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 CaneWarning:


I've been saying all along that the West Coast of Florida and panhandle need to watch this one...if it develops.
Doubt it.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
I think our next invest may now be forming east of SA,heck it should be a invest now IMO based on sat presentation........
Member Since: October 5, 2007 Posts: 20 Comments: 4970
2644. pottery
Sorry. I should have referenced the post number and not quoted the long article...
Member Since: Posts: Comments:
D MAX D MAX DAMX




ok all wish one is 93L

Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting FLWeatherFreak91:
Have you noticed the model trends, though? The latest ones show a bending back towards the ne.


I've been saying all along that the West Coast of Florida and panhandle need to watch this one...if it develops.
Member Since: Posts: Comments:
I agree with freak those models trends will continue to bend toward the north and east toward the west coast of FL
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2638. Hhunter
bastardi says it will go. it will go
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2637. 786
Comradez, thanks! excellent explanation
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Quoting FLWeatherFreak91:
That "little NE curve" that wasn't there at all on the 12z runs may turn into a larger ne turn on the next model run. So don't say that just the panhandle is in danger.
Hold up. We don't even know that this system is going to develop. I'm not going to go out and say that all of Florida is in danger when in reality it isn't. Anyways, unless the trough that is expected to dig into the GOM and strengthens to be a beast the western coast of Florida really shouldn't have to worry about what 93L does.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2635. beell
Probably the biggest impediment to development of 93L is its size. Cyclonic flow is covering most all of the Caribbean. It is a very large wave. A big broad..............wave

This is the 18Z GFS/700mb

Link

I know we shouldn't lean on the NAM too much but you get the general idea.

This is the 00Z NAM/700mb:

Link

Pretty sure the 00Z GFS will show something similar. And a trend towards closing off at 700mb within 24 hours as a guess.
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Quoting spathy:
I can not believe all this evening I have not read the word
DMAX!
What a let down.
I had a whole beverage game based on that tonight!


Can't believe I'm making this my one post for the night but this made me LOL
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2633. pottery
Quoting Comradez:


That's a fair question that is very difficult to answer. Clearly systems like 93L suggest that the standard list of factors (SST, moisture, and shear) does not entirely account for a tropical cyclone's genesis.

What I would love to have would be a temperature graph from a column of air around 93L's supposed LLC. The relevant variables would be the humidity and the lapse rate along the column of air.

My guess is that the convection east of 93L is robbing 93L's LLC of moisture, thus requiring parcels of air to get higher in the atmosphere before they cool off enough (from the natural pressure decrease and expansion of air (which makes sense if you can imagine air particles spreading out and banging into each other and causing friction less often)) in order to replace the dry adiabatic lapse rate with the saturated adiabatic lapse rate as the lapse rate that the environmental lapse rate needs to be greater than in order to make the parcels of air continue moving upwards. (At the saturated adiabatic lapse rate, condensing water vapor releases latent heat, giving the parcels of air more heat relative to their surroundings, increasing the severity of the lapse rate gradient, and causing those parcels of air to continue moving upwards). If the air at the surface isn't moist enough, it won't ever rise as high as it needs to in order for the saturated adiabatic lapse rate to take over and spur on more convection.

Alternatively, if the humidity near the surface is at 100%, but the environmental lapse rate is smaller than even the saturated adiabatic lapse rate (in other words, the surface is too cool and/or the upper atmosphere is too warm), then you won't get convection in that case either.

So another hypothesis is that the thunderstorm belt to the east of 93L's supposed LLC is fanning out air that has received a lot of latent heat from condensation, and this air in the upper atmosphere in the outflow from those thunderstorms is (adiabatically, not necessarily absolutely) warmer than the air that might try to rise from the bottom near the LLC, and so that air can't even get going where it can start to condense water vapor and release its own latent heat to power it upward.

This is why, I suppose, it might be bad (for development) to have a large disorganized region of competing centers of development right close to one another, like we sorta seem to have here.

