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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1896. Drakoen
11:29 PM GMT on June 22, 2010
HWRF point at you Patrap
Member Since: October 28, 2006 Posts: 57 Comments: 30264
1895. Patrap
11:29 PM GMT on June 22, 2010
Waiting for my Pizza Dough to rise..

Making somew deep Dish Supreme..Ol Style from Scratch
Member Since: July 3, 2005 Posts: 423 Comments: 127848
1894. alaina1085
11:29 PM GMT on June 22, 2010
Quoting MiamiHurricanes09:
Things should pan out nicely tonight.

The conditions are all there for it too. Wait and see if 93L takes advantage. Thanks for the info :)
Member Since: August 2, 2006 Posts: 0 Comments: 1240
1891. MiamiHurricanes09
11:28 PM GMT on June 22, 2010
Quoting Patrap:
925mb

ooow-ee
? What model is showing this?
Member Since: September 2, 2009 Posts: 130 Comments: 21150
1890. GTcooliebai
11:28 PM GMT on June 22, 2010
Anybody got a chart on the position of the High over the Atlantic, that shows this "so called" trough in the Southeast??
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1889. mrsalagranny
11:28 PM GMT on June 22, 2010
Hello Patrap.How are you tonight?
Member Since: June 6, 2010 Posts: 0 Comments: 853
1887. MiamiHurricanes09
11:28 PM GMT on June 22, 2010
Quoting Tazmanian:




mode runs are being a wishcaster
Well if you consider the conditions that will be present in the western Caribbean and GOM the GFDL might be a downcaster.
Member Since: September 2, 2009 Posts: 130 Comments: 21150
1886. Patrap
11:27 PM GMT on June 22, 2010
925mb

ooow-ee
Member Since: July 3, 2005 Posts: 423 Comments: 127848
1884. MiamiHurricanes09
11:27 PM GMT on June 22, 2010
Quoting alaina1085:

That would explain the better rotation then. Interesting to see how things pan out tonight.
Things should pan out nicely tonight.
Member Since: September 2, 2009 Posts: 130 Comments: 21150
1883. all4hurricanes
11:27 PM GMT on June 22, 2010
Quoting GreenMe2225:
93L = worth the wait.
It better be or I'm giving up on 2010
Member Since: March 29, 2008 Posts: 0 Comments: 2370
1882. Tazmanian
11:27 PM GMT on June 22, 2010
Quoting MiamiHurricanes09:
Category 2 hurricane in the GOM...




mode runs are being a wishcaster
Member Since: May 21, 2006 Posts: 5091 Comments: 114960
1881. CybrTeddy
11:26 PM GMT on June 22, 2010
rcmansour, your more annoying than the wife. I blog on here just to avoid that, not encounter more of it.
Member Since: July 8, 2005 Posts: 259 Comments: 23916
1879. MiamiHurricanes09
11:26 PM GMT on June 22, 2010
Quoting nrtiwlnvragn:
18Z 93L GFDL consistent with prior runs.


HOUR:126.0 LONG: -90.79 LAT: 27.26 MIN PRESS (hPa): 966.37 MAX SURF WIND (KNOTS): 86.15
Category 2 hurricane in the GOM...
Member Since: September 2, 2009 Posts: 130 Comments: 21150
1878. mrsalagranny
11:26 PM GMT on June 22, 2010
Thank you for replying.I havent been on in a day or so and was curious.Maybe it will just go away.
Member Since: June 6, 2010 Posts: 0 Comments: 853
1877. alaina1085
11:25 PM GMT on June 22, 2010
Quoting MiamiHurricanes09:
From what I am seeing on satellite, 850mb vorticity, and MIMIC-TPW the area of broad low pressure is at 75˚W.

