Tropical wave has potential to develop into tropical depression

By: Dr. Jeff Masters , 2:09 PM GMT on August 07, 2006

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A tropical wave over the mid-Atlantic near 12N 42W, about 1300 miles east of Barbados, has the potential to develop into a tropical depression. However, the long-term survival of this system is questionable. The wave has a well defined surface circulation, and is currently under about 10-15 knots of wind shear, due to upper level winds from the east. As the wave moves westward over the next 36 hours, it should encounter an area of lower wind shear where these upper level winds will relax, and I believe a tropical depression will probably develop by Tuesday night. However, as the wave continues westward at 15-20 mph, it is forecast to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system northeast of Puerto Rico (Figure 1). This strong wind shear should weaken or destroy the wave. This is shown well by the GFDL model, which intensifies the wave into a weak tropical storm by Wednesday, then dissipates it later in the week. None of the other computer models develop the wave at all.


Figure 1. Water Vapor satellite image from 8:45am EDT August 7. Note the substantial dry air (brown colors) to the northwest of the tropical wave we're watching, and the upper level low to the northwest of the wave that is expected to bring strong westerly wind shear later this week.

Intense thunderstorm activity associated with the wave is mostly on the west side of the circulation, due to the strong upper-level winds from the east pushing all the convection over to that side. There is a substantial amount of dry air to the northwest of the wave, as seen in the water vapor image from this morning (Figure 1.) This dry air has resulted in a decrease in the intensity and areal coverage of the wave's thunderstorm activity this morning. If we do get the expected decrease in wind shear later today and tomorrow, this should allow the thunderstorm activity to build back in over the circulation center.


Figure 2. Preliminary model tracks for the mid-Atlantic tropical wave.

For today, it does not appear that this tropical wave is going to be a major threat. I'll be back with an update on Tuesday. Elsewhere in the tropical Atlantic, there are no threat areas to talk about.

Jeff Masters

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1516. stormchasher
9:13 PM GMT on August 08, 2006
hey guys accuwweather dropped 91L HA wouldnt it be funy if it devoloped!!LOL:)
Member Since: July 30, 2006 Posts: 40 Comments: 1295
1513. STORMTOP
3:36 PM GMT on August 08, 2006
turtle when are we officially starting the cape verdes season this year...i cant see anything developing this month and we may not see our first hurricane until labor day ...now that is kind of strange..the african dust which i said all along will stop any thing that comes off the coast from developing...gents we are in for one boaring season until mid september and october seems to be a very active month..so you can throw the cape verdes season in the toilet like everyones predictions on here this year...weatherguy03 needs to study a little more and lighten up with his b/s he is giving you..he never commits to anything he wont give you a srraight answer when you ask him a question...like i said people this hurricane season is in the books and by the way IT IS WRITTEN IN STONE!!!!!!!!!!!!!!!!!!!StormTop
1512. Cavin Rawlins
3:33 PM GMT on August 08, 2006
Hey Jp, I new blog is up
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1507. thelmores
3:22 PM GMT on August 08, 2006






been blob watchin this mornning.... certainly not tropical... but interesting none the less.... perhaps due to its close proximity.... :)
Member Since: September 8, 2005 Posts: 0 Comments: 3805
1506. hurricane23
3:14 PM GMT on August 08, 2006

Member Since: May 14, 2006 Posts: 8 Comments: 13804
1504. hurricane23
3:10 PM GMT on August 08, 2006
Here is the text of the outlook...

CLICK HERE


Member Since: May 14, 2006 Posts: 8 Comments: 13804
1503. Cavin Rawlins
3:09 PM GMT on August 08, 2006
With the peak of the Atlantic hurricane season upon us, experts from NOAA are reiterating their prediction for an above-normal number of storms. NOAA scientists warn this year's relatively quiet start is not an indication of what the remainder of the season has in store. "This year's three named storms may pale in comparison to the record nine storms that formed through early August 2005, but conditions will be favorable for above-normal activity for the rest of this season—so we are not off the hook by any means," said retired Navy Vice Adm. Conrad C. Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. For the entire 2006 season, which ends November 30, NOAA is projecting a total of 12 to 15 named storms of which seven to nine will intensify to hurricanes, including three or four becoming major hurricanes—rated at Category 3 or higher.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1502. Pipsneyy
3:09 PM GMT on August 08, 2006
LOL, ya beat me
1501. Pipsneyy
3:07 PM GMT on August 08, 2006
00
ABNT20 KNHC 081502
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT TUE AUG 8 2006

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A SMALL AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
CENTERED ABOUT 825 MILES EAST OF THE WINDWARD ISLANDS...AND IS
MOVING WESTWARD 15 TO 20 MPH. ALTHOUGH THUNDERSTORM ACTIVITY IS
MINIMAL AND UPPER-LEVEL WINDS ARE ONLY MARGINALLY CONDUCIVE FOR
DEVELOPMENT...THIS SYSTEM STILL HAS SOME POTENTIAL TO BECOME A
TROPICAL DEPRESSION DURING THE NEXT DAY OR SO.

