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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545. unf97
Quoting StSimonsIslandGAGuy:
Hey UNF97, Canewarning. 93L still looks pretty ragged. My guess yesterday of no development before Wednesday night just might be right!

Weather here is hot and humid, with highs near 88 and lows near 74 the past few days.


Hey SSIGuy, Yes it is an extremely humid day in Jax. I don't know which is worst, this week's humidity, or last weeks 100 degree+ temps we had for 4 days.
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can anyone explain why the WPac has been so quiet this season so far?
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HELP!
My iggy feature isnt working! :/
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Quoting EarthMuffin:
Please post models to back this up, fake JFV, and prove you're the real deal.


Tsk tsk, if he was real he waould have referred to StormW as master Chief...he'll get dropped soon enough....click
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Quoting StSimonsIslandGAGuy:
Hey UNF97, Canewarning. 93L still looks pretty ragged. My guess yesterday of no development before Wednesday night just might be right!

Weather here is hot and humid, with highs near 88 and lows near 74 the past few days.


Hey! I'm starting to wonder if this thing will develop, and if it does, maybe not until Thursday.
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Quoting tropicfreak:


aww man what ashame, so many spelling errors.


Ahhhm yes, a prime example of our "excellent" public education system in Florida!
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Can someone post the most current 850 vorticy map? I'm not on my laptop so I don't have the links saved!
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I can see the circulation forming west in time, not north, I don't understand where all of you are getting north and land interaction from. I'm looking at a nice broad low right now, needs to tighten and close.
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**REPOST**
Hurricane Celia (Category 2)
*NEW* Graphics Update
Time: 8am PDT/11am EDT
Images made by cyclonekid
Click on images to make them larger


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Quoting GTcooliebai:

So basically a stronger system would feel a weakness in the ridge thus pulling it towards FL. And a weaker system follows the lower level steering which would take the storm west into Texas?



Exactly. If you look at the various GFDL runs, it swings east and west with intensity.
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529. unf97
Quoting GTcooliebai:

So basically a stronger system would feel a weakness in the ridge thus pulling it towards FL. And a weaker system follows the lower level steering which would take the storm west into Texas?


If this scenario evolves in this particular way, a stronger tropical cyclone would get picked up by the trough, yes. But, this is still a ways off in time and we will still have to remain vigilant as conditions often change of course.
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Quoting Acemmett90:

lol at worst those are cat 1's and they are not tropical in nature


A cat 1 non-tropical system? That would be a first...
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Quoting JFVfromFlorida:
Hi whats up guys.


i call bs...and >>>>>theres the door...enjoy iggyland :)...

93 is gonna take most of the day to consolidate... i think by tonight, overnight during dmax we will see another side...
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#522

Not with the iggy feature.

And 3 Letter Hybrids go there immediately,..and the ones quoting them
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Quoting Acemmett90:

lol at worst those are cat 1's and they are not tropical in nature
They're not tropical? Would you mind telling us what you think they are then? lol
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Shen, that won't work...the trolls will just ask their moms for an extra $20 on their weekly allowance....


;)
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You know, I'm sure the "real" JFV is still on this blog under a different handle, trying to post normal things like the rest of us.

He wasn't a troll, he just asked really ridiculous questions...

We turned JFV into a troll and talked about him so much that now a real troll took his handle and is bothering us.
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520. MahFL
Quoting tropicfreak:


aww man what ashame, so many spelling errors.


Like your's, and your typo ?
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Quoting GTcooliebai:

So basically a stronger system would feel a weakness in the ridge thus pulling it towards FL. And a weaker system follows the lower level steering which would take the storm west into Texas?


