The tropics are quiet

By: Dr. Jeff Masters , 1:11 PM GMT on September 06, 2009

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Considering that this is historically the peak week of the Atlantic hurricane season, the tropics are quiet. There is an area of disturbed weather in the middle Atlantic (95L) that NHC has been mentioning in their Tropical Weather Outlook the past day, but this disturbance is entering a region of high wind shear and is not a threat to develop.

A strong tropical wave with plenty of rotation is emerging off the coast of Africa this morning, and this wave is a good candidate to show some development this week as it heads west-northwest over the Atlantic. The wave is under about 15 knots of wind shear, and is being developed by several models, including the GFS and ECMWF. However, the models show that this new wave will be pulled northwestward by a strong trough of low pressure this week, and it appears unlikely that the wave will make the long crossing of the Atlantic necessary to threaten any land areas. Another wave with plenty of spin will emerge from the coast of Africa two days from now, and will also have a chance to develop.


Figure 1. Morning satellite image of 95L and a new tropical wave with potential to develop, emerging from the coast of Africa.

An area of concentrated thunderstorms has developed off the North Carolina coast in association with the remains of an old cold front. This system is under about 20 - 30 knots of shear, and is not tropical. However, it will bring heavy rain just offshore of North Carolina's Outer Banks today as it slides north-northeastward along the coast.

I'll have an update Monday.

Jeff Masters

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Quoting futuremet:


The low the NOGAPS is showing is the surface in the East GOM that might develop. Look near eastern Texas, and you will signs of cyclogenesis.

A tiny patch of vorticiy is already showing up just north Cuba......wait a minute....this is the same thing that happened with Claudette.



I thought hey were 2 different things as well. The NAM was showing something farther east as well.
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1693. IKE
Quoting futuremet:


The low the NOGAPS is showing is the surface in the East GOM that might develop. Look near eastern Texas, and you will signs of cyclogenesis.

A tiny patch of vorticiy is already showing up just north Cuba......this the same thing that happened with Claudette.



I hadn't looked at the vorticity map. Thanks...I see it now.
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Quoting futuremet:


The 06z GFS has it making landfall earlier in this run. That is because it forecast the longwave trough to amplify less, thus, causing this sysem to move NE. If it amplifies farther south, the developing low will move ENE. It all depends on how much the trough will amplify.


Morning everyone. The GFS and ECMWF have this in the same area at 168 hrs. The CMC Nola at 144. Storm said in his update last night anywhere from TX/LA east. So who knows?
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Quoting futuremet:


Yes...a moderate chance.
When will the window of oppurtunity be?
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Quoting stormsurge39:
Is there a high chance of developement in GOM,if the wind sheer lets up in time?


Yes...a moderate chance.
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Quoting IKE:


Models don't seem to have a good handle on it yet...too far in advance. 00Z NOGAPS shows....a low making landfall in the Florida panhandle. GFS is much further west.

Models should come into better agreement as it approaches.



The low the NOGAPS is showing is the surface in the East GOM that might develop. Look near eastern Texas, and you will signs of cyclogenesis.

A tiny patch of vorticiy is already showing up just north Cuba......wait a minute....this is the same thing that happened with Claudette.

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Is there a high chance of developement in GOM,if the wind sheer lets up in time?
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1686. IKE
Quoting futuremet:


The 06z GFS has it making landfall earlier in this run. That is because it forecast the longwave trough to amplify less, thus, causing this sysem to move NE. If it amplifies farther south, the developing low will move ENE. It all depends on how much the trough will amplify.


Models don't seem to have a good handle on it yet...too far in advance. 00Z NOGAPS shows....a low making landfall in the Florida panhandle. GFS is much further west.

Models should come into better agreement as it approaches.

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Quoting IKE:
Oh....happy Labor Day everyone.

Like you said previously futuremet, this may be the last shot for the northern gulf-coast.


