Caribbean disturbance 94L dumping heavy rains on Jamaica

By: Dr. Jeff Masters , 4:44 PM GMT on June 05, 2011

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A large, wet, and disorganized tropical disturbance (Invest 94L) continues to spread heavy rain to the Central Caribbean near Jamaica. Rain has fallen continuously at Jamaica's Kingston Norman Manley Airport since midnight, with 1.89" having fallen from midnight to noon local time. Sustained winds of 24 mph also affected Kingston between 7am and 8am this morning. Satellite-estimated rainfall amounts of 1.4" per hour occurred in ocean regions 100 miles to the southeast of Kingston this morning, and heavy rains of up to 1/2" per hour are probably affecting portions of Jamaica early this afternoon, judging by the recent increase in heavy thunderstorm activity seen on visible satellite loops. This imagery also shows a slow increase in organization of 94L in recent hours, with spiral bands beginning to develop to the southeast of the center. There is a broad, poorly-defined circulation apparent that is not well enough defined to make 94L a tropical depression. Water vapor satellite loops show a region of dry air on the west side of 94L, and this dry air is interfering with the storm's organization. However, upper air balloon soundings from Kingston and the Cayman Islands taken at 8am EDT this morning show much moister air at mid levels of the atmosphere compared to Saturday (2% humidity at 500 mb on Saturday, compared to 49% this morning at Grand Cayman), and 94L appears to be gradually overcoming its dry air issues. Wind shear remains in the moderate range, 15 - 20 knots, and is predicted by the SHIPS model to remain below 20 knots through Tuesday morning. Water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm.


Figure 1. Rainfall rates of up to 1.4" per hour (pink colors) were estimated by the F-15 satellite for 94L at 6:02am EDT Jun 5, 2011.

Since 94L is so large and is battling dry air, it is taking its sweet time to develop, and today's mission by the Hurricane Hunters has been cancelled. A new mission is scheduled for Monday afternoon at 2pm EDT. This morning's 06Z model runs are pretty unimpressed with 94L, with most of them showing little or no development. At 2pm EDT on Sunday, NHC gave the disturbance a 40% of developing into a tropical depression by Tuesday. If 94L stays to the south, its chances of development are greater, since a band of very high wind shear of 30 - 50 knots lies over Cuba and the southern Bahama Islands. The disturbance is expected to meander slowly westward or northward over the next two days, with Jamaica and southeastern Cuba being the primary targets for very heavy rains of 4 - 8 inches through Tuesday. Haiti and Central Cuba can expect somewhat lesser rains of 3 - 6 inches. If 94L does develop into a tropical depression and moves northwards over Cuba by Wednesday, I don't see the storm attaining hurricane strength, due to the high wind shear. The primary threat from 94L will be very heavy rains, capable of causing life-threatening flash flooding.


Figure 2. Afternoon satellite image of the Central Caribbean disturbance 94L.

Jeff Masters

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Quoting wunderkidcayman:

its 2011 not 2010 you need to buy a ne calander

What's a "ne calander"? ;-)

Comment date fixed...
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1896. IKE

Quoting Levi32:
Current position based on high-resolution visible:



Loop
That's where I see the spin too.
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1895. beell
Thanks, CV. I worked pretty hard on both of them.
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Basically getting closer to the Yucatan over the past few days
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Quoting Neapolitan:
Even if 94L fails to make it beyond invest stage, take heart, tropic watchers: just 360 days, 9 hours, and 42 minutes until the 2010 hurricane season gets underway!

Woo-hoo!

its 2011 not 2010 you need to buy a ne calander
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1891. Levi32
Current position based on high-resolution visible:



Loop
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No new blogs?
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1889. IKE

Quoting Neapolitan:
Even if 94L fails to make it beyond invest stage, take heart, tropic watchers: just 360 days, 9 hours, and 42 minutes until the 2010 hurricane season gets underway!

Woo-hoo!
2010? wth?
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Even if 94L fails to make it beyond invest stage, take heart, tropic watchers: just 360 days, 9 hours, and 42 minutes until the 2012 hurricane season gets underway!

