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 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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Quoting GetReal:


The spin is still there, and stalled just inland. It would not have to go far to get back over the GOM.


Is it my imagination or has it turned very westward after landfall. If the latter, that would make reversing itself a struggle perhaps -- maybe making it more likely that it will simply redeploy core back to the GOM/BOC area.
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the BAMS models seems very reasonable...lol
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Quoting trHUrrIXC5MMX:



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

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...
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Quoting LargoFl:
yes the stronger storms..blowing a shattered tree across the street at 100 mph or more at my house, I'd want that heavy plywood up
Why do I feel I'd be more concerned about the frame than the actual "glass"???

Member Since: October 25, 2005 Posts: 19 Comments: 22307
Question for Levi

is it possible for the remnants of Helene to redevelop and say come as far east of the Florida panhandle?
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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.
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Quoting HurricaneDean07:

NHC will dumb down the Sat estimates... You can still expect to see a 90 Mph Cat 1 - 105 Mph Cat 2.


Looks too good to be a Cat 1 in my books, potential post season upgrade?
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Quoting floridaboy14:
anyone see the GFS ensembles? lots have 94L into florida and north carolina. bermuda and the east coast need to watch this one
yes everyone on the east coast needs to be very watchful this week
Member Since: August 6, 2011 Posts: 4 Comments: 39057
Quoting WalkingInTheSun:


Actually seems to be getting a slight bit past blobulation point, to me: maybe slightly post-blobular in characteristics.


You're a fast learner. :)
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Quoting CybrTeddy:
Raw T# for Gordon have shot up to 5.6.

It deserves it. IMO.
Very good looking at this hour... It just needs to hold for about 2 hours more, and it shall be a Category 2... at the 5 pm.
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Quoting Grothar:


We bought a stand alone generator Briggs & Stratton and the installation was finished the morning Katrina hit. Best investment we ever made. Adds a lot of value to one's home as well. It runs everything in the house.
This is especially useful if everything u use in the house is electrical / stove, water pump, etc. Our biggest problem with the no power scenario is no running water.

I've been thinking carefully recently about the value of solar power in the aftermath of a hurricane. I know I've seen some "roll-out" style panels that can be taken down before a storm hits. IMO a solar generator would be 100% best bet post hurricane, so long as your roof is still there...

Member Since: October 25, 2005 Posts: 19 Comments: 22307
Quoting Hurricanes4life:

Yeah and the raw and adjusted have it at 5.6... or about 105Kt, major Cane?



Portugal better do something for the people living in the Azores...evacuations should be ordered...
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Quoting floridaboy14:
anyone see the GFS ensembles? lots have 94L into florida and north carolina. bermuda and the east coast need to watch this one


I havent had any time to look at the 12z Ensembles..can you post them?
Member Since: August 19, 2006 Posts: 13 Comments: 15662
Quoting Hurricanes4life:

Yeah and the raw and adjusted have it at 5.6... or about 105Kt, major Cane?

NHC will dumb down the Sat estimates... You can still expect to see a 90 Mph Cat 1 - 105 Mph Cat 2.
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Raw T# for Gordon have shot up to 5.6.
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They don't issue hurricane warnings on the Azores very often... although they are not highlighted on the NHC map...
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72 hours
Member Since: August 19, 2006 Posts: 13 Comments: 15662
458. Skyepony (Mod)
Models did horrible with Helene. No winners here on track. On intensity they did alright.
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Quoting Hurricanes4life:
For Gordon 08L
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 18 AUG 2012 Time : 174500 UTC
Lat : 34:00:36 N Lon : 37:28:59 W


CI# /Pressure/ Vmax
5.1 / 963.0mb/ 92.4kt


Final T# Adj T# Raw T#
4.9 5.6 5.6

Estimated radius of max. wind based on IR : 28 km

Center Temp : +11.2C Cloud Region Temp : -57.8C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 95km
- Environmental MSLP : 1015mb

Satellite Viewing Angle : 56.0 degrees

Holy crap.

NHC should go with 90-100 at the 5 pm advisory.
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Quoting trHUrrIXC5MMX:



wow....105 - 110 mph

Yeah and the raw and adjusted have it at 5.6... or about 105Kt, major Cane?
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I'm getting a real big feeling of deja vu here. In 2006, Hurricane Gordon caused Hurricane Warnings in the Azores.