Correct.. actually just a LLC with a midlevel connection to it. If its a weak low swirl.. it will still move west but if its a well organized LLC with midlevels it will feel the weakness and move north and NE. Sometimes the LLC if its weak will move west while the midlevel moisture will move NE as it decouples.
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Quoting Patrap:
This Season on NOLA Wasp Wars Uptown

Yellow Jackets 2

Patrap 0


I battled a whole bunch of wasps yesterday...but I won...lol... :)
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Please post models to back this up, fake JFV, and prove you're the real deal.
Quoting JFVfromFlorida:
MAJOR HURRICANE CAT 4/5 IS 80% LIKELY TO OCCER.
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On a different note, with only 4 depressions and 1 named storm, the WPAC has been unusually quiet so far this year...

Link
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512. IKE
Quoting nrtiwlnvragn:


Ya, you can see that well on the 850mb vort.


That is a huge difference.

Quoting scottsvb:
Well from looking @ the longer range models.. whatever is in the central GOM east of 90W and north of 22N will move N then NE. The weaker the broad low (if any) will continue though W towards the western GOM. Anything with a close LLC will move north early next week and NE as the eastern U.S. trough digs down to the GOM from 90W eastward.


I agree with you. That is a significant trough in the east.

Mets from the Tallahassee office have been mentioning the eastern USA trough early next week....

"THEN BOTH THE GFS AND 12Z EURO SHOWS THE RIDGING
BREAKING DOWN AS A TROUGH DIGS ALONG THE EASTERN SEABOARD ON
TUESDAY."
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting StormW:


OUCH!


It was a ambush chief..they was under the BBQ Pit,..just a lurking on their Nest.

And I came bouncing out with the Coals and Mesquite and it was Ugly.


But that Raid Insta Kill was fast Like Puff da Magic Dragon Orbiting.

They went down fast..and permanently.
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Quoting DestinJeff:
Is thay an L in the North Central GOM?


Click to enlarge.


Actually by Weds if there is a tropical low that forms.. it will probably be off the carolinas.. but really TBH anything over 72hrs is just not worth reading into unless all models are in 100% agreement.
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Quoting scottsvb:
Well from looking @ the longer range models.. whatever is in the central GOM east of 90W and north of 22N will move N then NE. The weaker the broad low (if any) will continue though W towards the western GOM. Anything with a close LLC will move north early next week and NE as the eastern U.S. trough digs down to the GOM from 90W eastward.

So basically a stronger system would feel a weakness in the ridge thus pulling it towards FL. And a weaker system follows the lower level steering which would take the storm west into Texas?
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Quoting tropicfreak:


ok should i ban him.
Admin will be on him quickly. Just flag and ignore.
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Ignore user button is my best friend.
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Quoting jasoniscoolman09:
95E LOOK LIKE ITS GETTING BETTER.
Agreed. Could have TD Five-E today.
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would you expect 93l to become:

1)Just t.d
2)Tropical storm
3)Hurricane
4)Major Hurricane
5)Just bluff

I'm with 2 right now. It depends how long it will stay in the warm-shearless waters of the Caribbean.
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Quoting JFVfromFlorida:
You have bean rpeorted so say whatever u want i ignore you now jn.


aww man what ashame, so many spelling errors.
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I wonder what would happen if the WUground went to a 2 level system for posting privileges. Those who pay get unlimited posts per day and those who don't get a limited reasonable # per day. This would allow serious folks who can't spend i.e. kids learning and folks on fixed incomes to participate but would make it expensive for someone who wants to monopolize the blog (read troll) to get perma-banned and have to create a new unlimited handle. Might keep the background noise to a dull roar.
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Well from looking @ the longer range models.. whatever is in the central GOM east of 90W and north of 22N will move N then NE. The weaker the broad low (if any) will continue though W towards the western GOM. Anything with a close LLC will move north early next week and NE as the eastern U.S. trough digs down to the GOM from 90W eastward.
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Quoting IKE:


Thanks. That's in line with the ECMWF.

Interesting that it shows 93L and then the trough/cold front I mentioned, may pick it up.


Ya, you can see that well on the 850mb vort.
Member Since: September 23, 2005 Posts: 14 Comments: 11307
wasps!!! be careful, Pat!!!!!
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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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