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JAN 20th-22nd potential..


NaoPos

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EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

201 PM EST MON JAN 17 2011

VALID 12Z THU JAN 20 2011 - 12Z MON JAN 24 2011

EXPECT A LARGE SCALE MEAN TROF TO PERSIST OVER THE ERN HALF OF

CANADA INTO THE ERN HALF TO 2/3 OF THE CONUS FOR MOST OF THE

PERIOD. THERE ARE INDICATIONS THAT THE RIDGE OVER THE ERN PAC

WILL TRY TO BUILD INTO THE NWRN CONUS/WRN CANADA BY EARLY NEXT

WEEK. DIFFS STILL EXIST WITH DETAILS AMONG LATEST MODEL/ENSEMBLE

SOLNS AND CONSECUTIVE RUNS OF INDIVIDUAL MODELS BUT AS A WHOLE

AGREEMENT APPEARS TO HAVE IMPROVED COMPARED TO RECENT DAYS.

DAYS 3-5 THU-SAT MAINTAIN A SOLN SIMILAR TO THE 00Z ECMWF. AS OF

EARLY DAY 3 THU THERE ARE TIMING DIFFS WITH THE COLD FRONT SURGING

THRU THE SRN PLAINS WITH THE 00Z/06Z GFS SLOWER THAN ECMWF-BASED

GUIDANCE. NEITHER SCENARIO IS AN OUTLIER COMPARED TO THE FULL

SOLN SPREAD. GIVEN THAT SUCH SURGES CAN SOMETIMES BE FCST A

LITTLE TOO SLOW... THE FASTER PORTION OF THE ENVELOPE SEEMS

REASONABLE. BY DAY 4 FRI THERE IS A MODERATE AMOUNT OF SPREAD

REGARDING POSSIBLE SFC DEVELOPMENT NEAR THE EAST COAST. THE 00Z

CANADIAN IS A DEEP/WWD EXTREME COMPARED TO OTHER MODEL/ENSEMBLE

SOLNS AND THE 06Z GFS IS RATHER FAR WWD AS WELL. THE 00Z GEFS

MEAN IS A SLOWER AND SLIGHTLY WEAKER VERSION OF THE 00Z ECMWF. ON

THE OTHER HAND THE UKMET AND CANADIAN/ECMWF ENSEMBLE MEANS SHOW

LESS DEVELOPMENT THAN THE 00Z ECMWF... LEAVING THE 00Z ECMWF AS A

GOOD INTERMEDIATE SOLN AT THIS TIME. BY DAY 5 SAT THE MAIN

FEATURE OF NOTE IS A WAVE REACHING THE PLAINS OR MS VALLEY. A

FASTER TREND OF THE 06Z GFS VERSUS THE 00Z GFS/GEFS MEAN ADD

SUPPORT TO THE 00Z ECMWF SCENARIO BUT THERE REMAINS ENOUGH

TIMING/DETAIL SPREAD TO KEEP CONFIDENCE MEDIUM TO LOW. FARTHER

WWD THE 00Z ECMWF IS ONE OF THE STRONGER SOLNS WITH A SHRTWV

REACHING THE NWRN CONUS BY EARLY SAT. THIS FEATURE IS FARTHER NWD

IN THE 00Z CMC AND HINTED AT IN WEAKER FORM BY ECMWF ENSEMBLES AND

THE UKMET. WILL AWAIT 12Z GUIDANCE FOR ANY CONFIDENT ADJUSTMENTS

TO THE ECMWF HANDLING OF THIS FEATURE IN LIGHT OF ECMWF PREFERENCE

ELSEWHERE.

