Two minor disturbances in the tropics today

By: Dr. Jeff Masters , 3:05 PM GMT on July 09, 2006

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Two areas in the tropics bear mentioning today, but the long range chances of either of these disturbances developing into a tropical storm are low. The first area is associated with a cold-cored upper level low pressure system north of Puerto Rico and east of the Bahama Islands. A tropical wave is passing through the area as well, and the combination is producing heavy thunderstorms and gusty winds over a large area of ocean. This activity will move slowly northwest over the next few days, but wind shear--currently 10 to 20 knots over the region--is expected to increase, keeping this system from developing.

A large tropical wave about 1300 miles east of the Lesser Antilles Islands is moving west-northwest at about 15-20 mph. Wind shear has dropped to 5-15 knots over a large region surrounding the wave, and some slow development is possible today and Monday. However, wind shear is forecast to increase sharply in the wave's vicinity on Tuesday, and the wave is pushing northward into an large area of dry air and African dust. These factors make the longer-term growth of this wave doubtful.

High wind shear will continue over the Gulf of Mexico for the next few days, so I don't expect any development there, and the rest of the tropics are quiet.

On Monday, I'll take a look at what one expects in a normal July in the tropics, and speculate on what will happen the next two weeks.

Have a great Sunday, everyone!
Jeff Masters

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425. bamaweatherwatcher
2:25 AM GMT on July 12, 2006
424. thelmores
1:43 PM GMT on July 10, 2006
Randrewl, think i see what you may be speaking of....just to the east of south caicos, and to the southwest of the upper low......

we'll have to watch this...
Member Since: September 8, 2005 Posts: 0 Comments: 3805
423. chessrascal
1:43 PM GMT on July 10, 2006
That upper level low has some fairly strong convection i'd say.
422. ForecasterColby
1:32 PM GMT on July 10, 2006
Dry air degrades storms because tropical cyclones derive their energy from water vapor. To explain why, we'll need some Physics 101:

-- When a gas condenses to a liquid, it releases heat.
-- When a liquid evaporates into a gas, it absorbs heat.

What happens is this - when the sun strikes the warm tropical waters, it causes evaporation (the sunlight is taken in so that the water can evaporate). When it condenses inside a tropical cyclone, it releases heat which fuels the system. Dry air = less vapor = less energy = weaker storm. Hope that helps.
421. Cavin Rawlins
1:29 PM GMT on July 10, 2006
my blog has been update to inlcude severe weather, with radars and severe weather outlooks.

AMO Vs Global Warming On Hurricane Activity
From since the start of 1995 upon until the present there has been increase hurricane activity in the Atlantic and rare formations as seen above for Cyclone Catarina. There are currently to theories to explain the increase activity. There is the theory of Global Warming and NOAA’s explanation of the Atlantic Multidecadal Oscillation.

In your opinion, which is the more likely cause of increase hurricane activity. You can also give reasons why.

You can leave your comments at my blog.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
420. ForecasterColby
1:22 PM GMT on July 10, 2006
Depends on the systems. Most tropical cyclones have a high pressure system sitting on top of them, but I think the answer to what you're asking is no. Some lows (usually extratropical ones, tropical systems do not) split up.
418. thelmores
1:15 PM GMT on July 10, 2006
hmmmm..... the CMC Model 850mb vorticity is at it again.....

the latest version has a low developing east of the bahamas, and tracking to myrtle beach in less than 3 days! LOL the gfs hints at a little something (stress LITTLE!) in about the same time period.....

ahhh.... we could use the rain! :)

also appears to have 96l crossing over jamaica in about 5 days...... but the gfdl shows no significant development....

besides alberto, has the cmc been right on anything? :)

and happy anniversary Dennis (930mb).....

oh, we also had a shark bite yesterday about 40 miles south of myrtle beach.....

have a good week everybody! :)
Member Since: September 8, 2005 Posts: 0 Comments: 3805
417. EdMahmoud
1:10 PM GMT on July 10, 2006
Probably not terrorism, but its early- explosion levels Manhattan apartment building.
Member Since: October 19, 2005 Posts: 0 Comments: 254
413. AUradar
12:48 PM GMT on July 10, 2006
okay, so if dry air impedes a tropical storm, will this drought we've been having translate into milder storms? Or does a drought over land have nothing to do with air moisture over the water?
Member Since: July 10, 2006 Posts: 0 Comments: 10
412. EdMahmoud
12:47 PM GMT on July 10, 2006
IIRC, while dry air entrainment at mid levels can sometimes make thunderstorms extra cool, because all else being equal dry air is heavier than humid air (has to do w/ weight of diatomic nitrogen vs water) increasing the CAPE, tropical systems like a moist column at low and mid levels, and dry air will tend to evaporate water droplets that have already condensed, which cools the parcel, kind of the opposite of the normal tropical process where heat is released through condensation.

