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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AL, 93, 2010062300, , BEST, 0, 156N, 752W, 25, 1010, WV
Member Since: August 2, 2007 Posts: 19 Comments: 19234
That intense downward motion from the MJO basically dies before it makes it to our basin, thus not much in the way of a convection suppressor.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
2194. IKE
Quoting ezcColony:


Southern Mississipii? What direction is it moving? Is the low over the Gulf? Will the low go over the Gulf?


SYNOPSIS FOR THE GULF OF MEXICO
430 PM CDT TUE JUN 22 2010

.SYNOPSIS...A TROPICAL WAVE WILL CONTINUE TO GENERATE SCATTERED
SHOWERS AND TSTMS OVER THE N GULF WATERS TONIGHT INTO THU.
OTHERWISE A WEAK RIDGE EXTENDING ALONG 30N WILL KEEP LIGHT TO
MODERATE E TO SE BREEZE ACROSS MOST OF THE GULF THROUGH TONIGHT.
A WIND SURGE ASSOCIATED WITH THE TROPICAL WAVE OVER THE CENTRAL
CARIBBEAN WILL REACH THE FAR SE GULF LATE TONIGHT AND WED...THEN
WILL SPREAD ACROSS THE S PART OF THE GULF BASIN THROUGH SAT.
WINDS WILL DIMINISH LATE SAT AND SUN AS THE WAVE IS EXPECTED TO
MOVE INLAND OVER THE YUCATAN.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting StormW:


It shouldn't


I would have preferred you have said, "It won't."
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Quoting StormW:


Yeah...HWRF track is indicative of deep layer steering level.

img src="Photobucket" alt="" />

Where is a link to this HWRF track?
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Quoting Drakoen:
BAMM models have shifted northward
They probably see that the upper level ridge by Texas and the southeastern U. S is holding strong.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
2188. Drakoen
They are also slowing down 93L a lot too...
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Quoting SouthALWX:

MJO and the epac season is 15 days ahead of the atlantic. nothing surprising to me yet.

So in theory the Atlantic will blow up at the end on June.
Member Since: Posts: Comments:
EP, 05, 2010062300, , BEST, 0, 108N, 930W, 30, 1006, TD
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting sailingallover:

I know how ot worry about hurricanes living on ST Thomas. But in all reality even though possibilities are endless for 93L trying to pick where a waves the is currently beating itself against Hispanola is going to re-curve and hot the mainland is a total crap shoot..

Also while the SST in the GOM are warm what is the depth of that warm water. I can't find my Oceanic heat content site. Anybody have a great one?


Link
Member Since: September 23, 2005 Posts: 13 Comments: 10471
2184. Patrap
The Gulf Coast is experiencing some weather from a Low inland interacting with a Tropical Wave




473
fxus64 klix 221849
afdlix


Area forecast discussion
National Weather Service New Orleans la
149 PM CDT Tuesday Jun 22 2010


Short term...(tonight-thursday)...inverted trough off the coast of
Louisiana with associated upper level disturbance creating enough
convergence with ample deep layer moisture available for numerous
showers/isolated thunderstorms across the coastal waters. Earlier
today this activity was having a hard time penetrating inland...but
with surface heating early this afternoon expect coverage &
intensity of convection to increase over land areas. The main
threats will be locally heavy rainfall...frequent lightning in a few
storms and downburst winds 40 to 50 miles per hour in stronger cells. Expect
activity to wind down later this evening but will still carry a
20%-30% pop overnight for lingering convection.


This system will be slow to exit the area overnight/Wednesday moving
east to west and will provide a high end scattered chance of
precipitation again on Wednesday as we will have a deep fetch of
onshore flow...though afternoon maximum temperatures are forecast to
recover a couple/few degrees higher than highs realized today across
most areas. Pop chances will decrease to 20%-30% on Thursday as the
upper level system migrates further away from the area taking deeper
layer moisture with it. Highest pop chances on this day will reside
across the west.


Long term...(thursday night-tuesday)...deep layer ridging will
reinforce its will over the region until Saturday as it gradually
migrates further northeastward. This will allow for the return of
onshore flow with deep moisture return to the area Mon-Tue.
Parameters will warrant a 20%-30% pop mention in the forecast Friday-
sun with a return to 40% Mon-Tue. Highest chances will be south of
the Interstate 10 corridor. Temperatures are forecast slightly
above climatology with afternoon highs maxing out into the Lower/Middle
90s.
Member Since: Posts: Comments:
Maybe Jimmy Buffets free concert will turn ito a fund raiser for the Gulf if 93L gets its act together. He will be performing with Kenny Chesney @ the Beach for free on July 1st or not

Mike
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Quoting IKE:


NWS fronts on SSD has a 1015mb low over southern Mississippi.


