93L slow to develop, but bringing heavy rains to Haiti

By: Dr. Jeff Masters , 1:50 PM GMT on June 22, 2010

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A modest region of intense thunderstorms (Invest 93L) is over the central Caribbean, a few hundred miles south of Hispaniola. This disturbance has the best chance to become Tropical Storm Alex of any system we've seen so far this year. We don't have any buoys near 93L, but pressures at the ground stations surrounding the storm are not falling. A pass of the ASCAT satellite over the Central Caribbean at 9:45 pm EDT last night revealed a modest wind shift associated with 93L, but nothing at all close to a surface circulation. Top surface winds seen by ASCAT were 15 - 20 mph. Water vapor satellite loops show that 93L is embedded in a large region of moist air. The atmosphere over the Caribbean has moistened over the past day, which should aid development of 93L. Wind shear is a low 5 - 10 knots. The high wind shear associated with the strong winds of the subtropical jet stream are over the northern Caribbean, too far north to interfere with development, but close enough to provide good upper-level outflow for the storm. Visible satellite loops show high level cirrus clouds streaming away from 93L to the northeast, evidence of the upper-level outflow channel that is developing to the storm's north. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The main negative for 93L continues to be lack of spin. The University of Wisconsin 850 mb relative vorticity analysis is showing that spin at 850 mb (roughly 5,000 feet in altitude) has increased over the past day, but 93L needs to acquire additional spin before it can grow more organized. I speculate that it is this lack of spin that contributed to the loss of much of 93L's heavy thunderstorm activity last night. The storm is now going through a cycle where it is building another respectable mass of heavy thunderstorms, and the increased inflow of low-level air that will feed these thunderstorms will likely enhance 93L's spin today. The Hurricane Hunters are on call to investigate 93L on Wednesday afternoon.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.

Forecast for 93L
NHC is giving 93L a 40% chance of developing into a tropical depression by Thursday morning, which is a reasonable forecast. Given the storm's current lack of spin and relatively modest amount of heavy thunderstorms, the earliest I'd expect 93L to become a tropical depression would be Wednesday afternoon, with Thursday more likely. Wind shear is expected to be low, less than 10 knots, over the central and western Caribbean this week. Water temperatures will be warm, dry air absent, and the MJO favorable. I don't see any major impediments to the storm becoming a tropical depression by Thursday, and it is a bit of a surprise to me that the computer models have been reluctant to develop 93L. The GFS, NOGAPS, and UKMET models do not develop 93L, and the ECMWF model doesn't develop 93L until after it crosses the Yucatan Peninsula and enters the Gulf of Mexico in a about a week. The current (2am EDT) run of the GFDL model predicts 93L will be a weak tropical storm in the Gulf of Mexico in five days; its previous run had 93L as a major hurricane in the Gulf. Given all this model reluctance and the current disorganization of 93L, I give the storm a low (less than 20% chance) of becoming a hurricane in the Caribbean. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica, eastern Cuba, and southwestern Haiti today through Wednesday. These rains will spread to the Cayman Islands and central Cuba by Thursday, and western Cuba and Mexico's Yucatan Peninsula on Friday. The current run of the SHIPS model has 93L slowing down late this week to a forward speed of just 6 knots (7 mph) from its current speed of about 10 mph, in response to a weakening in the steering currents. A trough of low pressure is expected to swing down over the Eastern U.S. early next week. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast in the oil spill region. This is the solution of the Canadian GEM model. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards towards the Texas coast. This is the solution of the ECMWF model. The amount of wind shear in the Gulf of Mexico next week is highly uncertain. There is currently a band of high shear near 30 knots over the Gulf, and some of the models predict this shear will remain over the Gulf over the next 7 - 10 days. However, other models predict that this band of high shear will retreat northwards and leave the Gulf nearly shear-free. The long-term fate of 93L remains very murky. My main concerns at this point are the potential for 3 - 6 inches of rain in Haiti over the next two days, and the possibility 93L could become a hurricane in the Gulf of Mexico next week.

Elsewhere in the tropics
None of the reliable computer models is calling for tropical cyclone formation elsewhere in the Atlantic over the next seven days.

Floods in China and Burma kill over 250
The deadliest and most destructive weather-related disaster on the planet so far this year is occurring in southern China and northern Burma, where a week of heavy rains has caused flooding that has claimed over 250 lives. The heavy rains and floods ravaging 10 southern Chinese provinces had killed 199 and left 123 missing as of 11:00 a.m. Tuesday, a Ministry of Civil Affairs statement said. Damage is estimated at $6.2 billion. Floods and landslides in neighboring areas of Myanmar (Burma) have claimed at least 63 lives in the past week.


Figure 2. Paramilitary policemen help evacuate residents from Wanjia village of Fuzhou City, East China's Jiangxi province, June 22, 2010. Days of heavy rain burst the Changkai Dike of Fu River on June 21, threatening the lives of 145,000 local people. Local authorities have ordered immediate evacuation, and the army and paramilitary police have begun conducting rescue operations. Image credit: Xinhua.

