Disturbance 90L close to tropical depression strength; TD 2 may rise again

By: Dr. Jeff Masters , 2:02 PM GMT on August 14, 2009

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A strong tropical wave (90L), with a large circulation and a moderate amount of heavy thunderstorm activity, is a few hundred miles southwest of the Cape Verdes Islands, off the coast of Africa. This morning's QuikSCAT pass shows that 90L has a large circulation, but this circulation is not yet well-formed, as it is elongated along an east-west axis. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are gradually becoming better organized, with some spiral banding evident on the south side of the storm. Satellite intensity estimates from NOAA already put 90L at tropical depression strength with 30 mph winds, but the storm does not yet have a well enough formed circulation to be classified as a depression. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two was. However, there is some dry air from the SAL being sucked into the circulation of 90L, and this is retarding its development.

Wind shear is moderate, about 10 - 15 knots, but is forecast to fall to the low range, 5 - 10 knots, later today. Shear is then forecast to remain low for the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow 90L to develop into a tropical depression by Saturday, and potentially reach hurricane strength by Wednesday. Most of our reliable models strengthen 90L into a hurricane by Wednesday, when the storm is expected to be near the northern Lesser Antilles Islands. One important outlier is the ECMWF model, which has 90L passing to the north of the islands, and eventually recurving out to sea east of Bermuda. The ECMWF was by far the most reliable model for forecasting hurricane tracks last year. However, all of our models are pretty unreliable going out 5 days in advance for systems that have yet to reach tropical depression strength. Once 90L becomes a tropical depression and develops a well-formed circulation, the models will have a better handle on forecasting where it will go.


Figure 1. The remnants of Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).

Tropical Depression Two may come back
Tropical Depression Two died yesterday, but may rise again. Satellite loops of the remnants of the storm show that heavy thunderstorms are again attempting a comeback near the axis of what is now a tropical wave. However, dry air continues to interfere with the development of the thunderstorm activity, and moderately high wind shear of 15 - 20 knots is also inhibiting the process. Wind shear over the remnants of TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next four days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to the north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that any re-development of the storm will be slow to occur. NHC has given the system a medium (30 - 50% chance) of becoming a tropical depression again by Sunday morning. Only one reliable model, the NOGAPS, is predicting regeneration of TD 2. The NOAA Hurricane Hunters are flying research missions into the remnants of TD 2 today and Saturday.

I'll have an update Saturday morning, or earlier, if significant developments occur.

Jeff Masters

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Quoting MrSea:


that was Dean?


Yessir. Dean.
Member Since: August 10, 2009 Posts: 3 Comments: 672
Quoting Funkadelic:
WoW! TD3 is moving at a preety good clip for a large storm 17mph according to the NHC. What does this mean for future track? I would think further west probabley


At this rate it might just go under South Florida. Bad news for the Gulf if that happens.
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Quoting cirrocumulus:
Ana just crossed into the warmer water boundary of 28 degrees Celsius.


she is like a crack baby, having a tough time since childbirth
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Quoting SeniorPoppy:


Rather be in the center of the cone now. Look what happened with Ike last year. It just kept trending south until South Florida was out of the cone.
yup
5179. MrSea
Quoting HurricaneKyle:
You guys want to know something stunning?
Tropical Depression 3.

Tropical Depression 4 in 2007. (4th advisory)



that was Dean?
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Quoting Weather456:



lol lol


I couldn't tell the difference apart. They have to be one of the most similar tropical cyclone advisory's ever.
Member Since: August 10, 2009 Posts: 3 Comments: 672
Dr. Masters has wisely waited until the 11AM advisory and updates.

He's working on his new blog now, I'm sure.
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5176. centex
The south trend continues.If it keeps up through tomorrow, I think they will be GOM in the end.
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First forecast advisory takes newly designated TD3 to 105 mph, Category 2 status, on day 5 after reaching hurricane strength on day 4.
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5174. Seastep
Quoting Weather456:
hmmm. dead center in the cone



That's usually good news. Was in the center of Ike at 5 days. Passed S. :)
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Quoting HurricaneKyle:
You guys want to know something stunning?
Tropical Depression 3.

