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 JFVfromFlorida:

now I know this isnt him, JFV is from Miami and thus comes with the idea that no other city exists outside of NY,Miami, and LA so he would never post this. It would have been a picture of the Dolphins, and the Miami Hurricanes.
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Quoting StormW:
Here ya go...zoom in on this

RGB LOOP


looks to be some rotation there.... or I am just seeing things.
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15.5N,74.5W would be the area where it appears a COC is and possibly a closed surface low trying to form,one must not over analize the sat loops,your eye's start play'n tricks on you!!!
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It looks like it is heading in the general direction of Jamaica to me. You can see a surface circulatoin trying to form south of DR.
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590. xcool
hey ike & Drakoen & pat.
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Quoting Jeff9641:


Yes as this system is moving more NW than models are suggesting. Infact you can throw them out the window right now.


The system is not moving NW, it is moving WNW
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Quoting FLWeatherFreak91:
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.

Who is the real monster here, Frankestien, or we who created him...
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Quoting StormW:
Here ya go...zoom in on this

RGB LOOP


half the images are blanked out lol, that has been happening a lot with the SSD site lately
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Floater - Rainbow Color Infrared Loop

Check Bad Frames 7 and 8 to get the image loop without them
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Quoting NRAamy:
Shen, that won't work...the trolls will just ask their moms for an extra $20 on their weekly allowance....


;)


Don't think our main problem is a kid. Masquerades as a kid using several handles at once, then when gets bored throws in something outrageous to stir things up knowing will get the heave-ho. If they were paying they would have run up a bunch more than $20/week/
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93L continues to get better organized...


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580. IKE
12Z NOGAPS through 72 hours.

Seems to be in line with the newer version of the GFS, on 93L.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting charlottefl:
Afternoon everyone! Can one of the mets please help me out here. I know there is no LLC but is the COC right in the picture?


Photobucket


I have it south of there
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Floater - RGB Color Infrared Loop
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Thanks Ike, looks like it to me, it's lines up with the vorticity map, just wanted to be sure..

Quoting IKE:


I'm not a met...but that's close to where I see it too.
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Well I do not know if 93 will do anything or not, but imho today is the first time that it has taken on the "look" that it wants to organize.
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Quoting watchingnva:


yea its getting there...its averaging between 92-96 across the area...gonna be right around 99/100 today...and im the smart one going to the pool at 2-3....lobsterization for me tonight...lol


yeah it brutal, idk if its as humid there as it is down here. supposed to get some big storms tonight cause of it though
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572. IKE
Quoting charlottefl:
Can one of the mets help me out here. I know there is no LLC but is the COC right in the picture?


Photobucket


I'm not a met...but that's close to where I see it too.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting sporteguy03:


yes


I agree, this is why systems don't normally form in the Central Caribbean, either too close to S America or too close to Hispaniola
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Quoting ATL:
Do you guys think land interaction with mountainous Hispaniola may be hindering development?


yes
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Quoting GTcooliebai:

I noticed it too, one broad low to the Southwest of the main blob near Haiti which is also showing some cyclonic turning. I notice that BAM solution for this system has been [retty consistent so far, looks like 93L will past South of Jamaica. That's where I believe development will take place.


I've been forecasting 93L to take a southern route until it reaches the Yucatan. Should it be a storm, it moves north into the GOM. The cyclonic turning is all from the anticyclone right over it. A circulation may indeed form southwest of this mess,as per my original thinking. If you were an invest, you would want to stay SOUTH of any hindrance.
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Afternoon everyone! Can one of the mets please help me out here. I know there is no LLC but is the COC right in the picture?


Photobucket
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting tropicfreak:


afternoon watch, already scorching hot out!


yea its getting there...its averaging between 92-96 across the area...gonna be right around 99/100 today...and im the smart one going to the pool at 2-3....lobsterization for me tonight...lol
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Quoting StadiumEffect:
Can someone post the most current 850 vorticy map? I'm not on my laptop so I don't have the links saved!






there ya go, last 2
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looks like its forming well north of the model forecast..

should hit HAITI directly.. and then move onto cuba.. and perhaps if it develops further "maybe into a TD or "TS which I doubt it can do in 12-24 hours") it can move into the bahamas.. the shear is what I'm looking at mostly though since there is a band of strong shear north of hispanola and over eastern cuba.
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562. IKE
93L looking a little better.

Center appears to be between 16-17N and 71-72W to me....moving north of west.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting reedzone:
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.

I noticed it too, one broad low to the Southwest of the main blob near Haiti which is also showing some cyclonic turning. I notice that BAM solution for this system has been [retty consistent so far, looks like 93L will past South of Jamaica. That's where I believe development will take place.
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Climo on a good day favors the Western Caribbean much more than the Central and Eastern for Formation.

If you been following the Intensity Guidance graphs,,they all show the Warm column being Sustained further West thru time.

As climo favors.


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Quoting FLWeatherFreak91:
They're not tropical? Would you mind telling us what you think they are then? lol


They look......tropical!!!!
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I know that developed storms can have their circulations disrupted by the mountains of Haiti but I have to assume, at this juncture, that the interaction with Haiti is going to prevent any significant development in the short term as the complex keeps inching towards the Island.
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551. ATL
Do you guys think land interaction with mountainous Hispaniola may be hindering development?
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I don't know why the majority of people on this blog is looking down (or seems to be anyway) on 93L... IMO it is getting much better organized for the time being.
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548. Gorty
Come check out mine:

http://www.wunderground.com/blog/Gorty/show.html
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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.


Not as hot as it had been, though. The three days of 100+ air temps last week were brutal. This feels like spring weather again compared to that.
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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.