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Feb 11-12 "Potential"


phlwx

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The ruc is going pretty bullish on the norlun for tomorrow evening much like the wrf nmm model from this afternoon. that is a 1-2 inch per hour band spreading southeast

Just a side note the wrf nmm model is the best model for norlun and inverted troughs.

I was just gonna post something about this. That feature, if their is a wildcard to this event it could be that. If that tracks over the area it could bring a few surprises. Should have some pretty heavy snow bands with it, and good ratios with temperatures crashing with it.

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I was just gonna post something about this. That feature, if their is a wildcard to this event it could be that. If that tracks over the area it could bring a few surprises. Should have some pretty heavy snow bands with it, and good ratios with temperatures crashing with it.

Brings back reminders of feb2008 the inverted trough that day ended up being better then the actual storm.

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Brings back reminders of feb2008 the inverted trough that day ended up being better then the actual storm.

I will never forget that storm. I was up at Millersville University sitting in my dorm watching this band set up right over my house. i thought "Okay nice little band will drop an inch or two" and then it just sat there all night intensifying. Called home thinking we got 3-4" wound up with 9". Just unbelievable. We can only hope that type of setup happens tomorrow again! I'll never forget Rob G sitting in his forum calling for a band to explode over the area later that evening. As much crap as he gets, he damn well called that band. Nailed it.

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I will never forget that storm. I was up at Millersville University sitting in my dorm watching this band set up right over my house. i thought "Okay nice little band will drop an inch or two" and then it just sat there all night intensifying. Called home thinking we got 3-4" wound up with 9". Just unbelievable. We can only hope that type of setup happens tomorrow again! I'll never forget Rob G sitting in his forum calling for a band to explode over the area later that evening. As much crap as he gets, he damn well called that band. Nailed it.

Is that the event where PHL airport got like 8 inches and 10 miles north an inch or two?

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I will never forget that storm. I was up at Millersville University sitting in my dorm watching this band set up right over my house. i thought "Okay nice little band will drop an inch or two" and then it just sat there all night intensifying. Called home thinking we got 3-4" wound up with 9". Just unbelievable. We can only hope that type of setup happens tomorrow again! I'll never forget Rob G sitting in his forum calling for a band to explode over the area later that evening. As much crap as he gets, he damn well called that band. Nailed it.

Rob G wasn't the only one to call for it. The NAM was honking that band for about 3 to 4 runs straight...

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Brings back reminders of feb2009 the inverted trough that day ended up being better then the actual storm.

Yeah, that was an impressive band that set up (February 3, 2009). Just for kicks, I went back to look up the post mortem I issued on this event the very next day. For those interested in reviewing it, here it is.

.POST MORTEM /FOCUSED HEAVY SNOW TUESDAY NIGHT/...

WELL, QUITE THE MESOSCALE EVENT UNFOLDED LAST NIGHT ACROSS THE LOWER

DELAWARE VALLEY. WHILE THE COASTAL STORM WAS WELL NORTHEAST OF OUR

AREA, A WELL DEFINED MID LEVEL SHORT WAVE SCOOTED ACROSS OUR AREA

WITH THE MAIN FOCUS ACROSS THE PHILADELPHIA METROPOLITAN AREA. THE

COMPUTER MODELS WERE INDICATING THAT A BANDED FEATURE WOULD

DEVELOP, HOWEVER THESE MESOSCALE FEATURES ARE TOUGH FOR THE MODELS

TO RESOLVE BECAUSE THEY ARE ON THE SMALLER SCALE AND DEPEND ON

CERTAIN VARIABLES COMING TOGETHER AT THE RIGHT TIME. HOWEVER,

THERE WERE SIGNALS THAT THIS COULD OCCUR BUT THE LOCATION WAS UP

IN THE AIR. IT TURNS OUT THAT THE FORECAST LOCATION WAS TOO FAR

NORTH WITH THE 12Z MODEL RUNS ON TUESDAY, BUT THE 18Z AND 00Z

MODELS BEGAN TO GET A BETTER HANDLE ON THE ORIENTATION AND

LOCATION OF THE INTENSE BANDED FEATURE. SO, WHAT CAUSED THIS?

