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August 2020 General Discussions & Observations Thread


Rtd208
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...Northeast...

   Weak mid-level disturbance will eject across the lower Great Lakes
   ahead of the main upper trough positioned farther west over the MS
   Valley. This lead feature should encourage a weak surface low to
   track from southern ON into southwest QC by mid evening. Any
   appreciable mid-level height falls will remain north of the
   international border, along with the primary large-scale mass
   response.

   Early in the day1 period, deep convection will likely be ongoing
   within a corridor of low-level warm advection, along the nose of a
   pronounced LLJ. This LLJ will shift north across upstate NY into
   southern ON/QC during the afternoon hours as a surface warm front
   advances north of the border. At this time it appears the primary
   focus for sustained, organized deep convection will be noted
   immediately ahead of the surface low. Latest model guidance suggests
   strong boundary-layer heating will occur ahead of the surface low
   across western NY where temperatures should warm rapidly through the
   mid 80s. Renewed surface-based convection should evolve in the lee
   of Lake Ontario then track northeast. If the surface warm front were
   to be delayed advancing north into QC, low-level shear would be
   improved markedly across northern NY which would prove more
   supportive for supercells and tornadoes. Additionally, there is also
   some concern for strong convection along the trailing warm front
   that extends southeast across the Hudson Valley. While
   boundary-layer warming may not be as strong/focused as farther
   north, sustained warm advection and high PW-airmass should result in
   scattered strong convection. Forecast wind profiles favor some
   supercell threat, though clustering is also possible. Damaging winds
   should be the primary concern. 

   Farther south, a belt of seasonally strong mid-level flow will
   extend from the base of the trough over the southern Appalachians
   into the northern Middle Atlantic. While neutral/weak height rises
   are expected across this region, boundary-layer heating and
   orographic influences should encourage at least isolated
   thunderstorms. While poor lapse rates will limit convective updraft
   strength with this activity, modest cloud-layer flow should allow
   for some organization, along with a threat for localized wind
   damage.

day1otlk_1200.gif

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The next 8 days are averaging 83degs., or 6.5degs. AN.      [GFS has been off by +5 from reality].

75*(93%RH) here at 6am, thin overcast.

Isiais:

Looks like 1" to 4" (least to the E) around here on Tues.   Winds 30 knots+ for a while.       Goes by fast it seems---- central NJ to Cape Cod in 6 hours.

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Morning thoughts...

The northern Middle Atlantic region entered August will below to much below normal precipitation. Through August 1, rainfall amounts for select cities were:

Allentown: 22.81” (3.41” below normal)

Harrisburg: 22.33” (1.52” below normal)

New York City: 22.73” (6.23” below normal)

Newark: 23.74” (0.98” below normal)

Philadelphia: 23.74” (0.91” below normal)

Scranton: 19.84” (1.91” below normal)

With the exception of New York City’s Central Park, the combination of today’s thunderstorms and Tropical Storm Isaias’ rains will likely erase all of the year-to-date precipitation deficits.  Already, in part due to a thunderstorm that brought 0.90” rain in the past hour, nearly half of Allentown’s precipitation deficit as of August 1 has been wiped out. Very heavy rain was currently falling in the vicinity of Easton.

The heaviest rains from Isaias will likely impact an area that runs from Washington, DC across eastern Pennsylvania/northwestern New Jersey where 3”-6” rain is likely. East of there, a 2”-4” rainfall is likely. New York City’s Central Park will probably see 1”-3” from Isaias. The 0z UKMET was alone in focusing the heaviest rains from Isaias to the east of that area. Overall, there is good agreement among the guidance as to the general focus of Isaias’ rains. 

The expansive western Atlantic ridge responsible for Isaias’ track will block most of the cool air from the Plains States from coming eastward. As a result, temperatures will return to mainly above normal levels following Isaias’ departure.

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Tropics 80/75.  Had about 0.09 overnight.  Dew point temps in the low to mid 70s next two days.  Clouds look to have some breaks in the next hour and we'll see how fast we can warm ahead of more afternoon and evening storms perhaps strong to severe and plentiful.  Very warm airmass with 850MB >18c today, only clouds and storms would limit widespread 90s.  On Monday ahead of Isiaas, again pending on clouds and showers/storms, should see widespsread 90s in the region. Isaias impacts starting Tuesday pm and continue into the night.  3 - 5 inches of rain area-wide, leaning towards wetter scenario.  Much discussion happening separately on that front in multiple threads.  Beyond there Thu looks like pleasant day of temps near or below normal.  

 

Warm and wet 8/7 - 8/13.  Limited 90s but humid and warm.  Bit of a ridge north of the region replay from May and June could lead to onshore flow with multiple storm chances when winds come out of the south.  Rockies ridge moves east into the Plains towards the middle or end of next week with next potential sustained heat and perhaps strong heat as WAR possible expands west as well.

 

 

 

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South Florida/Keys-like here 83/76 now.  Sun breaking through.  Could be the hottest heatindex day here or close to it, this summer.  Those mold spore allergies are trough the roof the next 10 days or so.  Thu the one dryish day 8/6.

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11AM Roundup


ACY: 86/76
PHL: 84/73
New Brnswk: 83/78
TTN: 83/75
BLM: 82/81
LGA: 82/73
JFK: 82/76
EWR: 81/75
TEB: 80/74
ISP: 80/74
NYC: 80/73
 

 

Sun breaking through into much of NJ now working its way north, expect big jum next few hours.

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The high dew points are allowing the HX to reach 100°.

Newark Liberty PTSUNNY   88  76  67 SE12      29.86F HX  99
Teterboro Arpt MOSUNNY   89  76  65 S14       29.85F HX 100
Bronx Lehman C   N/A     86  75  70 S13         N/A  HX  95
Queens College   N/A     84  75  74 S16         N/A  HX  92
Breezy Point     N/A     79 N/A N/A S14         N/A
Brooklyn Coll    N/A     82  75  78 SE14        N/A
Staten Island    N/A     88  77  70 SE7         N/A  HX 100
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FLASH FLOOD WATCH for  TUESDAY!      Up to 6" in places.

SREF still says NYC will have trouble reaching 1.5".       Got to go west for the higher totals, minus an isolated convective event within the city.

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