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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Nice to see you back Nash!
Member Since: September 10, 2007 Posts: 0 Comments: 11265
2294. Patrap
heya nash..
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Quoting BayouBorn1965:
Truecajun, people will be people, good and bad. Personally, we keep up our hurricane stash all year long. Katrina taught us many lessons the hard way, especially about how there will be others around you that will need for you to share your supplies, and that is exactly what we did and will continue to do when the next big one blows us away. :)


yes. we share too and have had others share with us - BBQ mostly. i'm just saying that it was sad on so many levels and for so many reasons. i have compassion, but i think that if we didn't condition people to be dependent, they wouldn't be so. but you are right, they are what they are, and no we cannot just turn our backs.
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2290. IKE
Quoting futuremet:


Futuremet...that says Sept 30th, 2009.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2289. Levi32
Quoting nash28:
StormW, StSimons, Pat, Drak, etc...

Missed you guys!


Nash! Good to see you buddy.
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Quoting hurricanehanna:
well, just thought I'd pop in...will be back later as things develop *crosses fingers that they don't!*

Ok Hanna, see ya later! Have a good evening.
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2287. JLPR2
Quoting Acemmett90:

get ready for a wet night ahead dude


*sigh* Just when ti was starting to clear a little :S
I want sunshine! XD
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2286. nash28
StormW, StSimons, Pat, Drak, etc...

Missed you guys!
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.
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2283. Patrap

2km Storm Relative IR Imagery with BD Enhancement Curve
0045 UTC



2km Storm Relative IR Imagery with BD Enhancement Curve

The same infrared imagery shown in the earth relative framework is displayed in a storm relative framework, with a 2km resolution and enhanced with the "BD Curve" which is useful for directly inferring intensity via the Dvorak Enhanced IR (EIR) technique. Scaling is provided by two lightly hatched circles around the center. The two circles have radii of 1 and 2 degrees latitude, respectively.
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Quoting Jeff9641:


I guess we will see won't we!


Jeff…Chucktown is a very credible blogger. Give his posts some consideration. He is trained professionally in field of meteorology.
Member Since: September 10, 2007 Posts: 0 Comments: 11265
well, just thought I'd pop in...will be back later as things develop *crosses fingers that they don't!*
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I think we can safely say now that even with mostly ever factor in the favor of 93l the lack of a surface low has been the key.

I still think the second a strong organized surface low does appear we are going to see RI. The question is when (and if) that happens. The simple process of predicting when and if a surface low forms has to be one of the most challenging things in forecasting in general.

I still give it 50% with 50% being watch out possible major or the other 50% nothing at all. I really do not see the middle here ie. a weak trop storm...

This thing is ALL or NOTHING.
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2278. JLPR2
I'm not liking the direction in which this band is moving, 93L wants to drench PR -.-

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Quoting StormW:
Okay...I see a lot of scraps starting over model guidance track and arguing about Florida, LA/AL, etc.

WE AIN'T GOT NOTHING TO TRACK YET!

Amen. The natives are jonesin Storm. There will be plenty of time for that.
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Quoting Levi32:


I am not either. I don't expect the longwave trough to stick around long at all over the eastern seaboard before getting kicked right back out to the east by the ridge over the central-eastern US which is holding strong. I don't see this getting recurved all the way into Florida at this point, unless it develops really far north near Cuba.
Nor do I, but you know how the blog wishes for a cane to hit Florida.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 92Andrew:
I must admit, I don't understand why people continue to post model tracks on 93L. What will be the COC is not located south east of jamaica but, instead, it is located just south of Haiti.

Look at this floater: http://www.ssd.noaa.gov/goes/flt/t1/flash-ir2-s.html

Clearly, there's a circulation of some kind just south of the Haitian/DR border. If that is not the MAIN center, then the system has a very low chance of developing, as it has a strong mid to upper level low which dwarfs in size the supposed LLC south east of Jamaica.

Anyone have any thoughts on the center of the system?

What center are you looking at the LLC is probably by jamacia but the center in the upper atmosphere may be near Haiti. And a lot of times the LLC is barely visible
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2273. Patrap
Floater - RGB Color Infrared Loop
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Quoting Jeff9641:


I guess we will see won't we!

(Enter the old country western challenge jingle:"Owee Owee OOOO")
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one bamm on top of another. and right next to the major models.the cone will be tight.
that weather in la/ms-that's the tw split off from 92L-i think-mixed in with an ull. so 92 still lives in another form!
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Quoting 92Andrew:
I must admit, I don't understand why people continue to post model tracks on 93L. What will be the COC is not located south east of jamaica but, instead, it is located just south of Haiti.