No training in met whatsoever on my part, just a lowly petroleum engineer, so take that with a few grains.
Member Since: October 19, 2005 Posts: 0 Comments: 254
411. EdMahmoud
12:39 PM GMT on July 10, 2006
Hmmm, interesting stuff about tropical disturbance 96L

0Z Canadian Global has it as a tropical cyclone moving WNW and approaching the Yucatan Sunday, while the 0Z GFS is

a little less aggressive, a tad slowly, a bit further North, but suggesting possible development in the Gulf this time next week

UK Met tropical guidance isn't showing development in next 72 hours.

6Z GFS seesm to try to develop it, but then destroys it as it crosses Hispaniola.
The remnants of the wave then appear to try to start redeveloping past the Yucatan.

Interesting stuff.

Yurpian Community predicts an East Pac storm, but no Atlantic Basin activity
Member Since: October 19, 2005 Posts: 0 Comments: 254
410. Stormy2day
12:25 PM GMT on July 10, 2006
ooo ooo ooo ...wait, I can answer that! It was my newbie question a couple days ago. Answer is yes ...it does ...but, I can't remember the "why" part. LOL
Member Since: June 29, 2006 Posts: 0 Comments: 306
409. EdMahmoud
12:25 PM GMT on July 10, 2006
Speaking of moving into a less favorable environment-

You can see the shear starting to impinge on the Western side of the system on the WV loop.
Member Since: October 19, 2005 Posts: 0 Comments: 254
408. Stormy2day
12:24 PM GMT on July 10, 2006
Morning nash,
Another beautiful day in the Bay!
se – ese winds at 10ish mph, pressure rising, temp rising, humidity dropping and less cloud cover. Too bad it is a Monday!

...my second cup of coffee was much better than the first!
Member Since: June 29, 2006 Posts: 0 Comments: 306
407. AUradar
12:24 PM GMT on July 10, 2006
okay, stupid newbie question. Does dry air degrade a tropical storm??
Member Since: July 10, 2006 Posts: 0 Comments: 10
406. nash28
12:16 PM GMT on July 10, 2006
Good morning Stormy. How are things?
Member Since: July 11, 2005 Posts: 190 Comments: 16972
405. Stormy2day
12:01 PM GMT on July 10, 2006
A question came to me this morning when my dog dropped a sea shell into my cup of coffee and I didn't notice until I got to the last sip (bless her heart!)

...is it possible for a system to develop under another system so that when you look at satellite images, you don't see the storm underneath?
Member Since: June 29, 2006 Posts: 0 Comments: 306
404. bappit
11:46 AM GMT on July 10, 2006
Interesting that the worst shear seems to move west ahead of 96L. 96L never is under it.
Member Since: May 18, 2006 Posts: 10 Comments: 5961
403. ScienceCop
8:20 AM GMT on July 10, 2006
The Evening's Storm Damages: Consider it light for the year 2006, which brings 5 tornadoes per day.

0000 hours July 10, 2006 Zulu time, 7 pm WST, 8 MST, 9 CST, 10 pm EST.

What happened since the top and bottom pictures.

0600 hours Zulu time, 11 pm WST, 12 MST, 1 CST, 2 pm EST.


