Tropical Storm Helene arrives; 94L a potential threat to the Lesser Antilles

By: Dr. Jeff Masters , 10:41 PM GMT on August 17, 2012

After a long path across the Atlantic that mirrored the track of Hurricane Ernesto, Tropical Depression Seven finally got its act together enough over the Bay of Campeche tropical storm breeding grounds to earn the name Helene. Helene's formation on August 17 ties 2012 with 1933 for the 2nd earliest appearance of the Atlantic's eighth tropical storm. Only 2005 had an earlier formation date of the season's eighth storm. Most of this year's storms have been weak, though, so the total Accumulated Cyclone Energy (ACE) of 21 is not that much higher than the normal year-to-date ACE of 15, based on a 1981 - 2010 ACE climatology. The normal yearly ACE for the Atlantic is 104. Helene doesn't have much room to work with before landfall, but has the potential to be a prodigious rainmaker for Mexico, with NHC predicting 5 - 10 inches for portions of Northeast Mexico. This part of the coast is not in drought, so will be prone to heavy flooding. Fortunately, Ernesto's main rains fell to the south of where Helene's rains are falling. Helene's rains should remain south of Texas, though we can't rule out a few thunderstorms bringing 1 - 2 inches of rain to extreme South Texas on Saturday and Sunday.


Figure 1. Afternoon satellite image of Helene.

94L a potential threat to the Lesser Antilles
A large tropical wave emerged from the coast of Africa Thursday night, and was designated Invest 94L by NHC this Friday morning. The models have been impressed this system, and develop it into a tropical storm by the middle of next week. The latest set of 12Z (8 am EDT) model runs are divided on how far west 94L will make it before curving more to the northwest. The ECMWF model keeps 94L weak for the next 5 - 6 days, and has progressively been bringing the storm closer to the Lesser Antilles Islands with each successive run. The ECMWF predicts 94L will pass very close to the northern Lesser Antilles August 24 - 25 as a weak tropical storm. The 12Z GFS model predicted recurvature of 94L well to the east of the Lesser Antilles and Bermuda, but the latest 18Z run has the storm plowing through the Lesser Antilles on Thursday, August 23, as a strong tropical storm, then becoming a hurricane in the Eastern Caribbean. Given that our two top models for forecasting hurricane tracks are increasingly showing a threat to the Lesser Antilles, residents of the islands should pay close attention to the progress of 94L. The eventual track of 94L will depend on the strength of the storm over the next seven days, which is difficult to forecast, since 94L will have the usual trouble with dry air to the north from the Saharan Air Layer (SAL.) With the models changing their tune drastically from run to run, its tough to say what land areas might be most at risk from the storm in the long term. In their 2 pm EDT Tropical Weather Outlook, NHC gave 94L a 10% chance of developing into a tropical depression by Sunday afternoon.


Figure 2. MODIS satellite image of Invest 94L taken at 8 am EDT August 17, 2012, off the coast of Africa. Image credit: NASA.

Jeff Masters


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

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

Viewing: 126 - 76

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36Blog Index

Quoting Levi32:


When forecasting the weather you cannot call this neutral ENSO. It is an El Nino.



If the CPC wants a long-term average to "officially" declare it an El Nino event, that's fine, but that doesn't change the fact that it is already here and affecting the Atlantic this season.


if the numbers keep fluctuating, I dont see how this can be an El Nino if one day we in Neutral conditions and the next day as you guys are saying we are experiencing EL Nino conditions..the week a major makes its way across the atlantic with neutral and el nino conditions wont convince me otherwise that we are in an El Nino..and where does it say on the CPC website that it has to be consistent for them to declare it, I tried looking for it but couldnt find it?
Member Since: December 31, 1969 Posts: Comments:
Quoting reedzone:
Well at least we can all say 07L eventually became a Tropical Storm.
You betcha!
Member Since: Posts: Comments:
Quoting ylibrach:
I am about to cry :( .. I am flying out to the Dominican Republic on Monday for 7 days. These latest models have me freaking out. Should I cancel my trip? I am pretty much going to lose all the money I paid for it. How accurate are these models in general?


