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Bogus GFS Model Forecasts of Atlantic Tropical Cyclone Genesis

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

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

Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Look at the GFS...

Link

I say IF we get a run like that most of the hurricane season, I WILL BE HAPPY. Looks like the waves may tend to move NW across much of the Lesser Antilles like they did in 2011, which was a rainy year in the N Leewards. In 2013 however, they loved to stay south... a nightmare for me.
1003. ricderr
Quoting 994. ScottLincoln:

Pretty decent amount of flooding over the last 36 hours or so in SW Minnesota, SE South Dakota, and NW Iowa. The last big round of storms produced 3-6" of rainfall in some areas, flooding fields, overflowing some small lakes, and causing a few new records on area streams. I-90 was even closed due to high water for a while.


The new river records are mostly confined to the Rock River which flows from SW MInnesota into NE Iowa, then eventually into the Missouri River. A busy time for the WFO Sioux Falls and Missouri Basin RFC folks, for sure.

KELO-tv has a big collection of photos from the event. One of the first photos shows the failure of a small dam in a Minnesota state park.

Unfortunately, more rainfall is on the way over the next several days.


1) Warmer world = more rainfall = more flooding.

2) Warmer world = altered rainfall distribution patterns and greater rainfall intensity. Greater rainfall intensity = greater runoff into watercourses without soil irrigation = more drought. Higher evaporation rates intensify drought.

Changing polar jet stream activity makes both 1) and 2) more prolonged, intensifying floods and droughts still further.

Conclusion. We are well and truly ******
00z ECMWF is thinking we'll get TS Douglas out of the NHC's circle in a few days.
Quoting 973. SLU:



0.8mm of rain for the first 15 days of June at our international airport .... The average for June is between 125 mm - 150mm


We didn't get much rain too :/ 10 mm would be generous...

I saw some pics of St Lucia on Facebook, it's so dry :(
Quoting 1004. yonzabam:



1) Warmer world = more rainfall = more flooding.

2) Warmer world = altered rainfall distribution patterns and greater rainfall intensity. Greater rainfall intensity = greater runoff into watercourses without soil irrigation = more drought. Higher evaporation rates intensify drought.

Changing polar jet stream activity makes both 1) and 2) more prolonged, intensifying floods and droughts still further.

Conclusion. We are well and truly ******

Already documented, at least for the Midwest:

http://www.rockymountainclimate.org/reports_3.htm

http://www.sciencedaily.com/releases/2013/03/1303 13182312.htm
1009. ricderr
you can find the weekly ENSO upadte here....as tropic pointed out......the 3.4 value has dropped to 0.4,,,,,,at this rate it will take at least until mid to late august before we will see a three month means for the 3.4 region at el nino levels...you can go to earthwinds here and see that the west blowing winds have died down once again and may be making a shift towards the west finally....but we saw the same exact thing this time last week and then they picked up strong once again blowing to the west later in the week.......
1010. FOREX
I hate when I'm the only Wishcaster on the blog right now.


The CATL wave should bring us welcomed rain... if the GFS is right.
1012. Patrap
We are talking about something, that affect's the entire Earth, problem's, that transcend Nation's.
Isaac Asimov

Tony Abbott lauds coal during Texas speech, says climate change shouldn’t limit use of fossil fuels

June 14, 2014

TONY Abbott has visited the energy capital of the USA to insist he does not want the battle against climate change to limit the use of any type of fuel.
Promoting his plan to scrap the carbon tax in front of an audience of energy executives in Houston, Texas, Mr Abbott said he wanted Australia to become a centre of cheap energy.
While he said Australia should look towards new energy sources, he said we should also focus on cheap and reliable energy.
“Affordable, reliable energy fuels enterprise and drives employment,” Mr Abbott said.
“It is the engine of economic development and wealth creation.”
“Australia should be an affordable energy superpower, using nature’s gifts to the benefit of our own people and the wider world.”

Abbott talks security with US

The PM defended Australia’s existing energy exports and said we have a long term future exporting black coal, LNG and uranium.
“It is prudent to do what we reasonably can to reduce carbon emissions,” he said.
“But we don’t believe in ostracising any particular fuel and we don’t believe in harming “economic growth.”
“For many decades at least coal will continue to fuel human progress as an affordable, dependable energy source for wealthy and developing countries alike.”

