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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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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Guys.. there is no surface LLC forming..lol
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Quoting Jeff9641:

Yup this system is going to clip SW tip of Haiti and go just north of Jamaica.

Wow if that happens,hmm... wonder what the models will say?
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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
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Could have a TD by 11pm
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This GFDL 18z run last night was actually more or less accurate...

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Quoting Hurricanes101:
ssd site moved the floater but did not move the lat/lon lines lol

Ohh, thats what's going on, LOL
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636. MahFL
Quoting unf97:

Hey SSIGuy, Yes it is an extremely humid day in Jax. I don't know which is worst, this week's humidity, or last weeks 100 degree+ temps we had for 4 days.

Last weeks 102's were the worst for me.
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635. IKE
NOGAPS takes the vorticity to SW LA. Looks a little fast on movement.
Member Since: June 9, 2005 Posts: 23 Comments: 37938
Quoting stillwaiting:
you can see surface clouds moving north towards haiti,if their is a surface low forming its around 75w imo...

Doesn't look like it on the shortwave loop. 72W is looking better and better.

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ssd site moved the floater but did not move the lat/lon lines lol
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629. xcool
Appears to be developing l lc
hmmmm ?
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Quoting Hurricanes101:

actually I have the latest version

I have had that issue as well, I refreshed a couple of times and then got all the frames. Hope that helps.
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I have the center around 15N 71.4W

ssd floater is screwed up, they have the coordinates displaced big time
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Appears some sort of circulation is forming within 93L. I've tried looking for radars, no luck.
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you can see surface clouds moving north towards haiti,if their is a surface low forming its around 75w imo...
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623. xcool
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HWRF 12z:

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Quoting VAbeachhurricanes:

yeah it brutal, idk if its as humid there as it is down here. supposed to get some big storms tonight cause of it though

looks like temp wise you guys down there wont be as hot, but with the dewpoint near 80...its still gonna be miserable...

Cheltenham Square, Virginia Beach, Virginia (PWS)
Updated: 4 min 11 sec ago
Mostly Cloudy
82.4 °F
Mostly Cloudy
Humidity: 92%
Dew Point: 80 °F
Wind: 1.0 mph from the SW
Wind Gust: 9.0 mph
Pressure: 30.07 in (Falling)
Heat Index: 93 °F

according to wu, you guys are only going to get up to 88-90 down there...

were getting hotter temps with a lil lower dew point (only 70-72)...so were sitting at 93-94 now...and there aint no slowing down it looks like...
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Quoting Drakoen:
It looks like it is heading in the general direction of Jamaica to me. You can see a surface circulatoin trying to form south of DR.

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.
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Trying to look for radars anywhere in Hispaniola, no luck.
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Quoting RecordSeason:
Well, with or without 93L, we are about to get a pretty significant rain event in SELA.

This TS is an outlier, and it's the heaviest rain I've seen in years...

Severe - Gulf


Scattered thunderstorms continue to develop offshore this morning.
Thunderstorms development will likely continue into the afternoon as a weak trough moves westward across the region. The most concentrated area of thunderstorms currently stretches from just southwest of Breton Sound northeastward to just west of Pensacola. These storms are generally moving slowly to the northwest. Additional scattered thunderstorms are also occurring farther offshore.
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614. Gorty
I think right now, it is heading due west.
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Quoting Hurricanes101:

downloading the latest version now

actually I have the latest version
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Quoting kmanislander:

Actually, I think we should start a movement to bring back Dave " my friends" Schwartz. Now there was an entertaining fellow.

No doubt! Dave Schwartz was our favorite...now TWC is a commercialized shell of it's former self. There's always YouTube...where you can watch and bask in the nostalgia of when TWC was in its prime.
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Lots of percentages being thrown around these parts today. Here, THEN, are some odds of my own:

0%: chance 93L will develop into a Cat 5 by this evening.
0.2%: chance the eye of whatever 93L develops into passes directly over the DWH.
5%: chance 93L will eventually develop into a major hurricane.
40%: chance the NHC currently gives 93L for becoming a tropical depression.
50%: chance of rain on Cuba due to 93L and/or its descendants.
60%: chance the NHC currently gives 93L for fading into nothingness before even becoming a TD.
65%: chance Dr. Gray gives Florida to receive a landfalling hurricane this season.
70%: chance of rain on Hispaniola due to 93L and/or its descendants.
75%: chance there'll be a named storm somewhere in the GOM this year.
97%: chance that every model will get some things wrong and some things right this season.
98%: chance there'll be a named storm somewhere in the North Atlantic/GOM this season.
99%: chance that either shear, land interaction, lowers SSTs, an ill-timed MJO, dry air, Saharan dust, an ERC, or just garden-variety bad mumbo jumbo will conspire to cause a rash of premature RIPs on this blog.
100%: chance the first North Atlantic storm this season will be named Alex;
150%: chance that some on this blog will dispute that prevous chance.

(Oh, yeah: 0.6%: chance Team USA goes on to win the 2010 World Cup.)

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It's really organizing in these afternoon hours.
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Good afternoon...

93L is attempting to consolidate at low levels and from my point of view a low is developing @ 17N 71W, which coincides with the 850MB VORT max in the same region.
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605. ATL
Part of the reason there are so many trolls is because you guys are so easily trolled...
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Quoting StormW:

What version of flash player do you have?

downloading the latest version now
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Uh, Pat...

I know I'm probably seeing things, but what the hell is going on over us? Theres a nice chunk of 850 vort sitting overtop of SELA moving slowly sw. Moreso than 93l, in fact.
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601. IKE
Quoting DestinJeff:

Ike, you notice a discernable northward sift in the last frame of that loop?

Yup. At 96 hours the vort is north of the Yucatan. Things getting a little clearer on the 3-4 day track.
Member Since: June 9, 2005 Posts: 23 Comments: 37938
Quoting IKE:

I was thinking Jamaica too. Looks headed north of west...280 degrees?

That looks about right
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597. IKE
Quoting Drakoen:
It looks like it is heading in the general direction of Jamaica to me. You can see a surface circulatoin trying to form south of DR.

I was thinking Jamaica too. Looks headed north of west...280 degrees?
Member Since: June 9, 2005 Posts: 23 Comments: 37938
Quoting JFVfromFlorida:

now I know this isnt him, JFV is from Miami and thus comes with the idea that no other city exists outside of NY,Miami, and LA so he would never post this. It would have been a picture of the Dolphins, and the Miami Hurricanes.
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Dr. Masters (r) co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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