Tropical wave bringing heavy rain to northern Lesser Antilles

By: Dr. Jeff Masters , 1:57 PM GMT on July 18, 2010

A tropical wave near 18N, 60W is entering the northernmost Lesser Antilles Islands and is generating some disorganized heavy thunderstorm activity. This wave is under about 20 knots of wind shear, due to strong upper-level westerly winds. The strong upper-level winds are associated with the counter-clockwise flow of air around an upper-level cold-cored low pressure system a few hundred miles north of Puerto Rico. As the wave progresses west to west-northwest through Tuesday, thunderstorm activity will increase, due to interaction with the upper low. The rains from these thunderstorms will bring the threat of flooding to Puerto Rico on Monday, the Dominican Republic on Tuesday, and Haiti on Wednesday. The upper low will also bring high wind shear of 20 - 30 knots over the the wave on Monday and Tuesday. No development of the wave is likely until at least Thursday, when it will be over the eastern Bahamas and eastern Cuba. At that time, shear is expected to drop below 20 knots, and the wave has the potential to develop. However, none of the reliable computer models is calling for tropical cyclone development over the next seven days. I expect that this wave will eventually enter the Gulf of Mexico early next week. NHC is giving the wave a 10% chance of developing into a tropical depression by Tuesday.


Figure 1. Morning satellite image of tropical wave entering the Lesser Antilles Islands.

Next post
I'll have a new post on Monday.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Member Since: December 31, 1969 Posts: Comments:
Quoting Patrap:
Lotsa bottom current this evening deep under DWH,,in this rov Look at the BOP & Well head.

Skandi_ROV 1

Dang Pat that thing sure is Swaying there huh...


Taco :o)
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Quoting CJC111:
That's the first I've seen someone of referencing a condiment caster :)
Well, you have to concider the source....LOL
Member Since: December 31, 1969 Posts: Comments:
Quoting Drakoen:


No, just sitting back and watching the usual troll-drama on this blog...waiting for a good moment to post.


Drama caster??
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Quoting extreme236:
Caribbean AOI still has a way to go before it were to develop...however the convection has been persisting all day without any significant waning.
Looks like all the moisture that was in the Caribbean the past few days is consolidating in the wave SE of Jamaica.
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1432. CJC111
That's the first I've seen someone of referencing a condiment caster :)
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1430. JRRP

Quoting StormW:
Some mechanics on the MJO:

MJO Summary

interesting
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1429. aquak9
Quoting bappit:

Yah, I'm interested to see if it can ketchup and keep up.



ketchup-caster
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1408. Drakoen

Noticed they were specific, "It was found that the model’s composite storm structure and track lengths are realistic." but not on actual track, just the length of the track. I don't generally put much weight in any seasonal track forecasts, except for generally "westerly".
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evening...

Hmmm... Just now finishing with a rain squall which included a wind gust to 40 mph. It surprised me since nothing noticeable shows on the satellite.
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Jet Stream is primed to allowed a Southeast US Landfall.

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1423. CJC111
Drakoen, thanks for the article. Very interesting. cirrocumulus, your post about the sunspots has me curious. We see flare during DMAX and less during DMIN. I've seen others ask if conditions might be too good for storm development. Is it something like getting burned by dry ice? It's not the temperature that burns but rather the difference in temperature. With record SST readings, is there anything that would show a warmer than normal upper atmosphere causing a more stable environment which would limit hurricane activity? Thanks again for any input.
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Quoting Patrap:
Lotsa bottom current this evening deep under DWH,,in this rov Look at the BOP & Well head.

Skandi_ROV 1
Was looking at that earlier and ya gotta say to yerself. Dang I hope that's the ROV movin' and not tha well head.
Member Since: December 31, 1969 Posts: Comments:
Thank You StormW in case you do leave the blog. Wish you the Best whatever you do, take care, Dennis
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Caribbean AOI still has a way to go before it were to develop...however the convection has been persisting all day without any significant waning.
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1418. bappit
Quoting stillwaiting:
one can note on the wv loop that a anti cyclone in the ul is starting to build in from the east over the pr aoi....

Yah, I'm interested to see if it can ketchup and keep up.
Member Since: December 31, 1969 Posts: Comments:
1417. Patrap
Lotsa bottom current this evening deep under DWH,,in this rov Look at the BOP & Well head.

Skandi_ROV 1
Member Since: December 31, 1969 Posts: Comments:
Quoting EtexJC:
I will say this, after what... two-three years reading this blog, Storm has taught me the most about weather and i for one keep coming back for his insight (no offense to the others that put up valuable info too).


I second that thought. StormW has been a source of great information about tropical weather.

You can't let the morons get to you. Keep the good information and your helpful insights flowing... because people like me pay attention.
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one can note on the wv loop that a anti cyclone in the ul is starting to build in from the east over the pr aoi....
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This is what the CMC shows. 2 Tropical systems effecting
the US in 4-5 days.

Interesting Indeed....


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1411. bappit
Quoting PanhandleChuck: It is known as the Constantly Making Cyclones model

Check it out .......................

It says:

Prior to 2009, the CMC GEM had a tendency to over-forecast genesis of TCs. The recent changes to the model upper boundary are believed to decrease the false alarm ratio for TC genesis, particularly at day 3 and beyond in the forecast period.

By the way, the Doctor's tropical weather web page needs to be updated. It says this NOAA web site was last updated in 2007. It was last updated 24 July 2009.

Edit: removed extraneous "Updated", miscellaneous edits
Member Since: December 31, 1969 Posts: Comments:
Quoting StormW:


Ditto! that's some great information!
Evening Storm W!! i read a post earlier that said you might leave blog??? I certainly hope not, I always value your input and expertise on tropical weather...as well as answering my questions too. You are certainly appreciated by me.
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Good evening everyone!