Wind and ocean current forecast for the BP oil disaster
Southeast to east winds less than 10 knots will blow in the northern Gulf of Mexico today through Saturday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should cause little motion of the oil slick, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) The latest on 93L
2) Which model is the most reliable?

Today's show will be 30 - 40 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

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Quoting germemiguel:
banding feature....8N40W....future 94L



That certainly bears watching.
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11:00 pm NHC Advisories: GRAPHICS UPDATE


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banding feature....8N40W....future 94L

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Quoting MiamiHurricanes09:
That rotation is caused by an MCV in the mid levels that is over land.



I would suggest to you that Vorticity does not confirm what you are saying now in my opinion!



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2692. pottery
Quoting taco2me61:
not any more there Pottery

Taco :o)

heheheheh
just pushin'
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I think another factor that we might be dealing with is an upper-level anticyclone that is a bit too strong for this stage of development.

As an analogy, picture yourself trying to start a fire. Once the fire is rip-roaring, you can blow on it all you want and it will only get stronger from all of that fanning. But when starting the fire with just a little flame, if you blow too hard you blow the flame out before it can ever get started.

So, when a system is just getting going with a strong anticyclone right over it, unless that anticyclone is EXACTLY on top of the LLC, then all of that "ventilation" instead becomes shear on the fragile convection around the LLC. But later, when the system is stronger, it can benefit from a strong anticyclone, even if it is not exactly over the LLC, as long as it is near it.

So perhaps the best upper-level environment for cyclogenesis is merely a gentle anticyclone.
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2690. Seastep
Quoting MiamiHurricanes09:
Still a while before D-Max.


Having some fun Miami... irrelevant.
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2689. leo305
the area of low pressure that was moving into the lower antilles this morning is going to merge with the convection near puerto rico/DR.. I assume it will devlop
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Quoting clwstmchasr:
Very cool. First time using WIFI on an airplane. Right now somewhere over S Carolina heading for Tampa.



hmmm they went you ues your laptop on a airplane??? i was thinking they had rules about that or at lest drung take off and landing
Member Since: May 21, 2006 Posts: 5089 Comments: 114041
Quoting MiamiHurricanes09:
Same thing here in Miami. Thing is that there is anticyclone placed aloft deflecting shear, so don't know what they're talking about. Well I'm off to bed. Good night all!


maybe it's too complicated the viewers so they just keep it simple by saying that shear is the problem?? his name is Dave Naussbam. He's young, so it's hard to say if he respected yet. Well, I guess the young usually aren't.
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Quoting Patrap:


Lotsa time between now and How this thing comes off the Yucatan TS.

Once in..theres only one way out for a Cyclone in the GOM,

I urge all GOM Residents though to pay close attention come Later this week as it becomes clearer as to track and intensity.



YEP good advise as the door always closes when it enters that open door from the South...it always takes residents somewhere wanting to eat someones meal.
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Quoting Tazmanian:




ok



can you tell me wish one is 93L??????












PLZS
That large area of convection to the east of the Dominican Republic will probably detach itself from 93L and affect the Bahamas later. Ok now I'm out.
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Quoting pottery:

AH!! But people on here have been saying that shear has NOT been the issue with 93L...
Who is your local Met., and is he respected?
not any more there Pottery

Taco :o)
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Quoting TampaSpin:


LOOK at this LOOP!!!! EAsily seen here! Although this is not a Visible so i would not speculate to much what we are seeing until i see a True Visible Satellite or Vorticity tightens up with this SPIN!
Floater - Infrared Channel 2 Loop
That rotation is caused by an MCV in the mid levels that is over land.

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Quoting Patrap:
The Flue is open..the Fuse is Lit.

Bada Bing,Bada Boom.

Jus Like dat,

Floater - Rainbow Color Infrared Loop


Yeah, it's on.
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Quoting pottery:

AH!! But people on here have been saying that shear has NOT been the issue with 93L...
Who is your local Met., and is he respected?
Same thing here in Miami. Thing is that there is anticyclone placed aloft deflecting shear, so don't know what they're talking about. Well I'm off to bed. Good night all!
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Quoting MiamiHurricanes09:
A mesoscale convective vortex (MCV) is a low-pressure center within an mesoscale convective system (MCS) that pulls winds into a circling pattern, or vortex. With a core only 30 to 60 miles wide and 1 to 3 miles deep, an MCV is often overlooked in standard weather analysis. But an MCV can take on a life of its own, persisting for up to 12 hours after its parent MCS has dissipated. This orphaned MCV will sometimes then become the seed of the next thunderstorm outbreak. An MCV that moves into tropical waters, such as the Gulf of Mexico, can serve as the nucleus for a tropical storm or hurricane.




ok



can you tell me wish one is 93L??????












PLZS
Member Since: May 21, 2006 Posts: 5089 Comments: 114041
2678. scott39
The track of 93L will change 20 times, if and when it hits land! It is irresponsible to say that certain parts of the Gulf Coast have nothing to worry about! Everyone from Mexico to W FL. need to watch with caution and prepare when and if it comes to you.
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does anyone else see a almost closed circulation center near the morant cays 50 mi sse of jamaica
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Quoting Patrap:
The Flue is open..the Fuse is Lit.

Bada Bing,Bada Boom.