Woo-hoo!
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hey guys after looking at the wider picture it seems that the convection to the west is now pushing eastbound toward the convection south of Jam
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Quoting beell:


Ease up, Levi. It was spurious humor.
:-]


Spurious humor is always good...:) relaxes tension....cause ole 94L is slowwww goooo...Byw, a hello to all .
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1885. Levi32
Quoting beell:


Ease up, Levi. It was spurious humor.
:-]


Lol.
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1884. Levi32
Quoting CyclonicVoyage:


I personally don't believe conditions will be any better than they are today for 94L.


Agreed.
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1883. IKE

Quoting DestinJeff:
94L does seem to have the best chances of the invests thus far to actually develop, I believe.
WISHCASTER!
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Gotta give you credit on your Avatar Beell, pretty darn hilarious. Although I thought the Grandma one was better.
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Quoting stormpetrol:
I see the surface low now clearly on visibleLink around 18/81.4, Interesting scenario taking place with all the convection approaching the low from WSW/SW , and the convection drifting west from east!

the only thing I see there is a weak elongated circulation I belief a new one is developing E aaround or under the convection s of jamaica there seems to be a few swirls developing in the area
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1879. beell
Quoting Levi32:


What. Typical GFS elongation?


Ease up, Levi. It was spurious humor.
:-]
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Quoting Levi32:


If that happens things would become more interesting.


I personally don't believe conditions will be any better than they are today for 94L.
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LLC almost due west of Jamaica
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1875. Levi32
Quoting beell:
LOL. There's always this:



What. Typical GFS elongation?
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Good Morning. That ongoing sheer to the North of the disturbance and relative position of the sub-tropical jet, which now appears to have dipped down a bit south of Cuba, is really hindering development......Favorable sheer in the upper levels is the missing ingredient and the anti-clyclone has not been able to fight it off sufficiently although it came pretty close yesterday........I think it is losing the battle at present.
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Complete Update

TS BUSTED FORECAST ALIBI





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1872. beell
LOL. There's always this:

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I see the surface low now clearly on visibleLink around 18/81.4, Interesting scenario taking place with all the convection approaching the low from WSW/SW , and the convection drifting west from east!
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1870. Levi32
Zoomed-in high-resolution visible loop of 94L
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1869. Levi32
Quoting CyclonicVoyage:



Looking at the progress of the western convection to the east, 94L's center may indeed be covered soon.


If that happens things would become more interesting.
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Quoting Levi32:


As long as we can see the surface circulation exposed on visible, there's no reason to send the recon. We're only going to need that if this system gets to the point where it hides itself beneath convection and it becomes hard to determine its true organization. An exposed low center tells us all we need to know.



Looking at the progress of the western convection to the east, 94L's center may indeed be covered soon.
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Quoting reedzone:
Starting to see a tighter low around 80W and 17N, west-southwest of Jamaica.. Anybody seeing what I'm seeing?



Not really seeing any at the surface in that location. Still seeing a pretty defined circulation at around 18 N and 82W at this time.
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I am reading 29.76 right now here in Grand Cayman
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Information About Disturbance (Invest 94L)


Storm information valid as of: Monday, June 6, 2011 12:00 Z
Coordinates: 17.7N 81.6W (View Map or View Storm Centered Satellite Image)

Location: 112 miles (180 km) to the S (187°) from George Town, Cayman Islands (GBR)

Distance Calculator: How far away is this storm from me?

Pressure (MSLP): 1006 mb (29.71 inHg | 1006 hPa)

Sustained wind speed (1 min. avg.): 25 knots (29 mph | 13 m/s)

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1861. Levi32
Quoting cchsweatherman:
Its a shame that the NHC rescheduled today's recon mission for tomorrow since it would be helpful to actually see whats going on with this system finally and give the computer models some more assistance with the ultimate evolution of this system.


