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: 1226 - 1176

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 LargoFl:
if it just stays right there half on the coast half off..and continues northward, might be a good thing for the parched area's of southern texas, most of the models have this down to a Low again sooner than later, for now something to watch,wait and see what happens


Yep if she could ride the coast up and pump some rain into those areas it would help. As long as it's not too much in one place.
Member Since: Posts: Comments:
1225. LargoFl
Member Since: Posts: Comments:
1224. LargoFl
Quoting AtHomeInTX:
To me Helene looks to be at least partly onshore. I know there's a circulation to the west but the one just on the coast that's firing convection is what I'm talking about.

if it just stays right there half on the coast half off..and continues northward, might be a good thing for the parched area's of southern texas, most of the models have this down to a Low again sooner than later, for now something to watch,wait and see what happens
Member Since: Posts: Comments:
She's very near the 22n line and about due east of Tampico
Member Since: Posts: Comments:
To me Helene looks to be at least partly onshore. I know there's a circulation to the west but the one just on the coast that's firing convection is what I'm talking about.

Member Since: Posts: Comments:
1221. LargoFl
Member Since: Posts: Comments:
1220. LargoFl
Member Since: Posts: Comments:
1219. scott39
look for the track of Helene to go NNW on the next advisory.
Member Since: December 31, 1969 Posts: Comments:
1218. LargoFl
...................Good Morning Folks..looks like we are going to have a very active tropical week ahead huh..ok around here, still not a drop of rain but..some area's of florida got a good soaking yesterday and probably the next few days as well.....have a great weekend everyone
Member Since: Posts: Comments:
1217. LargoFl
Member Since: Posts: Comments:
1216. scott39
Helene is starting to put on a color-convection show for us.
Member Since: December 31, 1969 Posts: Comments:
1215. Walshy
Member Since: Posts: Comments:
00z UKMET 120 hours. Developing storm off the islands.
Member Since: Posts: Comments:
A few rain bands showing up on the Brownsville Radar.
Member Since: Posts: Comments:
Quoting STXHurricanes2012:
I wonder what is the HPC's take on Helene this morning on the model runs!


Well from 0z runs

PREFERENCE: GFS/ECMWF/UKMET
CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE

THE NAM/GFS AND OTHER MODELS SHOW VARYING SOLNS FOR ENERGY FROM
T.S. HELENE AND/OR ONE OR MORE OTHER IMPULSES NEAR THE WRN GULF
COAST TO THE S OF THE RIO GRANDE... WITH SOME STREAMING NEWD INTO
THE SE AHEAD OF THE ERN CONUS TROF AND SOME LINGERING OVER THE WRN
GULF. TYPICAL BIASES SHOULD FAVOR THE GFS/ECMWF/UKMET WHICH ARE
GENERALLY A LITTLE WEAKER/LESS CONCENTRATED VERSUS THE
NAM/CANADIAN GLBL WITH WHAT ENERGY REMAINS NEAR THE MEXICO COAST.
CONSULT LATEST NHC DISCUSSIONS/ADVISORIES FOR FURTHER INFO
REGARDING T.S. HELENE.
Member Since: Posts: Comments:
1211. SLU
THE NEXT TROPICAL WAVE WILL IMPACT THE TROPICAL N ATLC WATERS
LATE SUN INTO MON...MOVING THROUGH THE E CARIBBEAN TUE AND WED
WITH LITTLE FANFARE. ALL EYES WILL BE ON THE FOLLOWING WAVE
CURRENTLY OVER THE CAPE VERDE ISLANDS WITH ATTENDANT LOW PRES
NEAR 12N27W AT 0600 UTC. ALL GLOBAL MODEL GUIDANCE...ESPECIALLY
THE GFS...RAPIDLY DEVELOPS AND INTENSIFIES THIS LOW AS IT MOVES
W-NW WITH ASSOCIATED CONDITIONS IMPACTING THE TROPICAL N ATLC
BEGINNING LATE TUE THROUGH THU. THIS LOW/TROPICAL WAVE HAS A
MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS AND INTERESTS IN THE E CARIBBEAN ISLANDS SHOULD CONTINUE
TO MONITOR ITS PROGRESS DURING THE NEXT SEVERAL DAYS.