Tropical Depression 4 in 2007. (4th advisory)



the big difference is though, 2007's ridge was a monster. Dean has the most consistent path of anything storm I ever track. It is unlikely TD 3 will follow.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting canesrule1:
Miami in the center:


Rather be in the center of the cone now. Look what happened with Ike last year. It just kept trending south until South Florida was out of the cone.
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5170. Skyepony (Mod)
Zoo~ Thanks, realized the best preforming model brings it in just south of me.. I should go clean out the canal..
Member Since: August 10, 2005 Posts: 162 Comments: 37829
5169. cg2916
Finally, after all this waiting and anticipation, we have it.
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the nhc most read the blogs
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5167. Drakoen
Quoting Relix:
I just can't find where the WNW turn will occur ... if ever. Really.


Pull up the steering layers.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
Ridging forecasts, anyone who isn't totally consumed in the 11AM advisory?
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Hmm, the advisory has Ana at 60kts for basically 3 days straight despite waddling along the Bahamas with her feet in toasty waters.

Maybe shear is what they're counting for, which would be understandable... but you'd think with waters that hot, you'd get strengthening.
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Quoting HurricaneKyle:
You guys want to know something stunning?
Tropical Depression 3.

Tropical Depression 4 in 2007. (4th advisory)




lol lol
Member Since: July 24, 2005 Posts: 407 Comments: 19076
5161. MrSea
Link

TD 3 on noaa
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5160. Relix
I just can't find where the WNW turn will occur ... if ever. Really.
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hmmm. dead center in the cone

Member Since: July 24, 2005 Posts: 407 Comments: 19076
You guys want to know something stunning?
Tropical Depression 3.

Tropical Depression 4 in 2007. (4th advisory)


They're identical.
Member Since: August 10, 2009 Posts: 3 Comments: 672
Quoting stormwatcherCI:
Hurricane Eloise--A powerful hurricane that formed in September, 1975, Eloise was a Category Three Hurricane with sustained winds of 125 mph, and gusts of up to 156 mph. It produced a 12 to 16 foot storm surge along the Florida Coast from Ft. Walton Beach to Panama City, Florida. With a minimum central pressure of 28.20 inches, Eloise was the first major hurricane to make a direct hit on this area in the 20th century, and caused some $1 billion dollars in damage as well as 21 deaths.


My first ever hurricane hunt was in Eloise. She lifted me off my feet as I hung onto a light pole. At dawn, her neon pink eye made landfall. Incredible visuals that morning. You had to be there to appreciate it.
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good morning all...I see we have a TS now! Anyone mind giving me a run down on whats happening?
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5155. Drakoen
The track takes it across the extreme northern islands
Member Since: October 28, 2006 Posts: 57 Comments: 30490
5154. cg2916
We have TD 3! And I think the NHC is watching this blog. Earlier we were talking about Ana being pronounced Ah-na, and take a look at their advisory.
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NHC has issued the 1st advisory on TD3
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Miami in the center:
5151. jipmg
Quoting PensacolaDoug:
"Bill" to be is diving towards the sw. Was that predicted?


yes it was, a WSW movement then a W to WNW movement later on as it gains strength.

As for ANA still a TS, and expcted to stay a TS by the NHC
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5150. Drakoen
Quoting atmoaggie:

A nice scenario: Don't post them here at all.
I think we all know where to get it.


And even when you say that we still get people that post them
Member Since: October 28, 2006 Posts: 57 Comments: 30490
First advisory is out now. Cue the multiple posts with the same thing ;)
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Minimal windshear in the eastern gulf and plenty of moisture
Member Since: September 4, 2007 Posts: 0 Comments: 490
5146. WAHA
Quoting Ameister12:
Poll time!!!

What intensity do you think 03L is going to peak out at?

A)Tropical Storm
B)Cat. 1
C)Cat. 2
D)Cat. 3
E)Cat. 4
F)Cat. 5

D or E
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Ana just crossed into the warmer water boundary of 28 degrees Celsius.
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5144. jpsb
Quoting CycloneOz:


Why for heaven's sake? Is it because forecaster Bevens does not see any model support for it?

Please...anyone...someone...why?
I think it is lacking a surface low, that is my take anyway, however I did read a few pages back that the low goes down to 5k feet. That seems pretty close to the surface to me. I am still watching this blob. My thinking is that if it gets well into the gulf SOMETHING is going to happen.
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WTNT33 KNHC 151434
TCPAT3
BULLETIN
TROPICAL DEPRESSION THREE ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
1100 AM AST SAT AUG 15 2009

...TROPICAL DEPRESSION THREE FORMS IN THE EASTERN ATLANTIC...

AT 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL DEPRESSION THREE
WAS LOCATED NEAR LATITUDE 11.5 NORTH...LONGITUDE 34.0 WEST OR ABOUT
740 MILES...1190 KM...WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.

THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 17 MPH...27 KM/HR...
AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE
OF DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. SLOW STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...
AND THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM LATER
TODAY OR ON SUNDAY.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB...29.71 INCHES.

...SUMMARY OF 1100 AM AST INFORMATION...
LOCATION...11.5N 34.0W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...WEST OR 265 DEGREES AT 17 MPH
MINIMUM CENTRAL PRESSURE...1006 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
500 PM AST.

$$
FORECASTER BEVEN
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting CaicosRetiredSailor:
BULLETIN
TROPICAL STORM ANA ADVISORY NUMBER 14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
1100 AM AST SAT AUG 15 2009

...ANA...PRONOUNCED AH-NA...MOVING QUICKLY WESTWARD WITH LITTLE
CHANGE IN STRENGTH...

INTERESTS IN THE LEEWARD ISLANDS...THE VIRGIN ISLANDS...AND PUERTO
RICO SHOULD MONITOR THE PROGRESS OF ANA. A TROPICAL STORM WATCH MAY
BE REQUIRED FOR PORTIONS OF THE LEEWARD ISLANDS LATER TODAY.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA
OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR NATIONAL METEOROLOGICAL SERVICE.

AT 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL STORM ANA WAS
LOCATED NEAR LATITUDE 14.3 NORTH...LONGITUDE 48.3 WEST OR ABOUT
920 MILES...1480 KM...EAST OF THE LEEWARD ISLANDS.

ANA IS MOVING TOWARD THE WEST NEAR 16 MPH...26 KM/HR. A TURN TOWARD
THE WEST-NORTHWEST IS EXPECTED DURING THE NEXT COUPLE OF DAYS.
THIS MOTION COULD BRING THE CENTER OF ANA NEAR THE LEEWARD ISLANDS
ON MONDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/HR...WITH HIGHER
GUSTS. SOME SLOW STRENGTHENING IS FORECAST DURING THE NEXT
48 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

...SUMMARY OF 1100 AM AST INFORMATION...
LOCATION...14.3N 48.3W
MAXIMUM SUSTAINED WINDS...40 MPH
PRESENT MOVEMENT...WEST OR 270 DEGREES AT 16 MPH
MINIMUM CENTRAL PRESSURE...1005 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
500 PM AST.

$$
FORECASTER BEVEN


Is that the real advisory???
...ANA...PRONOUNCED AH-NA...????
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TD BORN JUST UPDATED
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5140. Mikla
Quoting leftovers:
does anyone know of a major making landfall e cen florida? a fellow blogger and i researched this and we couldnot find one ever

Doesn't look like it...
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5139. jpsb
Quoting CycloneOz:


Why for heaven's sake? Is it because forecaster Bevens does not see any model support for it?

Please...anyone...someone...why?
I think it is lacking a surface low, that is my take anyway, however I did read a few pages back that the low goes down to 5k feet. That seems pretty close to the surface to me. I am still watching this blob. My thinking is that if it gets well into the gulf SOMETHING is going to happen.
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TD3 up too.
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Quoting CycloneOz:


Why for heaven's sake? Is it because forecaster Bevens does not see any model support for it?

Please...anyone...someone...why?

Lack of lower level convergence and expected lack of upper anticyclone.

I see Intel AMD said the same thing as I was a getting my coffee filled.
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Quoting extreme236:
Ana advisory coming out. Still a TS.

Link plz
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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.