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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627. JLPR2
So... is anyone wondering why we don't have a floater yet for 94L? I am. XD

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Quoting Doppler22:
Everyone is saying Gordon is a Cat 2... but on the NHC website it still says Cat 1???


ATCF update which is fed through from the NHC says Category 2. 90% of the time it is accurate.
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625. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #7
TROPICAL DEPRESSION 16
3:00 AM JST August 19 2012
====================================

SUBJECT: Tropical Depression In Sea East Of The Philippines

At 18:00 PM UTC, Tropical Depression (1006 hPa) located at 18.1N 125.4E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as moving southwest slowly.

Dvorak Intensity: T2.0

Forecast and Intensity
========================

24 HRS: 17.7N 125.4E - 35 knots (CAT 1/Tropical Storm)
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Ihe 12z Euro is strange. Maybe its waiting for more development.
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Quoting Doppler22:
Everyone is saying Gordon is a Cat 2... but on the NHC website it still says Cat 1???



AL, 08, 2012081818, , BEST, 0, 340N, 375W, 90, 969, HU
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Quoting MAweatherboy1:
Gordon's eye seems to be shrinking:



Why does that sound bad to me?

Quoting WalkingInTheSun:


Absolutely they do!
It hacks me when experts clam up on REAL info simply because they are predicting something else to happen!


I do wonder, with how it jumped, if it could make Major. It would be extremely unlikely though. If it did, it might be a first in another regard. First Storm to be retired for damage to Europe.
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Quoting allancalderini:
I really want Ernesto tcr to come out I want to know if it was indeed a cat 2 at landfall.


me too...it had an eye forming right after landfall..
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Quoting WeatherNerdPR:

OK Taz, for you.
(but I still think Cody should hush).

Helene shouldn't be classified anymore.

It's pathetic.



and you could be right


AL, 07, 2012081818, , BEST, 0, 225N, 987W, 25, 1009, TD
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Everyone is saying Gordon is a Cat 2... but on the NHC website it still says Cat 1???
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I really want Ernesto tcr to come out I want to know if it was indeed a cat 2 at landfall.
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617. HadesGodWyvern (Mod)
Quoting MAweatherboy1:

They should. The people in the Azores are expecting no more than a low end Cat 1, and now he's just 10 kts off from major hurricane status... They need to know about that.


Meteo France is monitoring

"HURRICANE GORDON 34.1N 38.6W AT 18/15 UTC, 983, MOVING EAST AT 16 KT, EXPECTED NEAR 35.0N 31.4W BY 19/12 UTC, THEN 36.1N 27.8W BY 20/00 UTC.

ACORES, IRVING : FROM 18/18 UTC TO 20/00 UTC AT LEAST : CYCLONIC 10 OR 11 LOCALLY 12 ( 75 KT ) WITHIN 40 NM OF CENTER OF GORDON, GALE 8 OR 9 WITHIN 130 NM OF CENTER. SEVERE OR VIOLENT GUSTS."
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Quoting Tazmanian:




both of you hush or i put you in time out lol



this kind on that part

OK Taz, for you.
(but I still think Cody should hush).

Helene shouldn't be classified anymore.

It's pathetic.
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Quoting WeatherNerdPR:

You hush.

Both of you hush and I'll hush.
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Oops, Stripling's new. Needs to clean up his grammar and/or get a proofreader before publishing NHC Discussion.

A VIGOROUS TROPICAL WAVE IS LOCATED IN THE ERN ATLC ALONG
27W...WITH A ASSOCIATED 1008 MB LOW NEAR 14N27W EMBEDDED WITHIN THE MONSOON TROUGH. THIS WAVE IS RACING WESTWARD AROUND 20 KT...AND IS NOW FORECAST BY THE GLOBAL MODELS TO MAINTAIN THIS FAST MOTION ACROSS THE ATLC DURING THE NEXT SEVERAL DAYS.