Those Tornadoes in Colorado tonight were in Acapulco the noon before.
402. bocaman
7:46 AM GMT on July 10, 2006
yeah, I think that the crucial point for this storm will be for it to hold together from this time until about 5:00 this afternoon, If it maintains, or even gains more convection throughout these next 12 hours, we may see a tropical depression. I'm off to bed.
401. quakeman55
7:41 AM GMT on July 10, 2006
Maybe a little...I am sure there will be some more convection flaring up before long though.
Member Since: March 31, 2002 Posts: 1 Comments: 1276
400. bocaman
7:37 AM GMT on July 10, 2006
It looks like some dry air has infiltrated the eastern and northern part of the disturbance
399. bocaman
7:34 AM GMT on July 10, 2006
Yeah the north side of it definitely needs to fill in a little bit though, most of the deep convection is on the SW side
398. quakeman55
7:28 AM GMT on July 10, 2006
Oh it does already have an LLC heading...NHC said in their discussion that there is a 1011 MB low associated with it...was seen on visible imagery earlier today. Though just now I can almost see it on IR imagery as well, and it is getting a better shape, becoming more consolidated with what appears to be some spiral banding going on. I wouldn't be surprised if it is upgraded to depression status later on today.
Member Since: March 31, 2002 Posts: 1 Comments: 1276
397. bocaman
7:22 AM GMT on July 10, 2006
I agree with the 280 heading
396. bocaman
7:21 AM GMT on July 10, 2006
what do you say quakeman??
395. bocaman
7:19 AM GMT on July 10, 2006
looks like, and I say it looks, from just observation like a LLC.
394. bocaman
7:17 AM GMT on July 10, 2006
Do I see a vortex?? 11N 42.5W on the 6:45UTC frame
393. quakeman55
6:58 AM GMT on July 10, 2006
Eh slightly...I'd estimate it to be on a 280 degree overall heading right now.
Member Since: March 31, 2002 Posts: 1 Comments: 1276
391. hurricane23
6:51 AM GMT on July 10, 2006
going to bed.....be back tommorow morning.
Member Since: May 14, 2006 Posts: 8 Comments: 13640
390. quakeman55
6:49 AM GMT on July 10, 2006
According to the CMC and GFS shear maps (moreso with the GFS), the low-shear area will accompany 96L on its trek westbound...at least for a few days anyway. After that, high shear forecast in the Caribbean could be different, especially if there is a good anticyclonic flow around the system, which is already evident on its northern side.
Member Since: March 31, 2002 Posts: 1 Comments: 1276
386. hurricane23
6:41 AM GMT on July 10, 2006
I think the morning hours from about 6am-12pm noon time will be key to see if it can hold together.
Member Since: May 14, 2006 Posts: 8 Comments: 13640
384. quakeman55
6:37 AM GMT on July 10, 2006
Yeah that's what I've been thinking too hurricane23...
Member Since: March 31, 2002 Posts: 1 Comments: 1276
383. hurricane23
6:35 AM GMT on July 10, 2006
convection continues to flare with 96L.the morning hours will be key.
Member Since: May 14, 2006 Posts: 8 Comments: 13640
382. hurricane23
6:30 AM GMT on July 10, 2006
Guys iam about to go to bed!But before i go i just i just finished looking at the shear tendency loop and you can clearly see that the area of higher shear just to the west of this system before the Leeward Islands, is moving westward just ahead of the system, this tells me that is in response to the anticyclonic flow above 96L, so by the time 96L gets to that spot it should be gone by then if the anticyclonic flow stays above it.

be back tommorow.good nite adrian

Member Since: May 14, 2006 Posts: 8 Comments: 13640
378. hurricane23
6:06 AM GMT on July 10, 2006
Early - Cycle Intensity Guidance
Free Image Hosting at www.ImageShack.us
Member Since: May 14, 2006 Posts: 8 Comments: 13640
377. quakeman55
6:05 AM GMT on July 10, 2006
It even wants to develop the PR blob and take it towards the SE coast. That is less likely as we know it does tend to overdevelop things out there. I'd say the 96L invest development is more believable though.
Member Since: March 31, 2002 Posts: 1 Comments: 1276
376. quakeman55
6:04 AM GMT on July 10, 2006
Yeah the CMC does show a good run going on...develops it and takes it into the Caribbean. I'm gonna go check the others right quick too.
Member Since: March 31, 2002 Posts: 1 Comments: 1276
375. hurricane23
5:51 AM GMT on July 10, 2006
Iam seeing some slow developement with 96L.

2:05AM Discussion NHC.

TROPICAL WAVE IS ALONG 41W/42W S OF 15N MOVING W 10 KT WITH A
WELL DEFINED 1011 MB LOW ALONG THE WAVE NEAR 11N. ALTHOUGH THIS
LOW/WAVE IS BETTER ORGANIZED...IT IS ANTICIPATED TO MOVE INTO A
LESS FAVORABLE ENVIRONMENT SLOW ANY TROPICAL FORMATION WILL BE
SLOW TO DEVELOP. SCATTERED MODERATE/STRONG CONVECTION IS FROM
9N-12N BETWEEN 39W-45W
.




Member Since: May 14, 2006 Posts: 8 Comments: 13640

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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.

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