Is one run only,but the models are shifting more to the west NOW
Member Since: December 31, 1969 Posts: Comments:
Quoting Cat5hit:


To the simple minded, yes...



ZING!
Member Since: Posts: Comments:
Think about it ladies and gentlemen, really, who needs the models, climatological history dictates a recurve(94L).....sometime...somewhere and with the jet dipping down early driving cold fronts south and east, well..it's almost like a barrier, especially for those long travelers from the dark continent. If the scenario doesn't change, ie. jet retreats, we'd best just keep an eye on our own backyard. C'est la vie!
Member Since: Posts: Comments:
94L at 20%

AN AREA OF DISTURBED WEATHER ASSOCIATED WITH A TROPICAL WAVE IS
LOCATED WELL SOUTH OF THE CAPE VERDE ISLANDS. SOME SLOW DEVELOPMENT
IS POSSIBLE DURING THE NEXT FEW DAYS AS THIS SYSTEM MOVES TOWARD
THE WEST AT 15 TO 20 MPH. THIS SYSTEM HAS A LOW CHANCE...20
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
Member Since: December 31, 1969 Posts: Comments:
Quoting wxchaser97:
This could happen with 94L, same name but 12 years apart.
I hope your right.
Member Since: December 31, 1969 Posts: Comments:
I am about to cry :( .. I am flying out to the Dominican Republic on Monday for 7 days. These latest models have me freaking out. Should I cancel my trip? I am pretty much going to lose all the money I paid for it. How accurate are these models in general?
Member Since: Posts: Comments:
East coast threat

GFS ensembles

Member Since: Posts: Comments:
This could happen with 94L, same name but 12 years apart.
Member Since: December 31, 1969 Posts: Comments:
Quoting DavidHOUTX:


You do realize your blog name can easily be mistaken for something else right?

Cat****

XD
Member Since: December 31, 1969 Posts: Comments:
Peak flight level winds they are finding is 40 mph... dont know how you can say this is still a tropical storm...

Member Since: Posts: Comments:
Quoting MAweatherboy1:
Is it possible that Helene dissipates inland, then comes back out over the Gulf and restrengthens and becomes Isaac and then 94L becomes Joyce?


No if it retains a circulation and is trackable then it will retain it's name which would be Helene.

In fact the GFS has been keeping Helene sitting in the SW Gulf for quite a while.
Member Since: Posts: Comments:
Quoting Levi32:


Probably. I think you'll see the models in general eventually shift to between 80W and 65W for the recurve though.
Levi quick question. is MJO back into theGOM and carribean yet or is it still days off?
Member Since: Posts: Comments:
can anyone answer my question. why does EVERY cape verde storm ALWAYS recurve? in 2004 they went right into the coast. ever since then everything either goes out to sea or curves into the coast like irene. now a days, there are so many troughs that nothing can hit the coast DIRECTLY. thoughts and comments?
Member Since: Posts: Comments:
Quoting Hurricanes101:
its pretty interesting to see a few of the models keep Helene offshore for about 4 or 5 more days, the NHC has her inland overnight tonight

will be interesting to see which plays out; could it possibly move inland and then come back over water?

Helene has been a persistent wanderer since 500 miles East of the Antilles, however just now she lost her convection. Maybe she WILL dissipate in MX. Ignomious death, if you ask me.
Member Since: December 31, 1969 Posts: Comments:
Quoting Felix2007:


You missed the forecast of DOOM!!!



DOOM! The world's about to end and I missed it. :(
Member Since: Posts: Comments:
Well at least we can all say 07L eventually became a Tropical Storm.
Member Since: Posts: Comments:
Quoting WeatherNerdPR:
Seems next week will be rather interesting. Helene, Isaac and Joyce all at the same time.