DAYS 6-7 SUN-MON INCORPORATE 50-60 PCT OF THE 00Z ECMWF ENSEMBLE

MEAN WITH THE 00Z ECMWF AS CONFIDENCE DECREASES IN THE SPECIFICS

OF THE OPERATIONAL RUN. THE 00Z ECMWF IS WITHIN THE FULL SOLN

SPREAD OVER THE WEST/PLAINS BUT CURRENT MODEL/ENSEMBLE DIFFS AND

ECMWF RUN TO RUN CONTINUITY CHANGES REQUIRE A BLENDED APPROACH TO

ACCOUNT FOR UNCERTAINTY. MEANWHILE ENSEMBLE SUPPORT IS LACKING

FOR THE 00Z ECMWF IDEA OF A WELL DEFINED SFC LOW BEING LOCATED OFF

THE NEW ENGLAND COAST AS OF EARLY DAY 7 MON... AS GUIDANCE

CONSENSUS SHOWS BROADER FLOW ALOFT THAN FCST BY THE 00Z ECMWF.

THE PREFERRED BLEND STILL YIELDS A WEAK WAVE BUT IS MUCH CLOSER TO

THE MIDDLE OF THE FULL ARRAY OF GUIDANCE.

12Z UPDATE... AS OF EARLY DAY 3 THU THE 12Z ECMWF HOLDS BACK THE

SRN PLAINS COLD FRONT SOMEWHAT... BRINGING IT CLOSER TO OTHER

NON-ECMWF GUIDANCE. BY FRI THE ECMWF SHOWS A SLIGHTLY WWD TREND

WITH THE TRACK OF LOW PRESSURE TRACKING OFF THE NEW ENGLAND COAST.

THE 12Z CMC CONTINUES ITS EXTREME TRAITS FROM ITS 00Z RUN... THE

GFS IS A SLIGHTLY SLOWER VERSION OF THE ECMWF... WHILE THE GEFS

MEAN IS ON THE SLOW EDGE OF GUIDANCE. ENOUGH SPREAD EXISTS TO

PRECLUDE DRAMATIC CHANGES ASIDE FROM ADJUSTING THE INITIALLY

PREFERRED 00Z ECMWF SOMEWHAT TOWARD THE 12Z VERSION. BEHIND THIS

SYSTEM 12Z GUIDANCE OFFERS NO COMPELLING REASON TO ALTER THE PRIOR

FCST ISSUANCE. THE 12Z ECMWF HAS FAVORABLY TRENDED WEAKER WITH

ANY POTENTIAL DAY 7 MON SYSTEM OFF THE NEW ENG COAST BUT HAS

TRENDED WWD WITH A LEADING SAT-SUN WRN ATLC SYSTEM WHICH REMAINING

GUIDANCE KEEPS FARTHER OFFSHORE.

DAYTIME TEMPS OVER THE CNTRL/ERN STATES SHOULD AVERAGE BELOW

NORMAL WITH SOME DAY TO DAY VARIABILITY. SOME LOCATIONS OVER THE

PLAINS/MS VALLEY MAY SEE ONE OR MORE DAYS WITH HIGH TEMPS 10-20 F

BELOW NORMAL. PORTIONS OF THE GREAT BASIN SHOULD BE AT OR BELOW

NORMAL WHILE AREAS CLOSER TO THE WEST COAST SHOULD BE NEAR OR

SLIGHTLY ABOVE NORMAL. DURING THU-FRI EXPECT A SHIELD OF MSTR TO

BRING LGT-MDT SNOW N AND RAIN S ACROSS THE ERN HALF OF THE CONUS.

THERE IS UNCERTAINTY OVER THE TRACK/STRENGTH OF LOW PRESSURE THAT

MAY DEVELOP NEAR NEW ENGLAND AROUND FRI... SO CONFIDENCE IS MODEST

REGARDING EXACT SENSIBLE WEATHER IMPACT OVER THAT REGION. BEHIND

THIS SYSTEM THE NRN PLAINS TO GRTLKS MAY SEE ONE OR MORE PERIODS

OF SNOW. MEANWHILE SOME MSTR SHOULD BRIEFLY RETURN TO THE

NORTHWEST LATE WEEK-WEEKEND BEFORE A DRYING TREND SUN-MON. ALSO A

MODEST AREA OF SNOW MAY SLIDE SEWD ACROSS THE ROCKIES/GREAT BASIN

DURING THE WEEKEND.

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This storm has powderkeg potential. The SREF height-fields are amazing--and almost all feature a full phase over the plains with the GOM coming into play. The SREF height field wiped the floor clean with the global ops for the last storm in this range. CMC is not out to lunch here--although this may not be what some want since it wouldn't all be snow.

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This storm has powderkeg potential. The SREF height-fields are amazing--and almost all feature a full phase over the plains with the GOM coming into play. The SREF height field wiped the floor clean with the global ops for the last storm in this range. CMC is not out to lunch here.

Coming from you, I have goosebumps :thumbsup:

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This storm has powderkeg potential. The SREF height-fields are amazing--and almost all feature a full phase over the plains with the GOM coming into play. The SREF height field wiped the floor clean with the global ops for the last storm in this range. CMC is not out to lunch here--although this may not be what some want since it wouldn't all be snow.

Thank you for this. It brings some sanity back into the thread ;) I am looking forward to following your thoughts thru the days coming!

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This storm has powderkeg potential. The SREF height-fields are amazing--and almost all feature a full phase over the plains with the GOM coming into play. The SREF height field wiped the floor clean with the global ops for the last storm in this range. CMC is not out to lunch here--although this may not be what some want since it wouldn't all be snow.

I assume U are referring to the weekend Storm storm and not beyond as I saw there was some potential into next week as well..

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This storm has powderkeg potential. The SREF height-fields are amazing--and almost all feature a full phase over the plains with the GOM coming into play. The SREF height field wiped the floor clean with the global ops for the last storm in this range. CMC is not out to lunch here--although this may not be what some want since it wouldn't all be snow.

Why do you think the GEM is showing a bomb while the GFS and particularly the EC do not?

The last time I asked you a question the answer was stellar so I expect another 5-star reply ;)

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Why do you think the GEM is showing a bomb while the GFS and particularly the EC do not?

The last time I asked you a question the answer was stellar so I expect another 5-star reply ;)

GFS 12Z op solution really isn't a huge deal ATM. A comparison of the 0-6-12Z operational runs is far far more revealing, and each run trends more amplified with the diving trough/dynamic tropopause and an eastern budge to the western trough. The final result is a better phase at 84. http://www.atmos.alb..._trend_500.html

Compare at 84 hrs of the 12Z run. The12Z GFS is about 2 runs from going loco if the phase comes in better and the trough continues to nosedive S. The deep dynamic DT and a farther S solution would result in potentially tropospheric deep cyclogenesis. Positive feedback for the win--and the GFS solutioon would look awfully like the CMC with tiny changes in the placement of the western trough and eventual phase resulting in a GOM tap.

GFS ensembles are way more amped than the op--and this reminds me of last storm where the GFS made slow changes to its height field even while the mean was way more amped. SREF/NAM height fields wiped the floor with the operation globals--and they are very amped here--more so than the globals. All this is suddenly making this event all the more interesting. ECM is a fat outlier--but it too has made some very positive changes with amplification. It really is the biggest outlier in its western wave--and it has a weak phase. Right now still a somewhat low probability (less than 40), but the probability is increasing rapidly for a CMC like solution.

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This storm has powderkeg potential. The SREF height-fields are amazing--and almost all feature a full phase over the plains with the GOM coming into play. The SREF height field wiped the floor clean with the global ops for the last storm in this range. CMC is not out to lunch here--although this may not be what some want since it wouldn't all be snow.

I said this in the Jan 18-19th thread last week

Do not worry. let the rain wash away the dirty snow. If history repeats itself, usually after an event like this, the fresh new cold air from the high in Quebec sets up for the next snowmaker usually 3-4 days down the road from this next rain/mix event. So often I hear old timers say that you got to have fresh artic air in place for a good snow event. This cold air we have now is stale as a 4 day old dunkin doughnut. I would like a new white coating in a week or so. I still say this is going to happen

I am forecasting this today:

I am also saying that this storm could deliver up to a foot or more of the white stuff to us by Saturday morning with below zero temps at night to follow with the raditional cooling. All I can say is get ready for some literally butt cold and shoveling. All snow must be shoveled by Saturday morning otherwise an ice brick warning will be issued for strained backs

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I said this in the Jan 18-19th thread last week

Do not worry. let the rain wash away the dirty snow. If history repeats itself, usually after an event like this, the fresh new cold air from the high in Quebec sets up for the next snowmaker usually 3-4 days down the road from this next rain/mix event. So often I hear old timers say that you got to have fresh artic air in place for a good snow event. This cold air we have now is stale as a 4 day old dunkin doughnut. I would like a new white coating in a week or so. I still say this is going to happen

I am forecasting this today:

I am also saying that this storm could deliver up to a foot or more of the white stuff to us by Saturday morning with below zero temps at night to follow with the raditional cooling. All I can say is get ready for some literally butt cold and shoveling. All snow must be shoveled by Saturday morning otherwise an ice brick warning will be issued for strained backs

1993 redux.

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GFS 12Z op solution really isn't a huge deal ATM. A comparison of the 0-6-12Z operational runs is far far more revealing, and each run trends more amplified with the diving trough/dynamic tropopause and an eastern budge to the western trough. The final result is a better phase at 84. http://www.atmos.alb..._trend_500.html

Compare at 84 hrs of the 12Z run. The12Z GFS is about 2 runs from going loco if the phase comes in better and the trough continues to nosedive S. The deep dynamic DT and a farther S solution would result in potentially tropospheric deep cyclogenesis. Positive feedback for the win--and the GFS solutioon would look awfully like the CMC with tiny changes in the placement of the western trough and eventual phase resulting in a GOM tap.

GFS ensembles are way more amped than the op--and this reminds me of last storm where the GFS made slow changes to its height field even while the mean was way more amped. SREF/NAM height fields wiped the floor with the operation globals--and they are very amped here--more so than the globals. All this is suddenly making this event all the more interesting. ECM is a fat outlier--but it too has made some very positive changes with amplification. It really is the biggest outlier in its western wave--and it has a weak phase. Right now still a somewhat low probability (less than 40), but the probability is increasing rapidly for a CMC like solution.

A good analysis.

I think we need to be concerned about the fact that both pieces of energy are outside the RAOB network at the moment. Solutions could change significantly in either direction as the waves get onshore.

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any word on the 12z Euro Ens?

They don't come out on Allan's site until 4:30, but I thought some of you got them around 3:00...

Before last week's Miller B, one 12z run the op was out to lunch, but the ens agreed with the other models. Then the op came on board at 0z.

they come out at 345 on allans site.

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I am also saying that this storm could deliver up to a foot or more of the white stuff to us by Saturday morning with below zero temps at night to follow with the raditional cooling. All I can say is get ready for some literally butt cold and shoveling. All snow must be shoveled by Saturday morning otherwise an ice brick warning will be issued for strained backs

You bring up a pet peeve of mine...

SNOW DOESN'T FREEZE ROCK HARD JUST BECUASE IT IS GONNA GET REALLY COLD.

Sorry for yelling ;)

But seriously, I've heard the media do this time and again... "better shovel the snow before it gets really cold or you'll never get rid of it!" Uh, yeah, how about no! Snow doesn't just magically freeze solid just because it gets really cold after a storm... if it stays all snow (and given the GEM that IS a question right now), then it'll still be snow the next day. It won't magically change into a brick or get heavier or much denser just because the temperature dropped to 5 degrees.

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You bring up a pet peeve of mine...

SNOW DOESN'T FREEZE ROCK HARD JUST BECUASE IT IS GONNA GET REALLY COLD.

Sorry for yelling ;)

But seriously, I've heard the media do this time and again... "better shovel the snow before it gets really cold or you'll never get rid of it!" Uh, yeah, how about no! Snow doesn't just magically freeze solid just because it gets really cold after a storm... if it stays all snow (and given the GEM that IS a question right now), then it'll still be snow the next day. It won't magically change into a brick or get heavier or much denser just because the temperature dropped to 5 degrees.

Ray, doesnt it freeze "rock hard" from alternating freeze-thaw cycles? Even with daytime temps below freezing, the sun melts some of it, which refreezes at night.

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