Yup, the GOM probably has 2 more chances to get something going: the developing surface trough, and that will form in the western GOM.
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Quoting IKE:


I see the 6Z GFS takes a low into Texas in about a week, then heads it NE as the trough then heads toward the gulf-coast.


The 06z GFS has it making landfall earlier in this run. That is because it forecast the longwave trough to amplify less, thus, causing this sysem to move NE. If it amplifies farther south, the developing low will move ENE. It all depends on how much the trough will amplify.
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1683. IKE
Oh....happy Labor Day everyone.

Like you said previously futuremet, this may be the last shot for the northern gulf-coast.
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1682. IKE
Quoting futuremet:
IKE, if something form in the GOM within 84hrs, it would probably be a minute mesoscale feature like Claudette. The models are showing an extending surface trough, but are inconsistent on where the main low will actually develop. Depending on where it forms, we might a tropical cyclone....or not.


I see the 6Z GFS takes a low into Texas in about a week, then heads it NE as the trough then heads toward the gulf-coast.
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First possible extratropical nasty of the year (They always seem to start earlier in El Nino seasons, too.)? Not seen a low this strong in a while.





Tightens up to 972 as it crosses north of Scotland from the latest synoptic charts, up to 80mph winds for them according to the UKMO.

Least it's shooting for the Iceland-Scotland Gap (What an original name) like all good and honest gales do.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
IKE, if something form in the GOM within 84hrs, it would probably be a minute mesoscale feature like Claudette. The models are showing an extending surface trough, but are inconsistent on where the main low will actually develop. Depending on where it forms, we might a tropical cyclone....or not.
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Quoting IKE:


Probably north...latest GFS doesn't show it. NOGAPS continues to show a vorticity heading into the big-bend of Florida.


It is the hybrid low that is coming from SE Texas we should look outflow. The low is caused by increased convection in SE Texas due to an upper trough. As the low ejects off the Texan coast, the favorable outflow in the GOM might help it develop further.
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1678. IKE
Quoting PensacolaDoug:
I see the low siiting in th mid GOM at the end if the NAM run. If (and thats a big if) it developes, where does it go?


Probably north...latest GFS doesn't show it. NOGAPS continues to show a vorticity heading into the big-bend of Florida.
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I see the low siiting in th mid GOM at the end if the NAM run. If (and thats a big if) it developes, where does it go?
Member Since: July 25, 2006 Posts: 0 Comments: 553
1676. IKE
Long-term from Birmingham,AL....

"WITH SOME AGREEMENT ACROSS THE BOARD...MODELS ARE SHOWING A CHANGE
IN THE PATTERN BY THE END OF THE WEEK AS A FAIRLY INTENSE UPPER
LEVEL CLOSED LOW COMES BARRELING OUT OF CANADA. IF THIS DOES
VERIFY...IT COULD MEAN SOME WICKED WEATHER FOR FOLKS ACROSS THE
EASTERN HALF OF THE CONTINENTAL U.S. FOR NOW...IT LOOKS LIKE WE
COULD SEE A FRONTAL PASSAGE ASSOCIATED WITH THIS FEATURE BY THE
BEGINNING OF NEXT WEEK...BUT WE WILL ALSO HAVE TO WATCH WHAT LOOKS
TO BE A VERY FALL-LIKE WARM FRONT THAT MODELS HAVE PROGRESSING OUT
OF THE GULF OF MEXICO. LIKE WHAT HAPPENS MANY TIMES IN THE
FALL...WE COULD GET ENOUGH SHOWER ACTIVITY AHEAD OF THE FRONT TO
ELIMINATE ANY TALK OF SIGNIFICANT WEATHER ASSOCIATED WITH THE ACTUAL
FRONT.

