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wdrag

Tropical connection NYC forum area Sun-Wed, 8/2-5/20- Tropical Storm Isaias

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SPC Day 2

...Northeast...
   Moderate destabilization near and south of the surface warm front,
   combined with veering wind profiles with 35-50 kt of effective
   shear, will result in a conditionally favorable environment for
   supercells across much of central/eastern PA/NY and northern NJ by
   Sunday afternoon. However, substantial uncertainty remains regarding
   storm coverage across the region with the most favorable
   environment. Large-scale ascent associated with the departing
   shortwave trough is expected to primarily remain north of the
   international border, with a capping inversion around 700 mb
   potentially limiting deep convection across much of the warm sector.

   At least isolated thunderstorm development will be possible along an
   eastward-moving surface trough Sunday afternoon. All hazards would
   be possible with any sustained deep convection. A Slight Risk has
   been introduced from northeast PA into central NY, where confidence
   in storm coverage is somewhat greater due to potentially stronger
   heating and instability compared to areas further north and east. 

day2otlk_0600.gif

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Good Saturday morning everyone, Little change from what was posted yesterday and possibly my last post until Sunday morning.At that time, I may start a separate SVR topic for Sunday alone. Need more time to evaluate but SVR is likely for at least a few locations in our forum Sunday.

On SVR: big CAPE of 3000J, HI near 100 PHL feeding the storms, decent wind aloft with only worry a little drop of the KI during the afternoon. Nevertheless, this could be a 2 or 3 SVR episode day. The first, northeastward moving storms during the morning with WAA, the second in the afternoon (still northeast moving), and the third a final trough passage  line from west to east between 5 and 10PM. Eastern LI may be completely shut out of this. Primary threat region is far w CT-NYC all NJ se NYS and ne PA. Please follow local   office and SPC guidance discussions.                                                                                                                                                                                                                                                                                                  

Thereafter a PRE is possible ~ a DCA-POU axis Monday night followed by squally excessive rain producing Isaias Tuesday afternoon-night. 

More details on possible impacts below. This does not include power outages but will add concerns on that tomorrow if still possible (SVR Sunday and Isaias squalls Tuesday)

1) Potential killer Rip Currents Monday-Wednesday for anyone who ventures into the waters s of LI.  I'd be wary of swimming, especially non expert surfers/non expert swimmers. The significant undercurrent 1 feet 15 second swell may start arriving this weekend. These long period subtle swells surprise swimmers with their energy and are sneaky dangerous. The higher surf just preceding and following the storm (within 18 hours) usually scares off most swimmers.  

2) Rainfall as per multiple ensembles and WPC guidance. My impression is that between 1AM Sunday and 1AM Wednesday, a few locations will see ~5-7" rainfall, with isolated (1 location) 10" amount not impossible. My guess is heaviest is NJ, se NYS, w CT... presuming track continues as modeled through 06z/1. To the right of Isaias, squally and less rain, possibly less than 1" total extreme eastern LI if Isaias tracks west of Montauk. 

3) Per  NHC 5AM Saturday 8/1 track: surge and wind field risks on the western side of ISAIAS are minimal but if the track shifts to where a portion of our area is on the eastern side of the TC, then those risks would significantly increase.  I think eastern LI to the southeast New England coast are vulnerable for at least some of these stormier impacts. Preparation should continue for that...ie gusts 50 knot.   

4) PRE:  Composites posted yesterday.  Where this PRE occurs, IF it occurs, is unknown but my best guess now is on an axis from vicinity DCA-POU Monday night based on 00z/1 modeling. Still could end up further north, again if it occurs.  Not a CLASSIC PRE (need a little more se low level inflo than currently modeled) but hints are in the qpf modeling.  Need to look a lot closer at guidance details and surface wind shift axis on Monday.  Just too early to be sure of occurrence and if so, where. I'm thinking it will but I don't know where. These 6-12 hour events can be easy 4-8" producers in 6-12 hours. I'm looking for narrow slices of darker or even brightly colored heavier QPF in the modeling 12-24 hours in advance of Isaias in the GFS/EC/GGEM.  If we get to 36 hours and it's still possible, then we shift to the NAM and HRRR SPC HREF.  

636A/1

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The Euro has for the most part hinted at this track for several days.

It did take it west for a few runs, but it has been on the idea of the center crossing LI.

Screenshot_20200801-074258_Chrome.jpg

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1 hour ago, wdrag said:

Good Saturday morning everyone, Little change from what was posted yesterday and possibly my last post until Sunday morning.At that time, I may start a separate SVR topic for Sunday alone. Need more time to evaluate but SVR is likely for at least a few locations in our forum Sunday.

