94L a threat to the Lesser Antilles; Gordon a hurricane; Helene hits Mexico

By: Dr. Jeff Masters , 3:24 PM GMT on August 18, 2012

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A large tropical wave that emerged from the coast of Africa Thursday night (Invest 94L) is located a few hundred miles southwest of the Cape Verde Islands off the coast of Africa, and is headed west at 15 - 20 mph. This storm is a threat to develop into a tropical storm that will affect the Lesser Antilles Islands as early as Wednesday. The storm is under moderate wind shear of 10 - 20 knots, and is over waters of 27.5°C. A large area of dry air lies just to the north of 94L, as seen on the latest Saharan Air Layer (SAL) analysis. This morning's 8:15 am EDT ASCAT pass caught the east side of 94L, and showed a partial surface circulation. Satellite images show just a modest amount of heavy thunderstorm activity, and I expect the earliest that 94L could develop into a tropical depression would be Sunday.


Figure 1. Morning satellite image of Invest 94L.

Forecast for 94L
The latest 8 am EDT run of the SHIPS model predicts that wind shear will be low, 5 - 10 knots, and ocean temperatures will gradually warm from 27.5°C to 28.5°C over the next four days, as 94L tracks westwards towards the Lesser Antilles. As is typical with storms making the crossing from Africa to the Antilles, dry air to the north will likely interfere with development. However, with shear expected to be low, dry air may be less of an issue for 94L than it was for Ernesto or TD 7. The storm should maintain a nearly due west track through Monday night, to a point near 50°W, about 700 miles east of the Lesser Antilles. At that point, a trough of low pressure passing to the north of 94L may be able to pull the storm more to the northwest, as suggested by the latest 06Z (2 am EDT) run of the NOGAPS model, and by three members of the GFS model ensemble forecast (Figure 2.) However, the models have been trending more towards a solution where this trough is not strong enough to influence 94L's path. This scenario will be more likely if 94L takes its time to develop, since a weaker storm will be smaller and shallower, and less likely to respond to the trough passing to the north. Our two best performing models, the GFS and ECMFW, both take 94L through the Lesser Antilles. The ECMWF, which predicts that 94L will stay weak and not develop, is faster, bringing the storm through the Lesser Antilles on Wednesday. The GFS model is slower, bringing 94L to the Lesser Antilles on Thursday as a hurricane. The models have shown poor run-to-run consistency in both the timing and the track of 94L, so it is difficult to assess which land areas might be most at risk, and when. A database of historical probabilities of storms in the same location as 94L maintained by Dr. Bob Hart of Florida State University reveals that historically, 45% of storms in this location have eventually hit land, with Canada (13% chance) and North Carolina (15% chance) the most likely targets. In their 8 am EDT Tropical Weather Outlook, NHC gave 94L a 40% chance of developing into a tropical depression by Monday morning.


Figure 2. The 00Z (8 pm EDT) run of the GFS model from August 17, 2012, was done 20 different times at low resolution using slightly different initial conditions to generate an ensemble of forecasts (pink lines.) The high-resolution operational GFS forecast is shown in white.

Gordon becomes a hurricane
Hurricane warnings are flying for the central and eastern Azores Islands as Hurricane Gordon heads eastwards at 18 mph. Gordon became the third hurricane of the 2012 Atlantic hurricane season at 5 am Saturday morning, and is sporting an impressive-looking eye on visible satellite loops. Gordon should be able to maintain hurricane status until Sunday, when wind shear will rise steeply to 30 - 40 knots, and ocean temperatures will drop to 25°C. The combined effects of high wind shear, dry air, and cooler waters will likely act to weaken Gordon to a strong tropical storm by the time it arrives in the Azores Islands Sunday night, but the storm will be strong enough to bring damaging winds and heavy rain to the Azores Islands. Gordon is not a threat to any other land areas, and the extratropical remnants of Gordon will not bring any strong winds or significant rain to Europe. The last time the Azores were affected by a tropical storm was in 2009, when Tropical Storm Grace brought 65 mph winds on October 4. No significant damage was reported. Ironically, the last hurricane to affect the Azores was the 2006 version of Hurricane Gordon, which caused minor damage in the Azores, consisting of mostly fallen trees and power outages. However, after Gordon became an extratropical low, four injuries due to falling debris from high wind were reported in Spain, and Gordon brought high winds and rain that affected practice rounds at the Ryder Cup golf tournament in Ireland. About 126,000 homes were without power after the storm in Northern Ireland and one injury was reported.


Figure 3. Morning satellite image of Hurricane Gordon.

Helene makes landfall in Mexico
Tropical Storm Helene made landfall near 10 am EDT as a tropical storm near Tampico, Mexico, with 40 mph winds. Helene's formation on August 17 ties 2012 with 1933 for the 2nd earliest appearance of the Atlantic's eighth tropical storm. Helene's rains should remain south of Texas, but moisture from Helene may feed into a stalled frontal system over the northern Gulf of Mexico and bring heavy rains to the northern Gulf Coast early next week.