TEMPERATURES SHOULD MODERATE AGAIN FOR NEXT WEEKEND...ESPECIALLY
WITH THE POSSIBILITY OF SOME ORGANIZED WEATHER ACTIVITY AND PLENTY
OF MOISTURE IN PLACE. CLOUDS SHOULD BE APLENTY...AND TEMPERATURES
ARE LIKELY TO RUN 3 TO 5 DEGREES BELOW NORMAL."
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1675. IKE
6Z NAM...
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1674. IKE
Long-term discussion from NO,LA.....

"LONG TERM...

LOOKING AT THE EXTENDED FORECAST...THE GFS AND ECMWF ARE IN FAIRLY
GOOD AGREEMENT. THURSDAY AND FRIDAY...THE PATTERN WILL BE LITTLE
CHANGED FROM THAT NOTED ON WEDNESDAY. AS A RESULT...EXPECT
DIURNALLY FORCED CONVECTION EACH DAY. OVERALL COVERAGE WILL REMAIN
IN THE LOW END CHANCE CATEGORY. HOWEVER...THE PATTERN IS EXPECTED
TO CHANGE MARKEDLY FOR THE WEEKEND. BOTH MODELS SHOW A VERY STRONG
UPPER LEVEL LOW DIGGING SOUTHWARD INTO THE CENTRAL PLAINS STATES.
AS THIS LOW DEEPENS...ANOTHER PLUME OF DEEP TROPICAL MOISTURE WILL
OVERSPREAD THE CENTRAL GULF COAST. A BROAD AREA OF ASCENT WILL
TAKE HOLD OF THE LOWER MISSISSIPPI VALLEY OVER THE WEEKEND. THIS
WILL BE DRIVEN BY A 70-80 KNOT JET STREAK DEVELOPING OVER THE GULF
COAST AND STRONG POSITIVE VORTICITY ADVECTION IN ADVANCE OF THE
DIGGING TROUGH AXIS OVERSPREADING THE AREA. WITH STRONG OMEGA
VALUES IN PLACE ALOFT AND AMPLE MOISTURE TO WORK WITH...HAVE WENT
WITH HIGH END CHANCE POPS FOR SATURDAY AND SUNDAY."
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HPC Preliminary Extended Forecast Discussion

WITHIN THE GULF OF MEXICO...A SIGNIFICANT NUMBER OF 12Z CANADIAN/12Z ECMWF ENSEMBLE MEMBERS BRING A LOW THROUGH THE WESTERN GULF INTO LOUISIANA THIS WEEKEND INTO EARLY NEXT WEEK. CONSIDERING THE EXPECTED FLOW PATTERN WITH A SIGNIFICANT TROUGH ACROSS THE MIDWEST AND WEAKER TROUGHING ACROSS TEXAS/NORTHEAST MEXICO...CYCLOGENESIS IN THE WESTERN GULF OF MEXICO IS POSSIBLE...SO ADDED THE CYCLONE TO THE PROGS FROM THE PREFERRED BLEND.


HPC Preliminary Graphics
Member Since: September 23, 2005 Posts: 14 Comments: 10902
Quoting 92Andrew:
What's the different between "ensemble models" and "computer models", specifically, with regards to their forecast tracks? For example, the forecast track for the new Invest off the African coast differs greatly between the ensemble models and computer models. Any information on this would be great. Thanks.


The ensemble models are the computer models run with a different set of initial conditions at a lower horizontal resolution. That graph shows each ensemble member from the GFS model. Each ensemble member has a different set of initial conditions, designed to represent the uncertainty in the initial conditions.

This link gives a good background ENSEMBLE FORECASTING AT NCEP but is somewhat old. The resolution and length of the run has changed since then.
Member Since: September 23, 2005 Posts: 14 Comments: 10902
1671. JLPR
Quickscat caught what appears to be half of a very defined LLC
I wish it would have caught all of it :(





well then... later
gonna check how 96L is doing later today
dont know if I should say goodnight or good morning lol xD
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...FIFTEENTH TROPICAL CYCLONE OF THE 2009 EASTERN NORTH PACIFIC SEASON FORMS...