1500. benirica
3:07 PM GMT on August 08, 2006
ABNT20 KNHC 081502
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT TUE AUG 8 2006

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A SMALL AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
CENTERED ABOUT 825 MILES EAST OF THE WINDWARD ISLANDS...AND IS
MOVING WESTWARD 15 TO 20 MPH. ALTHOUGH THUNDERSTORM ACTIVITY IS
MINIMAL AND UPPER-LEVEL WINDS ARE ONLY MARGINALLY CONDUCIVE FOR
DEVELOPMENT...THIS SYSTEM STILL HAS SOME POTENTIAL TO BECOME A
TROPICAL DEPRESSION DURING THE NEXT DAY OR SO.
Member Since: August 3, 2006 Posts: 0 Comments: 1143
1499. Pipsneyy
3:07 PM GMT on August 08, 2006
NHC still says it could develop
1498. sails1
3:07 PM GMT on August 08, 2006
I just notice some counterclock wise rotation on the east side of the Twave north of Cuba setting it's sites on SFLA. Does anyone catch that also?
Member Since: May 26, 2003 Posts: 0 Comments: 72
1497. TampaSteve
3:07 PM GMT on August 08, 2006
Looks like another slow week in the Atlantic...good!
1496. Cavin Rawlins
3:06 PM GMT on August 08, 2006
Noaa is still calling for a normal to active season. Why?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1495. 147257
3:06 PM GMT on August 08, 2006
ey doe ssomeone has a database of the loop of images the satelite images only give 14 images :O
Member Since: August 2, 2005 Posts: 7 Comments: 68
1493. Cavin Rawlins
3:05 PM GMT on August 08, 2006
This wind shear map is diffrent, and it was the one more accurate during Chris.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1492. hurricane23
3:05 PM GMT on August 08, 2006
NOAA'S NEW UPDATE.....

12-15 named, 7-9 hurricanes, 3-4 majors
Member Since: May 14, 2006 Posts: 8 Comments: 13804
1491. Pipsneyy
3:04 PM GMT on August 08, 2006
Wheres the new update?
1490. weatherblog
3:04 PM GMT on August 08, 2006
i'm gonna wait to see what dr.jeff says, i bet he's gonna say it is in marginally favorable enviroment and if it actually makes td status, that it will be entering more shear and won't last that long...and if he says that i totally agree with him!!
Member Since: July 10, 2006 Posts: 27 Comments: 1623
1487. DiamondDove
3:02 PM GMT on August 08, 2006
benirica, Montserrat can do it too, but the wind direction has to be just right. Yes, the moisture in the air can do it, too.
1486. 147257
3:02 PM GMT on August 08, 2006
hmmz saw it wrong have to clear up some cookies :$
Member Since: August 2, 2005 Posts: 7 Comments: 68
1485. CaneJunkie
3:02 PM GMT on August 08, 2006
nash,

Check the AVN loop. The intensity at the center is dissapating and the edges are losing roundness. I think the cloud tops are just expanding from the burst that the system had earlier this morning.
1483. MightyMouse
3:01 PM GMT on August 08, 2006
Hello everyone, here's a good satellite shot of Africa (and the rest of the world):

Link
1482. nash28
3:01 PM GMT on August 08, 2006
New models won't run until 2pm.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1481. nash28
3:00 PM GMT on August 08, 2006
You'r welcome diamonddove. We all continue to learn.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1480. CosmicEvents
3:00 PM GMT on August 08, 2006
Pulling up these maps of Africa and implying that there's something ominous or scary here is irresponsible. Go back and look at maps of Africa for the last 10 years on August 8. The African continent is ALWAYS loaded with storms at this time of year. There is nothing unusual here.
Member Since: August 3, 2005 Posts: 10 Comments: 5606
1479. 147257
3:00 PM GMT on August 08, 2006
no new computer modeles does that mean the gave the wave up
Member Since: August 2, 2005 Posts: 7 Comments: 68
1478. DiamondDove
2:59 PM GMT on August 08, 2006
Thanks, nash. So little do I know.
1477. alaina1085
2:59 PM GMT on August 08, 2006
ricderr~ Dr Lyons was talking about this last night. He said roughly close to 90 waves come off the coast of Africa during hurricane season, but only 10% of them will actually become tropical in nature.

Thats what HE said.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
1476. benirica
2:58 PM GMT on August 08, 2006
Visibility has to do with hummidity? I always thought that the days you cant see St. Thomas or the other islands off of Puerto Rico it was because there was either Saharan Dust or Ash from the volcano in Montserrat. Never knew it could also be because it was a humid day.
Member Since: August 3, 2006 Posts: 0 Comments: 1143
1475. DiamondDove
2:58 PM GMT on August 08, 2006
Michael, yes—whereas usually we are watching carefully systems that show promise of developing off the Cape Verdes and as they cross the Atlantic, last year it was astonishing to see nearly all of them developing north and west of us. This year is not shaping up to be the same, which is bad for us.
1474. nash28
2:57 PM GMT on August 08, 2006
The convection at the center doesn't appear to be dying to me. It looks like it's holding its own.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1473. stormchasher
2:56 PM GMT on August 08, 2006
hey guys oly a little bit before Dr masters blogs
Member Since: July 30, 2006 Posts: 40 Comments: 1295
1472. CaneJunkie
2:56 PM GMT on August 08, 2006
The convection at the center of 91L is dying off.
1471. ricderr
2:55 PM GMT on August 08, 2006
gulf....can you explain that matrix a bit more.....thanx
Member Since: June 27, 2006 Posts: 674 Comments: 21751
1470. nash28
2:54 PM GMT on August 08, 2006
The air at the surface has no bearing on formation. It is mid-upper levels.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1467. DiamondDove
2:52 PM GMT on August 08, 2006
Dry air over the Lesser Antilles? I don't think so. Here in Anguilla—which we affectionately refer to as Hurricane Alley—the humidity is so high I can barely see St Martin across the channel and St Barth is completely invisible—neither of which are usual. The sky is so filled with clouds there is nary any blue and we have been getting pelted with wicked showers several times a day/night since TS Chris passed a week ago. The winds are also high, although down today to 9 kts from 13–14 kts the past few days. I don't know what's going on in the upper atmosphere but I do know what's going on down here. Where is this dry air? Anyway, if 91L develops into a TD or TS, we may see the brunt of it. Not that the rain won't be welcome, but it creates one god-awful mess.

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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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