Jus Like dat,

Floater - Rainbow Color Infrared Loop


LOOK at this LOOP!!!! EAsily seen here! Although this is not a Visible so i would not speculate to much what we are seeing until i see a True Visible Satellite or Vorticity tightens up with this SPIN!
Floater - Infrared Channel 2 Loop
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2675. xcool
fires up
Member Since: September 26, 2009 Posts: 2 Comments: 15603
2674. will45
Read my post i said if it gets its act together.
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Quoting Seastep:
Oh, I forgot. It's DMAX.

Love it.
Still a while before D-Max.
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2672. pottery
Quoting truecajun:
our local met says that shear is hindering 93L right now, but it should move into more favorable conditions in 2-3 days.

AH!! But people on here have been saying that shear has NOT been the issue with 93L...
Who is your local Met., and is he respected?
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I think we all are especially after the last model runs. Maybe Mother nature is trying to take out BP their command post is right here in Houma, LA. LOL
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2670. Seastep
Oh, I forgot. It's DMAX.

Love it.
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Quoting TampaSpin:


YEP I am getting an ILL felling in my tummy for you all up there Pat! Just sayn Brother!
ok Tampa enoght talking about that!!!! Just wondering if we could send this to the Atlantic and not The Gulf of Mexico :o)

Taco :o)
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Quoting Seastep:


There is validity to the thought. In my experience, whatever the "curve" trend of the model consensus is generally continues in that direction over time.

But, no storm yet so really moot.
Exactly.
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I hardly ever post here, but that CMC run is insane.

Enjoy the conversation, though I am usually in lurker mode. Will be watching whatever is going to happen from here in Pensacola.
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2666. Patrap
Quoting TampaSpin:


YEP I am getting an ILL felling in my tummy for you all up there Pat! Just sayn Brother!


Lotsa time between now and How this thing comes off the Yucatan TS.

Once in..theres only one way out for a Cyclone in the GOM,

I urge all GOM Residents though to pay close attention come Later this week as it becomes clearer as to track and intensity.

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2665. Seastep
Quoting MiamiHurricanes09:
Doubt it.


There is validity to the thought. In my experience, whatever the "curve" trend of the model consensus is generally continues in that direction over time.

But, no storm yet so really moot.
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Quoting will45:


the ridge that will be moving off the east coast
Oh. Well it certainly can act as a weakness, let's see if 93L takes advantage of it.
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2663. will45
Quoting MiamiHurricanes09:
Weakness from what?


the ridge that will be moving off the east coast
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Quoting Patrap:
The Flue is open..the Fuse is Lit.

Bada Bing,Bada Bom.

Jus Like dat,

Floater - Rainbow Color Infrared Loop


YEP I am getting an ILL felling in my tummy for you all up there Pat! Just sayn Brother!
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It looks like I got out of the DR just in time. The dark clouds were starting to roll in as my plane took off yesterday morning.
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Quoting MiamiHurricanes09:
Love the new "headline" part.


Thanks!
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Quoting Tazmanian:
D MAX D MAX DAMX




ok all wish one is 93L

Maybe the CMC is not that far off LOL.
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Quoting will45:
If 93L gets its act together. It may well feel the weakness and be pulled further north
Weakness from what?
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our local met says that shear is hindering 93L right now, but it should move into more favorable conditions in 2-3 days.
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Quoting Tazmanian:



???????????????
A mesoscale convective vortex (MCV) is a low-pressure center within an mesoscale convective system (MCS) that pulls winds into a circling pattern, or vortex. With a core only 30 to 60 miles wide and 1 to 3 miles deep, an MCV is often overlooked in standard weather analysis. But an MCV can take on a life of its own, persisting for up to 12 hours after its parent MCS has dissipated. This orphaned MCV will sometimes then become the seed of the next thunderstorm outbreak. An MCV that moves into tropical waters, such as the Gulf of Mexico, can serve as the nucleus for a tropical storm or hurricane.
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2654. Patrap
The Flue is open..the Fuse is Lit.

Bada Bing,Bada Boom.

Jus Like dat,

Floater - Rainbow Color Infrared Loop
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2653. will45
If 93L gets its act together. It may well feel the weakness and be pulled further north
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Quoting RecordSeason:
MCC near DR and Haiti just lost the war. Low at 75W is free to develop.

IR2



???????????????
Member Since: May 21, 2006 Posts: 5089 Comments: 114041
Quoting AllStar17:
11:00 pm NHC Advisories: GRAPHICS UPDATE


Love the new "headline" part.
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Quoting RecordSeason:
MCC near DR and Haiti just lost the war. Low at 75W is free to develop.

IR2
Yeah looks like the MCV dissipated over land. You know what that means? 93L should begin to improve at the surface now since it doesn't have anything basically stealing its energy.
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2649. Patrap
Floater - RGB Color Infrared Loop
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Are any of the models predicting any other tropical cyclones coming off of africa?
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11:00 pm NHC Advisories: GRAPHICS UPDATE


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Quoting CaneWarning:


I've been saying all along that the West Coast of Florida and panhandle need to watch this one...if it develops.
Doubt it.
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About JeffMasters

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