I'll have a new post this afternoon, giving a quick global weather summary for July, the 4th hottest July in Earth's history.

Jeff Masters

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Quoting Skyepony:


Here's Debbie's final model average error to compare. Just as bad..

And I don't think there is any reason to assume that any of the models is correct as yet, for 94L. Track, intensity, timing will all be better analysed if it becomes a TS soon.
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Quoting icmoore:


Didn't do well with Debby either LOL everyone with the exception of a few kept saying she will be making that left turn soon it's a Texas storm.


Those missed turns on storms can get ugly...if people aren't prepared for them. TO prepare for them means gearing up for masses of people to move, etc. - not pretty in modern PC police minds if you make a mistake as it costs $$$.
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Quoting CybrTeddy:
There is no reason at all for this not to develop that I can think of. It's already developing as we speak. 24 hours ago, this model was showing a major hurricane. Very poor consistency.


Models always do poorly with invests since they have so little data to work with. You'll see them all over the place until 94L at least becomes a TD, and I wouldn't put a lot of faith in them until it becomes a TS. It gets a little tiring to have every update causing some here to predict a storm that crushes the Islands...Florida...the east coast...take your pick.
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such a fat moisture field ahead of 94L.. it's going to have a juicy journey :)
hope it doesn't become too dangerous!
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This is one of those times where you sit down and actually look at the patterns yourself and determine your own opinions instead of looking 100% at the models. They're there for guidance and forecasting aid, but the human brain will always be the best model. It's mid-August with favorable conditions even though some dry air is to the north. The SHIPS, ICVN, and LGEM intensity models are all showing this becoming a potent system by 120 hours. Every year usually has a major Cape Verde hurricane, even in 1997 and 2009 there was some. It's already at 50% as well with rotation becoming increasingly evident on the satellite loop. There is very little reason when all things considered that 94L shouldn't develop.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
Quoting Skyepony:


Here's Debbie's final model average error to compare. Just as bad..


LOL CMC out preformed the official forecast!
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Quoting Grothar:


Stay off those mushrooms.

Can I use the Hookah, then?
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Quoting CybrTeddy:
Don't get me wrong, the ECMWF is an excellent model with track as it nailed Ernesto's track and every storm this year except Debby, but has issues with intensity, it either way overdone (as it was predicting Fiona in 2010 to hit Florida as a Category 5 for a few days) or way underdone (Ernesto being an open wave at landfall where it was really a Category 1 to name a more recent example.) This is just from my unprofessional standpoint at least. It does a lot better with intensity with fully developed tropical cyclones.

I remember that! lol
Earl ripped her to shreds.
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Quoting Stormchaser2007:
The trend is your friend


I'll go with that !
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The central atlantic has proven to be a storm destroyer this season- so far- but conditions will be favorable once it enters the western atlantic .
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Quoting Grothar:


You're a fast learner. :)


Thanks. It helps to study blobularity as a hobby.
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POSS T.C.F.A.
XXL/INV/94/XX
MARK
12.86N/31.33W
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Quoting pottery:

Curiouser and Curiouser......


Stay off those mushrooms.
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The trend is your friend

Member Since: June 9, 2007 Posts: 4 Comments: 15950
513. Skyepony (Mod)
Quoting icmoore:


Didn't do well with Debby either LOL everyone with the exception of a few kept saying she will be making that left turn soon it's a Texas storm.


Here's Debbie's final model average error to compare. Just as bad..
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Quoting SLU:
18/1745 UTC 13.5N 32.7W TOO WEAK 94L -- Atlantic

WTF? Too weak?

Curiouser and Curiouser......
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Quoting trHUrrIXC5MMX:
They don't issue hurricane warnings on the Azores very often... although they are not highlighted on the NHC map...


Speaking of the Azores, I've read some info that indicates they used to be higher above sea level & that they & some other regions in E Atlantic could have been the fabled Atlantis of lore, when higher in elevation. One report from a sailing vessels Captain in 1800s told about finding a barren, harsh land where there previously was none out at sea plus some absolutely manmade artifacts upon going ashore -- land that was on no maps & has since been inundated again. Quite interesting.
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Quoting CybrTeddy:
Don't get me wrong, the ECMWF is an excellent model with track as it nailed Ernesto's track and every storm this year except Debby, but has issues with intensity, it either way overdone (as it was predicting Fiona in 2010 to hit Florida as a Category 5 for a few days) or way underdone (Ernesto being an open wave at landfall where it was really a Category 1 to name a more recent example.) This is just from my unprofessional standpoint at least.
Charleston S.C it was.
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looks like a wet tuesday morning for the panhandle of florida..with schools open
Member Since: August 6, 2011 Posts: 4 Comments: 42277
They always seem to under-cast the strenght of those north Atlantic storms. Chris is another example and good ol' Gord is putting on a show! beautiful eye!
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Quoting HurricaneDean07:

