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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I find it kind of humorous that many thought it was getting better organized today (me included) and boom NHC comes out and says its less organized lol

Guess that is why they are the professionals lol
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695. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE JUN 22 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE OVER THE CENTRAL CARIBBEAN SEA HAS BECOME LESS
ORGANIZED TODAY. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE
WAVE WILL LIKELY SPREAD ACROSS PORTIONS OF THE DOMINICAN
REPUBLIC...HAITI...JAMAICA...AND EASTERN CUBA DURING THE NEXT DAY
OR SO. THERE IS A LOW CHANCE...20 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HOWEVER...
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BECOME MORE CONDUCIVE FOR
SLOW DEVELOPMENT OF THIS SYSTEM OVER THE NEXT SEVERAL DAYS AS IT
MOVES WEST-NORTHWESTWARD AT ABOUT 10 MPH.


ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN/BLAKE

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Good afternoon everyone! From the visible it looks like 93L is starting to develop some rotation, certainly more than it had yesterday. Sure hope this stays away from the Florida Panhandle, I'm not as ready for this as I should be!
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692. IKE
...20 PERCENT...LOL!
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Down to 20% LOL

000
ABNT20 KNHC 221738
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE JUN 22 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE OVER THE CENTRAL CARIBBEAN SEA HAS BECOME LESS
ORGANIZED TODAY. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE
WAVE WILL LIKELY SPREAD ACROSS PORTIONS OF THE DOMINICAN
REPUBLIC...HAITI...JAMAICA...AND EASTERN CUBA DURING THE NEXT DAY
OR SO. THERE IS A LOW CHANCE...20 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HOWEVER...
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BECOME MORE CONDUCIVE FOR
SLOW DEVELOPMENT OF THIS SYSTEM OVER THE NEXT SEVERAL DAYS AS IT
MOVES WEST-NORTHWESTWARD AT ABOUT 10 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN/BLAKE

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Looking back over recent pages,
I didn't see this WindSat pass
from about 5 1/2 ago hrs posted.

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688. IKE
12Z CMC
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forgive the curiosity outside the tropics, but does anyone know where I might find a skew-t plot for the twin cities, MN?

Edit: hmmm, should have tried self sufficiency first.. found one at NOAA site, nevermind.
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Quoting txag91met:

Dude there is no center!


Telling peeps there is no LLC forming gives us headaches.. I tell them a few times, then give up.
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Quoting JFVfromFlorida:
Hi whats up guys.


are you JFV?
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12Z GFDL animation
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680. xcool
Hurricanes101 wow
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting Dakster:


How low can it go?


Until we hit PLAID!
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LRandyB 1:14 PM EDT on June 22, 2010
Quoting will45:
May have already been asked Randy but do you think HH will fly to invest tomorrow?


I think so. It's close enough that we can fly it from here at Keesler rather than deploy to St. Croix. The Plan of the Day shows about 3 and a half hours enroute, 4 hours on station flying the invest, and three and a half hours back for a total of 11 hours of flight time.

But because we are able to fly it from here and nothing has been expended yet, NHC could still cancel before the take off time in the morning if they felt it was not needed.

I got this response a min ago from Randy with HH
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677. xcool
models can change very fast/
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Kind of creepy, the way this thing is getting its act together, just as it is passes to the south of Haiti.

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Quoting Drakoen:
gfdl 12Z:



Looks like Gustavs' track just further west

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Quoting Hurricanes101:


actually I have the latest version



Responding to oneself should not be allowed...
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Dominican Republic radar: Link

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He's so smart the only hurricane he can think of is Katrina...

Trolling is more classy than this, dude. You gotta subtly bring up something controversial, and then make everybody mad.

John Hope Rule applies...we'll know more later this week. Until then...everybody enjoy discussing large piles of inconclusive evidence.....and ignoring fake JFV. Uneless you find it mildly entertaining....which I do.

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We have a few different opinions on where a developing COC is located, but only time will tell. I'm more inclined to think that the rotation visible within the convective mass near/over Hispaniola is mid/upper levels only. The best lower level would be further to the south and west.
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Quoting Skyepony:
BLAS is slowly disappearing from the products. Looks completely open & undone.

95E is coming along. I expect it named soon. Looks like a TCFA (Tropical Cyclone Formation Alert) has been issued on it. There's a little naked swirl just south of 10N.


Nice swirl.
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669. IKE
...
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gfdl 12Z:

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Quoting txag91met:

Dude there is no center!


you are right, now that I look at it

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Quoting txag91met:
Hey Jr mets...there is no low with this system yet...that system that is going into DR is anticyclonic vortex aloft with mid-level rotation. Nothing yet on 93L.

We can't be too sure if that is the area that is working its way down to the surface, if the southwest side begins to wrap around that area then I'll buy it. The next few hours will be telling.
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Quoting JFVfromFlorida:
OK u say whatever u want buts its good to finally nat get banned in a long time and if i do i wana tell you i hope miy house isn't destroyed.


Please give us all abreak and very slowly step back from the key board !!!!!!
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Quoting clwstmchasr:


Where do you expect them to shift?

Dude there is no center!
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661. xcool



guess old
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting DestinJeff:
blog is going to be going at Ludicrous Speed in short order ...



How low can it go?
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Quoting DestinJeff:
blog is going to be going at Ludicrous Speed in short order ...


But we've never gone that fast sir! XD

Anyway, the latest sounding from the vicinity of 93L is looking good.

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Quoting IKE:


I was watching MSNBC this morning at 4am. Met on there showed a track similar to that. Maybe a track a little closer to the northern Yucatan and bending more NW at that point.


Looks like todays 12z GFDL
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656. Skyepony (Mod)
BLAS is slowly disappearing from the products. Looks completely open & undone.

95E is coming along. I expect it named soon. Looks like a TCFA (Tropical Cyclone Formation Alert) has been issued on it. There's a little naked swirl just south of 10N.
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Hey Jr mets...there is no low with this system yet...that system that is going into DR is anticyclonic vortex aloft with mid-level rotation. Nothing yet on 93L.
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Quoting scottsvb:


That is not a surface reflection.. that is all in the midlevels. Everything in the LLVs is moving WNW.

Here is the best reason why we dont have a LLC. The pressure gradient of the winds between Hispaniola and S America is causing ESE winds. Now the winds slow down once it gets west of Haiti towards Jamaica.. this near 80W in 2 days will then give us the best chance of a circulation in the LLVs ..right now the gradient between the landmasses isnt letting anything to develop in the LLvs. Also Pressures are not falling.


Could this be the basis for the John Hope rule?
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650. IKE
Quoting Drakoen:
This GFDL 18z run last night was actually more or less accurate...



I was watching MSNBC this morning at 4am. Met on there showed a track similar to that. Maybe a track a little closer to the northern Yucatan and bending more NW at that point.
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Quoting nrtiwlnvragn:
12Z GFDL still central GOM as before.


HOUR:126.0 LONG: -91.34 LAT: 25.82 MIN PRESS (hPa): 974.19 MAX SURF WIND (KNOTS): 83.29


Looks good
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647. MahFL
71W 17N seems to be the sweet spot atm.
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Quoting asgolfr999:


Tsk tsk, if he was real he waould have referred to StormW as master Chief...he'll get dropped soon enough....click


and not one sir yet...not to mention the glaring absence of constant teh's.
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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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