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

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

Share this Blog
5
+

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

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: 4184 - 4134

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 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107 | 108 | 109 | 110 | 111 | 112 | 113 | 114Blog Index

4184. tkeith
Futuremet, what do you see that would turn these systems East as they near the Bahamas and Florida?

Some front coming down out of Canada?
Member Since: Posts: Comments:
Morning all
Member Since: Posts: Comments:
Yeah, that is kinda dangerous to be close to the water in the height of the storm. I have been in many hurricanes, well not near the water but a few miles or so from the beach.
Member Since: Posts: Comments:
.
Member Since: Posts: Comments:
Near Bushy Park, St. Phillip........not bad for view to the East & South for possible things to come.......!!
Member Since: Posts: Comments:
Quoting tornadofan:


That doesn't look good.
Member Since: Posts: Comments:
The weather here in central Florida is going to wet today.
Member Since: Posts: Comments:
4176. tkeith
4171. tornadofan 5:34 AM CDT on August 15, 2009

That's gonna keep me wet Sunday TFan...
Member Since: Posts: Comments:
Quoting Cotillion:
Still having trouble with dry air?

Ana WV Flash Loop


More dry air would be welcome at this time.
Member Since: Posts: Comments:
LOL Out to sea; this is why you don't trust long range

Member Since: Posts: Comments:
Still having trouble with dry air?

Ana WV Flash Loop
Member Since: Posts: Comments:
Member Since: Posts: Comments:
I notice in the 06GFS that Bill has a friend, and it's not Ana. The NOGAPS was hinting at this, as well:

Member Since: Posts: Comments:
Q,

Near Wildey. You?
Member Since: Posts: Comments:
Quoting bajelayman2:


Real nice wishes, thanks Wanderer.



Your welcome.
Member Since: Posts: Comments:
Stormchases? Only for the very errrrr 'brave' or foolish.

Especially in the islands.

I read in the news a few years back, unfortunately, that a guy photographing near the water in the midst of a storm, I think in Antigua, was lost.

So, wind = dangerous

Wind + water, especially sea = highly dangerous.
Member Since: Posts: Comments:
Quoting bajelayman2:
Hi Q, you in Barbados too?

Your advice is well given and taken.

I agree on 90L. Not pretty. Monster may be the word.


Morning Bajelayman2, what part of Bimshire are you located......
Member Since: Posts: Comments:
Quoting homelesswanderer:


When someone posted the first warning from the NHC earlier I got a little tear in my eye. Because it made it real again after all this waiting. I guess you never know how another season will affect you until it begins. I know, I know I'm such a girl. Ah well. I sincerely hope everyone in the islands and beyond come out ok. My thoughts are with y'all down there. Take care.


Real nice wishes, thanks Wanderer.

Member Since: Posts: Comments:
Who in here stormchases in hurricanes?
Member Since: Posts: Comments:
At what time *central time* was ANA born
Member Since: Posts: Comments:
Quoting Weather456:
A TROPICAL STORM WATCH MAY BE REQUIRED FOR PORTIONS OF THE LEEWARD
ISLANDS LATER TODAY.


When someone posted the first warning from the NHC earlier I got a little tear in my eye. Because it made it real again after all this waiting. I guess you never know how another season will affect you until it begins. I know, I know I'm such a girl. Ah well. I sincerely hope everyone in the islands and beyond come out ok. My thoughts are with y'all down there. Take care.
Member Since: Posts: Comments:
Hi Q, you in Barbados too?

Your advice is well given and taken.

I agree on 90L. Not pretty. Monster may be the word.
Member Since: Posts: Comments:
90L is less organized today then this time yesterday. Most of the models are not as agressive as they were also. Maybe 90L will be influence my more dust and shear then first thought but most models are still having it develop which means we more focus but it is still very far from the U.S.
Member Since: Posts: Comments:
That look like a circulation south of Florida?

Member Since: Posts: Comments:
Okay. Just prepare, are you on high ground?

Take care.
Member Since: Posts: Comments:
I remember David and Allen 'passing' Barbados.

They 'only' brushed us, but the trees that were torn out of the ground were massive, had trunks of six to eight feet diameter, ripped out just easily.

Then Ivan ramping up to CAT 3 just East of us.

ALL tracks had it right through us, up to two hours before.

Suddenly it took a sharp SouthWest turn, went below us and hammered Grenada.

So, in my view, NOTHING is out of the ordinary where storms are concerned.
Member Since: Posts: Comments:
4156. Prgal
Good morning! I see we have Ana already!
Member Since: Posts: Comments:
Good Morning Barbados and Islands. It will be an interesting week'n but by no suprise. It's a wait and see on which path Ana takes as she leads the way ahead of 9oL to the Islands, Mean while 90L is slowly transforming into a possible nightmare. We can call it what ever we want but its time for people to pay serious attention from Barbados in the South to the Islands in the North. Who knows, just be prepared......456 i'll be looking for your update.
Member Since: Posts: Comments:
GEE, I bet the 0-0-0 bets are lost, aren't they???
Member Since: Posts: Comments:
Quoting bajelayman2:


Which islands are you in? You know I'm sure.

As I am going to do this am, ensure you have enough tinned food, rice, biscuits and water to last a couple weeks at least.

Something to eat anyway. And plenty water.

Board up when necessary. Ensure vehicles have enough petrol and if you have a jenny, fuel for that too.

I got fuel yesterday. Going to restock food supplies this am.


I'm in saint kitts
Member Since: Posts: Comments:
My thoughts are with those in the Leeward Islands, I am hoping that people prepared and will take advantage of the weekend to do so. As been stated so many times here it only takes one.
Member Since: Posts: Comments:
Yeah, I just do not agree with the north-west curve in the current expected track.

I think both will barrel through us.

Am a bit worried, especially as I think while Ana will be CAT 1 when it passes us, Bill may be quite worse.

Not to scare anybody, that just my assessment, for what its worth from an amateur.
Member Since: Posts: Comments:
The 06Z model run for the GFS is still not depicting Tropical Storm Ana to stay organized. In my thinking it seems that Ana will be organized and either the GFDL or HWRF models should win.
Member Since: Posts: Comments:
TD was expected to be fish, now 60 knots forecast for the Bahamas.

I have to laugh how things changes.
Member Since: Posts: Comments:
Quoting Weather456:
well ana is now heading for me, what next?


Which islands are you in? You know I'm sure.

As I am going to do this am, ensure you have enough tinned food, rice, biscuits and water to last a couple weeks at least.

Something to eat anyway. And plenty water.

Board up when necessary. Ensure vehicles have enough petrol and if you have a jenny, fuel for that too.

I got fuel yesterday. Going to restock food supplies this am.
Member Since: Posts: Comments:
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
347 AM CDT SAT AUG 15 2009

.SHORT TERM...

AN VERY UNSETTLED PATTERN IS LOOKING TO SET UP ACROSS THE REGION
OVER THE NEXT 48 TO 72 HOURS...AS A FAIRLY VIGOROUS TROPICAL WAVE
CURRENTLY OVER FLORIDA AND THE EASTERN GULF OF MEXICO BEGINS TO
MAKE ITS PRESENCE KNOWN. THE INVERTED TROUGH AXIS ASSOCIATED WITH
THIS TROPICAL WAVE WILL PULL INTO THE CENTRAL GULF STATES SUNDAY
AND THEN SLOWLY PROCEED INLAND MONDAY INTO TUESDAY.

Lol. N.O. says the exact same thing Lake Charles does. We're the western gulf coast.

But they also say this...
.LONG TERM...

A REVERSION TO MORE TYPICAL MID-AUGUST CONDITIONS IS EXPECTED
WEDNESDAY THROUGH THE END OF THE WORKWEEK. TEMPERATURES SHOULD
RISE BACK TO NEAR NORMAL...IN THE LOWER 90S...AND OVERALL POPS
WILL FALL BACK INTO THE CHANCE CATEGORY. THIS PATTERN SHIFT WILL
BE DRIVEN BY A LACK OF ANY STRONG FORCING MECHANISMS IN THE
REGION...AND A BROAD MID AND UPPER LEVEL CENTERED OVER THE
SOUTHEAST SLOWLY SPREADING WESTWARD ACROSS THE REGION.

I'm assuming they mean ridge. With no "strong mechanisms" in place does that mean they expect things to stay that way for awhile? Just trying to learn.
Member Since: Posts: Comments:
Antarctic glacier 'thinning fast'

"One of the largest glaciers in Antarctica is thinning four times faster than it was 10 years ago, according to research seen by the BBC.

A study of satellite measurements of Pine Island glacier in west Antarctica reveals the surface of the ice is now dropping at a rate of up to 16m a year.

Since 1994, the glacier has lowered by as much as 90m, which has serious implications for sea-level rise.

The work by British scientists appears in Geophysical Research Letters.

The team was led by Professor Duncan Wingham of University College London (UCL)...."

Link

Member Since: Posts: Comments:
A TROPICAL STORM WATCH MAY BE REQUIRED FOR PORTIONS OF THE LEEWARD
ISLANDS LATER TODAY.
Member Since: Posts: Comments:
Quoting Weather456:
well ana is now heading for me, what next?


Bill and Claudette seem to be heading for you 456
Member Since: Posts: Comments:
90L has a Dvorak of 2.0.. if it keeps that (and the trends of organisation it's on), I'd expect TD3 at the next possible advisory which would be about 5 hours from now. (Or perhaps sooner, if they feel like - they can and have done before.)
Member Since: Posts: Comments:
Quoting jasoniscoolman10:
what is all that rain south of miami,fl?? maybe we need to watch it for a tropical D three...


FOR THE REMAINDER OF THE WEEKEND INTO NEXT WEEK...SUB-TROPICAL
RIDGE IS EXPECTED TO STRENGTHEN AND BUILD ACROSS THE GULF AND INTO
THE FORECAST AREA. THIS WILL HELP INCREASE MOISTURE VALUES ACROSS
THE FORECAST AREA AND THUS WILL ALSO INCREASE RAIN CHANCES.

BEST CHANCE OF SHOWERS AND THUNDERSTORMS LOOK TO BE ON MONDAY AND
TUESDAY AS A TROPICAL WAVE/INVERTED TROUGH...CURRENTLY LOCATED
OVER SOUTHEAST FLORIDA AND CUBA...MOVES NORTHWEST ACROSS THE
REGION.
PRECIPITABLE WATER VALUES AT OR ABOVE 2.2 INCHES WITH MEAN
RH OVER 70 PERCENT ON THOSE TWO DAYS...ESPECIALLY OVER EASTERN
ZONES...SO THERE WILL BE THE POSSIBLY OF LOCALLY HEAVY RAINFALL.

Also if this ridge hold and Ana does increase in speed I don't know how she could recurve before Florida.
Member Since: Posts: Comments:
4141. JRRP
90L
hmmmmmm....

Ana

Member Since: Posts: Comments:
well ana is now heading for me, what next?
Member Since: Posts: Comments:
Ana heading for you, 456?
Member Since: Posts: Comments:
1. SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE CENTERED
ABOUT 475 MILES WEST-SOUTHWEST OF THE WESTERNMOST CAPE VERDE
ISLANDS CONTINUES TO BECOME BETTER ORGANIZED...AND A TROPICAL
DEPRESSION MAY BE FORMING. IF CURRENT TRENDS CONTINUE...ADVISORIES
WILL LIKELY BE INITIATED LATER TODAY. THE LOW IS EXPECTED TO MOVE
WESTWARD AT ABOUT 15 MPH. THERE IS A HIGH CHANCE...GREATER THAN 50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.
Member Since: Posts: Comments:
4132. Not really, both Ana (previous TD2) and 90L are looking to ramp up and moving into warm water.

So, somebody is in for a lickin.
Member Since: Posts: Comments:
The 06z GFS 78 hrs. out still does recognize Ana.

Member Since: Posts: Comments:
Quoting tea3781:
Its moving due west right now. I think the convection is building to the southwest and thats what you are seeing.

Time Lat Lon Wind(mph) Pressure Storm type
------------------------------------------------------------------------
04 GMT 08/15/09 14.6N 45.8W 35 1005 Tropical Depression
09 GMT 08/15/09 14.6N 46.8W 40 1005 Tropical Storm


Okay, hope the official track is right.
Member Since: Posts: Comments:

Viewing: 4184 - 4134

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 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107 | 108 | 109 | 110 | 111 | 112 | 113 | 114Blog 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
49 °F
Overcast