93L slow to develop, but bringing heavy rains to Haiti

By: Dr. Jeff Masters , 1:50 PM GMT on June 22, 2010

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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sorry DaytonaBeachWatcher I don't see anything of the sort but what we could see it the relocation of the flight plans
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ok, the GFDL was not what I wanted to see this morning :(

I have seen people joke on here about ants, but what do you do when you walk out on your porch first thing in the morning and see a crab walk by? I had a small 2.5-3" crab strolling along my front porch and I do not live near a beach. Bad sign??? lol

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My biggest fear with anything like this in the Gulf is that it gets pulled to the NE by something. That is my fear with this storm. This isn't good for the Gulf at all, but some models don't strengthen it too much at least.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
The NHC may need to move the circle over 16N 75W.
Member Since: August 19, 2006 Posts: 0 Comments: 16308
And now closing from the outside it's Herbert's Box trying to take over John Hope at the inside rail.Photo finish hold all tickets please.
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We will know more once it emerges into the Southern Gulf. Looks like Tx might bear the brunt of this one.
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Looks like the model initiation procedures are about as good as everyone on here looking at "bogus" centers :))))
I always wondered why all the models started the L in the same place. It appears they all use GFS.
Guess Fields Creation
To avoid large observational increments in the 3DVAR
data analysis, we modify the guess fields before
the GSI uses them. Creation of the guess fields involves
the following steps:
a) Create a new HWRF domain based on the new
storm center position and interpolate 6h GFS
forecast data onto the new HWRF grids (outer
nest: 750x750, inner nest: 120x120);
b) Interpolate the 6h HWRF forecast data onto the
new HWRF grids, replacing the GFS data with
HWRF forecast data in the overlap region;
c) Separate the new data into the environmental
flow and the hurricane component;
d) Correct the intensity of the hurricane component
before inserting it back into the new HWRF
grids at the observed position;
e) If there are no 6h HWRF forecast data, we will
skip step (b) and replace the storm component
with a bogus storm in step (d).
The details in the intensity correction in step (d) are as
Member Since: September 1, 2009 Posts: 23 Comments: 1007
is there a good program for getting this blog on my droid phone?
Member Since: July 30, 2007 Posts: 6 Comments: 1448
Recon is cancelled i hear.
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Quoting Jeff9641:

Throw that one out. Should be centered on FL panhandle. Center relocated.

Believe me Jeff, I want to throw it out!
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Just woke up this morning, so my eyes are still a bit foggy, but this is what I see from the first few frames of the visible satellite:

I see a strong flow of low-level clouds moving SSW associated with the vort in the SE Caribbean. I also see low-level clouds moving S on the left side of the blob at 17N, 72.5W. According to my eyes, either one of these blobs could very well close off a closed LLC any time now, as they appear to be very close to doing so.
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Quoting gulfbreeze:

Not sure...why are you yelling?
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Quoting kmanislander:

Uh Oh. Contender #1 on the ropes !

Hopefully, they will cancel each other out.
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I should never have brought up the John Hope rule
Member Since: August 19, 2006 Posts: 0 Comments: 16308
Good Morning StormW and everyone...could someone please give me the latest on 93L?? Thanks a bunch!!
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The John Hope rule was in effect yesterday when the so called mid level circulation stayed offshore and developed into the area the NHC is focusing on today. However, of course the hope rule is going on today as we see several blobs competing for energy in the eastern and central caribbean.
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What time does the 12Z come out?
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aquak9 that recon flight plan is old
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Quoting aquak9:
Taz- do you understand what the John Hope Rule is?

Do you know why we keep referring to it?

It's NOT off-topic.

Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting txag91met:
Whatever it is it is getting ripped by the outflow from 93L.

I agree that it is being sheared now but more so by the anticyclone that is centered in the Western Caribbean. That 850 vort has been very persistent and should be monitored down the road.
Member Since: August 19, 2006 Posts: 0 Comments: 16308
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3416. Crawls
Blurb from local forecast this morning - Baton Rouge LA

By the end of the weekend we may be feeling the effects of a tropical wave out in the Caribbean Sea. Many of the weather models now have this wave moving into the Gulf of Mexico by the weekend.

Most of the models are in better agreement on the projected near term path and strength of this system as it continues to advance to the West at 10 mph. A majority of the models move this wave into the Yucatan Peninsula and then in the Southern Gulf of Mexico. It’s at this point the models tend to vary on their long range outlooks. As always we’ll keep a close eye on this system as it advances closer.
Member Since: August 17, 2007 Posts: 0 Comments: 272
This is an awful scenario. hope it doesn't pan out.

ugly model
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3414. aquak9
Taz- do you understand what the John Hope Rule is?

Do you know why we keep referring to it?

It's NOT off-topic.
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Stupid question possibly: wouldn't a tropical system located to the east of Lousiana actually be a good thing for them? Wouldn't the winds drive oil away from the coast?

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Quoting StormW:

Now that's the best thing I've heard this morning!

Uh Oh. Contender #1 on the ropes !

Member Since: August 19, 2006 Posts: 0 Comments: 16308
Learned that looking at satellites sometimes it is very hard to say if something is moving in a certain direction or center is relocating. At any rate since this is still a wave its center could pop up just about anywhere a long the disturbance.
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3409. 7544
hmm now some models have it goin north and then other show this right turn further south so if the trof is going to be strong
could we see more of a wilma tack in the next couple of runs . imo as of now all bets are off with the two new players showed up in the game stay tuned
Member Since: May 6, 2007 Posts: 0 Comments: 7087
Quoting RecordSeason:

That's what's puzzling to me.

The circulation that was previously near 75W much of yesterday is still near Jamaica, and the vorticity map is only about 3 hours old, and it shows by far the strongest vorticity being near Jamaica. It continues to show no vorticity near the new MCV by DR.

Will the REAL 93L please stand up?

I think the real low continues to be near Jamaica, it is simply having trouble organizing convection for some reason we still don't understand.

took the words right out of my fingertips. this whole situation is bizarre...
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The graphic from the NHC shifted farther north last night in response to modified environmental conditions favorable for development in that area.
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Wow, I must say 93L looks impressive to me this morning.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting kmanislander:

I think it is more than just that. Take a look at the lower right side of this image.

Whatever it is it is getting ripped by the outflow from 93L.
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The so called "mid level circulation" yesterday was actually embedded in a lower level environment as satellites continually kept the initial spin offshore until today we see Noaa reinforcing the "northern bias" of 8 last night. There is a blend of influences in the early stages of Caribbean storms.
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I'm lost now on this discussion about where the new blob came from. Does it matter ?. Can we just see what it does ?.
Member Since: August 19, 2006 Posts: 0 Comments: 16308
3398. aquak9

A. 23/1800Z
C. 23/1330Z
D. 17.0N 77.5W
E. 23/1700Z TO 23/2100Z
F. SFC TO 10,000 FT

A. 24/0600Z
C. 24/0100Z
D. 17.5N 79.5W
E. 24/0400Z TO 24/0830Z
F. SFC TO 10,000 FT

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Quoting aquak9:

i toldja, girl...."welcome to the addiction"

It helps to know I'm not alone. Finally changing my browser default to the blog because it's more important than my email
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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