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Sun July 11-Mon July 19 Pockets of FF/SVR and a modest heat wave


wdrag
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Started a topic that may not bear as much fruit as the recent ELSA of this past week but with the attached 6 hr FFG fairly low now in the immediate NYC suburbs, thought it might be good to heads up some of the potential. 

Sun afternoon-Tuesday---warm frontal residuals and moisture pooling in weak low lvl WAA and halfway decent winds aloft that diminish considerably on Tue, I think there will be pockets of FF producing thunderstorms that could yield spot 5" amounts in that 60 hour period (slow movers Tuesday).  Instability is related to considerable CAPE over 2000J in parts of the area Mon and Tue.  Warm fronts can be big rainfall producers and so my thinking is the biggest problems will be I80 south, though some of the modeling gets things cranking up to I84.  Suspect a few SVR Wet microbursts each day, especially Monday and Tuesday.

Additionally the heat wave should begin Tuesday in the non-marine wind influenced coastal plain with the HI 95-100 Tuesday, Wednesday, Friday and possibly right through the weekend if the 12az/9 EC op is incorrect and the GFS as of 18z/9 is correct on 576 thickness in our area next weekend.  My guess, once the heat wave starts, the debate shifts to it's big break... right now I favor longer than the EC and quite possibly lasting through next weekend.  Hottest day(s)?: I think Fri when some of modeling has HI 100-maybe 105 near NYC.

SVR seems likely to me on Wednesday the 14th due to increasing wind fields, then a drying out Thu-probably nothing that day, with fairly widespread SVR looming either next Fri or Sat when not only CAPE seems pretty large, but wind fields increase quite a bit and more easily sustain a big outbreak. TT toward next weekend increase a bit toward 48-50..not a huge svr signal but together with the wind fields and CAPE,  should be interesting.

In Summary: Lower FFG, high CAPE suggest pockets of excessive rainfall coming this week, along with SVR storms, esp Mon, Wed, FRI.   Who gets the worst and when??  

It does appear this will be more than the routine summer week, once again, with the big 500MB ridge along the east coast and troughing hugging the Great Lakes. 

 

Screen Shot 2021-07-09 at 10.06.14 PM.png

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Thanks! Seems like these heat patterns have been getting broken down in the modeling too soon. Highs may not get that excessive because of the wet ground but humidity could make up for it. Definitely looks like the same nasty humidity/heat pattern we've been having. The south shore might not be a bad place to be since Elsa likely chopped up the waters enough to cool them down and make the onshore flow a little better for a while. On the days we're on the periphery of the ridge would be the best for firing up storms? 

One thing almost for sure, if this pattern keeps up Elsa won't be the last tropical system coming through here this summer. 

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Good Saturday morning, fwiw - possibly my last update til Sunday.  If I were to do it again. Not much change. Modeling differs.  For now, models tend to end any heatwave Saturday, and are very reluctant to get it started Tue EXCEPT the EC and to some extent the NAVGEM.  I'll go with Tue-Sat 90 or better interior coastal plain where no seabreeze.  The HEAT is a little less my concern.  Latest EC OP has VERY large 5+ rainfall this week, but up in northern MA. My guess is further south near greater instability (our area).

All i can do is watch the models and reality and see how this evolves.

Regarding priming: Don't know.  the week after Sunday the 18th looks a little drier and very summer seasonable, but that can change.  

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Good Sunday morning everyone!  

July 11- D1 of thread in progress with early morning SPC marginal SVR, just to the west of the forum today, in the forum Monday, and nw NYS Tue but time to adjust all of these, plus SPC no mentions Wed, Fri-Sat due to their strenuous requirements for mentions in the D4-7 time frame.

QPF already 1/2-3/4" nMD fm WXUnderground and per Digital storm totals leaked into extreme s central PA s of LNS.  Convection already lining up southern PA and from my perspective heading for the northern or central NJ part of our subforum.

Modeling temps, the wavering position of the eventual decaying warmfront (should occur Wed), makes the beginning of the 90F heat problematic, more so than I anticipated when the thread was started Fri night.  NAM punches 90F up here Monday, but then suppresses southwestward Tue with its backdoor cold front. MOS has no heatwave. EC tries and GFS2m temps go for it Thu-Sat.  So, I may be wrong about this, but its so close for interior coastal plain that I stay with the general pattern.  Friday seems to continue to look the hottest of the week.

