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wdrag

Pockets damaging wind-power outage potential 4P-10P Sunday Nov 15, 2020

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Low to moderate confidence for a damaging wind event (scattered pockets). We're about 48 hours away and within a time that we should be looking for a possible significant event.

Not a lock for damaging south wind gust 40-60 MPH in squalls, with an isolated SVR thunderstorm associated with a cold frontal passage, or... brief westerly wind gust to 45-50 MPH within 3 hours of the CFP - associated with strong dry air advection and modest pressure rises.  

The NAM/UK/EC have 65-75 kt winds near 850 MB at about 7PM Sunday over LI.  RGEM even stronger. Op GFS is weakest.  As we draw closer to Sunday afternoon, intensity of the wind fields and instability-and any squall lines will need reassessments.  

The upper 50s SST may limit transfer but lapse rates and any squall lines/kinks or breaks in the lines will be important discriminators for a sizable power outage event on LI/CT. Further west... if damage is to occur in NJ/se NYS,  I'll look at hill towns first, and then along the immediate NJ coast, and especially IF, the currently modeled wind fields maintain intensity and can begin sooner as per the RGEM, which is the strongest of the models that I've seen from the 12z-18z/13 cycles. 

So, to avoid a damaging wind gust, NAM/RGEM/ECMWF/UKMET 65kt+ wind gusts need to weaken 10-15 kt, or a triple point low forms just s of LI. 

Have three 12z/13 RGEM graphics (slower than the NAM) 4P-7P-10P, added a prob for wind gusts 40+ MPH by the weaker 12z/13 GEFS. Added 18z/13 3K NAM turbulence Richardson # overturning graphic for LGA that is solid .25 up about 925 MB which may favor spotty mixing on the southerly flow and more widespread mixing on the slightly weaker westerly flow behind the front. Also added the 3K NAM modeled wind field from the 18z/13 3K NAM---also for LGA. 

 EC has 3 successive cycles of 40+ MPH for LI/CT and past two cycles 50-60 MPH. Uncertainty on 60 MPH but confidence for ~40, scattered 50 MPH is at at least moderate. RGEM timing below is slower than the 3KNAM.   By the way...models have the showers moving east at 62kt. 

722P/13

 

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Good Saturday morning everyone, 

No significant change to the topic. 00z-06z/14 modeling is a bit stronger. I think LI/CT eastward have a problem tomorrow evening. We'll see if the modeling holds.

SPC has now added a slight chance of thunder to our area in their D2 discussion and reasoned for possible future changes. 

LLJ intensifies as it approaches LI/CT. Have added HRRRX graphics for wind gusts (legend has the numbers). Shear continues strong with turbulent turnover up to 950 mb, within range of 50 knot gusts LI/CT.  Also have screen shot of the HRRRX squall line position around 7PM Sunday (faster than other modeling). Cells modeled to be moving 60-65 kt. You can see the 3K NAM profile for LGA tomorrow evening, and now the 00z/14 GEFS has much higher probs for 40 and 50 MPH gusts. 

Many of the models appear a bit slower but the HRRRX continues on track with yesterdays RGEM.  It's possible the window of opportunity might b e 1 hour fast but otherwise, I'd be thinking pockets of damaging wind on LI/CT Sunday evening.

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Walt, great thread. 12z 3km NAM has one of the more impressive November low topped squall lines that we have seen in a while. The Euro shows  55 mph winds just off the deck near the coast. 12z NAM wind gust product has increased to 60 mph potential on Long Island.

 

765BC6A3-A00B-4F77-A5D9-3342890A79E2.thumb.png.e7c7ef585154f1b274fd7b348f165e82.png
84E754AC-C934-4497-BAE6-48BB9B020425.thumb.png.77405517abaaf7f237022932844d9280.png
 

9B0D8CB7-FFED-4CF9-B5EB-6FB605605753.thumb.gif.cd28743d791b175e88c47a2f62ca26d4.gif

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Another vertical view.        We are at the Bottom/Center.       Rapid wind speed drop off just to the (left)west of us, and constant out over the water to the east.

https://proa.accuweather.com/pro/model-grads-pro.asp?mt=06&mod=gfs&gv0=D&hr=42&gs=crosssect&mv8=scheme:wind&map=conus&mv5=1000&mv6=300&mv7=40.61,-75,40.6,-73&uid=4061-75004060-7300wind

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7 hours ago, bluewave said:

Walt, great thread. 12z 3km NAM has one of the more impressive November low topped squall lines that we have seen in a while. The Euro shows  55 mph winds just off the deck near the coast. 12z NAM wind gust product has increased to 60 mph potential on Long Island.

