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Tornado vortex signature northwest of Williamsport, per Wunderground radar.

Did have a half decent couplet on storm relative velocity images there for awhile coming from Clinton into Lycoming counties.. seems to be less prounounced in the latest frames. Fortunately this is a very rural area. Back southwest is another feisty cell that might take a swipe at Lock Haven. Another storm to watch is moving through NW Bedford County in South Central PA as there is a couplet present there as well.

Also Severe Thunderstorm Watch was (re)issued at 11pm effective thru 7am this morning from the Laurels east thru the rest of PA, etc. Looks to be a noisy night.

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Did have a half decent couplet on storm relative velocity images there for awhile coming from Clinton into Lycoming counties.. seems to be less prounounced in the latest frames. Fortunately this is a very rural area. Back southwest is another feisty cell that might take a swipe at Lock Haven. Another storm to watch is moving through NW Bedford County in South Central PA as there is a couplet present there as well.

Also Severe Thunderstorm Watch was (re)issued at 11pm effective thru 7am this morning from the Laurels east thru the rest of PA, etc. Looks to be a noisy night.

I can't ever remember so many rotating storms in this area at this time of the night (midnight, 1-2am). I was really surprised a tornado warning wasn't put out for the Bedford County storm.

That begs the question, when was the last overnight tornado warning issued by CTP?

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BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE BINGHAMTON NY

227 AM EDT THU APR 28 2011

THE NATIONAL WEATHER SERVICE IN BINGHAMTON HAS ISSUED A

* TORNADO WARNING FOR...

NORTHERN CORTLAND COUNTY IN CENTRAL NEW YORK...

NORTHWESTERN MADISON COUNTY IN CENTRAL NEW YORK...

SOUTHEASTERN ONONDAGA COUNTY IN CENTRAL NEW YORK...

* UNTIL 300 AM EDT.

* AT 222 AM EDT...A SEVERE THUNDERSTORM...WITH A POSSIBLE

TORNADO...WAS LOCATED NEAR PREBLE. SIGNIFICANT DAMAGE...AND

UNCONFIRMED TORNADO REPORTS...HAVE BEEN RECEIVED FROM TOMPKINS AND

CHEMUNG COUNTIES.

* THE TORNADO WILL BE NEAR...

FABIUS AND 7 MILES SOUTHEAST OF LA FAYETTE BY 235 AM EDT...

POMPEY BY 240 AM EDT...

CAZENOVIA...WATERVALE AND 7 MILES SOUTHEAST OF MANLIUS BY 245 AM

EDT...

6 MILES NORTHWEST OF NELSON BY 250 AM EDT...

SULLIVAN AND CHITTENANGO BY 255 AM EDT...

LENOX...CANASTOTA AND WAMPSVILLE BY 300 AM EDT..

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I can't ever remember so many rotating storms in this area at this time of the night (midnight, 1-2am). I was really surprised a tornado warning wasn't put out for the Bedford County storm.

That begs the question, when was the last overnight tornado warning issued by CTP?

About the Bedford County storm and also the other storm that had a pretty solid couplet nw of IPT, there was an interesting near term update from CTP around 1am or so from one of the senior guys (La Corte or Dangelo)

.NEAR TERM /UNTIL 7 AM THIS MORNING/...

SVA246 CONTINUES THROUGH 11 AM...BUT HAVE BEGUN TO TRIM OFF THE WRN

COS. MULTIPLE DISCRETE SUPERCELLS ARE PRODUCING LITTLE/NO DAMAGE.

LOWEST LEVEL SCANS ON CLOSE INTO RADAR CELLS SHOWS LITTLE COHERENT

ROTATION BELOW 3KFT. THERE COULD BE A DISCONNECT BETWEEN THE

WILDLY IMPRESSIVE MESOS AND THE GROUND. THAT WOULD BE A VERY GOOD

THING.

FLOOD WATCH CONTINUES IN EFFECT...WITH ADD HEAVY RAIN POSSIBLE AND

VERY LOW FFG VALUES. STORMS ARE MOVING SO FAST AND THE HAIL

CONTAMINATION IS SO LIKELY THAT FLOODING MAY BE TOUGH TO COME BY.

SEVERAL STREAM GAUGES CHECKED RECWENTLY SHOW LITTLE/NO RESPONSE TO

RAIN FROM THE PAST 6-8 HRS.

HIGH PWAT AIR OF 1.5 TO 2 INCHES WILL DECREASE VERY SLOWLY IN THE

W AND STAY IN PLACE OVER THE EAST. MIN TEMPS OVERNIGHT WILL BE

NEARLY MID-SUMMER-LIKE...MAINLY IN THE LOWER TO MID 60S.

Otherwise, dead of night or early morning T-warnings are certainly very rare here for sure, I don't ever remember seeing one either .We've def had some early-mid evening stuff in the past.. but this time of night? Probably about nonexistent.

