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

Share this Blog
33
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 127 - 77

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14Blog Index

1 week out... Getting ripped to shreds:

Member Since: February 11, 2012 Posts: 83 Comments: 7834
Quoting wunderkidcayman:
Well as I said my Gut said Caribbean Hurricane 94L will be


Had some hot wings last night so not relying on my gut for the time being.
Member Since: Posts: Comments:
Well as I said my Gut said Caribbean Hurricane 94L will be
Member Since: Posts: Comments:
Quoting bajanmet:
Good afternoon,this is my first time on this blog.
Will 94l be passing close to Barbados, can any one help me with this question?
It may. Forecasts are still not set, since the system is still developing. I would monitor from Barbados for now...

Welcome to the blog, BTW.
Member Since: October 25, 2005 Posts: 19 Comments: 22312
Quoting 954FtLCane:


996 mb @ 132 hours.

"This is a future model run and is meant for entertainment purposes only,
follow the NHC and/or your local official weather office for all accurate up to date information regarding your specific area."

This model depicts the possibilities as per the GFS model at 132 hours from 0Z, August 18th 2012.




LOL hey look at the isobar at 1020 the shape of it looks like Tx
Member Since: Posts: Comments:


This is going to be interesting and potentially dangerous for the Greater Antilles.
Member Since: Posts: Comments:
this is the fourth dipiction of this area of preturb weather by gfs model run


next run 18z 5 pm est
Member Since: Posts: Comments:


993mb at 150
Member Since: Posts: Comments:
119. SLU
Quoting TropicalAnalystwx13:
Don't pay as much attention the intensity that the GFS shows as opposed to the track. The GFS is a global model, and as long as it shows intensification, we can use the hurricane models for the intensity forecast.



That's right. These synoptic scale models don't do an great job with the pressure and wind speeds of individual storms. The LGEM and ICON have been the NHC's most favoured intensity models recently.
Member Since: Posts: Comments:
Quoting redwagon:

Exactly, Africa just spit off two storms and another is about to splash down. My point being we can't possibly have confidence in any solution until the two entities currently comporting 94L either fully merge or break away from each other. I mean, really, how often do you see a storm forecast for upper-end Cat3/lower Cat4 in 120 hours from becoming an invest?
OK... now understand where u r coming from... I was thinking literally sending the HHers at one point... lol

I was pointing out the fact that the potential for multiple storms in a relatively short period of time has been suggested for quite a while... and I do believe the GFS was suggesting the Twave coming off Africa now is the one with the potential to be our next AOI. We don't often see storms intensify that rapidly in the E / Central ATL, especially if they then continue westward, but it is certainly w/in the realm of possibility. I think we see a FORECAST for such a storm more often than we should... lol

Member Since: October 25, 2005 Posts: 19 Comments: 22312
150 hrs and 1016 mb high sitting off the SE coast. No opening so far.

Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
Should get 50% or 60% at 2 pm EDT.


I'm thinking fifty, but if it continues its organization trend, I fully expect a sixty or seventy for this evening.
Member Since: Posts: Comments:


994 mb @ 138 hrs.... trending west Hispaniola hit on this run?

0z last night night had a direct hit on PR
Member Since: Posts: Comments:
Member Since: Posts: Comments:
150 hours:

Member Since: February 11, 2012 Posts: 83 Comments: 7834
144 final
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
Should get 50% or 60% at 2 pm EDT.



yep I think you are right
Member Since: Posts: Comments:
144hr final
Member Since: Posts: Comments:


996 mb @ 132 hours.

"This is a future model run and is meant for entertainment purposes only,
follow the NHC and/or your local official weather office for all accurate up to date information regarding your specific area."

This model depicts the possibilities as per the GFS model at 132 hours from 0Z, August 18th 2012.


Member Since: Posts: Comments:
108. SLU
Quoting bajanmet:
Good afternoon,this is my first time on this blog.
Will 94l be passing close to Barbados, can any one help me with this question?


dangerously close ... close enough to get hurricane force winds if this strengthens as much as the models indicate.
Member Since: Posts: Comments:
Should get 50% or 60% at 2 pm EDT.

Member Since: July 6, 2010 Posts: 113 Comments: 32256
Member Since: Posts: Comments:
Quoting 954FtLCane:


996 mb @ 126 hrs...
trending west it seems. movement to the NW noted


Trough lifting out and becomining zonal.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Don't pay as much attention the intensity that the GFS shows as opposed to the track. The GFS is a global model, and as long as it shows intensification, we can use the hurricane models for the intensity forecast.

