Eastern Pacific Hurricanes
1973, June 6: Hurricane Ava, 160 mph, 915 mb.
2010, June 25: Hurricane Celia, 160 mph, 921 mb
2014, May 25: Hurricane Amanda, 155 mph, 932 mb
2000, June 21: Hurricane Carlotta, 155 mph, 932 mb
2014, June 12: Hurricane Cristina, 150 mph, 935 mb


Figure 3. True-color MODIS image from the Aqua satellite of Hurricane Cristina at 18 UTC Thursday, June 12, 2014. At the time, Cristina was a Category 4 storm with 145 mph winds. Image credit: NASA.

Arabian Sea's Tropical Cyclone Nanauk dissipates
Tropical Cyclone Nanauk in the Arabian Sea has been torn apart by high wind shear of 25 - 30 knots and dry air, and is no longer a threat to Oman.

Have a great weekend, everyone!

Jeff Masters

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Come on now people. So we don't have dates on a Saturday night, but we're all we got. Let's try and have a nice evening and enjoy it.
Member Since: July 17, 2009 Posts: 71 Comments: 27403
Can't remember seeing those pink colours on the SAL image for a long time.
That's one serious dust-cloud !
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From Chantilly V.A yesterday
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578. flsky
The one time I was in Beaumont, the prevailing scent in the air was oil. Not pleasant.
Quoting 507. AtHomeInTX:

meanwhile in SETX. from a marsh fire southern Jefferson County.

David Wolter ‏@DavidWolter1 16m

This is something you might see in West Texas not SE Texas. Thick #smoke over #Beaumont is turning the sky brown.


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Quoting 576. Tazmanian:

Will finely added Climate175 two my ignore list has he does not no how two give it a rest all ready he's becomein vary pest with his post saying the same stuff over and over sigh there no need for it
Taz Climate175 doesn't mean any harm.
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Will finely added Climate175 two my ignore list has he does not no how two give it a rest all ready he's becomein vary pest with his post saying the same stuff over and over sigh there no need for it
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Pretty typical June so far... Most years don't feature TC development before the 3rd decade of the month in any event. The GFS is not whacked to suggest such development based on climatology. IF we see a Nward movement of ULT currently over the CAR [aka TUTT] we certainly have the Twaves and an active monsoonal area available to foment cyclogenesis. But as long as the bulk of the energy is focused over the EPac side of that broad low [and you can see how broad it is on petrel's sailing maps] we're unlikely to see anything in the WCar.... just my 2 cents....
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Farewell, adiós, au revoir, auf wiedersehen, arrivederci, Cristina...

Member Since: July 6, 2010 Posts: 113 Comments: 33316
Cloud tops being sheared to death.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
The highest TCHP has been in the N.W caribbean.But I've noticed since 2010 that storms have A.Ran into land so couldn't take advantage or b.Conditions in the caribbean just haven't been favorable at all.2014 looks like no exception.70 knots of shear?.Good luck with your fantasy storm GFS.lol.
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Quoting 569. hydrus:

Hello Taz..That would mean boredom for many, but I am all for no landfalls...:)



Yep this may be a 0-0-0 season

The fun will be in the E PAC and W PAC
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The Caribbean right now..
Member Since: September 24, 2013 Posts: 7 Comments: 5116
Quoting 566. Tazmanian:




That is what I been saying since may the Caribbean season will likely be closed for most if not all this season so don't look for any thing two fourm there
Hello Taz..That would mean boredom for many, but I am all for no landfalls...:)
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Quoting 567. Grothar:




Yep vary El Nino looking
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Member Since: July 17, 2009 Posts: 71 Comments: 27403
Quoting 563. hydrus:

Greetings Gro...I believe this will be the norm for most of this season. If Nino arrives by the time September is here, it will be well below average...Hopefully no landfalling hurricanes.