 

765BC6A3-A00B-4F77-A5D9-3342890A79E2.thumb.png.e7c7ef585154f1b274fd7b348f165e82.png
84E754AC-C934-4497-BAE6-48BB9B020425.thumb.png.77405517abaaf7f237022932844d9280.png
 

9B0D8CB7-FFED-4CF9-B5EB-6FB605605753.thumb.gif.cd28743d791b175e88c47a2f62ca26d4.gif

Cant add much more confidence ar 450P. Will rereview tomorrow morning. OKX has a wind advisory going... that should work at a minimum. Until I see model winds come down from what has been posted by all here today, I think power outages and wind damage-pockets... especially central-eastern LI northward through the CT River Valley at least up to BDL.  There are some helicity tracks, lightning and pea hail in the HRRR for se NYS into nw CT.  As SPC and others note... instability marginal for lightning but worthy to monitor and also any splitting of the squall line into segments and associated backing of wind in the line to se or east. (pres falls and a small chance of mess low moving rapidly n in the squall line. Will reevaluate tomorrow morning, including any downplaying of the event, if from my view it's needed.

 

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2 hours ago, LibertyBell said:

Basically looks like high winds to 60-70 mph and heavy rain between about 4 PM and 10 PM EST west to east across our area with no one location experiencing these conditions for longer than 30 min?

NOT the entire area: This downward transfer of momentum will most easily occur where the temperature reaches near 59F which I think will be the NJ coast, across LI/CT. It's also where modeling has constantly cyclically emphasized strongest wind.  I may be ~1 hour too fast on on the event but want to recheck tomorrow.  I am pretty sure the squall line will be moving east at about 60-70MPH so the strongest gusts should be for a ~30 minute period (at most?) followed by a 1 hour lull then an opportunity for a westerly wind  gust 40-50 MPH for an hour two, and then 3 hours after cap, winds should settle a bit, but still fairly windy Monday. 

No guarantees on 60 MPH but I think with some trees (oaks etc) still leaved (extra capturing sail), somewhat softer ground due to recent rains,   I think there is a pretty good chance of pockets of tree uproots/limbs down, power outages.  Modeling so far is not tamping down the risk.  Maybe tomorrow morning we'll lose 5 knots on the gusts?  

Even so,  I think it's wise to prepare for a few minutes of chaotic winds, rainfall "rates" of 1.5"/hr and possible interruptions of electric - internet service in CT/LI and I'm thinking now back to the nearest 5 miles of the NJ coast as well.  Additionally ridge tops in nw NJ/se NYS/ne PA may also experience this,  but am a little less convinced there.  

Let's check again tomorrow and see if the forecast needs downward adjusting. 

I am pretty sure a few of us will be reporting some damage-power outages Sunday evening, mainly between 6P-10P.  Not...last Augusts Isais massive outages but for some, there should be interruptions. 

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3 minutes ago, wdrag said:

NOT the entire area: This downward transfer of momentum will most easily occur where the temperature reaches near 59F which I think will be the NJ coast, across LI/CT. It's also where modeling has constantly cyclically emphasized strongest wind.  I may be ~1 hour too fast on on the event but want to recheck tomorrow.  I am pretty sure the squall line will be moving east at about 60-70MPH so the strongest gusts should be for a ~30 minute period (at most?) followed by a 1 hour lull then an opportunity for a westerly wind  gust 40-50 MPH for an hour two, and then 3 hours after cap, winds should settle a bit, but still fairly windy Monday. 

No guarantees on 60 MPH but I think with some trees (oaks etc) still leaved (extra capturing sail), somewhat softer ground due to recent rains,   I think there is a pretty good chance of pockets of tree uproots/limbs down, power outages.  Modeling so far is not tamping down the risk.  Maybe tomorrow morning we'll lose 5 knots on the gusts?  

Even so,  I think it's wise to prepare for a few minutes of chaotic winds, rainfall "rates" of 1.5"/hr and possible interruptions of electric - internet service in CT/LI and I'm thinking now back to the nearest 5 miles of the NJ coast as well.  Additionally ridge tops in nw NJ/se NYS/ne PA may also experience this,  but am a little less convinced there.  

Let's check again tomorrow and see if the forecast needs downward adjusting. 

