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 nash28:
Listen to the ebbs and flows of this wonderful piece of music.

This will be the hurricane season, and the people and hearts that will encompass the compassion to the human soul should one strike..



nice piece of music. it reminds of the feelings LOST gives me for some reason.
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2344. nash28
Goodnight Tom.

Cybr!! How are ya?
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2343. mobal
Quoting nash28:
Been a long time Ike:-) Good to see you:-) Needed a long break. A VERY long break.


Good to see you Nash
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2341. nash28
Heya Drak. Good to see you too man!
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Evening Nash great to see you again!
Member Since: July 8, 2005 Posts: 259 Comments: 23489
As I mentioned earlier, I think the HH’s will go out tomorrow in part due to the oil spill, unless 93L totally falls apart.
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2338. Patrap


..We can Blog if we want to..
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2337. nash28
Been a long time Ike:-) Good to see you:-) Needed a long break. A VERY long break.
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Quoting futuremet:


Where are you getting that radar?
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2335. Drakoen
Quoting nash28:
StormW, StSimons, Pat, Drak, etc...

Missed you guys!


Hey Nash28 Good to see you
Member Since: October 28, 2006 Posts: 57 Comments: 29864
i know y'all have explained this 1000 times, not necessarily to me, so i didn't pay attention much. but what is an aticyclone and how do you "spot" it?
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2332. nash28
Correcto Pat:-)
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Quoting AllStar17:


That's fine. That is what a blog is for. Calm, civil conversations.
Absolutely, :).
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2330. IKE
Quoting nash28:
93L is fighting proximity to land. Also remember, this invest is parked in the ECAR and this is typically no mans land. Give it another couple of days. It needs to clear the ECAR and move closer to the YUC Channel before we begin to see any serious formation.


Agree and nice seeing you on here.


Quoting Patrap:


Just like all the intensity Graphs have been forecasting since yesterday Morning.

Its the "Climo" favored area historically.



Yup. I doubt very seriously 93L has a massive blowup of convection tonight.

Models read like it's going to take 2-3 days to get going.
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Quoting extreme236:


Doesn't necessarily mean anything for tonight. Diurnal fluctuations play big parts in developing systems, but a system's fate doesn't really rest on them.
That was the point I was trying to make but I just was unclear. Don't think that the diurnal cycles will have much an affect on 93L, I just think it needs to organize itself without the help of the diurnal maximum.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2327. Patrap
How the Storm forms and where near the Yucatan and how it Navigates from there is gonna be the tricky dicky part.
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Celia weakens slightly, but still a Category 2 hurricane
Image made by cyclonekid

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Thanks for the answer Levi.
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2324. Patrap
Quoting IKE:
CONDITIONS ARE FORECAST TO BECOME MORE FAVORABLE FOR
SLOW DEVELOPMENT AS THE WAVE REACHES THE WESTERN CARIBBEAN SEA IN A
DAY OR TWO.
THERE IS A LOW CHANCE...20 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.


Just like all the intensity Graphs have been forecasting since yesterday Morning.

Its the "Climo" favored area historically.

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Quoting MiamiHurricanes09:
Yes I understand that, just pointing out what I've seen.


That's fine. That is what a blog is for. Calm, civil conversations.
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2322. IKE
Reading the TWO again, it reads like 93L will stay 93L until Thursday or Friday...then possibly develop.
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2321. nash28
93L is fighting proximity to land. Also remember, this invest is parked in the ECAR and this is typically no mans land. Give it another couple of days. It needs to clear the ECAR and move closer to the YUC Channel before we begin to see any serious formation.
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Quoting MiamiHurricanes09:
Over the past 3 days DMAX has done nil to 93L.


Doesn't necessarily mean anything for tonight. Diurnal fluctuations play big parts in developing systems, but a system's fate doesn't really rest on them.
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Quoting AllStar17:


Yeah.....however:
1. Every DMAX is different
2. The MCV will be moving inland over Haiti/D.R., which may allow more energy to shift to 93L instead of the MCV robbing energy from 93L.
Yes I understand that, just pointing out what I've seen.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:
Over the past 3 days DMAX has done nil to 93L.


Yeah.....however:
1. Every DMAX is different
2. The MCV will be moving inland over Haiti/D.R., which may allow more energy to shift to 93L instead of the MCV robbing energy from 93L.
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2317. IKE
CONDITIONS ARE FORECAST TO BECOME MORE FAVORABLE FOR
SLOW DEVELOPMENT AS THE WAVE REACHES THE WESTERN CARIBBEAN SEA IN A
DAY OR TWO.
THERE IS A LOW CHANCE...20 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
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2315. Patrap
www.hurricanecity.com/closeup
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Not sure if this has been covered but,

invest_RENUMBER_ep952010_ep052010.ren
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Quoting CyberStorm:
why are so many saying the storm is going there and here.there isnt even a storm yet and right now the blob in the carribean doesnt look like much of anything.Are you guys all talking about 93l?
lol
.
.
You must be new around these parts. That's what this blog does. It lives and breaths on a wish and a prayer. L after L, year after year.
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Quoting AllStar17:


Wait. We have to see how DMAX plays out.
Over the past 3 days DMAX has done nil to 93L.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting StormW:
Good evening, Cyber.
Good evening
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Quoting SouthDadeFish:
I've become very unimpressed that 93L cant fire any sustained convection remotely close to where the NHC places the center. Only intermittent popcorn convection. That's not going to cut it. I understand this is a process and it will take a while, but I would have expected to see more than this. Looking like the recon mission tomorrow may get scrubbed if it keeps this up.


Wait. We have to see how DMAX plays out.
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2307. JLPR2
Quoting IKE:
I think PR may miss out on that band of rain.


hurray! :)

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I've become very unimpressed that 93L cant fire any sustained convection remotely close to where the NHC places the center. Only intermittent popcorn convection. That's not going to cut it. I understand this is a process and it will take a while, but I would have expected to see more than this. Looking like the recon mission tomorrow may get scrubbed if it keeps this up.
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2305. IKE
I think PR may miss out on that band of rain.
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Quoting futuremet:


Check the date lol
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2303. JLPR2
you beat me to it Pat
XD
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2302. Patrap
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2301. nash28
Been busy. Working for Boeing in Charleston, SC. Love the job. Interning for local wx on weekends.
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Quoting IKE:


Futuremet...that says Sept 30th, 2009.


Lol, that radar must be out of service.
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2299. srada
I feel there is something to track with no disrespect to anyone..Dr. Jeff Masters has two paragraphs written in his blog on 93L and the NHC has given it a moderate chance to develop, the question as is to when? I am not wishcasting a storm at all..I dont even live in florida..
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2297. JLPR2
Quoting IKE:


Futuremet...that says Sept 30th, 2009.


ha! I knew it, it doesn't show the band of convection XD
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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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