I've been astonished at some of the parameters tonight...EHI's (0-1km) of 3-4 per mesoanalysis right now in the Susquehanna valley! Some of the other more obscure indices like the significant tornado parameter and supercell composite have numbers that are much higher than what would typically be seen. I'm actually getting pretty concerned about that region as this area of storms continues to press east out of the central counties. Very bad timing for any tornado prone area much less this area if we get some major cells that show up, specifically any discrete cells.

0-1km EHI (!!)

post-1507-0-31896200-1303973991.gif

Aforementioned sig tornado parameter map is below. Per the SPC definition, STP is "A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), surface parcel CIN (sbCIN), and surface parcel LCL height (sbLCL). This version of STP uses fixed layer calculations of vertical shear, and the surface lifted parcels, as an alternative to the "effective layer" version of STP." and "A majority of significant tornadoes (F2 or greater damage) have been associated with STP values greater than 1, while most non-tornadic supercells have been associated with values less than 1 in a large sample of RUC analysis proximity soundings."

post-1507-0-29854600-1303974015.gif

Very impressive stuff, hence why SPC is monitoring for a potential upgrade to a tornado watch.

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Well new watch will be coming out before 8z...will be interesting to see if it's a SVR or a TOR...blue line suggests it may be a STW but the color doesn't always correlate to what watch will be issued. I imagine they will discuss this with local offices and see what they want to do.

mcd0656.gif

MESOSCALE DISCUSSION 0656
  NWS STORM PREDICTION CENTER NORMAN OK
  0232 AM CDT THU APR 28 2011

  AREAS AFFECTED...CNTRL/ERN PA/NY...NWRN NJ

  CONCERNING...SEVERE THUNDERSTORM WATCH 244...246...

  VALID 280732Z - 280800Z

  THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
  244...246...CONTINUES.

  WITH WW 244 SCHEDULED TO EXPIRE AT 08Z...A REDEFINITION OF THIS WW
  ALONG WITH POSSIBLY WW 246 WILL BE COORDINATED SHORTLY WITH AFFECTED
  WFOS. OVERALL SCENARIO DESCRIBED PREVIOUSLY IN MCD 0652 REMAINS
  VALID WITH RISKS OF ISOLATED DAMAGING WINDS AND BRIEF TORNADOES
  PERSISTING /REF POSSIBLE TORNADO DAMAGE REPORT IN CHEMUNG COUNTY NY
  AT 0622Z/. THE QLCS ACROSS CNTRL PA HAS SHOWN A RECENT TREND FOR
  NEWD ACCELERATION IN THE PAST HOUR. AS SUCH...THE WW REDEFINITION
  WILL LIKELY INCLUDE PARTS OF ERN PA NEWD INTO THE HUDSON VALLEY NOT
  CURRENTLY COVERED BY A WW.

  ..GRAMS.. 04/28/2011


  ATTN...WFO...BTV...OKX...ALY...PHI...BGM...CTP...

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Well new watch will be coming out before 8z...will be interesting to see if it's a SVR or a TOR...blue line suggests it may be a STW but the color doesn't always correlate to what watch will be issued. I imagine they will discuss this with local offices and see what they want to do.

I think its a good chance the new watch box ends up being a severe thunderstorm watch given the primary threat appearing to be evolving into a straight-up squall line, at least in PA anyways. Up in NY there are still separate cells. Will def be interesting to see what happens..though it seems the possibility of the formation of discrete supercells (my biggest worry) ahead of or imbedded in the main line is starting to subside. Man if this situation were to be happening at the point of max daytime heating, there would be some big time trouble.

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I think its a good chance the new watch box ends up being a severe thunderstorm watch given the primary threat seems to be evolving into a straight-up squall line, at least in PA anyways. Up in NY there are still separate cells. Will def be interesting to see what happens..though it seems the possibility of the formation of discrete supercells (my biggest worry) ahead of or imbedded in the main line is starting to subside. Man if this situation were to be happening at the point of max daytime heating, there would be some big time trouble.

I am pretty amazed on what's occurring just east of the SYR area, the only instability is elevated, there really isn't a great deal of SB instability, any SB instability is very, very shallow. ML lapse rates completely blow...I guess that just shows how dynamic of a system this really is. Still getting quite a bit of tornado warnings though in NY too...despite the fact that this is mainly evolving into a squall line it appears the line is embedded with supercells and both 0-1 and 0-3km helicity values are quite high, LCL's are fairly low too. Going to be interesting to see what the new box is. Based on this system's history it really wouldn't shock me to see a TOR.

Oh God if this was peak heating we'd be looking at a 5/31/98 type event up this way, not sure if the instability values would be similar but this would be very bad. Kind of makes me wonder what will happen later on today is some areas are able to break out into some sun, ML lapse rates are forecast to weaken and latent heat release should help with this but models have really underdone the ML lapse rates tonight and if this remains true through the AM/early afternoon this could really change the complexion of things in certain spots.

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It is so bad around the Harrisburg area, multiple water rescues are in progress, trees down on houses, not to mention all the flooding calls the Fire Dept are handling. It really is insane here

I have yet to see a storm report out of there. If you see anything worthwhile, don't forget to call 1-877-633-6772 (CTP public line).

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