Look at this floater: http://www.ssd.noaa.gov/goes/flt/t1/flash-ir2-s.html

Clearly, there's a circulation of some kind just south of the Haitian/DR border. If that is not the MAIN center, then the system has a very low chance of developing, as it has a strong mid to upper level low which dwarfs in size the supposed LLC south east of Jamaica.

Anyone have any thoughts on the center of the system?
That is an MCV not a circulation. The circulation is to the south and west of the MCV.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2269. Patrap
Quoting hurricanehanna:

Yep . Cool new pic. What is it of?


Ironman 2
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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?
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2267. Levi32
Quoting GeoffreyWPB:
Let's put this to rest. Drak, Storm, Adrian, Levi%u2026If 93L does develop, do you see any scenario in which it would affect so. Florida? And I know nothing is set in stone this far out. Just asking what they see now.


I am not either. I don't expect the longwave trough to stick around long at all over the eastern seaboard before getting kicked right back out to the east by the ridge over the central-eastern US which is holding strong. I don't see this getting recurved all the way into Florida at this point, unless it develops really far north near Cuba.
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2265. srada
Quoting MiamiHurricanes09:
I don't find an Ernesto scenario likely for the time being.


LOL..neither did the forecasters..that storm fooled everyone..
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2264. nash28
StormW-

You have mail.
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Quoting Jeff9641:


Have you seen the new GFS? Very strong trough. New orleans to Tampa event. Panhandle most likely the up the eastern US. Lots of people are going to feel this one.


your wishing so hard its making noise geez


lol
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2262. Skyepony (Mod)
Fresh Windsat, just out..less than 3 hrs old..
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Quoting StormW:


Now that consensus is more along my thinking, right now...again..could very well change.


That is a pretty good consensus, but as we have seen with the ECMWF the last few days things can change rapidly.
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Quoting MiamiHurricanes09:
Florida. I don't see the trough being so far east and so strong to push the system towards Florida. A Louisiana event seems the most likely for the time being, but we all know how quickly that could change.


Same here...Nothing I have seen in the model forecasts shows a steering current towards central or so. Fla. IF 93L does develop, then it does look like the central Gulf to the Fla. Panhandle may come into play.
Member Since: September 10, 2007 Posts: 0 Comments: 11265
I must admit, I don't understand why people continue to post model tracks on 93L. What will be the COC is not located south east of jamaica but, instead, it is located just south of Haiti.

Look at this floater: http://www.ssd.noaa.gov/goes/flt/t1/flash-ir2-s.html

Clearly, there's a circulation of some kind just south of the Haitian/DR border. If that is not the MAIN center, then the system has a very low chance of developing, as it has a strong mid to upper level low which dwarfs in size the supposed LLC south east of Jamaica.

Anyone have any thoughts on the center of the system?
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Quoting Patrap:
Hiya hanna..good to c yas.

Were off to a stat seems for sure.


Yep . Cool new pic. What is it of?
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2256. Drakoen
Quoting GeoffreyWPB:
Let's put this to rest. Drak, Storm, Adrian, Levi%u2026If 93L does develop, do you see any scenario in which it would affect so. Florida? And I know nothing is set in stone this far out. Just asking what they see now.


I'm not seeing that indication at the moment.
Member Since: October 28, 2006 Posts: 57 Comments: 30562
2252. srada
Quoting xcool:
. srada byebye


because I dont agree with you, I should be dismissed..this is a blog and I do have a right to my opinion and I have been stating why I think so all in this blog today..havent you noticed the models shifting to the east? the center is developing and they are starting to get a handle of the tracking of this storm..dont be so hurridly to dismiss someones opinion just because its not your opinion
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2251. Patrap
Hiya hanna..good to c yas.

Were off to a start seems for sure.

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Quoting nolajet:


Isn't that usually a good thing this far out though, as the models generally shift on way or the other?

And no, that would not be good at all. :\

Supposedly thats the saying. We will just have to watch and wait. But I recall them pinning Gustav to Louisiana many days in advance. Alot of things to factor in tho.
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Hey everyone! I have my own blog, and would love for you guys to read it. The newest entry is about 93L and the tropics.

=)

Link
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Quoting srada:


Yeah but Ernesto found a way back after the mountains..this is not a far fetched scenario and it has happen before..
I don't find an Ernesto scenario likely for the time being.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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