GFS has shifted back to extending the heat Sunday. (more uncertainty for this thread but next Sunday is not intent of the thread)

FF/SVR: little change in thinking.  I see modeling and WPC are big to our north the next couple of days. Synoptically probably OK but FV3/HRDPS kind of like it pretty good down here too. CAPE suggests that we favor FF/SVR in the southwest part of the forum, mainly NJ/ne PA next 2 days, then open it up northward Tue-Wed.  Wind fields/TT continue marginal but the EC CAPE continues threatening as well as PW that this week will vary between 1.8-2.2", with the dry day continuing to be modeled for Thu. So I continue to look for max 5" in the subforum by Tuesday...we'll see what the contributions are the next 24 hrs and I won't be surprised by iso SVR tonight in NJ.

Only 1 other note of interest: Something in the upper levels near the Bahamas this morning is rotated nw-n-ne over our area Tue. No SFC reflection nor any 850 vort, but it's a slightly enhanced wind field. Unsure whether that will play a role Tuesday for big rain enhancement?

So, until he realities prevail... this thread is subject to possibly being overdone, but my personal prep continues to be for FF/SVR and AC needs this coming week, especially western fringe I95 corridor.  Will monitor fairly closely today.

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So far this Sunday afternoon, uninteresting here.  

However, modeling and now WPC joining, MDT-HIGH Prob tomorrow of excessive rain.  Won't surprise me if it starts overnight-predawn Monday along with embedded isolated SVR wind.  

So, Monday, Wednesday and now Saturday are the targeted big days of SVR/FF. 

Monday as per below: FF, iso embedded SVR;  WED to me looks pretty big for SVR and a few FF,  Saturday to me looks good for cool frontal outbreak with Sundays' cool down unknown (CFP or not??).  Noting TT on Wed getting close to 50 along with the big 2000+J CAPE, decent wind fields. EC OP offering marginal TOR threat. 

From WPC below tomorrow: This looks to be a useful scientific discussion of potential. 

 

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR THE
TRI-STATE AREA OF NY/NJ/CT...

...Northeast...
Two phased heavy-rain threat exists Monday. At the start of D2
(12Z Monday) there is likely to be ongoing thunderstorms moving
eastward along a stalled warm front over Southern New England and
eastern Upstate New York. Through the first half of the day, this
activity is likely to be the primary driver of flash flooding. As
the front stalls, PWs will continue to surge northward on
southerly flow ahead of a deep trough in the Midwest, rising to
1.75-2 inches or more, which is 2-2.5 standard deviations above
the climo mean. This southerly flow will additional draw higher
instability northward, with MLCape reaching 500-1000 J/kg,
although the greatest instability will remain south of the
boundary. Along this instability gradient however, periods of
showers and thunderstorms will train eastward on boundary-parallel
mean wind, with rain rates of 1-2"/hr producing 2-3" of rainfall,
and the HREF 12-hr probabilities suggest low-end potential for
spots of 5". This rain will occur atop soils that are above the
98th percentile for 40cm soil saturation according to NASA SPoRT
due to recent heavy rainfall, so heavy rainfall should quickly
turn to runoff and the SLGT risk was expanded only slightly from
inherited.

A more significant flash flood risk may develop in the aftn/eve in
the vicinity of the Tri-State area. A shortwave cresting the ridge
to the west will drop southeastward. At the same time, it will
suppress the front back to the south, and the interaction of this
shortwave with the low-level baroclinic zone will lead to renewed
thunderstorm clusters moving across the region. The 12z high-res
suite is in very good agreement in a focus of heavy rainfall
focused in the vicinity of NYC, with the HREF EAS probabilities
depicting a threat for 2", and the point probabilities suggesting
5" or more possible. FFG across this area is severely compromised
due to the presence of significant urban areas and recent heavy
rainfall which is 300%+ of normal the last 7 days. Rain rates of
1-2"/hr are likely, and after coordination with WFO OKX and PHI,
have raised a targeted MDT risk for the potential for slow moving
thunderstorms Monday evening as Corfidi vectors drop to 5 kts near
New York City.
 

Screen Shot 2021-07-11 at 4.54.16 PM.png

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The HREF did a good job on rainfall amounts with Elsa and the moisture streaming north the day before. So more flash flooding potential on top of already saturated ground. Parts of the area will make a run on their wettest July records.


39667F3C-E618-4CE2-82EA-2CB7607582ED.thumb.jpeg.23ffbcd2782a2f30e3db01d2b576068f.jpeg

B7AB08E9-C78E-44A5-8389-6269F84D98C7.thumb.jpeg.4be097f66c345d7cb9adacf866e1feac.jpeg

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2 minutes ago, bluewave said:

The HREF did a good job with Elsa and the moisture streaming north the day before. So more flash flooding potential on top of already saturated ground. Parts of the area will make a run on their wettest July records.


39667F3C-E618-4CE2-82EA-2CB7607582ED.thumb.jpeg.23ffbcd2782a2f30e3db01d2b576068f.jpeg

B7AB08E9-C78E-44A5-8389-6269F84D98C7.thumb.jpeg.4be097f66c345d7cb9adacf866e1feac.jpeg

If that winds up being right it looks like another 1.50"-3.00" is possible here. I have had over 6.00" of rain since Tuesday. 

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9 minutes ago, Rtd208 said:

If that winds up being right it looks like another 1.50"-3.00" is possible here. I have had over 6.00" of rain since Tuesday. 

Parts of the area are almost to 10.00” on the month so far.

Locust Valley 0.3 E 
Lat: 40.8813 
Lon: -73.5813 
* indicates Multi-Day Accumulation Report
Station         NY-NS-32
Date Precip in.
07/01/2021 0.52
07/02/2021 1.26
07/03/2021 1.67
07/04/2021 --
07/05/2021 --
07/06/2021 --
07/07/2021 0.22
07/08/2021 --
07/09/2021 5.81
07/10/2021 0.37
07/11/2021 --
Totals :  9.85 in.

 

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upton going all in:

-

From Monday afternoon through Tuesday morning.

* As a warm front lifts into the area on Monday, scattered to
  numerous thunderstorms will develop Monday afternoon. As the
  front sinks back to the south Monday night, the front will
  continue to focus thunderstorm activity and heavy rain potential
  over the watch area, especially in and around the New York City
  Tri-State area. This rain will be falling in areas hard hit by
  heavy rain and flash flooding late last week.

* Rainfall amounts of 2 to 3 inches are likely, with localized
  amounts over 4 inches possible.
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Based on Bluewave post-prompted me to add this...CoCoRaHs totals as gathered the mornings of 7/2-7/11.  Note the many 9's in CT with iso over 11. 

I see a 9+ in northern LI (possibly near Locust Valley?) and some 6's in NJ.  Here is where I trust radar/machine report mblend except tempering radar digital totals when HAIL is involved. 

 

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Screen Shot 2021-07-11 at 6.22.35 PM.png

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Good Monday morning everyone,  Please follow NWS info on watches/warnings this weeks thread.

SPC now has Marginal risk SVR parts of the suborum next 3 days.  Wind fields for SVR later this week/Sat have decreased so confidence is a little less.  Still overall, am most confident of any SVR late today, Wed afternoon, Sat.

Thursday continues to look like the rain free day, and maybe now Friday with action at the end of the week tending to be concentrated this coming weekend

Where all the new renewed rainfall after 10A today occurs,  debatable, but somewhere as depicted by WPC moderate risk excessive.

 

HEAT: Nearby 90F today, central NJ,  probably suppressed by the backdoor Tuesday, then spreads north late Wed with best chance persistent 90F days Thu-Sat. Low clouds north of the warm front will interfere with heat next 3 days...so the boundary between cloud cover and none will probably help concentrate redevelopment of convection daily, wherever that is. This may mean CT and possibly NYS has lower chances of TR+,late today/Tue.

 

Complex daily variations of what may happen. Let's take this day by day.  Am probably offline through at least 5P.

 

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  • wdrag changed the title to Sun July 11-Mon July 19 Pockets of FF/SVR and a modest heat wave
  • IrishRob17 unpinned this topic

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