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Remnant low Karen

GaWx

By GaWx,
in Weather Forecasting and Discussion

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Ed Lizard

Ed Lizard

Posted
Posted

we are also getting into the transition season. should not be a surprise that karen is experiencing sheer. 

 

Opal did pretty well in October.  1985's Kate did decently in November.

 

Being past prime Gulf season isn't helping, but 2013 has had a healthy dose of fail even in August and September.

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wxsmwhrms

wxsmwhrms

Posted
Posted

As I mentioned yesterday, the problem with the GFS has been showing a vertically coherent structure with Karen, while the EC and UK (and even NAM and GGEM) have been more accurate in showing more vertically tilted structure.  This is why they have been better in showing a track of the low level circ more toward LA.  GFS seems to be getting more in this sort of set up now.

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SN_Lover

SN_Lover

Posted
Posted

Opal did pretty well in October.  1985's Kate did decently in November.

 

Being past prime Gulf season isn't helping, but 2013 has had a healthy dose of fail even in August and September.

 Notice how cyclogenesis moves to the east as fall approaches. there are sometimes exceptions, but most of the time storms will form more east as the NH experiences increased shear and deeper troughs.  

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Srain

Srain

Posted
Posted

Steve, I agree. I think a cane is unlikely though there could be a few gust offshore to 65 or so.  Still too much shear.  Of course, none of us has much skill at forecasting intensity of tropical systems so we could be wrong.

Good to see you chiming in, Wes. One concern that I have is the flood potential from the merger of Karen and the shortwave/trough/cold front advancing E. The QPF totals suggested along with enhancement from uplifting along the Appalachian Chain are a bit more worrisome than any potential wind event that Karen may cause.

 

EXTENDED FORECAST DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

1200 PM EDT FRI OCT 04 2013

VALID 12Z MON OCT 07 2013 - 12Z FRI OCT 11 2013

...HEAVY RAIN POSSIBLE IN THE EAST...

...ANOTHER DEEP TROUGH DIGGING INTO THE WEST...

...EAST...

THE EVOLUTION OF THE GREAT LAKES CYCLONE IS KEY TO PREDICTING

WHERE AND WHEN THE ATTENDANT FRONTAL ZONE WILL ABSORB THE REMNANTS

OF TROPICAL STORM KAREN. THE 00Z OPERATIONAL ECMWF WAS A GOOD

OPTION FOR APPROXIMATING THE OFFICIAL NHC TRACK OF KAREN. ITS

SURFACE SOLUTION FOR THE GREAT LAKES CYCLONE IS ALSO

GOOD...ESPECIALLY EARLY IN THE PERIOD. THE ECMWF HAS CONSISTENTLY

BEEN ON THE SLOW SIDE...KEEPING THE UPPER LEVEL CYCLONE CLOSED AT

LOWER LATITUDES FOR A LONGER TIME. WE HAVE TENDED TO FAVOR AT

LEAST A LITTLE MORE PHASING OF THIS CYCLONE WITH ANOTHER SHORTWAVE

BRUSHING ACROSS SOUTHERN CANADA...SO WE CONTINUE TO BLEND THE

ECMWF SOLUTION TOWARD THE ECMWF ENSEMBLE MEAN AND NORTH AMERICAN

ENSEMBLE MEAN. THE RESULT IS MERGER OF THE TROPICAL REMNANTS INTO

THE FRONTAL ZONE SOON AFTER 12Z ON DAY 3... MONDAY...SOMWHERE NEAR

WESTERN SOUTH CAROLINA. THE GFS HAS BEEN CONSISTENTLY TOO FAR EAST

AND TOO INTENSE WITH KAREN...AND TOO FAST UP NORTH...SO WE

DISCARDED IT.

FROM DAY 3 INTO 4...SUFFICIENT UPPER LEVEL TROUGHING SHOULD EXTEND

TO THE LATITUDE OF KAREN...TO YIELD A BROAD FRONTAL WAVE LADEN

WITH TROPICAL MOISTURE. THIS SHOULD YIELD GENEROUS RAIN TOTALS AND

A RISK OF ORGANIZED FLASH FLOODING...FROM THE GEORGIA PIEDMONT AND

SOUTHERN APPALACHIANS NORTHEASTWARD THROUGH THE CENTRAL CAROLINAS

AND INTO VIRGINIA.

PLEASE REFER TO THE NATIONAL HURRICANE CENTER (NHC) FOR THE LATEST

INFORMATION AND FORECASTS CONCERNING KAREN.

...WEST...

ACROSS THE PACIFIC AND WESTERN NORTH AMERICA WE HAVE A SLOWLY

PROGRESSING WAVE TRAIN OF MEDIUM TO LONG WAVELENGTH. THE MODELS

HAVE HAD MUCH DIFFICULTY SHOWING ANY RUN TO RUN CONSISTENCY AT

SMALLER SCALES...PERHAPS OWING TO FORCING BY SOME RECURVING

TROPICAL SYSTEMS IN THE WESTERN PACIFIC...AS WELL AS THE TYPICALLY

DIFFICULT TRANSITION SEASON INTO AUTUMN. THIS BEING SAID...MODEL

AGREEMENT IS IMPROVING...WITH SOLUTIONS CONVERGING TOWARD A CLOSED

LOW CENTER FORMING AT THE BASE OF THE NEXT TROUGH IN THE SOUTHWEST

U.S. THERE ARE FEWER RUNS CLOSING THE LOW FARTHER WEST OFF

CALIFORNIA AND ALSO FEWER RUNS EJECTING MORE QUICKLY INTO THE

PLAINS. COMPARED TO THE PREVIOUS PACKAGE WE SLOWED THE PROGRESSION

JUST A HAIR...BUT SHOW ESSENTIALLY THE SAME CONCEPTS. THE TROUGH

DOES NOT LOOK PARTICULARLY COLD OR ANOMALOUS...BUT SHOULD INITIATE

PRECIPIATION IN THE INTERMOUNTAIN WEST AND ROCKIES...WITH A MILD

STRETCH OF WEATHER DOWNSTREAM.

BURKE

 

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PSUBlizzicane2007

PSUBlizzicane2007

Posted
Posted

Tropical Storm Karen would be a source of drought relief for many areas. A minimal tropical storm hitting this area would be beneficial overall. 

 

http://droughtmonitor.unl.edu/data/pngs/20131001/20131001_usdm_home.png

 

The only thing is that Karen is pretty much going to avoid all of the areas along the Gulf Coast that are in drought conditions.

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GaWx

GaWx

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  • Author
Posted

Considering the ECMWF didn't develop Karen at all, it didn't preform particularly well either (although it has done better after genesis).

I agree with Phil. There's no way IMO that the Euro has outperformed the GFS with Karen to this point considering that the Euro didn't even have a TD til the last minute! It really didn't have a Karen at all. So, how could it have done better with Karen without it having a Karen? Also, the gfs really didn't have strengtening resume until it started moving NE tomorrow. Finally, the gfs had it making it to about as far west as it is now, near 90 west. If there is almost no more westerly component of motion from here on out, that, too, would be much closer to the gfs. The Euro was further west.

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bluewave

bluewave

Posted
Posted

I agree with Phil. There's no way IMO that the Euro has outperformed the GFS with Karen to this point considering that the Euro didn't even have a TD til the last minute! It really didn't have a Karen at all. So, how could it have done better with Karen without it having a Karen? Also, the gfs really didn't have strengtening resume until it started moving NE tomorrow. Finally, the gfs had it making it to about as far west as it is now, near 90 west. If there is almost no more westerly component of motion from here on out, that, too, would be much closer to the gfs. The Euro was further west.

 

The Euro had a TD or TS signal from the 12z Tuesday run heading into LA further west of the GFS. I would score it higher than the 

GFS since it didn't over do the intensity and always had a struggling sheared system. 

 

 

12z Tuesday forecast

 

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DopplerWx

DopplerWx

Posted
Posted

The Euro had a TD or TS signal from the 12z Tuesday run heading into LA further west of the GFS. I would score it higher than the 

GFS since it didn't over do the intensity and always had a struggling sheared system.

 

 

12z Tuesday forecast

 

attachicon.gifNorth32America_msl_60.gif

i disagree.  the gfs has been consistent with showing a sheared system with pressures >1000mb for the past 2-3 days to this point.  karen looked good crossing the yucatan and everyone thought she was getting ready to blow up when the gfs showed it being weak and sheared with no intensification until turning ne after brushing the coast of la. is a ts landfall still possible? yes.  but it sure won't be pretty and winds will be displaced to the e of the center.  shear was going to be an issue and the gfs showed this pretty well.  

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NJwinter23

NJwinter23

Posted
Posted

i disagree.  the gfs has been consistent with showing a sheared system with pressures >1000mb for the past 2-3 days to this point.  karen looked good crossing the yucatan and everyone thought she was getting ready to blow up when the gfs showed it being weak and sheared with no intensification until turning ne after brushing the coast of la. is a ts landfall still possible? yes.  but it sure won't be pretty and winds will be displaced to the e of the center.  shear was going to be an issue and the gfs showed this pretty well.  

 

The hi-res images of the gfs runs actually showed karen consistently dropping into the 980s, but i believe it was doing it before land fall... all in all I think both had some pros and cons on how they handled it. The gfs probably recognized/formed the storm better yesterday, but was too east and likely strenghtened it too much for today into tmrw (remains to be seen)..the euro had its problems but the idea of a further west/weak surface low disjointed from mid level low idea seems to be working well.

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Ed Lizard

Ed Lizard

Posted
Posted

LLC looks just healthy enough I think it is unlikely a new surface low can form downshear under the convection.

 

Besides being barely West of PW below 2 inches per SPC based RAP analysis, it is also rotating in sub 72ºF dewpopints from the South.

 

Extra bummer about the approaching Texas cold front, it might have been sort of cool to go outside and actually watch a naked swirl of low clouds pass overhead.

 

 

Edit to Add

 

New page, new day/night naked swirl hotlink satellite loop.

 

ir2-animated.gif

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wxsmwhrms

wxsmwhrms

Posted
Posted

The hi-res images of the gfs runs actually showed karen consistently dropping into the 980s, but i believe it was doing it before land fall... all in all I think both had some pros and cons on how they handled it. The gfs probably recognized/formed the storm better yesterday, but was too east and likely strenghtened it too much for today into tmrw (remains to be seen)..the euro had its problems but the idea of a further west/weak surface low disjointed from mid level low idea seems to be working well.

Completely agree with this.  I certainly would not say the Euro performed "well" with Karen - I don't think any of the models have IMO.  However, I think the Euro idea of a highly sheared system with a surface feature that would track farther W and eventually approach the LA coast has been superior to the GFS idea of a more vertically coherent system tracking farther east and deepening with time.

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Superstorm93

Superstorm93

Posted
Posted

That's pretty awesome:

 

 

 

THE 12Z HWRF RUN SHOWED CONSIDERABLY LESS INTENSIFICATION WITH KAREN
COMPARED TO PREVIOUS RUNS AFTER ASSIMILATING DATA FROM THE FROM THE
NOAA P-3 TAIL DOPPLER RADAR. THIS MARKS THE FIRST TIME DOPPLER
RADAR DATA HAVE BEEN ASSIMILATIED INTO AN OPERATIONAL HURRICANE
MODEL IN REAL TIME.
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phil882

phil882

Posted
Posted

Both the GFS and the ECMWF showed a sheared system. The difference was that the GFS had the convection too robust in which the diabatic irrotational flow overcame the shear. I had a conversation with my advisor and his suggestion is that the cumulus scheme used in the GFS doesn't really handle slantwise convection properly (which is what this convection is doing in a sheared environment) and simulated the convection to be more upright. Thus the latent heat over Karen was overdone near the center and had an easier time modifying the upper level wind profile. That's obviously not happening right now. The ECMWF was too weak with initial genesis, but it had the right idea once the system moved into the GoM.

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