See this link for background info:
http://en.wikipedia.org/wiki/Lapse_rate

Thank You.
I have been trying to find a reasonable explanation for this, for 2 days.
Some of the terminology is beyond me, but I understand the concept.
Very plausible IMO.
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Quoting MiamiHurricanes09:
That little NE curve at the end might put the Florida panhandle at danger. But regardless still way too long to know for sure.
That "little NE curve" that wasn't there at all on the 12z runs may turn into a larger ne turn on the next model run. So don't say that just the panhandle is in danger.
Member Since: December 1, 2006 Posts: 2 Comments: 3634
oh this is nic all mode runs take 93L in too LA


and overe BP
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting Hurricanes101:


ssd still off
Way far east. And I'm talking almost 4˚ off.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
22/2345 UTC 17.4N 71.8W TOO WEAK 93L


ssd still off
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22/2345 UTC 17.4N 71.8W TOO WEAK 93L
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting jasoniscoolman09:
LETS HOPE NOT..
That little NE curve at the end might put the Florida panhandle at danger. But regardless still way too long to know for sure.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2624. Hhunter
Link
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Quoting Clearwater1:
that's just plain crazy! Take your pick, but not all three. I hope?
LOL, told you. I'm just sticking with 93L, whichever system it may be in that run.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
The guys on accuweather say people in florida don't need to worry about 93L.
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Quoting 786:
Hello! First time this year I am coming out of lurk mode. I am a bit perplexed with 93L can someone please explain what variable(s)is/are preventing 93L from developing a closed low as I was under the impression it was in a favourable environment (low shear, boiling SSTs, possible anticyclone...)


That's a fair question that is very difficult to answer. Clearly systems like 93L suggest that the standard list of factors (SST, moisture, and shear) does not entirely account for a tropical cyclone's genesis.

What I would love to have would be a temperature graph from a column of air around 93L's supposed LLC. The relevant variables would be the humidity and the lapse rate along the column of air.

My guess is that the convection east of 93L is robbing 93L's LLC of moisture, thus requiring parcels of air to get higher in the atmosphere before they cool off enough (from the natural pressure decrease and expansion of air (which makes sense if you can imagine air particles spreading out and banging into each other and causing friction less often)) in order to replace the dry adiabatic lapse rate with the saturated adiabatic lapse rate as the lapse rate that the environmental lapse rate needs to be greater than in order to make the parcels of air continue moving upwards. (At the saturated adiabatic lapse rate, condensing water vapor releases latent heat, giving the parcels of air more heat relative to their surroundings, increasing the severity of the lapse rate gradient, and causing those parcels of air to continue moving upwards). If the air at the surface isn't moist enough, it won't ever rise as high as it needs to in order for the saturated adiabatic lapse rate to take over and spur on more convection.

Alternatively, if the humidity near the surface is at 100%, but the environmental lapse rate is smaller than even the saturated adiabatic lapse rate (in other words, the surface is too cool and/or the upper atmosphere is too warm), then you won't get convection in that case either.

So another hypothesis is that the thunderstorm belt to the east of 93L's supposed LLC is fanning out air that has received a lot of latent heat from condensation, and this air in the upper atmosphere in the outflow from those thunderstorms is (adiabatically, not necessarily absolutely) warmer than the air that might try to rise from the bottom near the LLC, and so that air can't even get going where it can start to condense water vapor and release its own latent heat to power it upward.

This is why, I suppose, it might be bad (for development) to have a large disorganized region of competing centers of development right close to one another, like we sorta seem to have here.

See this link for background info:
http://en.wikipedia.org/wiki/Lapse_rate
Member Since: Posts: Comments:
Quoting wunderkidcayman:
even if that it the COC near 17.7N 72.9W I expect it to start moving WSW as shown is the steering map

There is no circulation "deep" enough to feel effects of steering. It will just continue to move towards the west.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
LOL, unless you want to scare the living daylights out of people I wouldn't post that CMC run, lol.
that's just plain crazy! Take your pick, but not all three. I hope?
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even if that it the COC near 17.7N 72.9W I expect it to start moving WSW as shown is the steering map

Member Since: June 13, 2009 Posts: 2 Comments: 12719
2616. xcool
TampaSpin .thanks i try alot.100%
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2615. Patrap
Quoting firematt255:
hey patrap where are you from? If you don't mind answering I often read your post they are very helpful.




