Caribbean Disturbance 92L Moving Over the Yucatan; Erin Forms Off of Africa

By: Dr. Jeff Masters , 2:40 PM GMT on August 15, 2013

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The tropical wave in the Western Caribbean near the Yucatan Peninsula (92L) is growing more organized this morning, after an evening when it lost most of its heavy thunderstorm activity. Satellite loops show a modest-sized area of heavy thunderstorms that are increasing in intensity and areal coverage, but there are a no signs of a surface circulation. Winds at surface stations in the Western Caribbean also do not show a surface circulation. The highest surface wind reports this Thursday morning were at Western Caribbean buoy 42056 about 140 miles east southeast of Cozumel, which had east winds of 25 mph, gusting to 34 mph, at 10 am EDT. Wind shear is a moderate 10 - 20 knots over the the wave, which should allow slow development today until its west-northwest movement at 10 - 15 mph carries it over the Yucatan Peninsula Thursday afternoon. Four hurricane hunter flights were scheduled to fly into 92L today--an Air Force mission tasked to provide a center fix early this afternoon, two NOAA P-3 missions aimed at collecting real-time radar data to feed into the HWRF model, and a flight by the NOAA jet to collect dropsonde data around the periphery of 92L. However, all of these flights were cancelled, given that 92L did not organize as much as much as it could have.


Figure 1. MODIS satellite image of Invest 92L taken at 12:30 pm EDT Thursday August 15, 2013. Image credit: NASA.

Forecast for 92L
92L will trek across the Yucatan Peninsula Thursday evening and arrive in the Southern Gulf of Mexico on Friday, when it will have the opportunity to strengthen. The 06Z Thursday SHIPS model forecast predicts that 92L will remain in an area of low to moderate wind shear through Saturday, and ocean temperatures will be a favorable 29 - 30°C. The topography of the Southern Gulf of Mexico's Bay of Campeche can aid in getting a storm spinning more readily, but 92L may be far enough north that this influence will be negligible. Given all these factors, 92L should be able to become at least a tropical depression by Saturday, A trough of low pressure over the northern Gulf of Mexico will dip down by Saturday evening over the Central Gulf of Mexico, potentially increasing wind shear to a high 20 - 30 knots, stalling any further intensification. This trough may also be able to pull the storm northwards to a landfall between Eastern Louisiana and the Florida Panhandle, as the 00Z Thursday run of the European model is suggesting. This would bring a plenty of tropical moisture into the Southeast U.S., resulting in a large area of 4+" of rain. However, the other models show a more westerly track for 92L, with landfalls possible in Texas or Mexico south of the Texas border, and there is high uncertainty where 92L may go once it enters the Gulf of Mexico. In their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave 92L a 50% of developing by Saturday, and a 60% chance of developing by Tuesday.


Figure 2. MODIS satellite image of Tropical Storm Erin taken at 10:30 am EDT Thursday August 15, 2013. At the time, Erin had maximum sustained winds of 40 mph. Image credit: NASA.

Tropical Storm Erin
The season's fifth named storm of the year, Tropical Storm Erin, has formed over the far Eastern Atlantic off the coast of Africa. Erin is over warm waters of 27°C and is under a moderate 10 - 15 knots of wind shear, which should allow continued development today and Friday. Erin is a small storm, as seen on satellite loops. The 12Z Thursday SHIPS model forecast predicts that wind shear will be low to moderate for the next five days, which favors development. However, the waters beneath Erin will steadily cool to a marginal 26°C by Friday, and the atmosphere will steadily get drier, as the storm encounters the Saharan Air Layer (SAL), discouraging development. Erin's west-northwest motion will cut the storm off on Sunday from a moist source of air to its south--the semi-permanent band of tropical thunderstorms called the ITCZ (Inter-Tropical Convergence Zone.) The storm should weaken beginning on Sunday, which would result in Erin turning more to the west as the east-to-west blowing surface trade winds begin to dominate the steering of the shallower storm. We may see a situation like occurred for Tropical Storm Dorian in late July--intensification to a 60 mph tropical storm, followed by a slow decay and dissipation. The latest run of the GFS model calls for Erin to dissipate well before reaching the Lesser Antilles Islands.

Typhoon Utor dissipates
Typhoon Utor has dissipated after hitting Southeast China about 150 miles southwest of Hong Kong on Wednesday as a Category 1 storm with 90 mph winds. The typhoon is being blamed for 1 death in China, and sank a 21-person cargo ship off the coast. In the Philippines, where Utor hit as a Category 4 storm with 140 mph winds on Monday, 8 deaths are being blamed on the storm, and damage is estimated at $20 million.

