Caribbean disturbance 93L to drench Honduras; 97L disturbance worth watching

By: Dr. Jeff Masters , 3:04 PM GMT on August 18, 2011

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A westward-moving tropical wave in the Central Caribbean a few hundred miles south-southwest of Jamaica, Invest 93L, has continued to increase in organization, and is close to tropical depression status. 93L is a small system, but has built up a respectable area of heavy thunderstorms around its center. A few low-level spiral bands are apparent on satellite imagery, but there is almost no upper-level outflow apparent, and a surface circulation is not obvious. 93L has moistened its environment somewhat over the past day, but dry air is still in evidence around the storm, particularly to the southeast, as seen on water vapor satellite images. Wind shear continues to be low, 5 - 10 knots. There is a hurricane hunter mission scheduled for this afternoon at 2pm EDT to see if a tropical depression is forming.


Figure 1. Morning satellite image of 93L.

Heavy rains from 93L will begin spreading over Northern Honduras and Northeast Nicaragua tonight. The forward motion of 93L will slow to 5 - 10 mph by Friday, so the storm could be a major rain event for Northern Honduras, with rain amounts of 4 - 8 inches likely by the time the storm reaches Belize on Saturday. Heavy rains will spread to Belize and Mexico's Yucatan Peninsula by Friday night or Saturday morning. The latest SHIPS model forecast shows wind shear remaining in the low range and the atmosphere steadily moistening over the next two days, which should allow 93L to reach tropical storm strength. All of the models agree that the ridge of high pressure steering 93L to the west will remain strong, forcing the storm into a landfall Friday in Northeast Honduras, or Saturday near the Belize/Mexico border. It is possible that 93L will have time to intensify into a Category 1 hurricane before then, though landfall as a tropical storm would be more likely, given the dry air that 93L needs to overcome, and the possibility that the storm will pass too close to the northern coast of Honduras. Regardless, heavy rain will be a major threat from 93L. NHC gave 93L an 80% chance of developing into a tropical depression by Saturday morning in their 8am outlook. If 93L does cross the Yucatan Peninsula and enters the Gulf of Mexico, a strong ridge of high pressure should keep the storm moving due west to make a second landfall along the Mexican coast, well south of Texas.


Figure 2. Morning satellite image of the tropical wave 97L midway between the Lesser Antilles and the coast of Africa.

Invest 97L midway between the Lesser Antilles and the coast of Africa
A tropical wave near 14°N 40°W, midway between the Lesser Antilles Islands and the coast of Africa, is moving westward near 15 - 20 mph. This wave, designated 97L by NHC this morning, has little heavy thunderstorm activity associated with it due to dry air, but an impressive amount of large-scale spin is obvious in visible satellite loops. 97L is expected to arrive in the Lesser Antilles Islands by Saturday. Over the past day, all four of our reliable models for predicting tropical storm genesis have predicted that this wave could develop into a tropical depression sometime Saturday through Monday, so 97L needs to be watched carefully. NHC gave 97L a 10% chance of developing into a tropical depression by Saturday morning in their 8am outlook, and it is unlikely that this storm will pose much of a threat to the Lesser Antilles. It will take several days for the storm to overcome the large amount of dry air surrounding it, even though wind shear is a low 5 - 10 knots. By Saturday, the wave will find a moister atmosphere and warmer sea surface temperatures near the northern Lesser Antilles, and more rapid development may occur. However, there is expected to be high wind shear associated with an upper level low pressure system to the north of Puerto Rico at that time, and this wind shear may interfere with development. 97L is expected to take a west-northwest track through the Northeast Caribbean bringing the storm near Puerto Rico by Sunday or Monday. Long-range model runs, which are highly unreliable, foresee that 97L could be a threat to Hispaniola, Eastern Cuba, the Bahamas, and Florida by the middle to end of next week.

Jeff Masters

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Quoting Tropicsweatherpr:


But not for those like me that live in one of the islands.
Quoting AegirsGal:
Unless you happen to be a resident of one of those islands. I can't imagine it would be best for them.


Well, yeah, obviously it would be bad for them if it were anything strong. However, models have been showing a fairly weak solution over the islands because of too much land interaction.

Rain would be the worst issue, which could be bad in mountainous areas.
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Here's a fun job!!

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TROPICAL DISCUSSION - INTERNATIONAL DESKS

Excerpt:

TROPICAL WAVE ALONG 39W AND SOUTH OF 19N IS A SYSTEM OF CONCERN.
THE NHC IS MONITORING THIS PERTURBATION FOR POSSIBILITY OF
TROPICAL CYCLOGENESIS AND WILL ISSUE THE OFFICIAL FORECAST. THE
WAVE IS TO ENTER THE ISLAND CHAIN ON DAY 03. AS RIDGE PATTERN
ESTABLISHES ALOFT...AND MJO CONDITIONS BECOME MORE
FAVORABLE...THIS IS LIKELY TO FAVOR RAIN SQUALLS AND HEAVY
CONVECTION. IN THIS AREA WE EXPECT RAINFALL AMOUNTS OF 15-20MM/DAY
AND MAXIMA OF 40-80MM/DAY. AS IT ENTERS THE GUIANAS...THE WAVE
WILL FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM/DAY.