000
WTPZ45 KNHC 070832
TCDEP5
TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152009
200 AM PDT MON SEP 07 2009

THERE HAS NOT BEEN MUCH INCREASE IN THE OVERALL COVERAGE OR
INTENSITY OF DEEP CONVECTION ASSOCIATED WITH THE LOW PRESSURE
CENTER WELL TO THE WEST-SOUTHWEST OF CABO SAN LUCAS.
HOWEVER...OVER THE PAST FEW HOURS WE HAVE OBSERVED A WELL-DEFINED
CURVED BAND OF CONVECTION THAT HAS WRAPPED FAIRLY CLOSE TO THE
CENTER. DVORAK CURRENT INTENSITY ESTIMATES ARE 25 KT AND 35 KT
FROM TAFB MIAMI AND SAB WASHINGTON RESPECTIVELY. A QUIKSCAT PASS
FROM 0230 UTC SHOWED A WELL-DEFINED SURFACE CIRCULATION WITH
HIGHEST NON-RAIN-FLAGGED WINDS OF 25 TO 30 KT. BASED ON THE
INCREASED ORGANIZATION OF THE SYSTEM...IT IS BEING UPGRADED TO A
30-KT TROPICAL DEPRESSION AT THIS TIME. OVER THE NEXT COUPLE OF
DAYS THE CYCLONE WILL BE MOVING THROUGH AN ENVIRONMENT OF
MARGINALLY WARM SSTS AND WEAK TO MODERATE SHEAR. MOREOVER THE
SHIPS MODEL OUTPUT AND THE PRESENCE OF A NEIGHBORING STRATOCUMULUS
CLOUD DECK INDICATES THAT THE AIR MASS IS NOT PARTICULARLY
UNSTABLE. GIVEN THESE FACTORS...ONLY MODEST STRENGTHENING IS
ANTICIPATED... AND THE OFFICIAL INTENSITY FORECAST IS VERY SIMILAR
TO THE CONSENSUS OF THE OBJECTIVE GUIDANCE. IN THE LATTER HALF OF
THE FORECAST PERIOD...INCREASING SOUTH-SOUTHWESTERLY SHEAR AND
COOLER WATERS SHOULD WEAKEN THE CYCLONE...PERHAPS AT A FASTER RATE
THAN SHOWN HERE.

INITIAL MOTION IS A RATHER SLOW 285/7. A WEAKENING MID-LEVEL RIDGE
TO THE NORTH OF THE CYCLONE WILL PROBABLY LEAD TO A LITTLE MORE
SLOWING OF THE FORWARD SPEED DURING THE NEXT 24 TO 48 HOURS.
THEREAFTER...A MID-LEVEL TROUGH NEAR 130W-140W LONGITUDE IS
EXPECTED TO CAUSE THE SYSTEM TO TURN NORTHWESTWARD AND THEN
NORTH-NORTHWESTWARD. THE OFFICIAL FORECAST TRACK IS ABOUT IN THE
MIDDLE OF THE OBJECTIVE TRACK MODEL ENVELOPE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 07/0900Z 15.5N 125.6W 30 KT
12HR VT 07/1800Z 15.8N 126.7W 35 KT
24HR VT 08/0600Z 16.2N 128.0W 40 KT
36HR VT 08/1800Z 16.5N 129.0W 45 KT
48HR VT 09/0600Z 16.9N 129.8W 45 KT
72HR VT 10/0600Z 18.5N 131.5W 45 KT
96HR VT 11/0600Z 21.0N 133.0W 35 KT
120HR VT 12/0600Z 23.5N 134.5W 25 KT

$$
FORECASTER PASCH
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Quoting 92Andrew:
What's the different between "ensemble models" and "computer models", specifically, with regards to their forecast tracks? For example, the forecast track for the new Invest off the African coast differs greatly between the ensemble models and computer models. Any information on this would be great. Thanks.