Just took a look at my map, and we haven't had an invest since 96L went all TD2 on us on the 7th... quite the lull without even an invest??
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1408. Drakoen
An ensemble of seasonal Atlantic hurricane simulations is conducted using The Florida State University/Center for Ocean–Atmospheric Prediction Studies (FSU–COAPS) global spectral model (Cocke and LaRow) at a resolution of T126L27 (a Gaussian grid spacing of 0.94°). Four integrations comprising the ensembles were generated using the European Centre for Medium-Range Weather Forecasts (ECMWF) time-lagged initial atmospheric conditions centered on 1 June for the 20 yr from 1986 to 2005. The sea surface temperatures (SSTs) were updated weekly using the Reynolds et al. observed data. An objective-tracking algorithm obtained from the ECMWF and modified for this model’s resolution was used to detect and track the storms. It was found that the model’s composite storm structure and track lengths are realistic. In addition, the 20-yr interannual variability was well simulated by the ensembles with a 0.78 ensemble mean rank correlation. The ensembles tend to overestimate (underestimate) the numbers of storms during July (September) and produced only one CAT4–level storm on the Saffir–Simpson scale. Similar problems are noted in other global model simulations. All ensembles did well in simulating the large number of storms forming in the Atlantic basin during 1995 and showed an increase in the number of storms during La Niña and a decrease during El Niño events. The results are found to be sensitive to the choices of convection schemes and diffusion coefficients.
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Quoting StormW:


Thanks. No problem...just had to vent today...happens sometimes. How's life in the Caymans? Got to visit Grand Cayman in my travels.
You're most Welcome. Life in the Caymans believe it or not as much as some complain with the economic down turn is probably still one of the better place to live at this time, you must definitely visit and you'll understand what I'm speaking of. Kindest regards, Hank.
Member Since: December 31, 1969 Posts: Comments:
Quoting HurricaneSwirl:


Thanks! I have no idea how I missed it. I went back and looked at TWO's and after Alex dissipated the TWO just said refer to the HPC for more information. While TD2 stuck around quite a while after it dissipated on the TWO because of HPC's advisories. So you're most likely right.


If you notice the last Public Advisory for TWO gives specific info for HPC advisories, while the one for Alex does not.
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1403. guygee
Quoting TropicalAnalystwx13:


Stop speaking in that language
I've been looking into Bolero's dialect, it is a form of Cuban slang or street language used by young people, it is not proper Spanish at all. I would wager even his grandparents could not understand some of his phrases and idioms.
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ECMWF is developing the Antilles wave in the GOMEX.. from 12z. Way to far out and way to inconsistent but we have model support.


Member Since: December 31, 1969 Posts: Comments:
looks like a mlc trying to working its way to the surface...PR AOI
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Quoting stillwaiting:
anyone see the cyclone starting to form north of PR this evening????

Storm hinted on the spin-up visible on the IR2
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A 2010 report correlates low sunspot activity with high cyclonic activity. Fewer sunspots appear to decrease temperature in the upper atmosphere, creating unstable conditions that help create cyclones. Analyzing historical data, there had been a 25% chance of at least one hurricane striking the continental US during a peak sunspot year; a 64% chance during a low sunspot year. In June 2010, the hurricanes predictors in the US were not using this information.[92]

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Quoting tropics21:
or Constantly Making Chaos


actually it was "redone" recently and with the upgrades
it is supposed to rival the GFS long term.
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1396. KYDan



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anyone see the cyclone starting to form north of PR this evening????
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CMC however, might not be too seriously insane with having two tropical waves affect Florida. GFS para 18Z



Member Since: December 31, 1969 Posts: Comments:
We got very little a cpl hour ago. But was just enough to water my (wifes) plants.
Member Since: December 31, 1969 Posts: Comments:
1391. Drakoen
Quoting nrtiwlnvragn:


Not sure they don't specifically say, but I believe it is. That sites concensus for the season:

There is a consensus that ASO 2010 will be a season of large AWP, weak Caribbean low level jet, weak southerlies from the Gulf of Mexico* and weak North Atlantic Sub-tropical high. As a consequence of these changes in the circulation features and the anomalous large AWP we expect a higher probability of the following:

1.Weaker than normal rainfall over southern Mexico
2.Weaker than normal rainfall over mid-west and North American monsoon region
3.Weaker than normal Tornado activity in the Tornado alley
4.Stronger than normal rainfall in South Florida and Cuba
5.Weaker than normal vertical shear in the maximum development region of the tropical Atlantic
6.Stronger than normal Atlantic tropical cyclone activity
* Although a majority of the models in this forum seem to display stronger than normal southerlies over the US at 850hPa, which may be a response to the cold SST in the Equatorial East Pacific.


Website under Consensus Forecast



Thanks for sharing! You're always on top of stuff like this
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1390. bappit
Quoting Patrap:
Low Cloud Product Image,Caribbean

cool, was wanting something like that the other day
Member Since: December 31, 1969 Posts: Comments:
Quoting HurricaneKatrina:
Are those paths predicted to happen?


They are from a Global Spectral Model, which are used for climate forecasting. I have not seen any work published comparing forecast vs. actual. Since it is a seasonal forecast (August, September, October) I would not put much weight in actual tracks, but would consider it for number of systems.
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Quoting TropicalNonsense:


it shows 2 tropical systems forming from the 3 existing waves we
are currently seeing in the carribean. One striking the Texas/Mexico
border area
similiar to ALEX and the other hitting the most populated
area in south florida near Miami/Dade.
I usually dont trust the CMC track
wise but it may be on to something. I will post a link in a min so you can
see for yourself. It's looks very interesting though for sure.


CMC Link
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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