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Quoting Stormchaser2007:
DGEX (Extrapolated NAM)



Do you have a link for this.?
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18z Suite

LGEM/SHIP have this heading WSW at the end of the period.

FULL
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Quoting kmanislander:


Lots of outflow boundaries in that loop confirming dry ingestion into the circulation. Until that stops 93L will continue to struggle to close off a surface low.


The low-level center also looks to be slightly off to the south of the mid-level center, indicating that the system isn't vertically stacked, which would inhibit significant development in the near term.
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Quoting Stormchaser2007:
DGEX (Extrapolated NAM)





Please Move the center of the circle off the keys.!!!
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Quoting Stormchaser2007:
DGEX (Extrapolated NAM)



This comes right over the Florida Keys where I live.
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Quoting kmanislander:


I wouldn't place too much store on satellite imagery to determine whether there is a closed surface low or not. In fact, sometimes you cannot even determine if there is a surface low from imagery, let alone closed or open.

Based upon ASCAT this morning it still had a lot of work to do to close off, the kind of work I would expect to occur over 12 to 18 hours.



Yep, but it's the only thing we have to go by right now. We'll see, as these smaller systems can spin up quickly. Really stinks that recon couldn't make it out there.
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Quoting stormhank:
By the time 97L gets to 50 west,,If Im reading the sst charts correctly, arent the sst's like 3-5 degrees warmer at 50 west than where 97 is located now??


1-1.5 degrees Celsius.
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Quoting P451:


Lots of outflow boundaries in that loop confirming dry ingestion into the circulation. Until that stops 93L will continue to struggle to close off a surface low.
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Quoting MississippiWx:


Yeah, it's going to change several more times. However, any chance of an out-to-sea solution seems low.

If it can skirt just south of the big islands, that would be the worst case scenario for the Gulf states. A track skirting just north would be worse for Florida/GA/SC.

A track directly over the islands would be best for everyone...lol.
Unless you happen to be a resident of one of those islands. I can't imagine it would be best for them.
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Link

97L
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Quoting MississippiWx:


Yeah, it's going to change several more times. However, any chance of an out-to-sea solution seems low.

If it can skirt just south of the big islands, that would be the worst case scenario for the Gulf states. A track skirting just north would be worse for Florida/GA/SC.

A track directly over the islands would be best for everyone...lol.

Unless your on the Islands of course ;)
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Quoting MississippiWx:


Yeah, it's going to change several more times. However, any chance of an out-to-sea solution seems low.

If it can skirt just south of the big islands, that would be the worst case scenario for the Gulf states. A track skirting just north would be worse for Florida/GA/SC.

A track directly over the islands would be best for everyone...lol.


But not for those like me that live in one of the islands.
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Quoting kshipre1:
ok Levi, sorry for this question but unless I am missing something obvious, with all the major models shifting westward what you are looking at to say that the west coast of florida is the average of this?

I know you explained this a few posts above but if you do not mind, can you quickly elaborate?

I just don't get it because ever since this morning, mostly everything says westward, thanks


The models will jump all over as always. We know that the pattern almost guarantees a threat to land at this point, and that is what matters. The wave isn't even developing yet. Regarding the track, we can't be very specific right now. We can only look at generalizations based on model trends and the overall pattern, which may very well shift west with time and include the gulf more often. However, this one run of the ECMWF is the only one that shows that solution thus far.
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93L approaching this buoy:

Atmospheric Pressure (PRES): 29.83 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY): -0.05 in ( Falling )



Link
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By the time 97L gets to 50 west,,If Im reading the sst charts correctly, arent the sst's like 3-5 degrees warmer at 50 west than where 97 is located now??
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Quoting MississippiWx:
If this were to occur, this hurricane would be in almost the same exact location as that K storm back in 2005 on the exact same date.

8/28:



I was in Bay St Louis when that K storm rolled in. I was one of the idiots that didnt think it would be "that bad". I pray that never happpens to any land mass again, especially to those people.
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18z SHIP text

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Quoting MississippiWx:


Satellite loops are just now showing hints of a closed low..it's close.


I wouldn't place too much store on satellite imagery to determine whether there is a closed surface low or not. In fact, sometimes you cannot even determine if there is a surface low from imagery, let alone closed or open.

