Western Caribbean disturabance 94L bringing heavy rains; Lupit's path uncertain

By: Dr. Jeff Masters , 2:39 PM GMT on October 21, 2009

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A broad 1008 mb low pressure area has developed near 10N 84W, inland over Costa Rica. NHC designated this disturbance Invest 94L yesterday, but is no longer issuing model products for the disturbance. This morning's QuikSCAT pass showed a broad circulation around the low, with top winds of about 30 - 35 mph over the extreme Southwestern Caribbean. Obviously, the center will have to move over water in order for significant development to occur, but recent satellite loops show that the low is pulling in an increasing amount of moisture from the Pacific, leading to heavy rains over Costa Rica and western Panama. Wind shear is low, about 5 - 10 knots, and there is deep layer of high moisture over the entire Western Caribbean, which both favor development if the center moves over water. Rainfall estimates from the Navy Research Lab indicate that 94L dumped up to three inches of rain over portions of Panama, Costa Rica, and Nicaragua over the past 24 hours.


Figure 1. Morning satellite image of Invest 94L.

The forecast for 94L
Wind shear is expected to remain in the low to moderate range, 5 - 15 knots, for the next five days in the Western Caribbean. Sea Surface temperatures are very warm, 29°C, and there is plenty of moisture through a deep layer of the atmosphere. The only major impediment to 94L becoming a tropical storm later this week would seem to be proximity to land. At present, only the GFS model develops 94L, but weeks it very weak. The GFS predicts the storm will take a north then northwesterly track across western Cuba early next week, then into the Gulf Coast of Florida later in the week. However, it is equally likely that 94L will stay bottled up in the Western Caribbean for the foreseeable future. I'll continue to give 94L a medium (30 - 50% chance) of eventually becoming a tropical depression over the next ten days. NHC is giving 94L a low (less than 30% chance) of developing into a tropical depression by Friday, which is a good forecast. Given 94L's current state of disorganization and location over land, Saturday is the earliest we should expect it to organize into a tropical depression. NHC has not put the Hurricane Hunters on call to fly 94L Thursday or Friday.

Rick misses Baja, hits Mainland Mexico near Mazatlan
Tropical Storm Rick made landfall near 10am EDT in Mainland Mexico just north of Mazatlan. Top winds measured at the Matatlan airport during landfall were 39 mph, gusting to 61 mph. The primary threat from Rick will be heavy rains of up to six inches in the mountains near Mazatlan. Rick's remains should being at most one inch of rain to south-central Texas on Thursday.

Typhoon Lupit weakens and slows; path now uncertain
Typhoon Lupit, now a Category 1 storm with 90 mph winds, continues to have difficulty dealing with a slug of dry air it wrapped into its core two days ago. Microwave imagery showed that the typhoon was missing a portion of its northern eyewall this morning. However, recent Infrared satellite loops show that the eye has warmed and become more distinct, a sign of intensification. Also, the cloud tops of Lupit's eyewall have cooled in recent hours, signaling that they are more vigorous and reaching higher into the atmosphere. Lupit is in an environment favorable for re-intensification, with low wind shear of 5 - 10 knots and warm sea surface temperatures of 28 - 29°C. It would not be a surprise to see Lupit intensify into a major Category 3 typhoon again by Thursday, though the official forecast from the Joint Typhoon Warning Center is less aggressive, calling for a Category 2 storm by tomorrow. Even in its current weakened state, Lupit is a prodigious rain-maker, with rainfall rates exceeding one inch per hour near its core (Figure 2).

The future path of the typhoon is now highly uncertain, as steering currents are weakening and the storm is slowing down. A weakness in the ridge of high pressure steering Lupit west-southwest is developing, and several models (ECMWF, GFS) now predict recurvature of the typhoon before it reaches the Philippines. This optimistic scenario is counterbalanced by the very pessimistic forecasts of the UKMET and NOGAPS models, which take the typhoon inland over the northern portion of Luzon 1 - 2 days from now, and then stall the storm for 2 - 3 days. This would cause a major flooding disaster, as the soils are already saturated and the dams completely full from the 20+ inches of rain dumped by Super Typhoon Parma in early October. If Lupit stalls for several days over Luzon, it would dump another 20+ inches of rain, triggering massive flash flooding and life-threatening mudslides.