In 2012, Hurricane Gordon is Hurricane Warnings in the Azores. Has there been another instance like this?
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Quoting Grothar:


It looks pretty good right now. Almost deserves blob status. I think it will consolidate earlier than they expect. Also notice the pre-blob coming off of Africa.



Actually seems to be getting a slight bit past blobulation point, to me: maybe slightly post-blobular in characteristics.
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anyone see the GFS ensembles? lots have 94L into florida and north carolina. bermuda and the east coast need to watch this one
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in case people didnt know..

Category One Hurricane

* Maximum Sustained Wind Speed: 74-95 miles per hour
* Damage Category: Minimal
* Approximate Pressure: Above 980 mb
* Approximate Storm Surge: 3-5 feet
* Examples: Hurricane Lili (2002) in Louisiana; Hurricane Gaston (2004) in South Carolina

Category Two Hurricane

* Maximum Sustained Wind Speed: 96-110 miles per hour
* Damage Category: Moderate
* Approximate Pressure: 979-965 mb
* Approximate Storm Surge: 6-8 feet
* Example: Hurricane Isabel (2003) in North Carolina

Category Three Hurricane

* Maximum Sustained Wind Speed: 111-129 miles per hour
* Damage Category: Extensive
* Approximate Pressure: 964-945 mb
* Approximate Storm Surge: 9-12 feet
* Examples: Hurricane Katrina (2005) in Louisiana; Hurricane Jeanne (2004) in Florida; Hurricane Ivan (2004) in Alabama

Category Four Hurricane

* Maximum Sustained Wind Speed: 130-156 miles per hour
* Damage Category: Extreme
* Approximate Pressure: 944-920 mb
* Approximate Storm Surge: 13-18 feet
* Example: Hurricane Charley (2004) in Florida; Hurricane Iniki (1992) in Hawaii; the Galveston Hurricane (1900) in Texas

Category Five Hurricane

* Maximum Sustained Wind Speed: 157 miles per hour and higher
* Damage Category: Catastrophic
* Approximate Pressure: Below 920 mb
* Approximate Storm Surge: More than 18 feet
* Examples: Only three Category 5 hurricanes have struck the United States since records began: The Labor Day Hurricane (1935) in the Florida Keyes, Hurricane Camille (1969) near the mouth of the Mississippi River, and Hurricane Andrew (1992) in Florida
Member Since: August 19, 2006 Posts: 13 Comments: 15662
Quoting Hurricanes4life:
For Gordon 08L
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 18 AUG 2012 Time : 174500 UTC
Lat : 34:00:36 N Lon : 37:28:59 W


CI# /Pressure/ Vmax
5.1 / 963.0mb/ 92.4kt


Final T# Adj T# Raw T#
4.9 5.6 5.6

Estimated radius of max. wind based on IR : 28 km

Center Temp : +11.2C Cloud Region Temp : -57.8C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 95km
- Environmental MSLP : 1015mb

Satellite Viewing Angle : 56.0 degrees



wow....105 - 110 mph
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LATEST ON GORDO---THE FAT MAN...LOL


click the Link for a larger image
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For Gordon 08L
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 18 AUG 2012 Time : 174500 UTC
Lat : 34:00:36 N Lon : 37:28:59 W


CI# /Pressure/ Vmax
5.1 / 963.0mb/ 92.4kt


Final T# Adj T# Raw T#
4.9 5.6 5.6

Estimated radius of max. wind based on IR : 28 km

Center Temp : +11.2C Cloud Region Temp : -57.8C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 95km
- Environmental MSLP : 1015mb

Satellite Viewing Angle : 56.0 degrees
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Quoting xtremeweathertracker:


Great video Levi, in my video i posted earlier today i discussed the possibility of Helene reforming over the western GOM....possibly a piece of her energy combined with the frontal system pushing into the GOM.


I think you are right about her reforming over the GOM,...or else maybe she dies out & remnants in BOC form a new system entirely.
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Also, Gordon is one of the best looking Cat 1. hurricanes I have seen in awhile, surprised they didn't give him a few more Knots at 2pm est.
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Quoting bajanmet:
What category 94l will be on the approaching the Antilles? I know it is still days away but I will still like to know.Reading some of these comments on 94l potential wind speed, it,s a bit scary. Some say it will recurve but when it comes to weather I just don't know.Ernesto was to pass to our south,it pass to the north.
That's why I was saying earlier you just have to watch. You should already have your preliminary preps in place anyway [sure most Bajans have an idea of what to do]. Now the idea is to keep an eye on 94L to see if it does live up to the lofty predictions. If it passes near Barbados as a storm, it could bring anything from Tropical Storm force to Cat. 3 winds, but the lower level winds seem more likely at this point.