Over the Mona Passage...yikes.


PR getting slashed by Isaac, not good...Hope stay north of us a recurve before 60w...
Member Since: Posts: Comments:
Quoting stormchaser19:

Here we go again everybody questioning GFS?


Do you trusts models past 144 hours out? That is more questioning their accuracy past a certain time period. The GFS is a good model but once you get past 5 days conditions change and newer models reflect those changes. A few weeks ago the GFS had a system getting close to the East Coast and that never happened.
Member Since: Posts: Comments:
Quoting ncstorm:


I tried to tell a blogger that the other day..we are not in an El Nino yet..the CPC still says watch and conditions are favorable for the next 6 months..

El Niño or La Niña Watch: Issued when conditions are favorable for the development of El Niño or La Niña conditions within the next six months.


When forecasting the weather you cannot call this neutral ENSO. It is an El Nino.



If the CPC wants a long-term average to "officially" declare it an El Nino event, that's fine, but that doesn't change the fact that it is already here and affecting the Atlantic this season.
Member Since: Posts: Comments:
Besidees for those initial TS winds the HH hasnt found TS winds for over 3 hours
Member Since: Posts: Comments:
So again those of us here in good ole Corpus Christi are gonna miss the "perfect" opportunity for significant rain absent any wind.... I was really hoping this morning that would not be the case. hey Dr. Masters, would you please change your synopsis just a little? lol Thank you!
Member Since: Posts: Comments:
Quoting floridaboy14:
why is everyone so certain it recurves? lets focus just a week out in which it approaches the islands. look at the euro run. doesnt want to recurve it. wants to take it back west. shows a very weak trough lifting out. lets wait before we talk long term track.


NTM we don't even have a storm to track yet. Just sayin'.
Member Since: Posts: Comments:
Anyone else notice this?
#1:
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 17th day of the month at 21:45Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Tropical Depression: Number 7 (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 10
A. Time of Center Fix: 17th day of the month at 21:24:50Z
B. Center Fix Coordinates: 20%uFFFD35'N 96%uFFFD05'W (20.5833N 96.0833W)
B. Center Fix Location: 161 miles (259 km) to the SE (135%uFFFD) from Tampico, Tamaulipas, M%uFFFDxico.
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 35kts (~ 40.3mph)
E. Location of the Estimated Maximum Surface Wind: 5 nautical miles (6 statute miles) to the SE (129%uFFFD) of center fix
F. Maximum Flight Level Wind Inbound: From 232%uFFFD at 39kts (From the SW at ~ 44.9mph)
G. Location of Maximum Flight Level Wind Inbound: 8 nautical miles (9 statute miles) to the SE (128%uFFFD) of center fix
H. Minimum Sea Level Pressure: 1005mb (29.68 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 23%uFFFDC (73%uFFFDF) at a pressure alt. of 273m (896ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 26%uFFFDC (79%uFFFDF) at a pressure alt. of 274m (899ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 24%uFFFDC (75%uFFFDF)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 1,500 feet
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 4 nautical miles
Remarks Section:
Maximum Flight Level Wind: 39kts (~ 44.9mph) in the southeast quadrant at 21:22:00Z
Sea Level Pressure Extrapolation From: Below 1,500 feet

