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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It's going to wait until my son is at scout camp. How's that for forecasting? LOL. It always works. Nothing makes a better week than storm prep and slogging around soggy scouts.
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945. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting alaina1085:

Is it even moving?


Yes
Member Since: October 28, 2006 Posts: 57 Comments: 29714
Quoting IKE:
And that's 6 days away on the ECMWF...just north of the Yucatan. That's next Monday. Anything after 144 hours is a coin-flip.


yup ECMWF does not develop 93L until Friday -Saturday now

people here will have no hair by then lol
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if i had to guess with 93L i would say central Mexico
Possibly next week and most likely not a threat to the US.

but it should be "Fun" to watch.

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941. IKE
And that's 6 days away on the ECMWF...just north of the Yucatan. That's next Monday. Anything after 144 hours is a coin-flip.
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convergence map looks right about where I had posted a surface low trying to form....
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This thing does better during the afternoon than at night. Strange.
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I think I see a spin in 93L. Could just be me tho.
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Quoting Drakoen:


Yes I am aware of that although this one showed some promise


John Hope's ghost is actively making sure this one doesn't develop.
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936. IKE
Quoting Hurricanes101:
Monday - 144 hours



You can see the high starting to erode.
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Quoting tornadodude:


Is that a real tornado headed for Tornadodude?

Looking vertically stacked to me ...




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Quoting Drakoen:
Seems like this thing isn't going to develop until it gets into the central or western Caribbean.

Is it even moving?
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It looks like on the visible and IR that 93L is starting to consolidate a bit more, popcorn convection around the broad low, reminds me of Andrea.
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#913 Hey T-Dude, how was your weather yesterday? Guess it was S Wisc turn for the spinners! You would have had some good chasing around here last evening. Nothing on our farm, but the cell that dropped a tornado about 10 miles from us, did go directly over us and the clouds were full of little spins. What a sight!Sounds like we could go under the gun again this evening.
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Too early to tell. If I had to doomcast one particular spot in the GOMEX, I'd have it near the East Texas-Louisiana area, based on its current course and likely course over the next couple days.
Quoting helove2trac:
If everyone had to guess which part of the gulf do yall think this thing is going

I say central gulf
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Why is it moving so slow it wont get into the gulf until next week so this weekend i guess someone in the gulf coast will be boarding up windows buying water and candles and can food
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Quoting ElConando:


The mysteries abound.



You can CLEARLY see the COC developing on this LSU Earth Scan animation.
Check it out ... Link
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Quoting StSimonsIslandGAGuy:


They almost never do develop between 70 and 75 W in the Caribbean. You know that better than anyone!


Yes I am aware of that although this one showed some promise
Member Since: October 28, 2006 Posts: 57 Comments: 29714
Quoting Hurricanes101:
*shhhh notice how quiet the blog is now, the power of the NHC TWO is working* lol


This blog rises and falls with the TWO.
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Quoting helove2trac:
If everyone had to guess which part of the gulf do yall think this thing is going

I say central gulf

I say W. FL maybe because I'm a wishcaster.LOL
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*shhhh notice how quiet the blog is now, the power of the NHC TWO is working* lol
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Quoting helove2trac:
They are probably watchin twc and saying only 20%
The models aren't showing much happening for the next two days. It may just keep rolling along how it looks now.
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If everyone had to guess which part of the gulf do yall think this thing is going

I say central gulf
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Quoting Drakoen:
NHC may be having some difficulty with inializing a center for 93L. No 18z coordinates yet.


The mysteries abound.
Member Since: September 6, 2009 Posts: 2 Comments: 3709
I think part of the issue was the recon on Wednesday, it made many think 93L would be a TD or TS by Wednesday, honestly though the models that have developed 93L has been consistent in not doing so until Friday at the earliest
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Quoting StadiumEffect:

The mid and low level "centers" aren't over the island, so land interaction is a non-issue in terms of developing (for now).

Your not thinking the mountains have anything to do with the convection to the north of the island trying to wrap around the system. I think it's cutting off the air flow. At least a little. Something is making this system not explode?
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NHC may be having some difficulty with inializing a center for 93L. No 18z coordinates yet.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
They are probably watchin twc and saying only 20%
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I wonder if anyone is paying attention (Obama, BP and everyone else) to this potential system heading towards the gulf, if they're not, they'd better start because this could end up being a big problem for them. That's all they need now!
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Monday - 144 hours

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Quoting CybrTeddy:
12z ECMWF predicts a storm very similar to Hurricane Dolly.



00Z run
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and when will that be?
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Sunday - 120 hours

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12z ECMWF predicts a storm very similar to Hurricane Dolly.

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Quoting GTcooliebai:
There is some upper level winds blowing from Southwest to Northeast over Jamaica right now from this satellite:

http://www.wunderground.com/tropical/tracking/at201093_sat.html#a_topad

Also interaction with Hispaniola is impedding development at the moment.

The mid and low level "centers" aren't over the island, so land interaction is a non-issue in terms of developing (for now).
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Regardless of any future weakening or strengthening due to any factors, there's currently definite low-, mid-, and high-level rotation centered around 71.2W / 16.8N. No?
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Seems like this thing isn't going to develop until it gets into the central or western Caribbean.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
No one took me seriously yesterday when I said most of the moisture from 93l would move towards Hispaniola today.

Sometimes you have to forget about the models and look at the satellite loops for a few minutes to see what is actually happening. Yesterday's big blog was really nothing more than a lot of convergence in a very moist environment... As it collapsed in shed of all the convection and expanded.

Convection is refiring again today and it looks like there is quite a lot more vorticity, but it's very close to hitting Hispaniola.
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Quoting StormW:
Out for a little...IF nothing changes in the forecast parameters for favorability...93L should develop.



Please dont be gone too long
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Friday - 72 hours

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Quoting Seflhurricane:
looks like tonight will be intresting 93L is trying to get into shape all it needs is dmin

You mean DMAX?
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Quoting StormW:
Out for a little...IF nothing changes in the forecast parameters for favorability...93L should develop.


Thanks for all Storm!

I was waiting for the spin to begin, looks like it finally has, but... now the question is which spin will win, the one with the cloud cover or the one where the storm is being tracked with little cloud cover?

Thinking it might have some interaction with those southern mountains of Haiti and Jamaica that will keep it from becoming much of a storm in any short period of time and will probably run into other obstacles, but if it hits that area of open ocean between Cuba and Yucatan with some spin and below 1000 pressure it could become a Hurricane quickly.
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New Orleans, Louisiana (CNN) -- A federal judge in New Orleans has blocked a six-month federal moratorium on deepwater drilling in the Gulf of Mexico. Several dozen plaintiffs had sued the Obama administration, arguing the ban would create long-term economic harm to their businesses.


http://www.cnn.com/2010/US/06/22/gulf.oil.disaster/index.html?video=true?video=true&hpt=T1
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Quoting sailingallover:

The low level deck is completely exposed where your lower west to east red arc is and not one low level cloud is going that way which is West to East.. put your cursor in one spot and watch. There are two high level arcs of clouds at 11N 73W heading NE but thats it.



true the circulation is open on the south side,but that should change as 93L is very much a vertically loose system w/multiple vorticies,I'm thinking to much SW sheer at the current moment for any lasting organization,as the area moves towards jamaica over the next 48hrs....
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Not exactly what the Gulf Doctor ordered, huh?



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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.