That is what I been saying since may the Caribbean season will likely be closed for most if not all this season so don't look for any thing two fourm there
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Quoting 406. scottsvb:



192hrs is pointless. Do you know about the feedback error the GFS has had in the past month?
192 hours is a lot closer time-wise than 252 hours, which is where it was showing up before....

Quoting 443. nrtiwlnvragn:

Naw.... TAFB would not place a low in the Southern Caribbean in four days. GFS must of taken over the surface forecast software.....



Not like that low isn't pretty much always there... just usually inland over Colombia... and IIRC someone around here gave the "name" for it.... What's more interesting to me is that Twave riding that far north when currently they're still passing through Panama...

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Quoting 562. Climate175:

Ok, dang don't have to be so rude.




Oh said I was being rude your the one that seem two not understand what s some one is trying two tell you and me being rude is a understatement
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Quoting 553. Grothar:

Wind shear is very high in the Caribbean




The Shear tendency looks like it will increase


Greetings Gro...I believe this will be the norm for most of this season. If Nino arrives by the time September is here, it will be well below average...Hopefully no landfalling hurricanes.
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Quoting 560. Tazmanian:



What are you not getting this year is a El Nino year or soon will be the Caribbean Sea will likely stay closed for some tome the Caribbean Sea is looking like what you will see in a El Nino year
Ok, dang don't have to be so rude.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
Quoting 559. Climate175:

I agree, you think July will provide anything or shear will be dominant through the whole month.



I think shear will be dominant through the whole month.
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Quoting 558. Climate175:

You think july will provide more favorable conditions, it should.


What are you not getting this year is a El Nino year or soon will be the Caribbean Sea will likely stay closed for some tome the Caribbean Sea is looking like what you will see in a El Nino year
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Quoting 557. Tazmanian:

The Caribbean is closed in tell future noticed for any tropical development this is likely going two be the case this season we will likely won't see any tropical development in tell august in two September and what ever tropical development we do see will be off the E costs


The Caribbean Sea has that El Nino look two it right now
I agree, you think July will provide anything or shear will be dominant through the whole month.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
Quoting 556. stormpetrol:


I agree, but it is slowly decreasing, albeit very slowly :)
You think july will provide more favorable conditions, it should.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
The Caribbean is closed in tell future noticed for any tropical development this is likely going two be the case this season we will likely won't see any tropical development in tell august in two September and what ever tropical development we do see will be off the E costs


The Caribbean Sea has that El Nino look two it right now
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Quoting 550. HurricaneHunterJoe:


It better relax a whole lot more....LOL

I agree, but it is slowly decreasing, albeit very slowly :)
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Shear is making development very difficult and no storms will form in the next few days. We are in an unfavorable pattern right now.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
Wind shear is very high in the Caribbean




The Shear tendency looks like it will increase

Member Since: July 17, 2009 Posts: 71 Comments: 27403
552. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #13
Gale Warning
TROPICAL STORM HAGIBIS (T1407)
9:00 AM JST June 15 2014
==============================

Northern South China Sea

At 0:00 AM UTC, Tropical Storm Hagibis (996 hPa) located at 22.0N 116.6E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The cyclone is reported as moving north slowly..

Dvorak Intensity: T2.5

Gale Force Winds
=============
180 NM from the center

Forecast and Intensity
==================
24 HRS: 24.4N 116.9E - 35 knots (CAT 1/Tropical Storm) Overland Southern China
48 HRS: 27.0N 119.1E - Tropical Depression Overland Central China
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Quoting 526. Climate175:

Shear is going to relax soon.


