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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I have a ominous feeling tonight 93L is going to organize and intensify overnight,something seems different w/93L,like charley feeling...../)
Member Since: October 5, 2007 Posts: 20 Comments: 4970
2745. JRRP
see you tomorrow




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2744. Seastep
And, even in the near term, stirring it up to let nature take its course more effectively underneath...
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Hey Pottery, not sure you heard the news from earlier... they got Dudus in custody today.
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2742. KEEPEROFTHEGATE (Mod)
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2741. ATL
Quoting Seastep:
I am being serious when I posit this.

I want to see a system go over the spill area. Not so sure it would be negative. Only way to know is for it to happen.

I am leaning towards it being a positive thing in the long term.

A 'cane would help disperse the oil. Yes it would carry it inland, but people forget just how little oil there is compared to the volume of water in the ocean.
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2740. KEEPEROFTHEGATE (Mod)
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2738. Seastep
Quoting KEEPEROFTHEGATE:
no no no its an oilcaster


Even better. LMAO.
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2737. Seastep
Hi Flood.

No one knows what would result.

Thinking dispersal would be good in the long term. Not so good in the near term.
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Quoting Patrap:
Well Im heading to the Wunderground Upstairs here.

Gonna be some Long Days ahead come the weekend most Likely.

Rest is a good thing always.

G'night as well.
Have a "Good Rest" it does look to be a very Long Weekend thats for sure :o)
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2735. KEEPEROFTHEGATE (Mod)
Quoting Tazmanian:




wishcaster
no no no its an oilcaster
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Quoting hunkerdown:
ironic that, tonight, all three local stations in Palm Beach County, Florida said that shear is low, conditions are favorable and there should be development in the days to come.

Wind shear you can see...that long roster tail of clouds going North of PR and NE into the atlantic is not just out flow..and there is some on the SE edge of the convection too..
The roster tail is also moisture that was stripped off 92L it will be really funny if a storm develops out there in the mid atlantic..
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2733. Seastep
Quoting Tazmanian:




wishcaster


lol
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Quoting Seastep:
I am being serious when I posit this.

I want to see a system go over the spill area. Not so sure it would be negative. Only way to know is for it to happen.

I am leaning towards it being a positive thing in the long term.


You need to get yourself a good slicker so you can be there...write us a report, huh?
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2731. Seastep
nite pat
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2730. KEEPEROFTHEGATE (Mod)
Quoting Patrap:
Well Im heading to the Wunderground Upstairs here.

Gonna be some Long Days ahead come the weekend most Likely.

Rest is a good thing always.

G'night as well.
later pat
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Quoting Seastep:
I am being serious when I posit this.

I want to see a system go over the spill area. Not so sure it would be negative. Only way to know is for it to happen.

I am leaning towards it being a positive thing in the long term.




wishcaster
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Just put up a new blog on93L
Member Since: May 16, 2009 Posts: 1 Comments: 1231
2727. pottery
Quoting Patrap:
Well Im heading to the Wunderground Upstairs here.

Gonna be some Long Days ahead come the weekend most Likely.

Rest is a good thing always.

G'night as well.

Sweet Dreams, Pat.
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2726. xcool
850mb vorticity NICE
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting Tazmanian:
with the gulf fill with oil may be evere one will leve town then stay and waiting it out with the hurricane un less they want too be swimming in oily gulf


i heard someone say that there would be more mandatory evacs due to the possibility of the oil coming far inland with surge and being spewed about with wind
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2723. Seastep
I am being serious when I posit this.

I want to see a system go over the spill area. Not so sure it would be negative. Only way to know is for it to happen.

I am leaning towards it being a positive thing in the long term.
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2722. Patrap
Well Im heading to the Wunderground Upstairs here.

Gonna be some Long Days ahead come the weekend most Likely.

Rest is a good thing always.

G'night as well.
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2721. pottery
Hi, Seastep,
All cisterns (3) and assorted watertanks have been overflowing for a week or so.
Been a particularly wet one.
No complaints.!
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Quoting Eyewall07:
Ok, Help me out here. I see that the latest run inizalize 93L at 15.5 & 75.5 ish. But looking at every available satelite, I can find anything that even resembles the look of a LLC. Comments ?


speed this loop up fast as it will go...
http://www.ssd.noaa.gov/goes/flt/t1/flash-ir2.html
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2719. KEEPEROFTHEGATE (Mod)
AOI/XX/XX
MARK
7.1N/39.9W
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with the gulf fill with oil may be evere one will leve town then stay and waiting it out with the hurricane un less they want too be swimming in oily gulf
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Quoting Patrap:
cmc 2010062212 Forecast 850vort Java Animation

Well this would give us a good start to the active season we have been expecting....
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2716. Patrap
00z Early Cycle NHC model tracks
Invest93
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)



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Quoting xcool:


NO WIND SHEAR





maybe they are viewing the anticyclone as wind shear since the system is still "young" - like previous poster said - sorry forgot your name and it's not on this page
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2714. Seastep
How you doing pottery? Trust the cistern is full.
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2713. KEEPEROFTHEGATE (Mod)
INV/93/L
MARK
17.1N/73.9W
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2711. pottery
Quoting hunkerdown:
ironic that, tonight, all three local stations in Palm Beach County, Florida said that shear is low, conditions are favorable and there should be development in the days to come.

They just do that, to confound people like me.
LOLOL
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Quoting Hurricanes12:


That system needs watching.


GFS shows wind shear droops in the CATL in 48hrs, that wave will have a chance in the long term.
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Ok, Help me out here. I see that the latest run inizalize 93L at 15.5 & 75.5 ish. But looking at every available satelite, I can find anything that even resembles the look of a LLC. Comments ?
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Possible circulation forming at 15.5 N, 74 W... imo. Take a good long look on IR channel 2 loop- i looked past the cold tops, tried to focus on low clouds.
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2707. xcool


NO WIND SHEAR



Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting pottery:

Nice Idea!
I had not thought of that possibility either...
Interesting.


i like the fire analogy! well done.
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hey good evening guys...just getting in from a long day...Whats the latest on 93L Someone...
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2703. beell
00Z GFS 700mb
Really big wave. Won't consolidate easily.
G'Nite, WU.

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



That system needs watching.
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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?
ironic that, tonight, all three local stations in Palm Beach County, Florida said that shear is low, conditions are favorable and there should be development in the days to come.
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2700. pottery
Quoting Comradez:
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.

Nice Idea!
I had not thought of that possibility either...
Interesting.
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2699. Seastep
Quoting clwstmchasr:
Very cool. First time using WIFI on an airplane. Right now somewhere over S Carolina heading for Tampa.


That is cool. What airline?
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Quoting JupiterFL:
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.

I'm supposed to fly in on Santiago, DR Thursday. Thinking its not looking too good right now
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Quoting germemiguel:
banding feature....8N40W....future 94L



That certainly bears watching.
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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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