Jeff Masters

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Quoting 1674. sar2401:

Yes indeed, quite spectacular. I've seen a few of these traveling through northern Arizona and New Mexico, and you can count on a few reports of UFO's right after the event. :-) I knew the Clovis/White Sands corridor has a number of supercells but I thought they usually came during the summer monsoons. I also thought actual tornadoes were fairly rare for the reason you stated. Even a "humid" day in Clovis during the monsoons will be something like a temperature of 90 and dewpoint of 63.


Yeah the monsoon season is definitely a good time of year for these storms, but that seems to favor western New Mexico and Arizona more. It certainly does impact eastern New Mexico as well tho.

In May and June, Eastern New Mexico and the adjacent parts of Texas tend to see a lot of storms. Depending on the location of the dryline, there can be some decent supercells. Clovis, however, is usually on the dry side.

One thing that part of New Mexico does have in its favor is elevation. The higher your elevation, the lower the dewpoint necessary for tornadogenesis. There was a tornado on the "cap rock" in the Texas Panhandle back in April when the dewpoint was 48 degrees. That's a rarity!
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Did someone say Blobzilla......LOL
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Quoting 1668. TropicalAnalystwx13:
The wave over western Africa already has a vigorous area of low pressure. It should emerge well south of the Cape Verde Islands.

Anybody have any thoughts on it?



I do indeed. A wave that vigorous has a tendency to close off a low very soon after exiting the coast, say by 25W. If that happens the odds become very high that it will not make it across but recurve well East of the islands and Bermuda.

It is a very rare year when a closed low that far out tranverses all the way to threaten the Islands and the Conus. The Atl. high would need to be particularly potent and so far the set up this year has not demonstrated that.

In summary,it has the appearance of being another Erin. Right now the low is near 4 W and 11 N. The convection is off to the NW of the circulation.

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Quoting 1687. Levi32:
Check out the latitude on that African wave on the CFS Day 4 forecast:



Funny how the GFS is showing it ending up well north of the islands. How did the CFS verify with latitude on Erin?
Member Since: July 8, 2005 Posts: 259 Comments: 23882
BULLETIN
TROPICAL STORM ERIN ADVISORY NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013
1100 PM AST THU AUG 15 2013

...ERIN HAS NOT STRENGTHENED YET...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...15.5N 29.1W
ABOUT 340 MI...550 KM W OF THE CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES

Member Since: April 29, 2009 Posts: 75 Comments: 14214
1687. Levi32
Check out the latitude on that African wave on the CFS Day 4 forecast:

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1686. sar2401
Quoting Skyepony:
Recent ASCAT of that wave ~43W.


We sailors used to call a wave chart that looked like that a "chaotic sea". I don't know if there's such a thing as a "chaotic sky", but that pass sure makes it look like there should be.
Member Since: October 2, 2004 Posts: 0 Comments: 14337
Quoting 1658. Camille33:

i saw it first!!

Kmanislander mentioned that wave at 45W earlier.
He's a pretty astute observer so it caught my attention.

Glad to see the African mega-blob got a name anyway, even if it ends up weakening in cooler waters, dry air, and heading off to sea. It had impressive beginnings, anyway.
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Near 40 W...
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1683. hydrus
Quoting 1675. KEEPEROFTHEGATE:
lots of water too wash everything away
This does give some folks a chance to dry out a little if more rain comes. UKMET is similar to the NAM..
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1682. KEEPEROFTHEGATE (Mod)
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1681. Skyepony (Mod)
Recent ASCAT of that wave ~43W.

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1680. Levi32
Quoting 1668. TropicalAnalystwx13:
The wave over western Africa already has a vigorous area of low pressure. It should emerge well south of the Cape Verde Islands.

Anybody have any thoughts on it?



GFS 700mb analysis is impressive. Models seem to stretch the wave out to the north after it emerges over water due to another weakness in the ridge off of Africa, enough to impede development. We'll see if the typical poleward bias comes into play again.



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1679. ncstorm
I know its been said to not look at the CFS but if you timed the Central atlantic wave and the beginning of the CFS ensembles, you see the possibility of this being threat..this was Tuesday's run








Member Since: August 19, 2006 Posts: 13 Comments: 15109
1678. hydrus
Quoting 1670. Patrap:
If Charlie Sheen was a met, I bet he would say the ULL is "Winning."



He would mind meld with it for a forecast...Charlie is out their like Pluto.
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1677. Relix
Kman, I have been watching 43W for a while (Pouch 20). I think tomorrow will be its lucky day.
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Quoting 1668. TropicalAnalystwx13:
The wave over western Africa already has a vigorous area of low pressure. It should emerge well south of the Cape Verde Islands.

Anybody have any thoughts on it?