Storm chased Jim Edds is in northern Luzon to document Lupit's landfall, and has some interesting photos of the preparations the residents are taking.


Figure 2. Rainfall rates observed by a polar-orbiting microwave satellite at at 10:24 UTC Wednesday 10/21/09. Lupit is expected to dump rains in excess of one inch per hour (red and pink colors) along its path. Up to 12 inches of rain in a 24-hour period are expected from the typhoon. Image credit: Navy Research Lab, Monterey..

I'll have an update Thursday morning.

Jeff Masters

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hello every one i have been lurking for a few days, reading and observing stats, this system so much reminds me of Paloma last year, i do believe devolpment is emminent to what degree ,we will have to see JMO
Member Since: August 14, 2008 Posts: 0 Comments: 1002
Member Since: July 24, 2005 Posts: 407 Comments: 19076
437. xcool
Grothar thank itry alot :)
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Quoting xcool:





You post nice shots
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Quoting Skyepony:


exaclty.. the one in the southern Bahamas looks more pronounced on the map xcool left then the one in the Caribbean the moment.


Yes the one in southern Bahamas has some pretty good looking cloud tops
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434. Skyepony (Mod)
Quoting will40:
411. Skyepony



Looks like the gfs developes two systems one north of Bahamas and then the one in the Caribbean


exaclty.. the one in the southern Bahamas looks more pronounced on the map xcool left then the one in the Caribbean the moment.
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Moving towards a weakness

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting stormwatcherCI:
SYNOPSIS...BROAD AREA OF LOW PRES OVER THE THE SW CARIBBEAN
SEA WILL REMAIN NEARLY STATIONARY THROUGH FRI...THEN BEGIN TO
DRIFT IN A GENERAL NORTHWARD DIRECTION FRI NIGHT THROUGH SUN
IN RESPONSE TO A WEAK FRONT THAT MOVES ACROSS CENTRAL FLORIDA.
ANOTHER AREA OF LOW PRES MAY AGAIN FORM OVER THE SW CARIBBEAN SEA
SAT THROUGH MON. LIGHT TO MODERATE TRADES WILL CONTINUE OVER THE
AREA THROUGH MON.




Yes i think thats what the GFS is seeing. Its picking up on the one drifting north then forms another one after that
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Pressure down to 1005mb in the southern Caribbean



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SYNOPSIS...BROAD AREA OF LOW PRES OVER THE THE SW CARIBBEAN
SEA WILL REMAIN NEARLY STATIONARY THROUGH FRI...THEN BEGIN TO
DRIFT IN A GENERAL NORTHWARD DIRECTION FRI NIGHT THROUGH SUN
IN RESPONSE TO A WEAK FRONT THAT MOVES ACROSS CENTRAL FLORIDA.
ANOTHER AREA OF LOW PRES MAY AGAIN FORM OVER THE SW CARIBBEAN SEA
SAT THROUGH MON. LIGHT TO MODERATE TRADES WILL CONTINUE OVER THE
AREA THROUGH MON.

Member Since: October 9, 2008 Posts: 0 Comments: 8242
429. xcool



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Quoting leftovers:
system is at the same place it was a couple days ago



If you track a mean center, as I was showing with the circles today, it never really left.
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Quoting stormwatcherCI:
I don't know what part of Cayman you are at but ain't no blue skies in EE. LOL

east of cayman we are having rain and overcast conditions. Our met service said that 94l spawned a trough.
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Off the tropics, thats one intense low forming in ne New Mexico looks to absorbing whats left of Rick.
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Quoting 786:
where that swirl is, is where the L was placed on the surface map earlier....
4.9inches all month, damn could have sworn we've had more than that the last 3 days
That is only at that weather station in EE. Been about 10" in the past couple days. Showing .20 for today and it has been pouring pretty much all day.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
411. Skyepony



Looks like the gfs developes two systems one north of Bahamas and then the one in the Caribbean
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Quoting Floodman:


April of 2005
Thanks Bongman eh,I mean Floodman...
Member Since: September 27, 2007 Posts: 1 Comments: 19608
Quoting 19N81W:
hey guys is that things starting to move N/NE now..I see a spin offshore? or am I being fooled?
If its moving what would be pulling it north?