A BLEND OF THE GFS AND ECMWF WAS USED THROUGHOUT THE NEXT 5
DAYS...WITH WINDS CAPPED AT 30 KT AND SEAS AT 14 FT...FOR NOW.
Member Since: Posts: Comments:
1210. scott39
Ive seen pathetic TCs change to major hurricanes. ExTD7 has died before and look how it came back. Any viral system that does not go inland and rides the coast is something to watch very closely. Im rooting for it, so Texas and the mid west can get much needed rain. Everyone should be pulling for this one.
Member Since: December 31, 1969 Posts: Comments:
I wonder what is the HPC's take on Helene this morning on the model runs!
Member Since: Posts: Comments:
1208. SLU
Quoting AtHomeInTX:


If so then I hope it recurves out to sea even faster.


keeping my fingers crossed too
Member Since: Posts: Comments:
Quoting scott39:
That is a strong trough coming down from the N for August. If Helene sits there.....it has no choice but to feel its effect and pull it more N.


If she gains a little latitude and holds herself together she might.
Member Since: Posts: Comments:
1206. VR46L
It Sure is going to be an interesting week next week!!!!

Member Since: Posts: Comments:
1205. scott39
That is a strong trough coming down from the N for August. If Helene sits there.....it has no choice but to feel its effect and pull it more N.
Member Since: December 31, 1969 Posts: Comments:
Quoting SLU:


Looks like it could be far worse than a just strong TS/ cat 1 hurricane. The latest LGEM, SHIPS and ICON intensity models all take it to 125 - 130mph in 5 days ...... Once this system gets going, there could be nothing to stop it .....


If so then I hope it recurves out to sea even faster.
Member Since: Posts: Comments:
Quoting Walshy:


Pathetic

Well it had no convection at all earlier...this is slightly better though.
Member Since: Posts: Comments:
Quoting scott39:
What is the latest GFS doing with Helene?


Just drifting it around where it is basically.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
1200. SLU
Quoting stoormfury:
looking at the steering currents this morning and coupled with the fact ,that there is no strong trough to pull 94L quickly north,94L will continue to track to the north of west for a few days.i anticipate the system will reach the lesser antilles as strong TS or a cat1 hurricane. my concern is what is going to be 95L following it's path.


Looks like it could be far worse than a just strong TS/ cat 1 hurricane. The latest LGEM, SHIPS and ICON intensity models all take it to 125 - 130mph in 5 days ...... Once this system gets going, there could be nothing to stop it .....
Member Since: Posts: Comments:
Quoting Walshy:


Pathetic


good
Member Since: Posts: Comments:
1198. pcola57
Quoting scott39:
Lets hope so


Yeah,still way behind.. :(
Member Since: Posts: Comments:
1197. scott39
What is the latest GFS doing with Helene?
Member Since: December 31, 1969 Posts: Comments:
1196. Walshy


Pathetic
Member Since: Posts: Comments:
6z NAM takes Helene off of the coast after a brief landfall!
Member Since: Posts: Comments:
1194. scott39
Quoting pcola57:
Precip. Forcast..Goddard..24hrs



Precip.Forcast..Goddard..48hrs..







Looks like some rain in the forcast for some of the drought stricken areas
Lets hope so
Member Since: December 31, 1969 Posts: Comments:
Quoting bigwes6844:
Gordon seems to have an eye forming! should be interesting in a few mins if it is a cane


Yep it made it.
Member Since: Posts: Comments:
1192. scott39
Dont count Helene out yet for the long term. She is going to be too close to the water to write her off.
Member Since: December 31, 1969 Posts: Comments:
Finally she's popping convection over the center again will see how this one goes.
Member Since: Posts: Comments:
Quoting STXHurricanes2012:

Interesting if this moves a tiny bit more east it'll be over water still and will be able to strengthen maybe.Will just have to see!


Yeah they have it drifting north just onshore. But that's close.
Member Since: Posts: Comments:
1189. pcola57

Looks like some rain in the forcast for some of the drought stricken areas
Member Since: Posts: Comments:
Quoting AtHomeInTX:
Moved it a little bit east.


Interesting if this moves a tiny bit more east it'll be over water still and will be able to strengthen maybe.Will just have to see!
Member Since: Posts: Comments:
1187. Kumo
Quoting zillaTX:
so much 94L focus, panic,worry.. look helene has not even made landfall! wtf?