On SVR: big CAPE of 3000J, HI near 100 PHL feeding the storms, decent wind aloft with only worry a little drop of the KI during the afternoon. Nevertheless, this could be a 2 or 3 SVR episode day. The first, northeastward moving storms during the morning with WAA, the second in the afternoon (still northeast moving), and the third a final trough passage  line from west to east between 5 and 10PM. Eastern LI may be completely shut out of this. Primary threat region is far w CT-NYC all NJ se NYS and ne PA. Please follow local   office and SPC guidance discussions.                                                                                                                                                                                                                                                                                                  

Thereafter a PRE is possible ~ a DCA-POU axis Monday night followed by squally excessive rain producing Isaias Tuesday afternoon-night. 

More details on possible impacts below. This does not include power outages but will add concerns on that tomorrow if still possible (SVR Sunday and Isaias squalls Tuesday)

1) Potential killer Rip Currents Monday-Wednesday for anyone who ventures into the waters s of LI.  I'd be wary of swimming, especially non expert surfers/non expert swimmers. The significant undercurrent 1 feet 15 second swell may start arriving this weekend. These long period subtle swells surprise swimmers with their energy and are sneaky dangerous. The higher surf just preceding and following the storm (within 18 hours) usually scares off most swimmers.  

2) Rainfall as per multiple ensembles and WPC guidance. My impression is that between 1AM Sunday and 1AM Wednesday, a few locations will see ~5-7" rainfall, with isolated (1 location) 10" amount not impossible. My guess is heaviest is NJ, se NYS, w CT... presuming track continues as modeled through 06z/1. To the right of Isaias, squally and less rain, possibly less than 1" total extreme eastern LI if Isaias tracks west of Montauk. 

3) Per  NHC 5AM Saturday 8/1 track: surge and wind field risks on the western side of ISAIAS are minimal but if the track shifts to where a portion of our area is on the eastern side of the TC, then those risks would significantly increase.  I think eastern LI to the southeast New England coast are vulnerable for at least some of these stormier impacts. Preparation should continue for that...ie gusts 50 knot.   

4) PRE:  Composites posted yesterday.  Where this PRE occurs, IF it occurs, is unknown but my best guess now is on an axis from vicinity DCA-POU Monday night based on 00z/1 modeling. Still could end up further north, again if it occurs.  Not a CLASSIC PRE (need a little more se low level inflo than currently modeled) but hints are in the qpf modeling.  Need to look a lot closer at guidance details and surface wind shift axis on Monday.  Just too early to be sure of occurrence and if so, where. I'm thinking it will but I don't know where. These 6-12 hour events can be easy 4-8" producers in 6-12 hours. I'm looking for narrow slices of darker or even brightly colored heavier QPF in the modeling 12-24 hours in advance of Isaias in the GFS/EC/GGEM.  If we get to 36 hours and it's still possible, then we shift to the NAM and HRRR SPC HREF.  

636A/1

Sorta of alarming with your post regarding tomorrow.

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GFS Para has been really consistent with this storm

It skirts the  coast of Florida

Never makes landfall there

gfsp_mslp_pcpn_frzn_neus_15.png

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1 minute ago, bluewave said:

August 4th to 5th may be the earliest that we got to two tropical systems here. I believe the previous earliest was August 18th, 1955 when Diane moved through after Connie.

Those 2 tropical systems caused some of the worst flooding ever in our area, especially in Connecticut. 

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KWO-35 did not sound very scary about wind or rains here on Tues, in the this morning's broadcasts.

Aren't we in for up to 1" of rain not directly connected to storm?       Then maybe 3"-4" more by Wed. AM?.          Wind gusts at least 30 knots+?       EURO has a total of 5.3" by Wed AM.

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Storm looks terrible right now. A lot of dry air. I’m surprised NHC still has this as a hurricane 

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There is southwest shear that is now affecting it and it is moving over Andros Island. It will be over very warm waters tonight and tomorrow and with less shear possible, it could still intensify some. It looks somewhat ragged now but the overall structure is staying in tact according the NHC.

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1 minute ago, MJO812 said:

Gfs shifted west when it comes up here

Heaviest rain is west of the city

So we get better winds?

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Looks pretty garbage-y on satellite. For me I’m looking to see where the heavy rain axis sets up. There’ll be better winds East of the track but I doubt this will be more than a 60mph TS when it gets here. It may be a 75-80 mph hurricane in NC but shear/dry air won’t be going away as a problem for it. 

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21 minutes ago, forkyfork said:

the gfs is one of the last models i'd use

Well to me (novice), the 00z Euro and the latest UKMET along with the CMC and the 06z HWRF all seem to be west when it approaches NYC and the 12z GFS is coming closer to them. In fact, unless I'm reading it wrong ... the GFS-para would now seem to be the outlier taking it a little further east.

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3 minutes ago, lee59 said:

Hurricane coming off Andros Island and it is about 150 miles to Miami. Now that it is over open water, we'll see what happens with intensification.

tons of shear and dry air wont do much to it for the next 12 hours or so.  might weaken even mote to be honest, it has a chance to strengthen once north of florida if it stays off the coast.

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6 minutes ago, lee59 said:

Hurricane coming off Andros Island and it is about 150 miles to Miami. Now that it is over open water, we'll see what happens with intensification.

Water means very little with the hostile upper air environment

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