My thinking is that forewarned is forearmed. If you keep track of the storm's progress with NHC, it will give you a good idea of what's going on with it. But worrying about a storm that is not likely to affect Barbados before Friday is over-stressing. Better to use the information to help you make informed decisions.

If you stick around the blog, read the Doc's post FIRST, and remember that a lot of what gets posted in the comments is people's opinions about possible options for the storm. This information can be useful because it gives you an idea of the storm's potential to harm you and yours. However, very few in here are experts or professional mets. We have some talented amateurs, and they often have worthwhile thoughts to share. The rest of the blog comprises enthusiasts with varying levels of knowledge, understanding, experience, and skill. Some of us are [ahem] very enthusiastic....

This is a great place to hang out if you want to stay on the leading edge of information about various tropical cyclones and in particular their formation. HOWEVER, I strongly advise, Use With Caution - it's highly addictive...

Quoting aislinnpaps:
Sometimes I wish there was a button for a simple 'I don't like this post', not that it's a bad one, just I don't agree or don't like what it says or shows.
I said this earlier... lol... we need a "this makes me unhappy" button... lol

Member Since: October 25, 2005 Posts: 19 Comments: 22307
I think 94L is gearing up faster than I thought, and the faster this thing straightens the more likely it will gain more latitude.
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Quoting Tazmanian:
that wave be hid 94L looks too be heading WSW

DOOM 2 ?
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I expect to see code red sometime tonight..not going to say the percentages..perhaps T.D 9 tomorrow and Isaac Sunday night or Monday...I'll be busy with the kiddies by then so I won't be around to see everything.
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Quoting weatherh98:


heard the new models came out:P


Wow, looks like they got that trajectory nailed down!
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Quoting GTcooliebai:
Euro begin initialization:




Reasonable initialization... Not all around the best..
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12z Euro running
48 hours
Member Since: August 19, 2006 Posts: 13 Comments: 15662
439. Skyepony (Mod)
94L hasn't had a whole lot of models run on it yet. What has hasn't done well. 94L model verification.
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Quoting SFLWeatherman:
Q. What will 94L be at 8PM
A.50%
B.60%
C.70%
D.80%
E.90%
I will say B OR C

B or C as well
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that wave be hid 94L looks too be heading WSW
Member Since: May 21, 2006 Posts: 5091 Comments: 115256
Quoting Levi32:
I strongly recommend not using the 60km FIM7. It is the worst of the bunch.

The 12z operational FIM (30km) 3 days out shows the remnants of Helene trying to redevelop and 94L chugging westward as a tropical depression.



I happen to like the FIM7. The colors are much nicer and vivid. Besides, the FIM (30km) had trouble loading this morning. Besides, I was posting the FIM (30km) all last night.
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Quoting Levi32:
I strongly recommend not using the 60km FIM7. It is the worst of the bunch.

The 12z operational FIM (30km) 3 days out shows the remnants of Helene trying to redevelop and 94L chugging westward as a tropical depression.



wow ok Levi thanks for the heads up!
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Quoting SFLWeatherman:
Q. What will 94L be at 8PM
A.50%
B.60%
C.70%
D.80%
E.90%
I will say B OR C


70%
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I saw the model runs posted earlier..and if that were to occur I might as well be reliving Isabel all over again.It would be something to see though as that would be two years in a row that D.C see's tropical storm conditions from both storms that start off with the same letter...
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Q. What will 94L be at 8PM
A.50%
B.60%
C.70%
D.80%
E.90%
I will say B OR C
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Quoting opal92nwf:

You can never assume anything...
will withstand*
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I strongly recommend not using the 60km FIM7. It is the worst of the bunch.

The 12z operational FIM (30km) 3 days out shows the remnants of Helene trying to redevelop and 94L chugging westward as a tropical depression.

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we've got a few days of rain ahead of us...so if Helene redevelops, the ground will be soaked. Always worried me about trees falling over...happened in Lili. Trees were down all over due to the saturated soil.
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Quoting Dakster:


I have three full 40lb propane tanks for a BBQ grill...

I am not saying that we shouldn't prepare - BUT my main fear is that if something major hits, someone in Texas may be enjoying my BBQ grill and propane.
Roflmao!!!..you know..its funny but..it could happen
Member Since: August 6, 2011 Posts: 4 Comments: 39057

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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.