If we could get some surface observations from the countries it would be good but those are sparce. I know of Dakar that has good observations.
Member Since: April 29, 2009 Posts: 75 Comments: 14214
1675. KEEPEROFTHEGATE (Mod)
Quoting 1669. hydrus:
I do not look at the NAM model often, but it has this system becoming very large, with a potent trough to the north.

lots of water too wash everything away
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1674. sar2401
Quoting tornadodude:


There are actually a decent number of supercell thunderstorms in Eastern New Mexico in the Spring/Summer.

Storms in this area and up through the plains can often have a "mothership" or "striated" appearance.

This storm in particular, although tornado warned, likely never had much chance of producing a tornado. With the temperature being 20 degrees warmer than the dewpoint, the cloud base is almost always too high to have a tornado touch down. Really hard to get the moisture to condense all the way down to the surface. Gorgeous storm.

Yes indeed, quite spectacular. I've seen a few of these traveling through northern Arizona and New Mexico, and you can count on a few reports of UFO's right after the event. :-) I knew the Clovis/White Sands corridor has a number of supercells but I thought they usually came during the summer monsoons. I also thought actual tornadoes were fairly rare for the reason you stated. Even a "humid" day in Clovis during the monsoons will be something like a temperature of 90 and dewpoint of 63.
Member Since: October 2, 2004 Posts: 0 Comments: 14337
Quoting 1670. Patrap:
If Charlie Sheen was a met, I bet he would say the ULL is "Winning."





Yes it is. Just sitting there shearing 92L like a sheep.

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1672. hydrus
Quoting 1668. TropicalAnalystwx13:
The wave over western Africa already has a vigorous area of low pressure. It should emerge well south of the Cape Verde Islands.

Anybody have any thoughts on it?

I ran the GFS yesterday. It had a 999 mb low over West Africa. It was still 200 miles from the Atlantic and looked like a tropical storm.
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Quoting 1654. stormpetrol:
Well as Kman predicted last night, what a relief with sunny skies and fresh breezes, a little hot as usual of course but what a beautiful day! I see 92L is holding it together convection wise pretty good tonight.Erin sames to want to move somewhat WSW in the last loops I've been watching.Bottomline, still an interesting season ahead , just starting!


Hi there

Yes, sunny today. How nice :-). I needed a break from the rain.

Next up is, possibly, 43 W. I hate saying I have a feeling about a wave but, well, I have a feeling LOL. Not a forecast of course !!.

The key is what happens between 45 and 60. The real sweet spot is actually between 55 and 60 so I will be watching for that but tonight is the first time it has shown some deep convection.
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1670. Patrap
If Charlie Sheen was a met, I bet he would say the ULL is "Winning."



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1669. hydrus
I do not look at the NAM model often, but it has this system becoming very large, with a potent trough to the north.

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The wave over western Africa already has a vigorous area of low pressure. It should emerge well south of the Cape Verde Islands.

Anybody have any thoughts on it?

Member Since: July 6, 2010 Posts: 113 Comments: 31883
Quoting 1660. Tornado6042008X:
AAAAAAAAHHH!!! The aliens have come to our planet and are dropping their alien juice to reproduce and take over our planet!................................J/K;) That is an impressive cloud structure Tornadodude.


It was on its way to Roswell
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Quoting 1658. Camille33:

i saw it first!!
actually no you didnt, someone mentioned it here yesterday and I forget the name.
Member Since: July 31, 2013 Posts: 0 Comments: 925
1665. Grothar
Remember a few days ago we named this Son of Blobzilla. Look out.

Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting 1662. Chucktown:
The ULL in the Gulf looks better than 92L. Just like the TUTT two weeks ago looked better than Dorian. Maybe we should start naming the ULL's. I don't think we are done with them yet this season.


Don't give TWC any ideas.
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Wickedawesome! ;)

Member Since: June 30, 2013 Posts: 12 Comments: 8086
The ULL in the Gulf looks better than 92L. Just like the TUTT two weeks ago looked better than Dorian. Maybe we should start naming the ULL's. I don't think we are done with them yet this season.
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I'm planning to drive from NOLA to Orange Beach, AL tomorrow night and return Sunday. I don't mind spending all weekend inside, but should I cancel due to the risk of driving in blinding rain?
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Quoting 1630. tornadodude:
This was the tornado-warned storm near Clovis earlier via @ariley081 on Twitter:

AAAAAAAAHHH!!! The aliens have come to our planet and are dropping their alien juice to reproduce and take over our planet!................................J/K;) That is an impressive cloud structure Tornadodude.
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the disturbance at 43W seems to be in a good environment. low wind shear and that will continue for a few days.also good 850mb vorticity as well as good convergence and divergence. should not be taken lightly.
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Quoting 1647. Gearsts:
Levi do you see the wave at 43w developing in the near future?

i saw it first!!
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Quoting 1653. Levi32:


It's worth watching if it can detach from the ITCZ.