Panic and worry? Probably not but definitely interest. Speculation and predicting the future track of a storm is a hobby for some folks here, they've already got a pretty good idea where Helene is going and therefore it is less interesting for some folks to continue to monitor it. Besides Helene will very likely not be much of a threat to anyone. The farmers and ranchers down in Mexico are definitely going to be digging those beneficial rains.
Member Since: Posts: Comments:
1186. Walshy
Hurricane Gordon

Member Since: Posts: Comments:
...GORDON BECOMES A HURRICANE...TROPICAL STORM WARNING ISSUED FOR THE CENTRAL AND EASTERN AZORES...
5:00 AM AST Sat Aug 18
Location: 34.0°N 40.7°W
Moving: E at 18 mph
Min pressure: 988 mb
Max sustained: 75 mph


Hurricane GORDON.


8-3-0.
Member Since: Posts: Comments:
1184. scott39
Quoting AtHomeInTX:
Moved it a little bit east.

I would look for that trend to continue, I wonder if some of that new convection to the SE and SW of the COC is going to try and wrap into it?
Member Since: December 31, 1969 Posts: Comments:
Moved it a little bit east.

Member Since: Posts: Comments:
1182. pcola57
.
Member Since: Posts: Comments:
looking at the steering currents this morning and coupled with the fact ,that there is no strong trough to pull 94L quickly north,94L will continue to track to the north of west for a few days.i anticipate the system will reach the lesser antilles as strong TS or a cat1 hurricane. my concern is what is going to be 95L following it's path.
Member Since: Posts: Comments:
Derived from (NHC) ATCF data for TropicalStormHelene for 18August6amGMT
MinimumPressure increased from 1006millibars to 1007millibars
MaxSusWinds held to 35knots(40mph)65km/h
Vector changed 339.4*NNWest@6.1mph(9.9km/h) to 323.2*NWest@7.2mph(11.5km/h)

CVM-CiudadVictoria
TAM-Tampico :: MMNU-Nautla :: VER-Veracruz :: VER-Ciudad del Carmen :: CPE-Campeche

The westernmost dot on the kinked line is where exTD.7's became a TropicalDepression again
The next dot NNWest of that dot is where TD.7 became TropicalStormHelene
The southernmost dot on the longest straight line is TS.Helene's most recent position

The longest line is a straightline projection thru exTD.7's 2 most recent positions to the coastline
17August6pmGMT: exTD.7 had been headed toward passage over LaPesca (nearCVMdumbbell,bottom)
18August12amGMT: exTD.7 had been headed toward passage over El Porvenir (nearCVMdumbbell,top)
18August6amGMT: exTD.7 was heading toward passage over Aldama in ~16hours from now (when this mapping was posted)

Copy&paste cvm, 23.9n97.75w-24.575n97.661w, cvm, tam, mmnu, ver, cme, cpe, pcm, 19.2n90.7w- 19.3n92.6w- 19.3n94.2w- 19.7n95.2w- 19.9n95.7w, 19.9n95.7w-20.3n95.9w, 20.3n95.9w-20.8n96.1w, 20.8n96.1w-21.3n96.5w, 20.8n96.1w-22.87n97.775w into the GreatCircleMapper for a larger-scale map and other information
The previous mapping for comparison
Member Since: Posts: Comments:
Quoting andsnowon:
Dare I note it? 94 a little power, but a def. recurve. Back out to sea. We're fairing too well this year by far. An invest bearing a watch has to be born in Carr/Gulf. Season far from over.
Hey Mexico, the US could sure use some rain please...


There are never any definites in tropical cyclone forecasting.


Most of the GFS ensembles have switched south as well.

Member Since: Posts: Comments:
94L, I assume, it's 94L, was placed in NYC & Newfoundland by the GFS earlier. It's possible location has been everywhere.
Member Since: Posts: Comments:
Dare I note it? 94 a little power, but a def. recurve. Back out to sea. We're fairing too well this year by far. An invest bearing a watch has to be born in Carr/Gulf. Season far from over.
Hey Mexico, the US could sure use some rain please...
Member Since: Posts: Comments:
Disregarding the euro run due to lack of model consistency - the previous runs had a major hurricane. the 00z CMC/GGEM have a good handle on the system's track and intensity IMO. There is no reason that 94L shouldn't develop into a powerful tropical cyclone and the Euro model has been showing it for days. Just typical that it would drop it.
Member Since: Posts: Comments:

Viewing: 1226 - 1176

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