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Severe storms 2015 general chatter

Ian

By Ian,
in Mid Atlantic

Corn fuel  

64 members have voted

  1. 1. When will DCA report its first spring thunder?

  2. 2. How many days with severe weather watches in the subforum in 2015?


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high risk

high risk

Posted
Posted

   I think that this does indeed warrant some watching.   One nice thing is that at this time of year, time of day is often not a big issue.   Whereas a late evening timing might hurt us in May or June, sfc heating often plays a lesser role in the fall, being trumped by advection.   In fact, the NAM shows us rising to near 70 Wednesday afternoon and then rising into the low 70's during the evening and staying there.   The NAM (and it seems like the GFS too)  right now has an early evening break in the rain, followed by a late evening frontal band moving into our area with 500-1000 sfc-based cape and fairly healthy shear.   Even the afternoon stuff, even though it may be too widespread for discrete updrafts, still has cape and a ton of shear and needs to be watched.

 

    Ultimately, I've seen WAY too many fall events here have buckets of shear but fail on instability and not get the job done, and the progged lapse rates for this event right now are terrible, but maybe this ends up being one of the rare fall events here that works out.

 

12z NAM still decent... but its a bit later than the 06z in that the time period to "watch" is 5-10pm and maybe a lil later into the night for anything meh severe

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high risk

high risk

Posted
Posted

  as I'm sure some of you have seen, the SPC day 2 has us in a marginal risk.   definitely looks like the best threat period is roughly 8PM-midnight or so, with a lot of guidance depicting a band or broken band of storms along the cold front.  NAM take us to around 70 during Wednesday afternoon and keeps us there until the front passes.   CAPE increases ahead of the front into the ~750 j/kg range, as some modest mid-level cooling occurs.    Strong shear is also in place during the afternoon, so that has to be watched too, but right now I'm thinking that it will be more widespread showers in an area of strong forcing and very limited cape, but if a discrete strong updraft can occur, that would need to be watched too

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Ian

Ian

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Low being so NW generally makes it harder to warm sector but if the NAM is right some severe seems a good bet. Hard to buy in without a ton of support tho the Euro isn't way far off.

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high risk

high risk

Posted
Posted

   this is a good point, and it must be noted that the NAM warms us up a lot during Wednesday morning during a time of showers. It's often hard to get the warm front to move through quickly here when it's raining, but it looks like there is decent agreement on the winds veeing around to southeast quickly tomorrow morning and strengthening.    And the NAM and GFS don't really have a ton of QPF for us tomorrow either which may limit the chance of a big rain shield hindering the progress of the warm front.

 

 

Low being so NW generally makes it harder to warm sector but if the NAM is right some severe seems a good bet. Hard to buy in without a ton of support tho the Euro isn't way far off.

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yoda

yoda

Posted
Posted

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
316 PM EDT TUE OCT 27 2015

.SYNOPSIS...HIGH PRESSURE OVER NEW ENGLAND WILL SLIDE EAST INTO
THE NORTH ATLANTIC TONIGHT...WHILE LOW PRESSURE NEAR LOUISIANA
TRACKS NORTHERLY TOWARD THE GREAT LAKES BY WEDNESDAY AND INTO
SOUTHERN CANADA BY THURSDAY. THE LOW WILL PUSH A WARM FRONT
THROUGH THE REGION WEDNESDAY FOLLOWED SHORTLY AFTERWARDS BY A COLD
FRONT WEDNESDAY NIGHT. ANOTHER COLD FRONT WILL CROSS THE REGION
THURSDAY. HIGH PRESSURE RETURNS FRIDAY AND LINGERS INTO EARLY NEXT
WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...RAIN IS HAVING A HARD TIME
TRYING TO MOVE NORTH AS SFC RIDGE AND LOW-LVL DRY AIR APPEAR TO
BE WINNING THE BATTLE FOR NOW. HOWEVER...AS WARM AIR ADVECTION
INCREASES IN RESPONSE TO STRENGTHENING LOW-LVL JET TONIGHT RAIN
WILL SPREAD NORTH THROUGH THE REST OF THE AREA REACHING THE MASON
DIXON LINE AROUND MIDNIGHT. RAIN IS EXPECTED EVERYWHERE LATE
TONIGHT THROUGH WED MORNING. IN THE AFTERNOON...WARM FRONT IS
EXPECTED TO START MOVING ACROSS THE AREA WITH PRECIP TURNING MORE
SHOWERY. MODEL SOUNDINGS ONLY SHOW SKINNY CAPE WITH 300-500 J/KG
AT BEST. LIFTED AND SHOWALTER INDICES DO BECOME NEGATIVE
SUGGESTING LOW-TOPPED CONVECTION A DISTINCT POSSIBILITY. BULK-
SHEAR VECTORS ARE STRONG IN THE ORDER OF 50-KT WITH 0-6KM MEAN
FLOW OF 45-KT SUGGESTING POTENTIAL FOR ORGANIZED FAST-MOVING
CONVECTION. BEST POTENTIAL FOR SEVERE CONVECTION APPEARS TO BE IN
THE 00Z-04Z WED NIGHT TIME FRAME. SPC DY2 OTLK ONLY HAS A MARGINAL
RISK FOR SEVERE BUT ALL DEPEND ON THE AMOUNT OF INSTABILITY IT CAN
BE REALIZED. CDFNT CROSSES THE AREA AROUND 06Z WITH PRECIP THREAT
ENDING SHORTLY THEREAFTER.

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yoda

yoda

Posted
Posted

LWX evening disco update from 9:15 pm:

 

AS LOW PRESSURE MOVES INTO THE GREAT LAKES WEDNESDAY
MORNING...A WARM FRONT LOCATED ACROSS THE CAROLINAS WILL PUSH
NORTH THROUGH THE MID- ATLANTIC DURING THE DAY WEDNESDAY. BEHIND
THE FRONT...STRONG THETA-E ADVECTION AND CONVERGENCE IS EXPECTED
ACROSS THE SOUTHERN APPALACHIANS AND INTO THE MID-ATLANTIC. THE
WIND FIELD IS IMPRESSIVE WITH 40-50KTS OF 0-6KT BULK SHEAR ACROSS
THE REGION. CLOCKWISE TURNING HODOGRAPHS ARE ALSO EVIDENT IN
FORECAST SOUNDINGS. INSTABILITY IS LIMITED WITH CLOUD COVER AND
RAIN IN THE REGION BUT SW FLOW IN THE MID- LEVELS WEDNESDAY
AFTERNOON INTO EVENING WILL ALLOW FOR MINOR STEEPENING OF LAPSE
RATES. CAPE VALUES LESS THAN 500 J/KG ARE POSSIBLE. USING THE
LATEST HI-RES GUIDANCE...THUNDERSTORMS MAY FORM IN RESPONSE TO THE
THETA-E CONVERGENCE/WARM FRONT WEDNESDAY AFTERNOON...WITH ANOTHER
ROUND IN THE EVENING AS A TROUGH AXIS MOVES THROUGH. THERE IS A
MARGINAL RISK OF SVR THUNDERSTORMS WEDNESDAY WITH DMG WINDS AND AN
ISOLATED TORNADO BEING THE GREATEST THREATS
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