NHC as of 8 p.m.
...TROPICAL WAVES...
A TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLANTIC EXTENDING AN AXIS FROM 21N45W TO 12N45W AND MOVING W NEAR 10 KT. TOTAL PRECIPITABLE WATER IMAGERY SHOW THE WAVE CONTINUE EMBEDDED WITHIN A MODERATE MOIST ENVIRONMENT AT THE LOWER LEVELS.
HOWEVER...METEOSAT SATELLITE IMAGERY SHOW SAHARAN DUST AND DRY AIR SPREADING OVER THE WAVE ENVIRONMENT WHICH IS SUPPRESSING CONVECTION.
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How much harm is the ULL to the north really doing to 92L and what role will it play in the track? It seems to be stealing a bit of 92L's convection.
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1655. sar2401
Quoting TimSoCal:


Is it just my imagination, or are there some deeper oranges over the Yucatan than there were over the Gulf of Honduras last night and this morning?

Yes, there are. Right around 19N,90W is where the low is developing over land, and firing off a fair bit of convection. What's interesting is this (what I believe to be the) low has been there for a couple of hours and has shown no inclination to move offshore. The BOC to the north of the Yucatan Peninsula seems to be eating clouds as soon as they try to form.
Member Since: October 2, 2004 Posts: 0 Comments: 14337
Well as Kman predicted last night, what a relief with sunny skies and fresh breezes, a little hot as usual of course but what a beautiful day! I see 92L is holding it together convection wise pretty good tonight.Erin sames to want to move somewhat WSW in the last loops I've been watching.Bottomline, still an interesting season ahead , just starting!
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1653. Levi32
Quoting 1647. Gearsts:
Levi do you see the wave at 43w developing in the near future?


It's worth watching if it can detach from the ITCZ.
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1652. JRRP

low shear for the wave in the CATL
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1651. ncstorm
Member Since: August 19, 2006 Posts: 13 Comments: 15109
1650. Patrap
Its like the play is set, the actor's dressed and the Orchestra is warming up...

Open da doors.


Let em in'





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1649. Grothar
The trough, the trough. Good night everyone.


Member Since: July 17, 2009 Posts: 71 Comments: 25996
Stop watching Erin. Here comes her bigger brother. Major Catastrophe... if not f I am wrong, the computer models won't be forever WRONG..,. FAIT
H IN THE COMPUTER MODELS!
pTRAP NO DISRESPECT YET follow the predicts of the comp. models
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1647. Gearsts
Quoting 1642. Levi32:
It's not completely over yet for 92L. Often it's hard to tell what these things will look like on the other side of the Yucatan. Also, visible satellite imagery suggests that the system is influencing the low-level flow over a much larger area than yesterday. ATCF confirms this by reporting the radius of the circulation to be 200 nautical miles. The larger a disturbance is, the harder it is to stretch it to the point of death, but we'll see how it looks once back over water.

Levi do you see the wave at 43w developing in the near future?
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1646. Patrap
Notice on the Late Viz to Night IR Loop here and note how much Atmosphere 92L is swinging around the Yucatan and Southern GOM.


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Quoting 1640. CybrTeddy:


FIM, CMC, HWRF, NAVGEM, seem to like this feature. Could get a mention in an upcoming TWO.


CMC NAVGEM HWRF FIM all busted high on the forecast intensity for this 92L, so take that with a grain of salt.
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1644. Patrap
Been mentioning 92 a Big Ballerina, once it can swing the mojo around, it could go the way of the ships intensity..maybe.
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Quoting 1636. sar2401:

That is one oddball looking storm, especially for Clovis, which gets, what, a couple of tornadoes a decade? Did this ever turn into a confirmed tornado?


There are actually a decent number of supercell thunderstorms in Eastern New Mexico in the Spring/Summer.

Storms in this area and up through the plains can often have a "mothership" or "striated" appearance.

This storm in particular, although tornado warned, likely never had much chance of producing a tornado. With the temperature being 20 degrees warmer than the dewpoint, the cloud base is almost always too high to have a tornado touch down. Really hard to get the moisture to condense all the way down to the surface. Gorgeous storm.
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1642. Levi32
It's not completely over yet for 92L. Often it's hard to tell what these things will look like on the other side of the Yucatan. Also, visible satellite imagery suggests that the system is influencing the low-level flow over a much larger area than yesterday. ATCF confirms this by reporting the radius of the circulation to be 200 nautical miles. The larger a disturbance is, the harder it is to stretch it to the point of death, but we'll see how it looks once back over water.

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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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