Tropical wave bringing heavy rain to northern Lesser Antilles

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

Share this Blog
3
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1488 - 1438

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49Blog Index

1488. JLPR2
Quoting stormpetrol:

The comma shape suggest to me its different entity, but to be honest I really don't know.


I'm thinking it could be trying to separate as of now.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
1487. bappit
Quoting StormW:
Check out Africa (left of picture)


Turn it on its side and it looks like Australia. :)
Member Since: May 18, 2006 Posts: 10 Comments: 6157
1486. xcool
JLPR2 .i think i'm gonna need Head On after all this done.
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting stormwatcherCI:


Actually it looks like the tail end of the same circulation.

The comma shape suggest to me its different entity, but to be honest I really don't know.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
CJC111, The odd thing is that I was personally wanting to add the sunspot report to the excellent developing record by Florida State to think that we indeed are going to have a heavy and intense system. I would think that even more instability would occur because of the contrast in SSTs and the the lower temperatures in the upper atmosphere. It's going to be a very interesting season.
Member Since: Posts: Comments:
1483. bappit
Quoting Patrap:


The ROV view swaying back and forth in about a 5-8 Kt bottom current.

Skandi_ROV 1

That's a fast current.
Member Since: May 18, 2006 Posts: 10 Comments: 6157
1482. JLPR2
Quoting xcool:
JLPR2 .to many AOl watching


haha!
That's true LOL!
Member Since: September 4, 2007 Posts: 7 Comments: 8747
1481. will45
Quoting stormwatcherCI:


Actually it looks like the tail end of the same circulation.


At the lat i think the ITCZ is part of it
Member Since: Posts: Comments:
1480. bappit
Quoting StormW:
Some mechanics on the MJO:

MJO Summary

The nitty gritty seems to be:

The MJO is known to modulate tropical cyclone activity in the Indian Ocean, Pacific Ocean, Gulf of Mexico, and Atlantic Ocean ... The MJO modulates this activity (particularly for the strongest storms) by providing a large-scale environment that is favorable (unfavorable) for development. For example, westerly wind anomalies at the surface in and just behind the area of enhanced convection of the MJO may generate cyclonic (anticyclonic) rotation north (south) of the equator respectively. At the same time, in the upper levels, anticyclonic (cyclonic) rotation develops along and just behind the area of convection resulting in a means to reduce vertical wind shear and increase upper-level divergence – both of which are favorable for tropical cyclone development and intensification. The strongest tropical cyclones tend to develop when the MJO favors enhanced precipitation. As the MJO progresses eastward, the favored region for tropical cyclone activity also shifts eastward from the Indian Ocean to the Pacific Ocean and eventually to the Atlantic Ocean (Figure 10). While this relationship appears robust, we caution that the MJO is one of many factors that contribute to the development of tropical cyclones. For example, it is well known that SSTs must be sufficiently warm and vertical wind shear must be sufficiently weak for tropical disturbances to form and persist.

If the MJO were to stay in one place, I do not see how these circulation anomalies aloft and at the surface that enhance TC formation could exist. As I understand it, the enhancement exists because of the dynamics as the wave propagates. If plots show the MJO staying in one place, then I assume that the phenomena used to track the MJO are being affected by other processes. In that case the data could be misleading.
Member Since: May 18, 2006 Posts: 10 Comments: 6157
1479. xcool
JLPR2 .to many AOl watching
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Africa in motion:


Link
Member Since: Posts: Comments:
1477. JLPR2
Quoting xcool:


Well that's interesting, the 850 is stretched towards that area of convection
Member Since: September 4, 2007 Posts: 7 Comments: 8747
A hail-producing mesocyclone is now heading directly for my location.
Member Since: Posts: Comments:
This looks interesting in motion.Link
Member Since: Posts: Comments:
1473. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting stormpetrol:

I think thats an separate area that bears watching alone, I don't like the lat its at, could be a Caribbean cruiser


Actually it looks like the tail end of the same circulation.
Member Since: Posts: Comments:
1471. gator23
Quoting guygee:
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.

thats a wager you would win. his idioms are very low class.
Member Since: Posts: Comments:
1470. JLPR2
Quoting stormpetrol:

I think thats an separate area that bears watching alone, I don't like the lat its at, could be a Caribbean cruiser


Yes, 6-7N a little too low right now, but it will be interesting to see if it becomes a separate entity and if it sustains itself longer.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Holguín is one of the provinces of Cuba, the third most populous after Ciudad de la Habana
Member Since: Posts: Comments:
Quoting JLPR2:
Look to the SW of the low, some persistent convection there, maybe the interaction between the wave and ITCZ?


I think thats an separate area that bears watching alone, I don't like the lat its at, could be a Caribbean cruiser
Member Since: April 29, 2007 Posts: 0 Comments: 8134
1467. JRRP
Quoting JLPR2:
Look to the SW of the low, some persistent convection there, maybe the interaction between the wave and ITCZ?


yea
Member Since: Posts: Comments:
1466. will45
Quoting JLPR2:
Look to the SW of the low, some persistent convection there, maybe the interaction between the wave and ITCZ?



Yes that what it looks like to me also. Be interesting to see how it does on its own
Member Since: Posts: Comments:
1464. EtexJC
Quoting StormW:


As far as the Caribbean, the conditions have been similar to monsoonal conditions for development of WPAC (Western PACifc)Typhoons.

There has been a pretty persistent SE flow from the deep tropics. The flow has been fairly weak for the most part. When the Atlantic sub-tropical ridge is weaker, it allows for a slower surface flow, and lowering pressures, which has been the case in the Caribbean. This allows an excess build up of moisture and heat energy, until we see convection start to "boil" as it is now. Then, the slow process begins of cyclogenesis.