Southern Mississipii? What direction is it moving? Is the low over the Gulf? Will the low go over the Gulf?
Member Since: Posts: Comments:
Quoting stormpetrol:

I thought the EPAC was supposed to be average or below this year, maybe they got the wrong basins in their predictions or its starting to look that way.


Its the upward MJO pulse, very strong to. That activity in the EPAC looks like its about to come into the Atlantic.
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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. :)
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Quoting sailingallover:
The one at 10N 40W is a mess of vorticity..
This one worries me...



old
Member Since: May 21, 2006 Posts: 5089 Comments: 114074
invest_RENUMBER_ep952010_ep052010.ren
Member Since: August 2, 2007 Posts: 19 Comments: 19234
The one at 10N 40W is a mess of vorticity..
This one worries me...
Member Since: Posts: Comments:
2176. IKE
Quoting Patrap:
00z Early Cycle NHC model tracks
Invest93
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)





Models shifting a little more east.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2175. Drakoen
BAMM models have shifted northward
Member Since: Posts: Comments:
Mr. StormW. Would you take a moment to calm me down about the weather that is just off the Gulf Coast. It will not develop, right?
Member Since: Posts: Comments:
2173. IKE
Quoting ezcColony:
The weather I'm talking about is just off the coast of Louisiana and Florida at this hour. I'm not talking about 93L, which is its own horror story in the making.


NWS fronts on SSD has a 1015mb low over southern Mississippi.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Patrap:
00z Early Cycle NHC model tracks
Invest93
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)







LA watch out time too start packing
Member Since: May 21, 2006 Posts: 5089 Comments: 114074
Quoting sailingallover:
Now this one does.. 8N 48W



16hrs old
Member Since: May 21, 2006 Posts: 5089 Comments: 114074
Quoting Drakoen:


ASCAT pass has not come out yet
Looks like people look at the time stamp at the top of the image instead of the purple one on the image.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
2168. Patrap
00z Early Cycle NHC model tracks
Invest93
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)



Member Since: Posts: Comments:
Now this one does.. 8N 48W
Member Since: Posts: Comments:
Thanks for answering my question!! :)
Member Since: Posts: Comments:
The weather I'm talking about is just off the coast of Louisiana and Florida at this hour. I'm not talking about 93L, which is its own horror story in the making.
Member Since: Posts: Comments:
Quoting StormW:


Yeah...HWRF track is indicative of deep layer steering level.

<>img src="Photobucket" alt="" />


So do you agree that it would be hard to get a storm to Texas? Or the deep steering levels don't show toward texas?
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Quoting sailingallover:
NEW ASCAT showing...
No surface Circulation!! Yes there's an upper level one.


Too bad that that ASCAT is much older than the time that the surface circulation developed. By the way it is 16 hours old, I don't consider that to be "new".
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Drakoen:


ASCAT pass has not come out yet


ouch you told him lol
Member Since: Posts: Comments:
2161. txjac
Wow ...a double ITCZ? When was the last time that happened?
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I saw an earlier post that mentioned the weather that is moving into the GOM. What's the story on this? Looking at the available maps, I see no reason why this system might not develop itself into a TC!
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2159. IKE
Quoting CaicosRetiredSailor:


http://cimss.ssec.wisc.edu/tropic2/#


93L headed to a bad spot...high TCHP.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
i think that thing next too 93L will be come 94L
Member Since: May 21, 2006 Posts: 5089 Comments: 114074
2157. Drakoen
Quoting sailingallover:
NEW ASCAT showing...
No surface Circulation!! Yes there's an upper level one.




ASCAT pass has not come out yet
Member Since: Posts: Comments:
Quoting Fluid:


The reality is that in any population of people, and especially so in cities, you are going to have a certain percentage that can not take the action necessary, for any number of reasons. They may be ill, they may have mobility problems, they may have cognitive problems, they may simply have no money, or they may be somehow tied so that they feel that they can't (threatened with loss of job, fearful of loss of pets, or home) or shouldn't (be in a helping profession and remain behind), may have intended to but was thwarted at the last minute (car breaks down, someone has an unrelated un-expected medical event, can't locate a family member) etc etc etc.

Yes, you can say "Hell with 'em!" , but once you cross that line, your society will inevitably decay into something that reflects that attitude through out all its behavior.
Member Since: Posts: Comments:
2155. IKE
Steamy in the Florida panhandle this Saturday.....

Saturday
Partly cloudy with a 20 percent chance of showers and thunderstorms. Highs around 100.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
NEW ASCAT showing...
No surface Circulation!! Yes there's an upper level one.


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Quoting hcubed:


The ants in my backyard are starting to build in new places - and they're putting the mounds on stilts.

Is that a bad sign?
Ants putting mounds on stilts?
Sounds like a B movie from the 50's.
I'd say that's a bad sign as far all things go, not only tropical cyclones.
Very bad news....unless you're an ant.
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dont look now but the wave next too 93L looks too have a spin with it and it looks the tops are geting colder
Member Since: May 21, 2006 Posts: 5089 Comments: 114074
Quoting connie1976:
what is ITCZ?
Intertropical Convergence Zone

The Intertropical Convergence Zone (ITCZ) is the area encircling the earth near the equator where winds originating in the northern and southern hemispheres come together.

The ITCZ was originally identified from the 1920s to the 1940s as the "Intertropical Front" (ITF), but after the recognition in the 1940s and 1950s of the significance of wind field convergence in tropical weather production, the term "ITCZ" was then applied.

Where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage more common in Australia and parts of Asia. In the seamen's speech the zone is referred as the doldrums because of its erratic weather patterns with stagnant calms and violent thunderstorms.

The ITCZ appears as a band of clouds, usually thunderstorms, that circle the globe near the equator. In the Northern Hemisphere, the trade winds move in a southwestern direction from the northeast, while in the Southern Hemisphere, they move northwestward from the southeast. When the ITCZ is positioned north or south of the equator, these directions change according to the Coriolis effect imparted by the rotation of the earth. For instance, when the ITCZ is situated north of the equator, the southeast trade wind changes to a southwest wind as it crosses the equator.

The ITCZ is formed by vertical motion largely appearing as convective activity of thunderstorms driven by solar heating, which effectively draw air in; these are the trade winds. The ITCZ is effectively a tracer of the ascending branch of the Hadley cell, and is wet. The dry descending branch is the horse latitudes.

The location of the intertropical convergence zone varies over time. Over land, it moves back and forth across the equator following the sun's zenith point. Over the oceans, where the convergence zone is better defined, the seasonal cycle is more subtle, as the convection is constrained by the distribution of ocean temperatures.

Sometimes, a double ITCZ forms, with one located north and another south of the equator. When this occurs, a narrow ridge of high pressure forms between the two convergence zones, one of which is usually stronger than the other.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Fluid:


The reality is that in any population of people, and especially so in cities, you are going to have a certain percentage that can not take the action necessary, for any number of reasons. They may be ill, they may have mobility problems, they may have cognitive problems, they may simply have no money, or they may be somehow tied so that they feel that they can't (threatened with loss of job, fearful of loss of pets, or home) or shouldn't (be in a helping profession and remain behind), may have intended to but was thwarted at the last minute (car breaks down, someone has an unrelated un-expected medical event, can't locate a family member) etc etc etc.

Yes, you can say "Hell with 'em!" , but once you cross that line, your society will inevitably decay into something that reflects that attitude through out all its behavior.


i agree with you too. that's why i said i sort of agreed with the previous post. there was definitely a mix of fully capable, but taking advantage, and truly dependent and incapable. some of those people have NEVER left the city. alot didn't fully understand what was going on, and many did not have the means to leave, just as you said. however, there were still those who have always had the govt. take care of them even though they are fully capable of taking care of themselves, so we shouldn't be surprised when these people expect the govt to save them from a cat 4 storm even though they were supposed to leave.
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Quoting gbreezegirl:
So here I sit in
Gulf Breeze wondering - hmmmm this is not looking so good for the home team. Even if it heads towards Texas or Mexico won't we be on the worst side to get an oilslick??
The Answer is Yes on the worst side of this storm and Crude will be everywhere....

Taco :o)
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2147. JRRP
Quoting connie1976:
what is ITCZ?

The Intertropical Convergence Zone
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http://cimss.ssec.wisc.edu/tropic2/#
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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.