SCATTERED SHOWERS AND THUNDERSTORMS WERE OCCURRING ARE FROM 11N-16N BETWEEN 27W-31W. CONDITIONS APPEAR CONDUCIVE FOR GRADUAL DEVELOPMENT DURING THE NEXT FEW DAYS...AND THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

GLOBAL MODELS HAS CHANGED SIGNIFICANTLY IN THE FORECAST OF THIS WAVE DURING THE PAST 2 DAYS...AND A MORE WWD TRAJECTORY INTO THE CARIBBEAN IS NOW SUGGESTED BY THE OPERATIONAL MODELS AS WELL AS THE ENSEMBLE MEANS.

INTERESTS ACROSS THE E AND NE CARIBBEAN SHOULD MONITOR THE PROGRESS OF THIS SYSTEM AS IT TREKS ACROSS THE ATLC.

Still, content is very good. Nice detail!
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Quoting WeatherNerdPR:

You hush.




both of you hush or i put you in time out lol



this kinding on that part
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94L is huge and impressive
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Quoting TropicalAnalystwx13:

Hush.

You hush.
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Euro has been trash all season GFS is king
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Quoting BahaHurican:
Something many in the US are not used to thinking about... very hard to evacuate from islands...


well...otherwise to suffer the wrath of Gordon...
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Quoting pottery:
Southern Caribbean swell chart shows 40' waves at the Islands on Aug 23rd.....

I think I'll go with the Euro.
Dissipation is Good!


What is the elevation of the islands?

Member Since: January 25, 2012 Posts: 33 Comments: 1520
Quoting MAweatherboy1:

They should. The people in the Azores are expecting no more than a low end Cat 1, and now he's just 10 kts off from major hurricane status... They need to know about that.


Absolutely they do!
It hacks me when experts clam up on REAL info simply because they are predicting something else to happen!
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Quoting washingtonian115:
Aletta who?.

The first tropical storm of the 2012 Pacific hurricane season.
Member Since: July 6, 2010 Posts: 113 Comments: 32706
605. Gorty
Quoting MAweatherboy1:
Gordon's eye seems to be shrinking:



Its common for a hurricane's eye to shrink and grow and back and forth like that.
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Quoting TropicalAnalystwx13:
There's still a while until advisory time, I wonder if they plan on doing a Special Update for Gordon.

Maybe. For the Azores' sake.
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Aletta who?.
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Quoting WeatherNerdPR:

Nobody cares.

Hush.
Member Since: July 6, 2010 Posts: 113 Comments: 32706
Gordon's eye seems to be shrinking:

Member Since: February 11, 2012 Posts: 84 Comments: 8000
Quoting Chiggy:
No consensus from EURO 12Z @ 120 hrs - weak system entering the eastern Caribbean...
But in the ECar at 120 hours, regardless of intensity, IMO suggests a certain complicity...

Quoting Clearwater1:
Just took a look at the GFS 12z and comparing it to previous runs it continues predict a track further west.

I remember last year, the GFS had Irene going up or near the spine of FL on at least 10 consecutive runs, maybe more. . . and we all know where it ended up. So, it is always a wait and see, but fun to track and speculate.

Can anyone tell me why (if it's true) the 00z and 12z are considered better and more accurate model runs?
00Z and 12Z get direct data input. The other two are extrapolated.
Member Since: October 25, 2005 Posts: 19 Comments: 22682
Quoting bajanmet:
TO BahaHurrican let me tell,I AM always prepared for hurricane season so how dare you try to say that I not. As a matter of fact also ALL BARBADIANS know about hurricane preparations. I have not come here to hang out unlike some people I have other things to do your highness.

????
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Quoting Clearwater1:
Just took a look at the GFS 12z and comparing it to previous runs it continues predict a track further west.

I remember last year, the GFS had Irene going up or near the spine of FL on at least 10 consecutive runs, maybe more. . . and we all know where it ended up. So, it is always a wait and see, but fun to track and speculate.

Can anyone tell me why (if it's true) the 00z and 12z are considered better and more accurate model runs?


They contain upper air observations from the release of ballons at various sites around the world, although that does not help much in the middle of the Atlantic since no model cycles have upper air data from there (other than obs from airplanes).
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Euro basically shows Ernesto part two which I'am not buying at the moment.I think at least a moderate or strong tropical storm.
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Quoting TropicalAnalystwx13:
If anybody cares, Tropical Storm Aletta's TCR is out.

