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 msuwxman:
Good timing for 93L. Get a LLC just in time for DMax.
You seem to forget that D-Max isn't until 2:00 AM EDT - 8:00 AM EDT. What 93L is about to go into is D-MIN.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting unf97:


I think right now, I'll give 93L a 60-70% chance that it will develop into a TD within the next 36 hours.



am with you and i give 93L 40% of be comeing a tD with in the next 24hrs
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Like I said earlier this debate will be so much better tomorrow after the two missions fly in the storm. They are a go for tomorrow so we will get much better data.
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Going by that satellite image...Still yellow at 8:00.
Member Since: September 10, 2007 Posts: 0 Comments: 11011
Quoting Snowlover123:


How soon is soon?




how about right now lol
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1490. Dakster
Quoting WinterAnalystwx13:


The MJO is in our basin.


I forgot about that one... Good point.
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1489. unf97
Quoting Dakster:
Back to weather...

Dr. M said 93L would be slow to develop and it apparently is doing just that.

I'd still say a 70% chance 93L at one point makes it to TD... Agree or disagree? I'll cite warm ssts, low shear, anticyclone above it as reasons. The reason is won't do it sooner is the hope affect and it will take time to organize itself.


I think right now, I'll give 93L a 60-70% chance that it will develop into a TD within the next 36 hours.
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Quoting Baltimorebirds:
I see 93L getting it's act togather.The wave south of it needs to be watched as well in my opinion of course,also while we'er watching 93l lets watch what comes off africa as the mjo should be coming to our basin soon.


How soon is soon?
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and look it froming right overe vary high TCH i hop i spell that right



thats not good
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1485. Drakoen
93L will probably wait until it gets into the central Caribbean to really organize.
Member Since: October 28, 2006 Posts: 57 Comments: 29935
I see 2 spins with 93L one around 15N/74W which I think is LLC and another around 17N/72W which I believe to be the MLC, do they consolidate or does one become the dominant center that is the question in my opinion.
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1483. xcool
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I don't see how 93L can get any spin out of prior set of NHC coordinates. I think the center is in process of shifting further North & East (just below Haiti / Dominican Republic boarder). It looks like circulation is fizzling out with the old coordinates.

It is hard to pin down a proper path for these pre-TD systems beause of the circulation relocations.
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1477. Drakoen
Member Since: October 28, 2006 Posts: 57 Comments: 29935
Good timing for 93L. Get a LLC just in time for DMax.
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Quoting Drakoen:


There's really nothing to pinpoint at the present time. You can see a broad area of low pressure forming which is supported by the cimss 850mb vorticity product.
Noticed that too.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1474. Dakster
Back to weather...

Dr. M said 93L would be slow to develop and it apparently is doing just that.

I'd still say a 70% chance 93L at one point makes it to TD... Agree or disagree? I'll cite warm ssts, low shear, anticyclone above it as reasons. The reason is won't do it sooner is the hope affect and it will take time to organize itself.
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1473. DDR
Quoting sailingallover:

Yes...all of them.. we lucked out with the wave that went over you last night and today it lost all it's convection yesterday evening.

You have another one day after tomorrow that so far has no rotation at all..but it's got a lot of convection going..

Then one out by 35-40W.. this one worries me because it has a low pressure trough just to it's north which appears to be enhancing it, giving it rotational energy and sucking moisture north. The good news is if it develop's it will probably go north of Trini if not more rain for you 4-5 days from now.. the bad news is it may come straight here to the Virgins...

Hey there
Yes thats true,it may not develop but it will ceratianly pull moisture into the islands,we do need to keep an eye on every wave...

That wave last night dissipated on our doorsteps lastnight,but the rains are definately coming again.
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oh crap looks like 93L is relly starting too spin up fast
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93L still is disorganzied. I predict a Code Orange for the next NHC discussion.

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Quoting Jeff9641:


Very powerfull mid level spin moving S of Haiti. This will be our storm I fell. I've seen so many storms form from mid level circulations.
That mid-level circulation as I said earlier will move over land. What you have to watch is the broad low level circulation around 75.0W 17.5N.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1469. NRAamy
THIS IS STORMTROP FROM MY BASEMENT WEATHER OFFICE IN MY MOMS HOUSE... STORMTROP

:)
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If any Judge has a vested interest in any case he/she is hearing, they should be recused. Just my opinion.
Member Since: September 10, 2007 Posts: 0 Comments: 11011
1467. Drakoen
Quoting MiamiHurricanes09:
Do you agree with post 1392 I made? I see the circulation around 75.0W 17.5N.


There's really nothing to pinpoint at the present time. You can see a broad area of low pressure forming which is supported by the cimss 850mb vorticity product.
Member Since: October 28, 2006 Posts: 57 Comments: 29935
93L could spin up fast
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Quoting NRAamy:
PT is killin' me....


It'll do it!
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1462. centex
I've not been trying to disect the little swirls but looking for the more overall spin which this system has lacked. I think we can say the system is starting to spin up today. The shear ban crossing eastern cuba is supposed to move out but could be a factor.
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Quoting stormpetrol:
93L looks like it might be coming together abit more.



thats not good
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Quoting Drakoen:


Yup. Mentioned it earlier when I was trying to figure out why the NHC lowered its chances.

Do you agree with post 1392 I made? I see the circulation around 75.0W 17.5N.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
thats not a good spot for a low too pop


low wind shear


+

+

whenn you get the rest
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1456. xcool
tropical weather, blog
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I just do not see this "broad surface low" SE of Jamaica... I see the mid level low just south of Hispanola with excellent curved banding on its N-E sides and convection now beginning to pop on its south side... but no broad low-level cyclonic signature apparent yet.
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1454. Dakster
Quoting NOLALawyer:


And you can rest assured that the US Attorney will take this to the 5th Circuit and see what they think about it.

Mike


That I do not doubt. Especially since we know who he takes his orders from.
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Can we take a time-out on the political aspect of the oil issue.... thanks. Or take it somewhere else.
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93L looks like it might be coming together abit more.
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oh crap
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Quoting Dakster:


I haven't read the entire ruling/opinion so I don't have my own opinion yet.

But isn't this why we have a court of appeals and a supreme court? If one "side" feels the law wasn't applied correctly then there is a higher court to go to. It is also one of the reasons why the higher courts are a panel and not heard by a single person.


A very good point, Dak
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Quoting ElConando:


He is a legit Met if you want to know his credentials.


Oh no, I already knew that. I just wanted to know if he saw it on satellite, new QuikSCAT, ect.
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Quoting Drakoen:


Yup. Mentioned it earlier when I was trying to figure out why the NHC lowered its chances.



Quite a small system it is now.
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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.