I wish I knew how to answer this question. But I did find this that explains the ensemble models. Hope it helps. :)

Link
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1668. JLPR
we lost our meteor
apparently it crashed somewhere in the Atlantic lol xD
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Ick! Lol.
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What's the different between "ensemble models" and "computer models", specifically, with regards to their forecast tracks? For example, the forecast track for the new Invest off the African coast differs greatly between the ensemble models and computer models. Any information on this would be great. Thanks.
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Quoting btwntx08:

am talking about the potential low in the gom not the low off sc
I apologize,I corrected the original post..lol I clicked on the wrong comment.. My bad
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Quoting TampaSpin:


Thanks....everyone gets lucky sometimes........LOL


You say that as if you lack sufficient ability to make accurate forecasts.

I think that most of the time, you are pretty good, Tampa. Don't degrade yourself.
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Actually the gulf stream is further east than what the low center is.. by quite a bit actually. this puppy is centered over shelf(shallow) waters.
Quoting TampaSpin:
One other thing of note......IT is over the Gulf Stream also.....things can happen very fast there.
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Quoting btwntx08:

thats ok btw we need to waych that potential low lets see what will happen with it


Yes I agree. Looking at the models and from Storms update looks like it could give us headaches From Brownsville to Fl. With that and all of the Atlantic possibilities and what's there already looks like DR.M might need a new blog name. Tropics aren't quiet. Lol.
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Quoting HurricaneKyle:


Hey after how Tampa nailed Claudette when we all thought he was crazy I'll take his word for it.


Thanks....everyone gets lucky sometimes........LOL
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One other thing of note......IT is over the Gulf Stream also.....things can happen very fast there.
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Oh ok. Thanks CJS. Didn't know where it was headed. :)

Ok. BT looked like a close call. Noticed it looked more towards CC but then hooked back south to you. And they don't need much room. Now there are 2 sayings...Remember the Alamo. And in this case Remember Humberto. Lol.

Sorry. My quote buttons went away.
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Quoting BurnedAfterPosting:
1015mb isnt low at all TS


Hey after how Tampa nailed Claudette when we all thought he was crazy I'll take his word for it.
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Quoting winter123:
SC low has heavy se shear but otherwise is tropical.
lol.. the center is situated just east of Cape Fear, (NC)....lol its' too far north to be considered a SC low now... lol
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Quoting BurnedAfterPosting:
1015mb isnt low at all TS


I DO UNDERSTAND that.....it is a 5mb drop in 24hrs........i understand that a 1010 is more like a tropical system....but, it has dropped 5mb in 24hrs......now down to 1014.7
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SC low has heavy se shear but otherwise is tropical.
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Quoting homelesswanderer:


That's what I was wondering, if anyone up there was being warned about it whatever it may be. It looks nasty. I'm not sure about the SSTS up there. Is that why they think it won't be tropical? As opposed to the gulf lows that spin up off of fronts.
oh... the waters are plenty warm off NC's coast.. It has more to do with the enviroment in the upper levels.. This system is likely gaining support from barclonic forcing... I think it is still possible to have a tropical depression; but from what I read in the NWS forecast discussion earlier, they said that it looks to move onshore sometime today.. so even if it does try to go warm core, it wont have much time to develop.
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yea its not tropical that low, at least not at this point; still attached to the front too
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Quoting cjswilmingtoneye:
Low off my coast is interesting... but prlly not tropical or subtropical.. there's a warm front in our area also.. The winds are getting gusty out tho, and my local NWS has handled rain with a short term... They say we could have some heavy rain today... from this low.. very impressive to look @ on radar though, even if it isn't anything.


That's what I was wondering, if anyone up there was being warned about it whatever it may be. It looks nasty. I'm not sure about the SSTS up there. Is that why they think it won't be tropical? As opposed to the gulf lows that spin up off of fronts.
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1015mb isnt low at all TS
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Wow! Wet, blowing & dropping pressure here on Pleasure Island. No matter what the weather in the am - gotta pick them maters!
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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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