105 Mph - 970 MB Category 2... Gordon.


yes...I'll agree with you but knowing the NHC... Im not sure... maybe 90 or 100 mph...conservative like always
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Member Since: August 6, 2011 Posts: 4 Comments: 42277
No consensus from EURO 12Z @ 120 hrs - weak system entering the eastern Caribbean...
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504. SLU
18/1745 UTC 13.5N 32.7W TOO WEAK 94L -- Atlantic

WTF? Too weak?
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ECMWF has been really bad this year, pretty surprising
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THE ERNESTO KINGDOM IS FINALLY AND OFFICIALLY OVER



BEGIN
NHC_ATCF
invest_DEACTIVATE_ep082012.ren
FSTDA
201208181631
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Quoting Hurricanes101:
Question for Levi

is it possible for the remnants of Helene to redevelop and say come as far east of the Florida panhandle?


Whatever pulse comes out of the western gulf will probably move into the north gulf coast and then northeastward along the front. I suppose it could end up near the eastern seaboard eventually, but it should no longer be tropical by that time, as it will be getting absorbed into the upper trough. If Florida feels any of it it will be rain, but not a developed tropical entity.
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Member Since: Posts: Comments:
Don't get me wrong, the ECMWF is an excellent model with track as it nailed Ernesto's track and every storm this year except Debby, but has issues with intensity, it either way overdone (as it was predicting Fiona in 2010 to hit Florida as a Category 5 for a few days) or way underdone (Ernesto being an open wave at landfall where it was really a Category 1 to name a more recent example.) This is just from my unprofessional standpoint at least. It does a lot better with intensity with fully developed tropical cyclones.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
Quoting LargoFl:
dont know if i caught the right pic..but the Nam has something Off the gulfcoast on tuesday.............


Probably the convective remnants of a cold front that should push down to the coast by late Monday. A low pressure area often seems to form off the tail end of these weak, stalled fronts.
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Member Since: August 6, 2011 Posts: 4 Comments: 42277
120 hours
Member Since: August 19, 2006 Posts: 13 Comments: 16225
114 Stormchaser2007:

Gordon sure is pretty for a Cat.1
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Quoting SLU:
18/1745 UTC 34.0N 37.5W T5.0/5.0 GORDON -- Atlantic

105 Mph - 970 MB Category 2... Gordon.
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updated
Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting Hurricanes4life:


Yeah, they are pretty hardy up there, they get extra tropical storms often that produce Cat 2 winds! Highly doubt it will be a major can when it arrives.



I was just saying anyway...they should though... or the Azores do something themselves...whatever
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The Islands directly in Gordon's path are Sao Miguel and Santa Maria. Sao Miguel is the most populated of the Islands in the Azores, at 140,000. Santa Maria is smaller, at 5,552.
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Quoting CybrTeddy:
The ECMWF is really doing bad this year with consistency. It's missed pretty much every storm but Beryl, Chris, and Debby until those storms are actually well developed. Even then, it missed out on Ernesto becoming a hurricane in the WCARB, and it wasn't like Ernesto was exactly a small circulation either at landfall.


Eh, every global model missed that one.
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Quoting Skyepony:
Models did horrible with Helene. No winners here on track. On intensity they did alright.


Didn't do well with Debby either LOL everyone with the exception of a few kept saying she will be making that left turn soon it's a Texas storm.
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Even the 12z UKMET develops 94L, don't see it too often that there's such a sharp disagreement between the two models.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
Quoting HurricaneDean07:

Not that intense.... You have to realize its going to be becoming Post-tropical as it passes through...
It will be a bad storm for them... But they've probably seen just as worst Winter storms...


well, people here stated that winds might be now between 105 - 115 mph... still a very strong storm even if becomes extratropical...I think whether its tropical or not is as dangerous and strong
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Quoting trHUrrIXC5MMX:
the BAMS models seems very reasonable...lol

LOLOL, bulls-eye on Port-Of-Spain....

That should freak the local populace right out !
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Member Since: August 6, 2011 Posts: 4 Comments: 42277
482. Skyepony (Mod)
Models over all did alright with Gordon. A few stand out. TVCN did really well.
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There is no reason at all for this not to develop that I can think of. It's already developing as we speak. 24 hours ago, this model was showing a major hurricane. Very poor consistency.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
96 hours
Member Since: August 19, 2006 Posts: 13 Comments: 16225
The ECMWF is already unreasonable.
Member Since: July 6, 2010 Posts: 113 Comments: 32877
478. SLU
18/1745 UTC 34.0N 37.5W T5.0/5.0 GORDON -- Atlantic
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Quoting trHUrrIXC5MMX:



Portugal better do something for the people living in the Azores...evacuations should be ordered...


Yeah, they are pretty hardy up there, they get extra tropical storms often that produce Cat 2 winds! Highly doubt it will be a major can when it arrives.
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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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