Uptown, New Orleans
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Quoting Patrap:
cmc 2010062212 Forecast 850vort Java Animation
LOL, unless you want to scare the living daylights out of people I wouldn't post that CMC run, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
hey patrap where are you from? If you don't mind answering I often read your post they are very helpful.
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2611. ATL
Quoting FLWeatherFreak91:
Have you noticed the model trends, though? The latest ones show a bending back towards the ne.

At this point there's a greater chance of this thing dissipating than hitting any one state. If the models are still pointing in the same direction (towards LA/north central Gulf Coast) when/if this is classified then we should take it seriously. If the blog isn't swamped by then, of course...
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2610. Patrap
cmc 2010062212 Forecast 850vort Java Animation
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2609. HadesGodWyvern (Mod)
National Hurricane Center
Tropical Cyclone Advisory #16
SEVERE TROPICAL CYCLONE CELIA (EP042010)
3:00 AM UTC June 23 2010
==================================

Subject: "CELIA" Weakens Into A Category One Hurricane

At 3:00 AM UTC, Hurricane Celia (977 hPa) located at 11.9N 107.3W or 460 NM south southwest of Manzanillo, Mexico has sustained winds of 80 knots with gusts of 100 knots. The cyclone is reported as moving west at 9 knots.

Forecast and Intensity
======================
24 HRS: 12.3N 111.0W - 90 knots (SVR Cyclone SSHS-2)
48 HRS: 13.3N 115.6W - 90 knots (SVR Cyclone SSHS-2)
72 HRS: 14.5N 119.5W - 80 knots (SVR Cyclone SSHS-1)
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Quoting 1900hurricane:

wow! looks amazing
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2607. HadesGodWyvern (Mod)
National Hurricane Center
Tropical Cyclone Advisory #1
TROPICAL DEPRESSION EP052010
3:00 AM UTC June 23 2010
==================================

SUBJECT: Another Tropical Depression Forms In The Eastern Pacific

At 3:00 AM UTC, Tropical Depression Five (1006 hPa) located at 11.0N 93.4W or 330 NM south southeast of Salina Cruz, Mexico has sustained winds of 30 knots with gusts of 40 knots. The depression is reported as moving west northwest at 8 knots.

Forecast and Intensity
======================
24 HRS: 12.0N 96.0W - 40 knots (Tropical Storm)
48 HRS: 13.5N 99.0W - 50 knots (Tropical Storm)
72 HRS: 14.0N 101.0W - 50 knots (Tropical Storm)
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2606. xcool
Patrap 2:wow
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Many storms in the same place as 93l start off looking as if they're going to hit the central gulf, then hook off to the right before expected. Just saying that the West Coast of Florida should not stop watching this system.
Member Since: December 1, 2006 Posts: 2 Comments: 3634
2604. Patrap
Quoting firematt255:
hello patrap if it follows your track we would get hammered here in terrebonne parish and i would be busy with here at the fire dept.


Dulac and Cocodrie would have trouble as well
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Quoting xcool:
TampaSpin:good job


I don't know where you get your colorful graphics all from but, you without a doubt post the best graphics on this blog...Thanks!
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Quoting WinterAnalystwx13:


Louisiana is the place with the highest chance of getting hit IMO.
Have you noticed the model trends, though? The latest ones show a bending back towards the ne.
Member Since: December 1, 2006 Posts: 2 Comments: 3634
As fun as all this is at the moment.



Night all :-)
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting wunderkidcayman:
MiamiHurricanes09 that one is old this is the new one



No it's not. Look at the time stamp.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2598. Patrap
Quoting IKE:
00Z NAM @ 84 hours...



Reminds me of Lili in 2002



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hello patrap if it follows your track we would get hammered here in terrebonne parish and i would be busy with here at the fire dept.
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MiamiHurricanes09 that one is old this is the new one



Member Since: June 13, 2009 Posts: 2 Comments: 12719

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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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