That would explain the better rotation then. Interesting to see how things pan out tonight.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
1875. Drakoen
11:25 PM GMT on June 22, 2010
HWRF 18z

Member Since: October 28, 2006 Posts: 57 Comments: 30264
1874. GTcooliebai
11:25 PM GMT on June 22, 2010
Quoting Acemmett90:

wow dont u have hw to do

LOLz
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1873. Tazmanian
11:25 PM GMT on June 22, 2010
Quoting rcmansour:
Told you guys RIP 93L...now 20% will be 0% within 24 hours. August earliest something will happen I'm thinking 8 storms at most




you are a ture downcaster
Member Since: May 21, 2006 Posts: 5091 Comments: 114960
1871. DehSoBe
11:24 PM GMT on June 22, 2010
How soon do you think the models will have a true COC? And do you think that could make any drastic changes to the runs? i.e. more northwest than west.
Member Since: June 14, 2010 Posts: 0 Comments: 34
1870. rcmansour
11:24 PM GMT on June 22, 2010
Told you guys RIP 93L...now 20% will be 0% within 24 hours. August earliest something will happen I'm thinking 8 storms at most
1869. ATL
11:24 PM GMT on June 22, 2010
Quoting mrsalagranny:
Hello everyone.What is the latest on 93L?

Taking it's time to get it's act together but I think the blog consensus is that it will eventually develop. It has a LONG way to go before becoming a threat to any part of the U.S. however.
1868. nrtiwlnvragn
11:24 PM GMT on June 22, 2010
18Z 93L GFDL consistent with prior runs.


HOUR:126.0 LONG: -90.79 LAT: 27.26 MIN PRESS (hPa): 966.37 MAX SURF WIND (KNOTS): 86.15
Member Since: September 23, 2005 Posts: 14 Comments: 11103
1865. MiamiHurricanes09
11:23 PM GMT on June 22, 2010
Quoting alaina1085:
When will 93L be at this oh so talked about 75 W?
From what I am seeing on satellite, 850mb vorticity, and MIMIC-TPW the area of broad low pressure is at 75˚W.
Member Since: September 2, 2009 Posts: 130 Comments: 21150
1864. Tazmanian
11:23 PM GMT on June 22, 2010
Quoting Drakoen:
You can definitely see a spin in the fluid on this MIMIC-TPW in the last couple of frames.




93L is takeing a vacan in MX
Member Since: May 21, 2006 Posts: 5091 Comments: 114960
1863. xcool
11:22 PM GMT on June 22, 2010
del
Member Since: September 26, 2009 Posts: 2 Comments: 15649
1861. GTcooliebai
11:22 PM GMT on June 22, 2010
Quoting RecordSeason:
BaltimorBirds:

According to the CMC, there is going to be 3 hurricanes form within the next 7 days, and at least one of them is going to hit NOLA, with the second one (which is actually 93L) hot on it's tails.

That doesn't make sense!
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1859. MiamiHurricanes09
11:22 PM GMT on June 22, 2010
Quoting Drakoen:
You can definitely see a spin in the fluid on this MIMIC-TPW in the last couple of frames.

You mean this? I see it too.

Member Since: September 2, 2009 Posts: 130 Comments: 21150
1857. alaina1085
11:22 PM GMT on June 22, 2010
When will 93L be at this oh so talked about 75 W?
Member Since: August 2, 2006 Posts: 0 Comments: 1240
1856. CybrTeddy
11:21 PM GMT on June 22, 2010
My bets they'll keep it at 20%, possibly 30%.
Member Since: July 8, 2005 Posts: 259 Comments: 23916
1854. Drakoen
11:21 PM GMT on June 22, 2010
You can definitely see a spin in the fluid on this MIMIC-TPW in the last couple of frames.

Member Since: October 28, 2006 Posts: 57 Comments: 30264
1853. mrsalagranny
11:21 PM GMT on June 22, 2010
Hello everyone.What is the latest on 93L?
Member Since: June 6, 2010 Posts: 0 Comments: 853
1851. MiamiHurricanes09
11:20 PM GMT on June 22, 2010
Quoting Baltimorebirds:
How strong do you see it getting???.I'd say weak cat 1 the most with those sst.
We'll know soon enough...
Member Since: September 2, 2009 Posts: 130 Comments: 21150
Quoting stormpetrol:
I don't know but on the RGB loop the spin around 16.8N/72.2W looks to become the dominant one.
That's a MCV not a circulation, the area to watch is near 75˚W 17.5˚N.
Member Since: September 2, 2009 Posts: 130 Comments: 21150
Quoting taco2me61:
LOL\
Thats why I like you :o)
You Love the Madness....

Taco :o)

:p If you cant handle the madness get out the blog! LOL.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
Quoting Baltimorebirds:
Where all the thcp is and hot water......
Warm SSTs aren't the only factor.
Member Since: September 2, 2009 Posts: 130 Comments: 21150

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.