I am pretty sure a few of us will be reporting some damage-power outages Sunday evening, mainly between 6P-10P.  Not...last Augusts massive outages but for some, there should be interruptions. 

Walt sounds like rainfall will be between 1-2 inches total like it was with the last event except that was over 3 days this will be over 30 min?  We now have a WA between 1 pm and Midnight

 

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1 minute ago, LibertyBell said:

Walt sounds like rainfall will be between 1-2 inches total like it was with the last event except that was over 3 days this will be over 30 min?  We now have a WA between 1 pm and Midnight.  Rates doesn't mean we get 1.5...just means that if the squall lasts 15 minutes... we should get close to .4".  WPC and SPC HREF seem to have a good handle on the rainfall generally 1/4-1" in the NYC forum Sunday afternoon-eve. 

 

 

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19 minutes ago, wdrag said:

NOT the entire area: This downward transfer of momentum will most easily occur where the temperature reaches near 59F which I think will be the NJ coast, across LI/CT. It's also where modeling has constantly cyclically emphasized strongest wind.  I may be ~1 hour too fast on on the event but want to recheck tomorrow.  I am pretty sure the squall line will be moving east at about 60-70MPH so the strongest gusts should be for a ~30 minute period (at most?) followed by a 1 hour lull then an opportunity for a westerly wind  gust 40-50 MPH for an hour two, and then 3 hours after cap, winds should settle a bit, but still fairly windy Monday. 

No guarantees on 60 MPH but I think with some trees (oaks etc) still leaved (extra capturing sail), somewhat softer ground due to recent rains,   I think there is a pretty good chance of pockets of tree uproots/limbs down, power outages.  Modeling so far is not tamping down the risk.  Maybe tomorrow morning we'll lose 5 knots on the gusts?  

Even so,  I think it's wise to prepare for a few minutes of chaotic winds, rainfall "rates" of 1.5"/hr and possible interruptions of electric - internet service in CT/LI and I'm thinking now back to the nearest 5 miles of the NJ coast as well.  Additionally ridge tops in nw NJ/se NYS/ne PA may also experience this,  but am a little less convinced there.  

Let's check again tomorrow and see if the forecast needs downward adjusting. 

I am pretty sure a few of us will be reporting some damage-power outages Sunday evening, mainly between 6P-10P.  Not...last Augusts Isais massive outages but for some, there should be interruptions. 

Walt why is 59 degrees the magic number.  I know in the summer convective temp that you reach for storms to initiate but not for winds in the fall with a squall line? 

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3 hours ago, wdrag said:

 

Also, I'm going to be driving at around 1 PM from NE PA thru NJ and NYC and into SW LI getting there around sunset or shortly thereafter.  Will the winds in NE PA and W NJ not be as strong?  And as far as the strongest winds and heaviest rain is concerned for NYC and SW LI, would that be a few hours after sunset, somewhere between 7 PM and 10 PM?

 

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Good Sunday morning everyone,

No changes in the topic philosophy except to delay 1 hour.  Please follow local warnings/statements/advisories.  Continues potent as advertised the last two days. The question is mixing down.  

Wind advisories continue for PHI/OKX.  

My expectation continues for damaging wind and power outages, with wind advisory criteria via squall line even back across much of NJ and NYC and ridges se NYS. Most powerfull wind potential of 60-65 MPH is for LI/coastal CT. Whether we equal or exceed 60 MPH is debatable. 50's expected and we shall see what that does to trees/power. 

Upstream OHIO and western NYS should see quite a burst this morning-midday.

Added graphics: Max gusts from the operational HRRR in MPH (EC 2-4 MPH stronger in some places). Experimental HRRRX timing of the squall line at 7P, 9P.  (this is a bit slower than the topic starter.  Experimental potential wind gusts from the HRRRX (you can see how it extends north into the CT River Valley - white = 50 KT/58MPH).  For planning purposes, that is what I'd be planning for, especially when you look at 3K NAM wind profile, turbulent transfer graphics.  The sounding itself doesn't look quite unstable enough for me in the low layers for LGA (think we need 59F+ and prefer lower 60s temp to increase the low level lapse rate) but the squall line may do the damage and I expect 40-45kt gusts at LGA/JFK and wont surprise at 53kt but the sounding-mixing is critical and so doubts do exist about more than 45KT NYC itself.  Here is the early morning discussion from SPC on the marginal risk. 