Link

Nobody cares.
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Quoting trHUrrIXC5MMX:
THE ERNESTO KINGDOM IS FINALLY AND OFFICIALLY OVER



BEGIN
NHC_ATCF
invest_DEACTIVATE_ep082012.ren
FSTDA
201208181631


His spin has almost stopped, think he gorged on to much moist air, ha. Now he'll just slowing waddle on north to hopefully take his leftover moisture to drought stricken regions.

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Quoting stormchaser19:

Yes,but when irene ,the storm changes the COC to other to the North of PR, i remember tha.....t is a difference system

Yes, that's for sure, but all systems and circumstances around them are different from one to the other. But those dozen or so nearly identical model runs had me a believer with Irene.
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Quoting TropicalAnalystwx13:

Yes, but that is for Tropical Depression Helene, not Invest 94L.
oh sorry I thought that was 94L so winds at 5pm will be the same yes?
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Quoting TropicalAnalystwx13:
There's still a while until advisory time, I wonder if they plan on doing a Special Update for Gordon.

They should. The people in the Azores are expecting no more than a low end Cat 1, and now he's just 10 kts off from major hurricane status... They need to know about that.
Member Since: February 11, 2012 Posts: 84 Comments: 8000
Quoting sar2401:


Well, people here who say things like that are wrong. It's doubtful that Gordon currently has winds anywhere near 115 mph, and it's going to weaken very rapidly over the next 24 hours. By the time it gets to the Azores, maybe 65 mph, and the Azores get winter storms wth winds in that range on a regular basis.


did you expect the Gordon to become a hurricane to start with???
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Southern Caribbean swell chart shows 40' waves at the Islands on Aug 23rd.....

I think I'll go with the Euro.
Dissipation is Good!
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Quoting Tropicalupdate:
That means Tropical Depression right when it says TD?

Yes, but that is for Tropical Depression Helene, not Invest 94L.
Member Since: July 6, 2010 Posts: 113 Comments: 32706
Helene seems to falling apart fast...except for possible regeneration in W GOM to NE of its "core". I wonder if reblobulation will occur as the new energy comes down from up north.
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FROM THIS WEBSITE Link FL STATE UNIVERSITY OF METEOROLOGY...

there is a 14% chance of a landfalling storm...94L !
an Irene story part II?
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Quoting Gorty:


Is that official?


Yes that is official. Latest T-number is a 5.0. That is 90kts or 104 mph.
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Quoting Tazmanian:
AL, 07, 2012081818, , BEST, 0, 225N, 987W, 25, 1009, TD
That means Tropical Depression right when it says TD?
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Quoting Felix2007:

Only 2 hurricanes to become major north of 38 N




What about Ophelia 11'?
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Quoting leicesterlass:
Am surprised by people saying now is the time to make preparations for 94L. Would have thought anyone living in hurricane prone areas would be prepared year round.


in our part of Texas I can't imagine waiting until there is one in the Gulf to buy plywood for windows. It's already cut and labeled in one of the barns.

That said, knowing how on unprepared some still are in coastal SE Texas, I would say that many people on the upper east coast might be even less prepared. If those people wait until something is actually going on to lay up a few supplies it will be too late. It is just prudent to have emergency supplies on hand because no one knows what the weather, or mankind, will do.

In our part of NM it doesn't take much to interrupt the flow of supplies in. I don't mean preparing for the zombie apocalypse but having extra on hand is wise.
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581. Gorty
Quoting Tazmanian:



yes

Ok thx. Hmm 80-105... RI?
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18Z BAM suite trended more Westwards - IF that means anything at this stage.
Can anyone please explain why hasn't HRWF & GFDL jumped on 94L yet..? Nothing on the model pages!!
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There's still a while until advisory time, I wonder if they plan on doing a Special Update for Gordon.
Member Since: July 6, 2010 Posts: 113 Comments: 32706
Quoting Gorty:


Is that official?



yes
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Quoting WeatherNerdPR:
A Cat. 2 heading to the Azores? Interesting.

Bust season. :P


Wow, it looks very good. Hope that the Azores get prepared.
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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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