Member Since: July 6, 2010 Posts: 113 Comments: 32256
Quoting GetReal:
I'm starting to think more of a westerly solution deeper into the Caribbean.

A weaker system in the short term , which seems to be the trend, is more likely to do that, so you may be right.
Member Since: February 11, 2012 Posts: 83 Comments: 7834
Does it looks to slowdown once it enters the Caribbean?
Member Since: Posts: Comments:


996 mb @ 126 hrs...
trending west it seems. movement to the NW noted
Member Since: Posts: Comments:
Webcam view in Corvo Island in the Azores, watching the approach of Hurricane Gordon.

Member Since: Posts: Comments:
I'm starting to think more of a westerly solution deeper into the Caribbean.
Member Since: Posts: Comments:
1017 mb high over Fla. This would mean a very late recurve if it panned out this way.



It is the evolution of the AB high and a bridging high on the SE coast that really needs to be carefully monitored to see if a weakness opens up off the Eastern seaboard. Without that, well, we know what happens.
Member Since: Posts: Comments:
45 redwagon: If you were a HHer and I handed you this map and said find the center of 94L, what coords would you use for your initial flight plan?

The ones the NHC provided.
Dammit, Jim, I'm a joyrider, not a navigator.
Member Since: August 21, 2007 Posts: 0 Comments: 4860
Member Since: Posts: Comments:
Member Since: Posts: Comments:


shear map at 120
Member Since: Posts: Comments:
Quoting kmanislander:


Did you see where the Western periphery of the steering high is though ?. Across Fla and into the central GOM. If that verifies big trouble ahead. Same set up we had in 2004 for the "I" hurricane.
I haven't been saying much, because pple keep pointing to how the GFS turns the storm N before FL... I guess dependent on this current trough still being in the vicinity.

Frankly, I don't want to consider any versions of 2004, 2008, or 2001 storms...
Member Since: October 25, 2005 Posts: 19 Comments: 22312


Looks actually further south, but slightly weaker than the last few runs.
Member Since: Posts: Comments:
This may get torn up by the islands:

Member Since: February 11, 2012 Posts: 83 Comments: 7834
quick global weather summary for July, the 4th hottest July in Earth's history.

It wasn't hot here in Sydney. In fact it was cooler than normal July down here.
Member Since: Posts: Comments:


999mb @ 114 hrs
Member Since: Posts: Comments:
Good afternoon,this is my first time on this blog.
Will 94l be passing close to Barbados, can any one help me with this question?
Member Since: August 8, 2012 Posts: 0 Comments: 8



Bermuda blocking high remaining intact at his time.
Member Since: Posts: Comments:
Quoting BahaHurican:
30W, 11N? Thereabouts?

I still don't know what all this has to do with THIS:

Quoting BahaHurican:
I wonder how many remember the GFS long range about 10, 12 days ago spitting out several storms in a row... looks like it had the correct general idea...


It was just such a non sequitur that it caught my eye.

Exactly, Africa just spit off two storms and another is about to splash down. My point being we can't possibly have confidence in any solution until the two entities currently comporting 94L either fully merge or break away from each other. I mean, really, how often do you see a storm forecast for upper-end Cat3/lower Cat4 in 120 hours from becoming an invest?
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Steering layers (Keep in mind these change a lot in time).

1000mb



990mb



970mb



950mb



940mb



below 940mb




It appears to me that the storm would definitely need to be a category 2 or 3 in the 5 to 7 day range in order for the 0600 GFS to verify...


1200 GFS is not yet done, but is nearing the 5 day mark, and it doesn't appear to be intensifying the system nearly as rapidly, it is keeping it very far S and looks like another weak system that may survive the E. Caribbean and re-intensify in the west.

We'll see soon enough.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
12z GFS is weaker than the 06Z run somewhat, but shows the same path.


Did you see where the Western periphery of the steering high is though ?. Across Fla and into the central GOM. If that verifies big trouble ahead. Same set up we had in 2004 for the "I" hurricane.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:

Not really.


Yeah,I spoke too soon.
Member Since: Posts: Comments:
Member Since: Posts: Comments:


102 hrs, 1002 mb
Member Since: Posts: Comments:
Morning RGB satellite captured all three of the systems we are watching in the Atlantic at various stages of development. Hurricane Gordon, T.D. Helene, and 94L:

Member Since: Posts: Comments:

Viewing: 127 - 77

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Mostly Cloudy
67 °F
Mostly Cloudy