THIS IS WHAT IS KNOWN AS A NORLUN INSTABILITY TROUGH. THERE WAS AN

INVERTED TROUGH AT THE SURFACE /VIA SURFACE OBSERVATIONS/ BENEATH

MIDLEVEL POSITIVE VORTICITY ADVECTION. THERE WAS A NARROW RIBBON OF

FRONTOGENETIC FORCING IN THE 925 MB TO 850 MB LAYER AND THERE WAS

INSTABILITY ALOFT. THE MAIN LIFT BECAME ORIENTATED NORTHWEST TO

SOUTHEAST ALONG AN INSTABILITY GRADIENT AS CONVERGENCE BECAME

MAXIMIZED ALONG THE TROUGH, WHICH LOOKED TO BE PLACED AT THE LEADING

EDGE OF THE POSITIVE VORTICITY ADVECTION. DOPPLER RADAR IMAGERY

SHOWED THAT THE SNOW SHIELD CONSOLIDATED INTO A MORE FOCUSED BAND

THROUGH THE EVENING AS MESOSCALE PROCESSES GOT UNDERWAY. A REVIEW OF

MODEL DATA VIA BUFKIT, INDICATED THE SNOW GROWTH REGION LOWERED

SUBSTANTIALLY IN THE EVENING WHICH LINED UP WITH HIGHER RELATIVE

HUMIDITY VALUES. BASED ON THE POSITION OF THE FRONTOGENESIS, IT

APPEARS THE LIFT WAS MAXIMIZED WITHIN A MUCH IMPROVED SNOW GROWTH

REGION, ALLOWING FOR EFFICIENT ICE CRYSTAL PRODUCTION. GIVEN THE

INSTABILITY THAT WAS IN PLACE, SNOWFALL RATES REACHED ABOUT 2

INCHES PER HOUR WITHIN THE HEART OF THE BAND AS THERE WAS A

CONVECTIVE CONTRIBUTION. THIS INTENSE SNOWFALL RATE WAS REPORTED

AT THE PHILADELPHIA INTERNATIONAL AIRPORT FOR A TIME. AS THE

ATMOSPHERE COOLED, THE SNOW TO LIQUID RATIO INCREASED AND PROBABLY

MAXED OUT TO ABOUT 20:1. AN INTERESTING OBSERVATION THAT WAS REPORTED

AT THE AIRPORT WAS THAT THE VISIBILITY DROPPED TO NEAR ZERO DURING

THE HEIGHT OF THE EVENT WITH A RUNWAY VISUAL RANGE AS LOW AS 600

FEET. NEEDLESS TO SAY, THESE TYPES OF EVENTS ARE DIFFICULT TO

FORECAST WITH A GOOD AMOUNT OF LEAD TIME. WHEN THEY DO OCCUR,

THERE IS A SIGNIFICANT IMPACT BUT IN A RELATIVE NARROW AREA, AS

THE SNOWFALL RATES ARE LOCALLY INTENSE. THE SETUP THAT OCCURRED

TUESDAY NIGHT DOES NOT HAPPEN OFTEN, BUT WHEN THEY DO, AREAS

UNDERNEATH THE BANDED FEATURE CERTAINLY GET A DUMPING OF SNOW.

AS A SIDE NOTE, THE LAST TIME PHILADELPHIA PICKED UP 8 INCHES OR

MORE OF SNOW DURING AN EVENT WAS FEBRUARY 11-12, 2006 WHEN 12.0

INCHES OCCURRED.

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For what it's worth.....

00z Nam blossoms precip. over the area after 3z......shutting the bulk of it down shortly after 12z. Little bullseye close to 0.30" right around Philly by 12z.

that mainly falls as snow per the NAM on wunderground north/west of the river (changeover line nudges southeast slowly). SV says a couple of inches in the N & W on the NAM....

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that mainly falls as snow per the NAM on wunderground north/west of the river (changeover line nudges southeast slowly). SV says a couple of inches in the N & W on the NAM....

yeah, looks like the radar is already showing signs of "filling in" to our southwest, sort of inline with the NAM's composite reflectivity forecasts.

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new nam sim radar for that norlun like feature...if i had to take a guess as of right now...the lancaster area down to dover looks like the path of this feature, though subject to change,

NAM_221_2012021100_F24_CREF_SURFACE.png

Should be interesting it seems like somebody could get a quick hit but the question is where.

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