That is a good question...

Looking the low level flow, the system should be heading west with the solid high over the SE USA but the steering flow near the disturbance is weak and does not point to any direction so it could be the low is simply pulling towards the area of lowest pressure or more pronounce vorticity.




or


look at the deep layer....a trough hanging north of the system...this upper trough could be affecting the lower level flow in some way to pull the disturbance north. This would be 100% valid if the system was deep.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
LOCALLY HEAVY RAINFALL POSSIBLE STARTING LATE TONIGHT THROUGH THURSDAY EVENING...

A COLD FRONT WILL MOVE ACROSS THE AREA THURSDAY AND THURSDAY NIGHT. STRONG SOUTH AND SOUTHEASTERLY WINDS AHEAD OF THE FRONT WILL CONTINUE TO DRAW UP GULF MOISTURE THROUGH THURSDAY. IN ADDITION... PACIFIC MOISTURE AND DISTURBANCES ROTATING OFF OF WEAKENING TROPICAL DEPRESSION RICK WILL BE MOVING OVER THE AREA. SCATTERED SHOWERS AND THUNDERSTORMS TODAY WILL BECOME MORE NUMEROUS OVERNIGHT TONIGHT AND THURSDAY AS THE FRONT APPROACHES.

THE PRIMARY THREAT WITH THIS EVENT WILL BE HEAVY RAINFALL... MAINLY ALONG THE FRONT LATE TONIGHT THROUGH THURSDAY EVENING. WIDESPREAD RAINFALL TOTALS OF 1 TO 3 INCHES ARE FORECAST... WITH ISOLATED TOTALS OF UP TO 4 INCHES POSSIBLE. THERE IS THE POSSIBILITY FOR THE MINOR FLOODING OF STREETS... FEEDER ROADS... SECONDARY ROADS.

MANY OF THE RIVER SYSTEMS ARE RUNNING ABOVE NORMAL... AND WILL CONTINUE TO REMAIN ELEVATED IF THESE RAINS DO MATERIALIZE.

Won't be the first time an E. Pacific Storm
affects us in LA.
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416. 786
OK so if the mid vort is drifting NE and the Low is stationary just East of Nic. what does that mean? yet another surface low could form, or far from vertically stacked..
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Quoting 19N81W:
hey guys is that things starting to move N/NE now..I see a spin offshore? or am I being fooled?
If its moving what would be pulling it north?



Could it be a developing LP in the Bahamas starting to attract it to the NE? GFS & the CMC show action there rather soon.
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413. 786
where that swirl is, is where the L was placed on the surface map earlier....
4.9inches all month, damn could have sworn we've had more than that the last 3 days
Member Since: Posts: Comments:
hey guys is that things starting to move N/NE now..I see a spin offshore? or am I being fooled?
If its moving what would be pulling it north?
Member Since: August 24, 2008 Posts: 0 Comments: 405
411. Skyepony (Mod)
StormChaser81~ I don't think the little blob the models are calling for in the Bahamas to come from the central Atlantic. If you watch the 850vort (near surface vorticity) on the models it is that weak blob over east Cuba & S Bahamas that trys & pull it together.. GFS has a near depression just east of FL in 5 days. Suprised how much stronger the gfs has gotten with it. CMC brings it over FL.
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Quoting reedzone:
Models are useless right now until a dominate low forms, that's when I believe models will develop soemthing again.


Some more nice words....

It could be the disturbance is too complex or complicated to be fully handled by the models, so we will have to derive any patterns from upcoming runs over the next few days...
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
Drak, I'm seeing a mid vort near 12.5N 80.W drifting NE. I'm thinking this is not the surface low?


That is mid level. I am looking just east of Nicaragua for the surface low which coincides with the NHC surface analysis.

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Quoting Grothar:


What day? and u got mail! Thanks.


sorry post 354....you said you were seeing 2 vort centers, look at the image I posted in 354.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Models are useless right now until a dominate low forms, that's when I believe models will develop soemthing again.
Member Since: July 1, 2008 Posts: 13 Comments: 7334
Quoting 786:
the swirl actually looks centered around 80W, 12-13N
Look at the sky on the webcam
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting hydrus:
I did not know of Dr.Masters blog until September 07. I have not had time to go back and read all the cool posts. Hopefully I can do that someday. I wonder how far back in time the archives go? do you know this?