As long as we can see the surface circulation exposed on visible, there's no reason to send the recon. We're only going to need that if this system gets to the point where it hides itself beneath convection and it becomes hard to determine its true organization. An exposed low center tells us all we need to know.
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All time record high for June yesterday in Houston at 105*
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1859. Levi32
Quoting reedzone:
Starting to see a tighter low around 80W and 17N, west-southwest of Jamaica.. Anybody seeing what I'm seeing?



No. Surface flow is straight southerly there. Loop
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Its a shame that the NHC rescheduled today's recon mission for tomorrow since it would be helpful to actually see whats going on with this system finally and give the computer models some more assistance with the ultimate evolution of this system.
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Quoting reedzone:
Starting to see a tighter low around 80W and 17N, west-southwest of Jamaica.. Anybody seeing what I'm seeing?


did you loop it or just look at the image
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1856. IKE

Quoting Levi32:


That's a pressure gradient of 3mb between Grand Cayman and buoy 42057 which is near 94L's center. That may imply a tighter center than yesterday.
That's a PWS. I should have stated that.
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Forgot to add link


Link
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1854. IKE

Quoting nrtiwlnvragn:


Ok IKE, give it up....what is your secret for getting rain forecasts?





ACROSS THE GULF COAST STATES...DIURNALLY-DRIVEN SHOWERS AND
THUNDERSTORMS ARE POSSIBLE WITHIN THE HOT AND STICKY AIR MASS.
WHILE THE COVERAGE WILL GENERALLY BE SCATTERED IN NATURE...IT
SHOULD PROVIDE SOME LOCALIZED RELIEF TO THE NEAR TRIPLE DIGIT HEAT
EXPECTED OVER THE REGION. SUCH CONDITIONS WILL PERSIST INTO THE
MIDDLE OF THE WEEK AS THE UPPER RIDGE CONTINUES TO HOLD ITS GRASP
FROM THE CENTRAL U.S. EASTWARD TOWARD THE ATLANTIC COAST.

lol....

30% chance today and then tomorrow....

Tuesday: A 50 percent chance of showers and thunderstorms after
11am. Partly sunny, with a high near 94. Heat index values as high as
105. Calm wind becoming east southeast around 5 mph. New rainfall
amounts between a tenth and quarter of an inch, except higher amounts
possible in thunderstorms.
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1853. Levi32
Quoting IKE:
Grand Cayman....


84.2F

Mostly Cloudy

Pressure:


29.83in

(Steady)




Action:
Quote
| Ignore User


Member Since: June 9, 2005 Posts: 23 Comments: 36391




That's a pressure gradient of 3mb between Grand Cayman and buoy 42057 which is near 94L's center. That may imply a tighter center than yesterday.
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Starting to see a tighter low around 80W and 17N, west-southwest of Jamaica.. Anybody seeing what I'm seeing?

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Quoting IKE:
Grand Cayman....



84.2 °F


Mostly Cloudy

Pressure:


29.83 in

(Steady)



Action: Quote | Ignore User
Member Since: June 9, 2005 Posts: 23 Comments: 36391


Ok IKE, give it up....what is your secret for getting rain forecasts?





ACROSS THE GULF COAST STATES...DIURNALLY-DRIVEN SHOWERS AND
THUNDERSTORMS ARE POSSIBLE WITHIN THE HOT AND STICKY AIR MASS.
WHILE THE COVERAGE WILL GENERALLY BE SCATTERED IN NATURE...IT
SHOULD PROVIDE SOME LOCALIZED RELIEF TO THE NEAR TRIPLE DIGIT HEAT
EXPECTED OVER THE REGION. SUCH CONDITIONS WILL PERSIST INTO THE
MIDDLE OF THE WEEK AS THE UPPER RIDGE CONTINUES TO HOLD ITS GRASP
FROM THE CENTRAL U.S. EASTWARD TOWARD THE ATLANTIC COAST.

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Quoting MahFL:
LLC SW of Jamaica.




I would agree with you if I knew where SW of Jamaica it is because I think there is one in that area as well so where it it lat & long please
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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.