And the check is in the mail!
Member Since: September 18, 2010 Posts: 0 Comments: 5294
Quoting 548. stormpetrol:



Shear is slowly but surely relaxing in the SW Caribbean, don't be so sure we won't see some kind of potential for development over the next 3-4 days, just sayin... stranger things have happened

It better relax a whole lot more....LOL
Member Since: September 18, 2010 Posts: 0 Comments: 5294
Quoting 531. Gearsts:



Nothing coming north through that, should it come to fruition.
Member Since: September 18, 2010 Posts: 0 Comments: 5294


Shear is slowly but surely relaxing in the SW Caribbean, don't be so sure we won't see some kind of potential for development over the next 3-4 days, just sayin... stranger things have happened
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Quoting 546. Hurricanes101:



the average is a storm every 1-2 years
Yea thank you for correcting me oops. Yes June is typically a quiet month.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
Quoting 540. Climate175:

TWC is predicting no tropical development in the next 10 days. So i think that comment i made about a tropical storm in June is starting to become unlikely with only two weeks left. The average is 1-2 storms.


the average is a storm every 1-2 years
Member Since: March 10, 2010 Posts: 1 Comments: 7874

Almost time to go Poof, looks really ragged in IR. 86.2F here today.
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Quoting 543. FOREX:



Yep. hopefully July will be a better environment for a storm or two to develop. I'm being patient like you asked me to be, but it ain't easy.
Yea we just need to get through this unfavorable period.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
543. FOREX
Quoting 542. Climate175:

Very high roaring shear.


Yep. hopefully July will be a better environment for a storm or two to develop. I'm being patient like you asked me to be, but it ain't easy.
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Quoting 541. FOREX:



Conditions aren't right for development right now. :(
Very high roaring shear.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
541. FOREX
Quoting 540. Climate175:

TWC predicting no tropical development in the next 10 days. So i think that comment i made about a tropical storm in June is starting to become unlikely with only two weeks left. The average is 1-2 storms.


Conditions aren't right for development right now. :(
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Quoting 539. FOREX:



Troll.
TWC is predicting no tropical development in the next 10 days. So i think that comment i made about a tropical storm in June is starting to become unlikely with only two weeks left. The average is 1-2 storms.
Member Since: September 24, 2013 Posts: 7 Comments: 5116
539. FOREX
Quoting 538. rutofthewild:

ARE THE MODELS FORCASTING A HUGE STORM ON JULY 23RD IN FLORIDA?


Troll, your comments the last two days have been nothing but childish. This blog contains adult language, adult content and serious subject matter. I am asking you nicely to unsubscribe from WU and find a more suitable place for yourself.
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Quoting 500. hurricanewatcher61:

A typical summer Florida pattern would favor the west coast seabreeze marching across the peninsula and running into the east coast seabreeze on the east coast or just inland. Seems like its been a few summers in which this was happening. I remember growing up on the space coast as a kid and each afternoon trying to get home from school when it was just about to storm like crazy, which was many many years ago, lol! How weather changes through the years.


That is incorrect, the typical summertime pattern for Florida is for storms to march westwards on the east coast seabreeze. The reason is because Florida is on the western side of the Bermuda High and the clockwise flow around that High Pressure typically provides Florida with a mean 1000-700mb wind out of the east or east-southeast.
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The northern storm went tornado warned.
Member Since: September 16, 2007 Posts: 0 Comments: 10100
Quoting 480. Sfloridacat5:



How can it be "Breaking News" if it's 2 days old?
Oh, I forgot. Everything is "Breaking News" when it comes to the news.


what ever happened to Just * In?
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Quoting Bluestorm5:


Look like it was actually a landsprout


I watched the feed from the start and it had a nice cloud to ground connection for a few minutes. It was still weak. Then it got hard to see the condensation funnel and all you could see was the dirt being kicked up and the funnel coming partially down to the ground.

It was pretty cool looking for a few minutes.
Member Since: September 16, 2007 Posts: 0 Comments: 10100
Quoting 532. allancalderini:

That is against 12 days from now, I take it as a grain of salt.
It shows low shear because it has a TC leaving the area.
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Quoting 528. Gearsts:

The same model developing a ghost TS
That is against 12 days from now, I take it as a grain of salt.
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Quoting 528. Gearsts:

The same model developing a ghost TS
GEM very different
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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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