The speech came after Mr Abbott met US President Barack Obama and agreed to disagree on the best way to tackle climate change.
Mr Obama wants a global carbon price while Mr Abbott wants to replace Australia’s carbon tax with a $2.5 billion “direct action” plan that includes paying companies to cut emissions.
Declaring he wanted closer ties with the largest city in Texas, Mr Abbott announced he would appoint an Australian consulate-general to the boom town.
After receiving a gift of Stetson cowboy hat, Mr Abbott let the audience know he felt like an honorary Texan, saying “yee ha”.

Houston is home to more than 100 Australian companies, including BHP Billiton, Woodside, Santos, WorleyParsons, Macquarie Group, Pryme Oil and Gas, Lend Lease and Brambles.
Houston is the largest city in Texas, which has an economy the size of the 13th largest country in the world.
Mr Abbott said the consulate-general Houston would allow Australia to “maximise the two-way trade and investment opportunities of the US energy revolution”.

Mr Abbott will today meet with a business delegations before visiting the Texas Medical Centre — the largest of its kind in the world — to promote his plan for a $20 billion Medical Research Future Fund.
1013. ricderr
00z ECMWF is thinking we'll get TS Douglas out of the NHC's circle in a few days.


hell..if the gfs long range model was to be correct...florida would be looking at their 4th storm of the season bearing down on them


what i have been trying to find out this past weekend without success.....seeing that even though we have el nino like conditions...the tradewinds aren't blowing as they should...and as such....is the atlantic basin being affected by ENSO conditions...or just typical conditions to be expected this time of year?
Quoting 1010. FOREX:

I hate when I'm the only Wishcaster on the blog right now.


Lol no you're not the only wish caster. I'm here too :-) And I want heavy rains, and tropical storms near my island!!
If I could hear the thunder everyday I would be so happy! But all I'm having right now is boring dusts in the sky, making it very ugly and dry :-(
Christina & Hagabis lost their floaters..

Cute little swirl off the east coast of FL this morning on radar.



This is the weakness that should draw up tropical wave into an inverted trough..



Kind of weakens & opens over FL again, then troughs across the Caribbean on wednesday..



The end solution has been changing with each run the last three days, today's is a sheared blob wanders the GOM, then comes across NFL. I'm still leaning toward sheared blob. The tropics overall globally has really pulsed down in the last day.
1016. ricderr
now let us look at some tropical models 5 days out

CMC says all is calm....


1017. ricderr
ecmwf says i see douglas...but no love for the tropic watching boys

Dusty, again and again.

1019. Patrap
Hey ric, look who got a media weather slot in nola.

: P

; )

Rut-roh

1020. ricderr
gfs....says...just a glimmer of hope that aint gonna happen...but you can look close and maybe wishcast a bit

1021. FOREX
Quoting 1014. CaribBoy:



Lol no you're not the only wish caster. I'm here too :-) And I want heavy rains, and tropical storms near my island!!
If I could hear the thunder everyday I would be so happy! But all I'm having right now is boring dusts in the sky, making it very ugly and dry :-(


lmao. We need a Wishcaster private chat rom.
Quoting 1021. FOREX:



lmao. We need a Wishcaster private chat rom.

You could always start your own blog... it could be on any weather-related topic you want it to be.

--> http://www.wunderground.com/blog/FOREX/addentry.h tml
1023. ricderr

Hey ric, look who got a media weather slot in nola.

: P

; )

Rut-roh


is that really you?.........freaking congrats.....


1024. ricderr
now let me read it and critique ya........LOL
1025. Patrap
Thanx ric,

I met with noladefender.com developer and bada-Boom.

A former wu blogger kitchengypsy recommended me for the slot.

So it worked out.

I'll be adding more local flavor and content as we slide into the Summer Pattern proper. The Summer Solstice arrives next week.
1026. ricderr

Thanx ric,

I met with noladefender.com developer and bada-Boom.

A former wu blogger kitchengypsy recommended me for the slot.

So it worked out.



I'll be adding more local flavor and content as we slide into the Summer Pattern proper. The Summer Solstice arrives next week.



too cool.....very professional....however you didn't hear that from me :-)
JeffMasters has created a new entry.
1028. JRRP
Quoting Patrap:
Hey ric, look who got a media weather slot in nola.

: P

; )

Rut-roh

Congrats, Pat!
Quoting 1025. Patrap:

Thanx ric,

I met with noladefender.com developer and bada-Boom.

A former wu blogger kitchengypsy recommended me for the slot.

So it worked out.

I'll be adding more local flavor and content as we slide into the Summer Pattern proper. The Summer Solstice arrives next week.
Congrats, Pat -- and spread the word!
1031. LargoFl
GFS might not have been so bogus afterall,looks like the Euro is slowly coming on board with something near south florida next week...