Based upon ASCAT this morning it still had a lot of work to do to close off, the kind of work I would expect to occur over 12 to 18 hours.

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18z Models just updated.

Seems like they have 97L making landfall in Hispaniola judging by their intensities.
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Quoting Boudreaux77:


I actually mentioned the same thing earlier on another forum. If it stays south enough, is it possible that this might just scoot west across the Gulf?


The pattern supports it turning north over the gulf if it were to get there. The new ECMWF is extreme and actually shows part of Texas open for a tropical system, but in the scenario depicted by the 12z run, the central gulf coast would get the storm. The glaring weakness between the western U.S. ridge and the Atlantic ridge argues for a straight north turn somewhere, as opposed to a WNW or NW track into land.
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Quoting atmoaggie:
Yeah, I know things will change (not sure what, yet) but this setup looks reasonably accurate...and I'm personally not hoping for this one to come our way.


Yeah, it's going to change several more times. However, any chance of an out-to-sea solution seems low.

If it can skirt just south of the big islands, that would be the worst case scenario for the Gulf states. A track skirting just north would be worse for Florida/GA/SC.

A track directly over the islands would be best for everyone...lol.
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ok Levi, sorry for this question but unless I am missing something obvious, with all the major models shifting westward what you are looking at to say that the west coast of florida is the average of this?

I know you explained this a few posts above but if you do not mind, can you quickly elaborate?

I just don't get it because ever since this morning, mostly everything says westward, thanks
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As I see it, as long as it chugs westbound like it's doing, you're looking more a GOM event, and that means Central to Western Gulf down the road if the current and short term track chugs west
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Quoting ncstorm:
The PMSL has had the same path several times now. I truly hope this does not pan out. Huge loss of life and property with hurricanes that have taken similar paths...Link
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Quoting cloudburst2011:


i didnt say that.. the mets are showing the models because thats there job and they are not going to lose any sleep if they are wrong or right...mets have the easiest job in the world they will always have weather they cant get laid off and the most important thing they will always get that big CHECK even if they are right or wrong...so tell me again how much pressure mets have...NONE...
All of us could take a lesson from the weather. It pays no attention to criticism. ...

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Quoting SouthALWX:
500 mb pattern, per the GFS.
Guess we here in the Tampa Bay area should start paying attention to 97L this coming week
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ECMWF 12z: Harvey and Irene

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Quoting Levi32:
It is worth noting that the global models have had a clear northward bias with almost every deep tropical system this year. It would make sense to see a solution west of Florida given that trend.


That bias appears to be due in large part to the models deepening nearly every system far too quickly. Perhaps they do not have a good handle on the dry air and lack of instability that has seen system after system struggle to organize to date.

97L is in the same environment so far and may travel more Westerly than some of the models are presently calling for which will undoubtedly see the track forecasts shift west over time.
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Quoting MississippiWx:
If this were to occur, this hurricane would be in almost the same exact location as that K storm back in 2005 on the exact same date.

8/28:

Yeah, I know things will change (not sure what, yet) but this setup looks reasonably accurate...and I'm personally not hoping for this one to come our way.
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12z ECMWF ensembles should be interesting.
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.
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Quoting kmanislander:
Just back on since this morning. I see that the HH had a mechanical and turned around before reaching 93L.
The ASCAT pass this morning did not show anything close to a closed low so more wait and see for this system.


Satellite loops are just now showing hints of a closed low..it's close.
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DGEX (Extrapolated NAM)



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Quoting Levi32:
It is worth noting that the global models have had a clear northward bias with almost every deep tropical system this year. It would make sense to see a solution west of Florida given that trend.


I actually mentioned the same thing earlier on another forum. If it stays south enough, is it possible that this might just scoot west across the Gulf?
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Quoting lottotexas:
And what would that average be ?


The average of the recent ECMWF runs is probably a track near northern Hispaniola, across the Bahamas, and into Florida. It will be interesting to see what the 0z tonight looks like, and if it flops back to the east as the last three in a row have.
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One interesting thing that was noted... is that 12Z ECMWF resembled 12Z run from yesterday which was weaker (almost none existent) but this time was stronger.

We'll see if the 00Z run tonight brings it back to how the 00Z from today was or close to this 12Z run.

Overall, there's has been a left bias on these runs given an added strength to the Bermuda High.
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Quoting NASA101:
Holy Smokes... 12Z EURO AT 240 hrs.... LOL..


now put that away - you are scaring the children- and me!
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It is worth noting that the global models have had a clear northward bias with almost every deep tropical system this year. It would make sense to see a solution west of Florida given that trend.
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97L is chugging pretty good westbound
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Just back on since this morning. I see that the HH had a mechanical and turned around before reaching 93L.
The ASCAT pass this morning did not show anything close to a closed low so more wait and see for this system.
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About JeffMasters

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

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