...Central Appalachians/Mid-Atlantic...
   An upper-level trough will move quickly east-northeastward across
   the southern Great Lakes region today. The system will become
   negatively tilted as a band of strong large-scale ascent moves into
   the central Appalachians. At the surface, a cold front will advance
   eastward into the central Appalachians with a pre-frontal trough
   developing ahead of the front. Thunderstorms will likely be ongoing
   along the pre-frontal trough at the start of the period across the
   Ohio and Tennessee Valleys. This line will move quickly eastward
   into the central Appalachians by midday. Ahead of the line, a
   corridor of maximized low-level moisture will exist with surface
   dewpoints mainly in the 50s F. This will be enough for weak
   destabilization ahead of the line. By afternoon, RAP forecast
   soundings have peak instability reaching the 200 to 400 J/kg range.
   This combined with extreme deep-layer shear of 100 to 110 kt and 40
   to 50 kt winds just above the surface, should enable a fine line to
   develop. The fine line is expected to quickly move across the
   Appalachian crest eastward into the foothills and coastal areas
   during the late afternoon and early evening. Isolated damaging wind
   gusts will be possible with this line of storms. A marginal risk has
   been introduced in this outlook for much of Pennsylvania, Maryland
   and northern Virginia extending eastward to the Mid-Atlantic coast.

603A/15

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11 hours ago, Oliviajames said:

Walt why is 59 degrees the magic number.  I know in the summer convective temp that you reach for storms to initiate but not for winds in the fall with a squall line? 

Low level lapse rate.... if its' isothermal or inverted, transfer from above is unlikely.  Today's modeled sounding looks marginally unstable enough to grab up to 950-925MB.  

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8 hours ago, LibertyBell said:

Also, I'm going to be driving at around 1 PM from NE PA thru NJ and NYC and into SW LI getting there around sunset or shortly thereafter.  Will the winds in NE PA and W NJ not be as strong?  And as far as the strongest winds and heaviest rain is concerned for NYC and SW LI, would that be a few hours after sunset, somewhere between 7 PM and 10 PM? Generally confined to ridges in ne PA/nw NJ. Mount Pocono I think has a chance for 40-48kt gust.  Yes, NYC and eastward 7-10P, then the e tip of LI worst 9P-11P. 

 

 

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54 minutes ago, wdrag said:

Low level lapse rate.... if its' isothermal or inverted, transfer from above is unlikely.  Today's modeled sounding looks marginally unstable enough to grab up to 950-925MB.  

Yeah, the 6z NAM has a 4 to 5 SD 925 mb jet near the coast. 

9B514A49-1CC2-497B-9BF6-13477758D2F2.thumb.gif.39e04f9b20b85c4ba417a60e258651f2.gif


 

 

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1 hour ago, qg_omega said:

Upton not very impressed

 

That’s the forecast for synoptic wind gusts. Stronger convective gusts with  the squall line will be covered with short fused SPS or severe thunderstorm warnings if necessary.

Have left the Wind Advisory in place as it was, for portions of
eastern New Jersey and the Delaware Beaches. In those areas,
synoptic mixing late this afternoon and especially this evening
should yield some 40-45mph gusts, though am a little doubtful we
will see advisory level synoptic winds. However, those areas
also stand the best chance of higher gusts associated with the
convective line in the later evening. Further west, synoptic
winds should remain below advisory levels, however shorter fused
wind threats associated with the convective line may need to be
covered by SPS or SVR products depending on how it evolves.
Bottom line, regardless of the mechanism most areas stand a
chance for a period of strong to locally damaging winds, mainly
during the evening hours.

 

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14 minutes ago, wdrag said:

Mount Holly NWS office. OKX is Upton-Brookaven. BOX is Taunton (Boston). 

Gotcha I guess I’m not part of the  Wind advisory i’m assuming  it’s really pertaining to the Jersey Coast area

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Looks like a good idea if the squall line verifies as strong as the models are showing.

Possible 1630Z upgrade...
   Full outlook update expected by 1630Z with consideration of a Slight
   Risk across the Mid-Atlantic/Northeast with convection rapidly
   progressing across this region during the evening to early tonight.
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2 minutes ago, wdrag said:

I didn't initially know PHI had an advisory when looking at their map, I saw the green flood advisory superceded (hid) the brown wind advisory. 

Wind advisories continue for PHI/OKX.  

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4 hours ago, wdrag said:

 

Looks like I'm leaving just ahead of it.  Getting out at 1 PM will be up near Mt Pocono on I-80 around 2 PM should get into Long Island between 4 and 5.

Looks like NE PA will be getting hit around 6 PM so I'll be on LI by then.

 

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