April of 2005
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Some nice words....

Models are pretty much not helpful at the moment since.....
Member Since: July 24, 2005 Posts: 407 Comments: 19076
403. 786
stormwatch, in GT, can see some blue skies North and South (mostly overcast), but I doubt this will last through the night. Its been interesting to observe the effect that DMIN and DMAX have on convection, some rain and lightening during the day and the skies come alive as soon as nightfalls
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Drak, I'm seeing a mid vort near 12.5N 80.W drifting NE. I'm thinking this is not the surface low?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
400. IKE
Quoting stormsurge39:
So there a day behind?


With what their talking about there on the 12Z ECMWF, they are.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Weather456:


look at post 564


What day? and u got mail! Thanks.
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398. 786
the swirl actually looks centered around 80W, 12-13N
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Quoting stormsurge39:
When is it suppossed to let up?


The high is located over the SE USA or I think the center has move offshore, regardless a high is to the north. Look for it to continue to drift east and a frontal trough swings across the area through Saturday....I'm pretty confident of this.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Reading back post you can see system at 14n 43w that the models are talking about I believe. NHC had a circle around it yesterday.
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Quoting 786:
thanks 456 I can't see more of a shift toward the SW Caribbean just warping of the broad low but of-course I'm only learning. From the vorticity map you posted looks like the EPac has a stronger vort.? All various weather reporters are still holding on to the Northern movement Sunday or Monday. Last night we had some torrential rains in Cayman with some good gusts, we are starting to see some blue skies which could be the result of a shift Southward.
I don't know what part of Cayman you are at but ain't no blue skies in EE. LOL
Member Since: October 9, 2008 Posts: 0 Comments: 8242
394. 786
..looks to be moving slightly NE, ok SOLD SW Carib. winning for now
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Quoting IKE:


That's the same "tropics watch" that they posted this morning. Here's the morning discussion...Link

Tallahassee weather office copies and pastes the afternoon long-term discussion from the one they use in the early morning. The only time they update the long-term discussion is the early AM.

Their talking about yesterdays 12Z ECMWF. Today's has dropped development in the western Caribbean.
So there a day behind?
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Quoting 786:
well the EPac vort is drifting East and the SW Carib vort drifting N..sounds like a battle of wills


That would mean the ATL side is winning.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
391. 786
wow from that sat. pic 456 posted can def. see the circulation in the SW Caribbean, much more pronounced than earlier
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390. IKE
Quoting StSimonsIslandGAGuy:
Extract from this afternoon's Tallahassee wx discussion:

TROPICS WATCH...THOUGH WE ARE QUICKLY APPROACHING THE END OF WHAT
WAS A RATHER SLOW TROPICAL SEASON FOR LANDFALLING STORMS...THE 00Z
GFS AND 12Z EURO SHOW A TROPICAL SYSTEM ENTERING THE WESTERN
CARRIBEAN BY LATE THIS WEEKEND. THE MODELS ARE NOT IN TOTAL
AGREEMENT WITH WHAT TO DO WITH IT ONCE IT EXITS THE CARRIBEAN. THE
EURO IS A BIT MORE AGGRESSIVE AS IT ADVANCES THE TROPICAL SYSTEM
INTO THE GULF AND ALONG THE WEST COAST OF FLORIDA BY MID WEEK WHILE
THE GFS IS A BIT SLOWER ON THE MOVEMENT OF THE SYSTEM WITH IT
GRADUALLY MOVING NORTHWEST INTO THE GULF THROUGH MID WEEK.
REGARDLESS...IT IS SOMETHING TO KEEP OUR EYE ON.


That's the same "tropics watch" that they posted this morning. Here's the morning discussion...Link

Tallahassee weather office copies and pastes the afternoon long-term discussion from the one they use in the early morning. The only time they update the long-term discussion is the early AM.

Their talking about yesterdays 12Z ECMWF. Today's has dropped development in the western Caribbean.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Weather456:


to the north
When is it suppossed to let up?
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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.