#2
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 17th day of the month at 22:45Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Tropical Depression: Number 7 (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 13
A. Time of Center Fix: 17th day of the month at 22:32:00Z
B. Center Fix Coordinates: 20%uFFFD42'N 96%uFFFD03'W (20.7N 96.05W)
B. Center Fix Location: 157 miles (252 km) to the SE (132%uFFFD) from Tampico, Tamaulipas, M%uFFFDxico.
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 27kts (~ 31.1mph)
E. Location of the Estimated Maximum Surface Wind: 10 nautical miles (12 statute miles) to the S (183%uFFFD) of center fix
F. Maximum Flight Level Wind Inbound: From 260%uFFFD at 30kts (From the W at ~ 34.5mph)
G. Location of Maximum Flight Level Wind Inbound: 10 nautical miles (12 statute miles) to the S (183%uFFFD) of center fix
H. Minimum Sea Level Pressure: 1005mb (29.68 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 23%uFFFDC (73%uFFFDF) at a pressure alt. of 304m (997ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 26%uFFFDC (79%uFFFDF) at a pressure alt. of 303m (994ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 23%uFFFDC (73%uFFFDF)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 1,500 feet
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 0 nautical miles
Remarks Section:
Maximum Flight Level Wind: 30kts (~ 34.5mph) in the northwest quadrant at 21:26:00Z
Sea Level Pressure Extrapolation From: Below 1,500 feet

Looking at the current recon mission, if those two center fixes are both correct, Helene is now moving NNE. Looks like they're coming in for a third pass/center fix, so I guess we'll see, but that's certainly worrying for folks on the gulf coast...
Member Since: Posts: Comments:
Quoting MAweatherboy1:
Is it possible that Helene dissipates inland, then comes back out over the Gulf and restrengthens and becomes Isaac and then 94L becomes Joyce?


highly unlikely, if it does come back over water, I dont think it would be over land long enough for it to completely lose its identity
Member Since: Posts: Comments:
Is it possible that Helene dissipates inland, then comes back out over the Gulf and restrengthens and becomes Isaac and then 94L becomes Joyce?
Member Since: Posts: Comments:


Member Since: December 31, 1969 Posts: Comments:
Quoting aislinnpaps:
I see we have Helene now. Anything else I miss?


You missed the forecast of DOOM!!!

Member Since: December 31, 1969 Posts: Comments:
El Niño/Southern Oscillation (ENSO) Diagnostic Discussion

"ENSO-neutral conditions continued during July 2012 despite above-average sea surface temperatures (SST) across the eastern Pacific Ocean (Fig. 1). Reflecting this warmth, most of the weekly Niño index values remained near or greater than +0.5°C (Fig. 2). The oceanic heat content anomalies (average temperature in the upper 300m of the ocean) also remained elevated during the month (Fig. 3), consistent with a large region of above-average temperatures at depth across the equatorial Pacific (Fig. 4). Although sub-surface and surface temperatures were above average, many aspects of the tropical atmosphere were inconsistent with El Niño conditions. Upper-level and low-level trade winds were near average along the equator, while tropical convection remained enhanced over Indonesia (Fig. 5).
However, convection increased near and just west of the International Date Line, which may eventually reflect a progression towards El Niño. The lack of a clear atmospheric response to the positive oceanic anomalies indicates ongoing ENSO-neutral conditions."
Member Since: Posts: Comments:
Quoting Jedkins01:


Anomaly with bright color and actual temps are 2 very different things. Storms can reach Newfoundland due to high speed but the water is still way too cold buddy.

Not really.

Member Since: December 31, 1969 Posts: Comments:
Quoting TropicalAnalystwx13:

The Atlantic is El Niño driven right now, whether or not one has been declared. Increased trade winds in the Caribbean, stronger troughs, etc.


says who?..conditions are favorable, dosent mean we are in an El Nino and if we were, why wouldnt NOAA declare it?.
Member Since: December 31, 1969 Posts: Comments:
its pretty interesting to see a few of the models keep Helene offshore for about 4 or 5 more days, the NHC has her inland overnight tonight

will be interesting to see which plays out; could it possibly move inland and then come back over water?
Member Since: Posts: Comments:
Quoting ncstorm:


I tried to tell a blogger that the other day..we are not in an El Nino yet..the CPC still says watch and conditions are favorable for the next 6 months..

El Niño or La Niña Watch: Issued when conditions are favorable for the development of El Niño or La Niña conditions within the next six months.