Thanks Storm, now i feel edumoncated again! LOL I hate it when i miss 2-3 days from learning this stuff!
Member Since: Posts: Comments:
1463. hydrus
Quoting StormW:
Check out Africa (left of picture)

BIG wave.Looks a little like the system that spawned Hurricane Allen in 80.
Member Since: Posts: Comments:
1462. JLPR2
Look to the SW of the low, some persistent convection there, maybe the interaction between the wave and ITCZ?

Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting StormW:


As far as the Caribbean, the conditions have been similar to monsoonal conditions for development of WPAC (Western PACifc)Typhoons.

There has been a pretty persistent SE flow from the deep tropics. The flow has been fairly weak for the most part. When the Atlantic sub-tropical ridge is weaker, it allows for a slower surface flow, and lowering pressures, which has been the case in the Caribbean. This allows an excess build up of moisture and heat energy, until we see convection start to "boil" as it is now. Then, the slow process begins of cyclogenesis.
Hi Storm. I know you don't do an analysis on the weekends but does this mean that you actually think something is beginning to pull itself together in the blob SE of Jamaica or is it elsewhere you are seeing it ?
Member Since: Posts: Comments:
1460. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1458. txjac
Quoting msgambler:
Was looking at that earlier and ya gotta say to yerself. Dang I hope that's the ROV movin' and not tha well head.


That's exactly what I thought when I checked it out ...lots of movement there
Member Since: Posts: Comments:
1457. KYDan
Quoting StormW:
Check out Africa (left of picture)



I hope you do not mind me adding another image to your post.

Is it unusual for the current storms to be this far south on the continent?

Member Since: Posts: Comments:
1456. CJC111
Another little excerpt from the back of my mind before I head out for the evening. I'm always impressed when I see some of the others here post and image of vortictiy at different levels or atmosphere structures that will determine tracks and see others who follow along and know what that means without having to research or ask. KYDan brought up a good point. Some of us need to have things explained to us. Please try not to be frustrated. Something I have found in my line of work is that sometimes I learn as much by answering a question as I do by asking one.
Member Since: Posts: Comments:
1454. Patrap
Quoting CanesfanatUT:


Dang! Can not get that to work - what's it showing Pat??


The ROV view swaying back and forth in about a 5-8 Kt bottom current.

Skandi_ROV 1
Member Since: July 3, 2005 Posts: 428 Comments: 129838
1453. EtexJC
Quoting taco2me61:

With all due respect that will happen soon enough.
Come August thru October they will start out in the Atlantic
and move across to the Gulf and or East coast...
Just a matter of time....

Taco :o)


It just feels like this year is different, maybe i'm not paying enough attention to the details....
Member Since: Posts: Comments:
Quoting stormpetrol:

Hi stormwatcher, been talking about it all day, this one is in a ticklish spot for us, This one these waves that could get going fast imo, I don't see much to hinder it and its movement is very slow, anyway looks like we might have a rainy and squally week here in the Caymans again.
I have been watching it closely. Don't know if it will develop but seems like it has just as good of a chance as anything else.
Member Since: Posts: Comments:
Quoting StormW:
Check out Africa (left of picture)




Is that one big wave? If it is holy s$#%
Member Since: Posts: Comments:
Quoting StormW:
Check out Africa (left of picture)


Holy Mackrel!! Frightful that covers at least 20-25% of the Continent.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
1447. JRRP
Member Since: Posts: Comments:
1446. CJC111
Stormw, is there much dust along with that thing coming off of Africa?
Member Since: 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! Can not get that to work - what's it showing Pat??
Member Since: Posts: Comments:
Quoting EtexJC:
I'm curious, but what has been the factor this year in the blow up of storms in the gulf/caribbean areas? I miss the old days when the storm would start waaaay out the Atlantic and make it's trip to the gulf...

With all due respect that will happen soon enough.
Come August thru October they will start out in the Atlantic
and move across to the Gulf and or East coast...
Just a matter of time....

Taco :o)
Member Since: Posts: Comments:
1443. KYDan
Quoting StormW:
Some mechanics on the MJO:

MJO Summary


Thank you very much for the link. I "think" I understand the article well enough to now feel more comfortable reading the posts here when MJO is referred to.

On the other hand, the figures presented at the end of the article have no meaning for me. They look like modern art which I can not interpret, while I know they are important graphical representations of MJO and it's affect on the atmosphere and oceans. I need to find some texts that explain the images to neophytes like myself.

Thanks again for sharing the info.

Dan
Member Since: Posts: Comments:
1441. EtexJC
I'm curious, but what has been the factor this year in the blow up of storms in the gulf/caribbean areas? I miss the old days when the storm would start waaaay out the Atlantic and make it's trip to the gulf...
Member Since: Posts: Comments:
Quoting stormwatcherCI:
Looks like all the moisture that was in the Caribbean the past few days is consolidating in the wave SE of Jamaica.

Hi stormwatcher, been talking about it all day, this one is in a ticklish spot for us, This one these waves that could get going fast imo, I don't see much to hinder it and its movement is very slow, anyway looks like we might have a rainy and squally week here in the Caymans again.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
i have we havent had a lot of track casters so this tells me there are a lot of uncertain with thr track of these aoi

Member Since: September 2, 2009 Posts: 130 Comments: 21194

Viewing: 1488 - 1438

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49Blog Index

Top of Page

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.

Local Weather

Overcast
29 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron