Tropical Depression Seven forms

By: Dr. Jeff Masters , 2:25 PM GMT on August 14, 2011

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The latest in our unusual number of weak tropical cyclones this season, Tropical Depression Seven, has formed to the southeast of Bermuda. Unless you live in Bermuda, TD 7 is not going to be a concern. Radar out of Bermuda shows an area of rain on the northern side of TD 7 beginning to approach the island, and rain from the storm will likely affect the island tonight and on Monday. TD 7 is not well-organized, and has only limited heavy thunderstorms, as seen on visible satellite images. While wind shear is a low 5 - 10 knots, dry air surrounds TD 7, and is keeping the storm from intensifying. None of the computer models foresee that TD 7 will ever become more than a weak tropical storm.


Figure 1. Morning satellite image of TD 7.

92L
TD 7 isn't the only system Bermuda needs to watch, Invest 92L is a day behind it, and will follow a path very similar to TD 7's. The disturbance will pass close to Bermuda on Tuesday, bringing the island a second round of tropical rains. However, Invest 92L is very disorganized, as seen on recent visible satellite loops. Dry air and close proximity to TD 7 will likely keep 92L from showing significant development over the next two days, with NHC giving the system just a 30% chance of developing into a tropical depression by Tuesday morning.

Elsewhere in the tropics
The disturbance midway between the Lesser Antilles Islands and the coast of Africa we've been tracking over the past few days, Invest 93L, has fallen apart and is no longer a threat to develop. This system will need to be watched once it enters the Caribbean later this week, though. None of the reliable models for predicting tropical cyclone formation predict development of this system or any new disturbances over the coming week.

Jeff Masters

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1825. asdip
Quoting SLU:


Where are you located?


Marigot Bay. Heavy rain too.
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Quoting kmanislander:


NHC says movement westward at 15-20 mph
Member Since: October 9, 2008 Posts: 0 Comments: 8272
Quoting hurricane23:


Ah...Gets posted 20 times..Cant wait for school to start.


Just for fun 06z GFS developes the wave currently rolling of africa into a pretty formidable cane.

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Quoting earthlydragonfly:
Anyone got a good link to the EURO?
Link
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1821. SLU
Quoting asdip:
Here in St Lucia, wind getting up , thunder and lightening.


Where are you located?
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via Stormcarib site:

8am and not so much as a fart from Gert.  NO wind, NO rain... not even a drizzle.  
 
.........  COFFEE!
 
sue
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Quoting kmanislander:


Hi, 93L is still a somewhat fragile system. It does not have a well established circulation and little going on at the 850mb level. Surface convergence is much improved though so it is trying to crank up.

The dry air is being pushed out of the way by the leading edge of the feature as it travels west and the low itself is embedded farther back near 55. I have centered the image below to the approximate position of the low which should help it fight off the dry air.

It is hard to know how the day will play out and there may well be some warming of the cloud tops later. The key will be forward speed. The high in the central Atlantic is quite strong and the steering flow fairly brisk all the way to Jamaica at this time so it will probably be 50/50 for it to hang on to 63W and build.



steering

Member Since: October 9, 2008 Posts: 0 Comments: 8272
Quoting ITCZmike:
Barbados this morning..wind shifted around.

All boats facing north.


That makes sense with surface low pressure to the east
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Quoting TropicalAnalystwx13:
Good morning everyone, just stopping by for a second before school. I see that Gert strengthened modestly last night, now up to 60 MPH. That being said, and another 24 hours or so to strengthen, I say there is a decent chance Gert becomes the first hurricane of the season. It is being protected by an Upper Level Anti-Cyclone, and dry air in that area is minimal. When recon flies out today they should find a strong tropical storm (65-70 MPH). Unfortunately, I won't be here when they fly out, so I'll have to read back when I get home!

Tropical Storm Gert Visible:





we got 93L back can you say ouch


Member Since: May 21, 2006 Posts: 5091 Comments: 114759
Quoting ProgressivePulse:
As we start to pick up in activity, please link the advisories and two's. I've seen many of blog page with nothing but repeated advisories and two's and many good posts lost in the fray.

Not that this email will help as I say it every year however, I'll keep trying.


Ah...Gets posted 20 times..Cant wait for school to start.
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Good morning everyone, just stopping by for a second before school. I see that Gert strengthened modestly last night, now up to 60 MPH. That being said, and another 24 hours or so to strengthen, I say there is a decent chance Gert becomes the first hurricane of the season. It is being protected by an Upper Level Anti-Cyclone, and dry air in that area is minimal. When recon flies out today they should find a strong tropical storm (65-70 MPH). Unfortunately, I won't be here when they fly out, so I'll have to read back when I get home!

Tropical Storm Gert Visible:


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Quoting SLU:
000
WTNT32 KNHC 151157
TCPAT2

BULLETIN
TROPICAL STORM GERT INTERMEDIATE ADVISORY NUMBER 6A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072011
800 AM AST MON AUG 15 2011

...GERT MOVING NORTHWARD...STORM CENTER EXPECTED TO PASS
JUST EAST OF BERMUDA LATER TODAY...


SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...31.5N 63.3W
ABOUT 100 MI...160 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...N OR 5 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BERMUDA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN
THE NEXT 12 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 AM AST...1200 UTC...THE CENTER OF TROPICAL STORM GERT WAS
LOCATED NEAR LATITUDE 31.5 NORTH...LONGITUDE 63.3 WEST. GERT IS
MOVING TOWARD THE NORTH NEAR 14 MPH...22 KM/H. A TURN TOWARD THE
NORTH-NORTHEAST AND AN INCREASE IN FORWARD SPEED ARE EXPECTED
DURING THE NEXT COUPLE OF DAYS. ON THE FORECAST TRACK...THE CENTER
OF GERT IS EXPECTED TO PASS JUST EAST OF BERMUDA LATER TODAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS EXPECTED DURING THE NEXT DAY OR SO.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110
KM...MAINLY TO THE NORTH AND EAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE RECENTLY REPORTED BY AN AIR
FORCE RESERVE RECONNAISSANCE AIRCRAFT WAS 1000 MB...29.53 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED ON BERMUDA LATER THIS
MORNING.

RAINFALL...GERT IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS
OF 1 TO 3 INCHES ON BERMUDA.

SURF...LARGE SWELLS GENERATED BY GERT ARE APPROACHING BERMUDA.
THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP
CURRENT CONDITIONS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL
WEATHER OFFICE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 AM AST.

$$
FORECASTER STEWART


they shouldn;t get too much on Bermuda if Gert stays 005 heading
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As we start to pick up in activity, please link the advisories and two's. I've seen many of blog page with nothing but repeated advisories and two's and many good posts lost in the fray.

Not that this email will help as I say it every year however, I'll keep trying.
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Quoting NICycloneChaser:
Ex-93L is back in the TWO - 10%. 92L at 0%.



ex 93L is now 93L
Member Since: May 21, 2006 Posts: 5091 Comments: 114759
1810. WxLogic
Quoting Cotillion:
Gert's pressure drops then. Wonder if it'll manage to scrape hurricane status - a 1 in 3 chance according to the NHC. It'd need to drop a few more millibars first, though.

Imagine Bermuda's a bit squally and wet.

morning to all *raises mug in salutations*


I can see Gert becoming our first minimal HURR.
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1809. SLU
...10 PERCENT... is a fair assessment from the NHC. They should wait for a low to form before sharpening the orange crayon
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Gert's pressure drops then. Wonder if it'll manage to scrape hurricane status - a 1 in 3 chance according to the NHC. It'd need to drop a few more millibars first, though.

Imagine Bermuda's a bit squally and wet.

morning to all *raises mug in salutations*
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Quoting stormwatcherCI:
Good morning. How much of a chance would you give it at this point of maintaining convection with the dry air you see in front of it ?


Hi, 93L is still a somewhat fragile system. It does not have a well established circulation and little going on at the 850mb level. Surface convergence is much improved though so it is trying to crank up.

The dry air is being pushed out of the way by the leading edge of the feature as it travels west and the low itself is embedded farther back near 55. I have centered the image below to the approximate position of the low which should help it fight off the dry air.

It is hard to know how the day will play out and there may well be some warming of the cloud tops later. The key will be forward speed. The high in the central Atlantic is quite strong and the steering flow fairly brisk all the way to Jamaica at this time so it will probably be 50/50 for it to hang on to 63W and build.



steering

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1000mb
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Quoting kmanislander:
Good morning

93L is doing what most weak waves do once they reach 55W and that is flare up in rather dramatic fashion. This is the "sweet spot" location I posted about a couple days ago.

The wave axis is just about at 55W and the window for development will last until about 63W or about 480 miles from its present location. The 850 vort is very weak but if it slows down a bit it still has time to get something going.

If nothing of note happens by 63W then there would probably not be any significant development before 75W or beyond.

Today's test for 93L will be to hold on to the best convection it has had for several days.
possible diurnal max?
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1802. asdip
Here in St Lucia, wind getting up , thunder and lightening.
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1801. SLU
000
WTNT32 KNHC 151157
TCPAT2

BULLETIN
TROPICAL STORM GERT INTERMEDIATE ADVISORY NUMBER 6A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072011
800 AM AST MON AUG 15 2011

...GERT MOVING NORTHWARD...STORM CENTER EXPECTED TO PASS
JUST EAST OF BERMUDA LATER TODAY...


SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...31.5N 63.3W
ABOUT 100 MI...160 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...N OR 5 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BERMUDA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN
THE NEXT 12 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 AM AST...1200 UTC...THE CENTER OF TROPICAL STORM GERT WAS
LOCATED NEAR LATITUDE 31.5 NORTH...LONGITUDE 63.3 WEST. GERT IS
MOVING TOWARD THE NORTH NEAR 14 MPH...22 KM/H. A TURN TOWARD THE
NORTH-NORTHEAST AND AN INCREASE IN FORWARD SPEED ARE EXPECTED
DURING THE NEXT COUPLE OF DAYS. ON THE FORECAST TRACK...THE CENTER
OF GERT IS EXPECTED TO PASS JUST EAST OF BERMUDA LATER TODAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS EXPECTED DURING THE NEXT DAY OR SO.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110
KM...MAINLY TO THE NORTH AND EAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE RECENTLY REPORTED BY AN AIR
FORCE RESERVE RECONNAISSANCE AIRCRAFT WAS 1000 MB...29.53 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED ON BERMUDA LATER THIS
MORNING.

RAINFALL...GERT IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS
OF 1 TO 3 INCHES ON BERMUDA.

SURF...LARGE SWELLS GENERATED BY GERT ARE APPROACHING BERMUDA.
THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP
CURRENT CONDITIONS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL
WEATHER OFFICE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 AM AST.

$$
FORECASTER STEWART


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Ex-93L is back in the TWO - 10%. 92L at 0%.
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Morning All.


Good call K-Man 55W and beyond for 93L. Problem now is that is has to hit land somewhere.
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000
ABNT20 KNHC 151157
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT MON AUG 15 2011

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM GERT...LOCATED ABOUT 100 MILES SOUTHEAST OF BERMUDA.

A TROPICAL WAVE LOCATED ABOUT 325 MILES EAST OF THE LESSER ANTILLES
IS PRODUCING A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS.
DEVELOPMENT OF THIS DISTURBANCE...IF ANY...SHOULD BE SLOW TO OCCUR
DURING THE NEXT COUPLE OF DAYS. HOWEVER...THIS DISTURBANCE WILL
PRODUCE BRIEF PERIODS OF LOCALLY HEAVY RAINFALL AND STRONG GUSTY
WINDS OVER PORTIONS OF THE CENTRAL AND NORTHERN LESSER ANTILLES
TODAY THROUGH TUESDAY. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...
OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WESTWARD AT 15 TO 20 MPH.

SHOWER AND THUNDERSTORM ACTIVITY HAS CONTINUED TO DIMINISH IN
ASSOCIATION WITH A BROAD AREA OF LOW PRESSURE LOCATED ABOUT 650
MILES NORTH OF THE NORTHERN LEEWARD ISLANDS. ENVIRONMENTAL
CONDITIONS ARE BECOMING LESS CONDUCIVE FOR DEVELOPMENT OF
THIS SYSTEM OVER THE NEXT COUPLE OF DAYS DUE TO PROXIMITY TO
TROPICAL STORM GERT. THIS SYSTEM HAS A LOW CHANCE...NEAR 0
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES TOWARD THE NORTH-NORTHWEST OR NORTH AT 15 TO 20 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER STEWART
Member Since: October 9, 2008 Posts: 0 Comments: 8272
93L is putting on a show this AM.
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Quoting HurricaneHunterJoe:


mojo rising


When MJO is rising... That means there is rising air in the Atlantic correct?

My observations that are recently must be sinking at least here in fl. since the thunderstorms have not been as widespread and Vigorous(lightning wise) when MJO is rising.

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Just updated:

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Quoting Tazmanian:
ex 93L has really came back too life this AM
def looking mo better
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Quoting earthlydragonfly:
Anyone got a good link to the EURO?


I asked that while ago. Everyone's link not working. :(
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1792. bappit
Quoting TomTaylor:
Right, but as you just said, these are mid-latitude cyclones. They transport heat over the mid-latitudes. Hardly over the tropics. Tropical cyclones are the best and most efficient way to remove heat from the tropics towards the poles.

To disagree with me you would have to say that is their purpose.
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1791. WxLogic
Well... just noticed 93L really got reactivated. A bit early than I expected.
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Quoting weatherh98:
mjo


mojo rising
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Quoting Tazmanian:



oh boy tthat sould get this blog going


YEP! :)
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Quoting kmanislander:
Good morning

93L is doing what most weak waves do once they reach 55W and that is flare up in rather dramatic fashion. This is the "sweet spot" location I posted about a couple days ago.

The wave axis is just about at 55W and the window for development will last until about 63W or about 480 miles from its present location. The 850 vort is very weak but if it slows down a bit it still has time to get something going.

If nothing of note happens by 63W then there would probably not be any significant development before 75W or beyond.

Today's test for 93L will be to hold on to the best convection it has had for several days.
Good morning. How much of a chance would you give it at this point of maintaining convection with the dry air you see in front of it ?
Member Since: October 9, 2008 Posts: 0 Comments: 8272
Great to see you back 93L. Hope you have a nice day
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Quoting GeoffreyWPB:
Here we go again...




oh boy tthat sould get this blog going
Member Since: May 21, 2006 Posts: 5091 Comments: 114759


With the lat/lon that the NRL has it at the center would be between the two blobs of moisture. 93L is pushing the western blob in front of it essentially protecting it from dry air.
Member Since: October 9, 2008 Posts: 0 Comments: 8272
Good morning

93L is doing what most weak waves do once they reach 55W and that is flare up in rather dramatic fashion. This is the "sweet spot" location I posted about a couple days ago.

The wave axis is just about at 55W and the window for development will last until about 63W or about 480 miles from its present location. The 850 vort is very weak but if it slows down a bit it still has time to get something going.

If nothing of note happens by 63W then there would probably not be any significant development before 75W or beyond.

Today's test for 93L will be to hold on to the best convection it has had for several days.
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Anyone got a good link to the EURO?
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Here we go again...

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1778. SLU
Quoting USAFwxguy:



Yeah that convection can collapse quickly as it approaches the dry air in the Eastern Caribbean




Although the anticyclonic flow aloft may help to ward off the impact of the dry air.


93L has developed its own envelop of moisture and its large cloudmass might help it to modify the surrounding environment.
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invest_REACTIVATE_al932011.ren
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Quoting Ribbitman:

About the same here in the Piny Woods,still no rain,100 or better everyday.Evaporation rate 1.5" a day,Toledo Bend is dropping like a rock,new record low's each day.Not a wishcaster but sure could use a 93L.


Yeah I know the lakes area is unbelievable. :( Rayburn's low too. We could use some rain that's for sure. I don't wishcast I Texascast! ;)
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93L is really geting its act togeter this AM
Member Since: May 21, 2006 Posts: 5091 Comments: 114759

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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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