Yes, we seem to be going back and forth with El Niño, I thought that by this month's end it would be nicely established, but no, maybe by September.
Member Since: Posts: Comments:
Quoting Cat5hit:
I was kinda hoping the long range forecasts had Florida in its sights. That is usually the LAST place they end up...



You do realize your blog name can easily be mistaken for something else right?
Member Since: Posts: Comments:
Quoting ncstorm:


I tried to tell a blogger that the other day..we are not in an El Nino yet..the CPC still says watch and conditions are favorable for the next 6 months..

El Niño or La Niña Watch: Issued when conditions are favorable for the development of El Niño or La Niña conditions within the next six months.

The Atlantic is El Niño driven right now, whether or not one has been declared. Increased trade winds in the Caribbean, stronger troughs, etc.
Member Since: December 31, 1969 Posts: Comments:
Seems next week will be rather interesting. Helene, Isaac and Joyce all at the same time.

Over the Mona Passage...yikes.
Member Since: Posts: Comments:
why is everyone so certain it recurves? lets focus just a week out in which it approaches the islands. look at the euro run. doesnt want to recurve it. wants to take it back west. shows a very weak trough lifting out. lets wait before we talk long term track.
Member Since: Posts: Comments:
Quoting reedzone:


Why not? It was only recurving the storm east of Bermuda for the past 5-10 runs... It may indeed switch back to that scenario, but the other models have shown a more western trend. We'll see.
Member Since: Posts: Comments:
Quoting RTSplayer:


As rigged/ridiculous as that looks, the SST anomaly probably supports it easily...



Anomaly with bright color and actual temps are 2 very different things. Storms can reach Newfoundland due to high speed but the water is still way too cold buddy.
Member Since: Posts: Comments:
Quoting JLPR2:
El Niño doesn't seem to be making much progress, more like a step forward and another one back, the small anomaly off SA is also expanding and getting colder.

August 2:


August 16:


I tried to tell a blogger that the other day..we are not in an El Nino yet..the CPC still says watch and conditions are favorable for the next 6 months..

El Niño or La Niña Watch: Issued when conditions are favorable for the development of El Niño or La Niña conditions within the next six months.
Member Since: December 31, 1969 Posts: Comments:
Quoting Tazmanian:
we are going too have so marh fun on the blogs the next few weeks


Lost sleep for sure!
Member Since: Posts: Comments:
Quoting Tazmanian:



AL, 94, 2012081718, , BEST, 0, 112N, 237W, 20, 1009, DB,


Thanks Taz
Member Since: Posts: Comments:
Must be a reason FIMS shows only 0z and 12Z GFS runs.(More accurate?)
Member Since: Posts: Comments:
Isaac will be a big one. The I storms always are.
Member Since: December 31, 1969 Posts: Comments:
Quoting stormchaser19:

Here we go again everybody questioning GFS?


Why not, it was only recurving the storm east of Bermuda for the past 5-10 runs... It may indeed switch back to that scenario, but the other models have shown a more western trend. We'll see.
Member Since: Posts: Comments:
Quoting stormchaser19:

Here we go again everybody questioning GFS?


I'm not questioning it, I'm simply stating I want consistency.
Member Since: Posts: Comments:
Quoting Levi32:


Probably. I think you'll see the models in general eventually shift to between 80W and 65W for the recurve though.
how are you so sure if it recurves? ECMWF wants to take it back west under a rebuilding ridge. i know there is supposed to be a weak trough off the east coast during which 94L approaches the islands but how confident are you it recurves ?
Member Since: Posts: Comments:
A recurve is certainly the likely scenario for 94L. The question is how close it gets before it starts to recurve. A lot of people associate recurve with storms going out to sea, which isn't always the case. Just look at Irene last year. It recurved, but caught a huge chunk of the US in the process. Once they get beyond 70W it's very tough for them to recurve without grabbing a piece of the East Coast.
Member Since: Posts: Comments:

Viewing: 126 - 76

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36Blog Index

Top of Page

Category 6™

About

Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather