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January Pattern and Storm Discussion


Cold Rain

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fwiw - JB seems to think the models are in error in locking off a trough in the southern rockies. He thinks it comes out and there is a sharp trough in the southeast with a low in lower 1/2 of GA. The picture he paints would be a major southeast/midsouth and southern apps snowstorm.

I have seen the models back a low southwest and pinch it off from the flow temporarily many times. I certainly woudn't say it can't happen. In fact I'd say the chances are better than 50/50 it does just that. JMO based on past experiences that were similar in nature.

While I'd always rather my lows cross in Fla., with those highs in the mix the chance for a big, strong Cad is there, and with the low in Ga. I might be able to avoid the worst of the zrain being close to the waa, lol. I love sleet, and the dance is always with zrain, or cold rain when I have a chance for sleet. So, I think I'd rather the low in Fla., the strong cad, and some sleet or snow here, lol. But like "the name I must not say" says, it could be zrain for some, in which case I'll take a good bit of it in cold rain, tho I've seen strong caa over come strong waa more than once. If we get some Cad we can never underestimate it, though that happens every time, lol. T

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Man this run just barely misses the phase. @117 moisture is creeping it's way into the Carolinas with a descent CAD signal looking like it's showing up.

Starts to lose the confluence over the northeast with all the northern stream energy coming down the backside of the ridge in the Dakotas. One particular piece traverses more east than south. In addition, it still looks to really be struggling with how the two streams are going to interact. If that confluence didn't get eroded, this would be a colder run than 12z it appears though. I wouldn't get too discouraged by this.

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Yeah, I like the way this run holds together a weak 850 low pretty much all the way across the south. Visibile from hour 111 to hour 129 save for one three-hour period (117) when it briefly opens up -- if that sucker can hold together, it's a big piece of the puzzle.

Starts to lose the confluence over the northeast with all the northern stream energy coming down the backside of the ridge in the Dakotas. One particular piece traverses more east than south. In addition, it still looks to really be struggling with how the two streams are going to interact. If that confluence didn't get eroded, this would be a colder run than 12z it appears though. I wouldn't get too discouraged by this.

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Any ideas on why the HPC is advising to discard what I would assume is the 12Z run of the GFS? This is from GSPs afternoon long term.

PER HPC ADVICE...I WILL DISCARD THE GFS AND FAVOR THE ECMWF THROUGH

THE EXTENDED PERIOD. THIS APPROACH WILL NOT CONCERN THE FORECAST

PROCESS WITH THE FREEZING RAIN EVENT DISPLAYED WITHIN THE 12Z GFS

SOLUTION ON THURSDAY. HOWEVER...THE 12Z ECMWF CONTINUES TO INDICATE

THAT A DEEP POSITIVELY TILTED H5 TROF WILL REMAIN ACROSS THE CENTRAL

CONUS THROUGH LATE NEXT WEEK. QG FORCING ASSOCIATED WITH THE TROF

WILL REMAIN DEEP ACROSS SOUTHERN TX AND THE NRN GULF COAST. THE

FORCING IS EXPECTED TO AID IN THE DEVELOPMENT OF SFC LOW PRESSURE

NEAR THE MOUTH OF THE MISSISSIPPI RIVER THURSDAY MORNING.

CIRCULATION AROUND THE LOW MAY RESULTED IN A STALLED FRONT ACROSS

THE DEEP SOUTH TO LIFT NORTHWARD AS A WARM FRONT ON

THURSDAY...RESULTING IN 925-850 MB FRONTOGENETIC FORCING ACROSS THE

SOUTHERN APPALACHIAN REGION ON THURSDAY. I WILL INDICATE CHC POPS ON

THURSDAY AND THURSDAY NIGHT. UNCERTAIN REMAINS HIGH WITH THE DETAILS

OF LLVL TEMPERATURE PROFILES AND THICKNESSES...THEREFORE...I WILL

BASE P-TYPE ON FORECAST SFC TEMPERATURES. MORNING TEMPERATURES

SHOULD RANGE FROM NEAR FREEZING ACROSS THE MTNS TO MID 30S EAST.

HIGHS WILL REMAIN LIMITED BY CAD-LIKE CONDITIONS...I WILL INDICATE

L40S ACROSS THE MTNS TO 40 TO 45 EAST.

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Any ideas on why the HPC is advising to discard what I would assume is the 12Z run of the GFS? This is from GSPs afternoon long term.

PER HPC ADVICE...I WILL DISCARD THE GFS AND FAVOR THE ECMWF THROUGH

THE EXTENDED PERIOD. THIS APPROACH WILL NOT CONCERN THE FORECAST

PROCESS WITH THE FREEZING RAIN EVENT DISPLAYED WITHIN THE 12Z GFS

SOLUTION ON THURSDAY. HOWEVER...THE 12Z ECMWF CONTINUES TO INDICATE

THAT A DEEP POSITIVELY TILTED H5 TROF WILL REMAIN ACROSS THE CENTRAL

CONUS THROUGH LATE NEXT WEEK. QG FORCING ASSOCIATED WITH THE TROF

WILL REMAIN DEEP ACROSS SOUTHERN TX AND THE NRN GULF COAST. THE

FORCING IS EXPECTED TO AID IN THE DEVELOPMENT OF SFC LOW PRESSURE

NEAR THE MOUTH OF THE MISSISSIPPI RIVER THURSDAY MORNING.

CIRCULATION AROUND THE LOW MAY RESULTED IN A STALLED FRONT ACROSS

THE DEEP SOUTH TO LIFT NORTHWARD AS A WARM FRONT ON

THURSDAY...RESULTING IN 925-850 MB FRONTOGENETIC FORCING ACROSS THE

SOUTHERN APPALACHIAN REGION ON THURSDAY. I WILL INDICATE CHC POPS ON

THURSDAY AND THURSDAY NIGHT. UNCERTAIN REMAINS HIGH WITH THE DETAILS

OF LLVL TEMPERATURE PROFILES AND THICKNESSES...THEREFORE...I WILL

BASE P-TYPE ON FORECAST SFC TEMPERATURES. MORNING TEMPERATURES

SHOULD RANGE FROM NEAR FREEZING ACROSS THE MTNS TO MID 30S EAST.

HIGHS WILL REMAIN LIMITED BY CAD-LIKE CONDITIONS...I WILL INDICATE

L40S ACROSS THE MTNS TO 40 TO 45 EAST.

They did that with the Christmas storm a couple years ago too.

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Any ideas on why the HPC is advising to discard what I would assume is the 12Z run of the GFS? This is from GSPs afternoon long term.

...MODEL CHOICE...

THE 00Z GFS WAS USABLE TO DAY 4...BUT THEN CONTINUED TO DISPLAY A

BIAS TOWARD FLATTER FLOW AND FASTER PROGRESSION THAN THE OTHER

MODELS ALL THE WAY FROM THE PACIFIC ACROSS NORTH AMERICA. THE GEFS

HAS BEEN DISPLAYING THE SAME BIAS TO A LESSER EXTENT. THE ECMWF

ENSEMBLE MEAN...AND AT TIMES THE NAEFS...HAS PROVIDED A GOOD

STARTING POINT THE PAST SEVERAL CYCLES. ONE OF THE STRONGER

SYNOPTIC FEATURES IS A LARGE 588 DECAMETER RIDGE GROWING OVER THE

CARIBBEAN ISLANDS. TELECONNECTIONS BASED ON A RIDGE CENTER JUST

EAST OF PUERTO RICO GIVES US RESULTS THAT MATCH REMARKABLY WELL TO

THE ECMWF ENSEMBLE MEAN...INCLUDING THE WIDESPREAD SUB-AVERAGE

TEMPERATURES OVER THE CONUS AND TENDENCY FOR INCREASED RAINFALL IN

SOUTHEAST GEORGIA AND NORTHERN FLORIDA. THEREFORE...WE CONTINUED

WITH THE ECMWF ENSEMBLE MEAN...BUT WERE ALSO ABLE TO USE THE 00Z

OPERATIONAL ECMWF AND UKMET. THE FEATURE OF GREATEST MODEL SPREAD

HAS BEEN THE TROUGH OR CLOSED LOW APPROACHING CALIFORNIA ON DAYS

6/7. SOME OF THE SOLUTIONS...INCLUDING THE 00Z ECMWF...HAVE THE

LOW CUTTING TOO DIRECTLY INTO THE NORTHWESTERN U.S. RIDGE. WE

MAINTAINED CONTINUITY BY TAKING A WEAKER FEATURE FARTHER SOUTH

ALONG THE COAST...WHICH IS SUPPORTED BY A FEW ECMWF ENSEMBLE

MEMBERS.

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Any ideas on why the HPC is advising to discard what I would assume is the 12Z run of the GFS? This is from GSPs afternoon long term.

PER HPC ADVICE...I WILL DISCARD THE GFS AND FAVOR THE ECMWF THROUGH

THE EXTENDED PERIOD. THIS APPROACH WILL NOT CONCERN THE FORECAST

PROCESS WITH THE FREEZING RAIN EVENT DISPLAYED WITHIN THE 12Z GFS

SOLUTION ON THURSDAY.

Here's what I found, Don:

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

159 PM EST SAT DEC 29 2012

VALID DEC 29/1200 UTC THRU JAN 02/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR

INGEST...

FINAL 12Z MODEL EVALUATION INCLUDING THE ECMWF

***SHORTWAVE TROUGH DIGGING SOUTHEASTWARD TOWARD THE UPPER GREAT

LAKES ON TUESDAY***

PREFERENCE: ECMWF

CONFIDENCE: AVERAGE TO BELOW AVERAGE

MODELS ARE SHOWING A FAIR AMOUNT OF SPREAD HERE AS WELL LATE IN

THE PERIOD. THE NAM DIGS THIS ENERGY FURTHER SOUTH INTO THE UPPER

GREAT LAKES REGION THAN 12Z GFS. THE 12Z GFS HAS TRENDED

FASTER/MORE AMPLIFIED THAN ITS 06Z RUN...BUT IS STILL SLOWER AND

FURTHER TO THE NORTH OF THE MODEL CONSENSUS. WHILE THE GFS LOOKS

TO BE ON THE SLOW SIDE OF THE GUIDANCE...THE NAM LOOKS TO BE TOO

AMPLIFIED.

PEREIRA

I know this doesn't directly refer to the system along the gulf, but it definitely has an effect on its path. The GSP office may be referring to this statement then.

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So from what we can gather is the GFS is to fast and zonal across the gulf and the Nam is to far to the south with the energy acroos the Great Lakes? I guess this can effect the high pressure moving across the lakes into the Northeast, yet the energy is sliding to far south. From what I can make of it they are either saying that we will not be cold enough because the high will not be as strong or in right place , it could be a stronger storm effecting more areas up the coast, or app runner you tell me what they are saying? As they don't give an Idea or sensible solution just what is wrong with the models and biases.

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Quick question about the 6z and 18z runs of the GFS: Is there any new data that are put into these model runs? Or are they just simply rehashes of the 0z and 12z model runs?

I believe there is new data ingested but not as much as 00z...same physics though so basically they are extensions of the 00z and 12z...could be wrong though.

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i would think the confidence of gsp would start getting higher on the storm next Thursday, but they don't mention it.

We've only had one model run that really showed something. Up to now it's just potential. Nothing happening but rain is the house and the house wins 9 out of 10 times. Their going to take the safe bet.

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