wdrag

Poser outages increasing rapidly in PA NJ due to wind.

In agreement... we'll let the #s decide what model did best tomorrow morning at 10 or whenever we get a chance to post. I think its highly premature to bet on NORTH of HPCHREF HRRR being the more accurate. Suggest be ready for the a lions worth coming 5P-midnight. I'll live with WPC forecast which also highlights HPC HREF etc. Will check back late today. Enjoy the midday break along I80, if it occurs.

Wantage NJ 0.45 as of 858A.

.33 Wantage NJ 743A, a bit higher amounts near the Delaware so far.

Rainfall steady since 415A in Wantage and measuring. Models seem to be a little light on the se flank (I95) this morning. Added ARI from WPC. Recurrence interval not often for these amounts. Definitely would not go north like EC and instead hug the HPC HREF down to I95 in NJ and LI. Wind gusts 35-45kt may take down some water sodden trees overnight. TOR risk in SNJ may briefly move up to NYC-LI this eve but that may be too far north? Strongest winds appear in the northerly flow overnight.

Another tropical related event is coming to much of the area as described by our IDA outlook thread participants. It may push the summer totals to near record levels, and possibly start the month of September with a months worth of rainfall in just one day, maybe even in 6 hours. Public impacts will be serious in some areas from the I-95 corridor and LI northward. Thank you for participating.

5-10 year rainfall recurrence interval per NWS updated 24 hr forecast issued this afternoon. Thread stands as written... we've mentioned 10" max which the 12z/30 SPC HREF and 18z/30 HRRR now seem to have, but overall I think 2-8" works well. Bulk in a Wednesday morning period (note the widespread 1-1.5" amounts today near I76 OHIO-W PA, which arrives by ~4AM), then Wed night-Thu morning torrents. G 35 kt. Not hammering wind harder at this time tho some of the modeling has 45 kt gusts which would be a big problem for parts of the saturated area-uproots-power. TOR potential dependent on northward incursion of the warm front. As much as we root for big events, it gets quite uncomfortable when embedded in 3 hours of torrents 1-2"/hr, wondering whether first time leaks/basement flooding occurs, how much submersible pump water rerouting should we do. We all should be well prepared to minimize impact. I plan to monitor NWS shorter fuse warnings/statements and handle detours Wed night-Thursday as flooding requires. Advice: do not cross flooded roads near streams at night. Too much risk of not seeing the dangers or respecting the powerful current of water which can be a killer. May post something late evening or overnight or otherwise back in the morning. Will begin an IDA OBS thread near 10PM tonight or 4AM Wednesday.

Little to add: My own expected tomorrow morning rainfall of 1/2-iso 3.5" of rainfall between 4A-Noon in I78-I80 NJ-NYC metro cannot be a PRE since just below criteria in distance, timing, and amount but this will be precursor event (plenty of banding support). The 03z/31 SREF ensemble qpf for LGA is appended...total ~4" there. The action between PIT and MRB at 750A (now), is a start and only with modest lift. That lift intensifies early Wed in our area. Continuing thread as initiated last week with minor title change confirmations. For now staying with max 8". Power outages a wild card dependent on wind gusts exceeding 40 knots... for now I expect some power outages but this is not an easy parameter to predict due to uncertainty on wind gusts but this risk exists. TOR: My guess from modeling is that central NJ may see a TOR early THU morning per modeled SIG TOR PARM nearing a value of 1 on the our southern edge. Needs further review in future times. River flooding will be significant with potential for a couple MAJOR in NJ/PA dependent on River BASIN ensemble qpf equaled or exceeded. Worst of remnant IDA should occur 4A-Noon Thursday. Leave plenty of extra time time, if driving. Expect detours, cars stuck in water in your typical flood prone areas, and then coming home Thu eve, the river rises will have started their bigger impact. Thursday is probably a good day to be more careful weatherwise.

The above should be just 4 images... It seems as one scrolls it repeated the first. If you take the time and advance you can see the evolution east. CO folks are starting to hope they get some of that RH as showers.

NORA remnants: see the EC PW changes near WY as PWAT through a previously very dry atmosphere, then extends east from the Plains into our area by the 5th or 6th with showers near Labor Day here. leaks

Will adjust the title Tuesday morning, by 7AM, to a MODERATE-isolated MAJOR event. (This isn't Irene Lee but it's going to be a problem storm as the 18z/30 GEFS continues on course. Have attached the latest NAEFS and GEFS inputs to river flooding and you can see a probable widespread minor to moderate event is ahead, provided the ensemble guidance is reasonable. Purple indicates potential for a MAJOR flood at that point for that river. GEFS on top and NAEFS beneath. Added the ARI last, from the afternoon cycle which shows, based on the WPC rainfall itself that this will probably be less than a 5 year recurrence rate (maybe more so ~2 year). That means nothing when incorporating antecedent ground saturation and stream flow, but rainfall wise... many homeowners with good drainage will say, no big deal. Hopefully they dont have to drive Thursday morning.

Bluewave posted a favorite of mine... showing the high likelihood of banded rainfall pert the NAM later Wednesday. Below I add what I think is more than enough NAFGEN in the 800-600layer and also the 900-500 layer to get sizable qpf convection going in southern PA by late in the day tomorrow-Tuesday.

Have no changes to previous days outlooks and as highlighted in the thread headline through the 12z/30 op data and 123z/30 GEFS/EPS qpf data. Do have to account for some non GFS/EC modeling south, but for now the ENS dictate the concerns. PLEASE follow NWS watches/warnings/statements, especially RIVER/small stream/basement flooding that is likely for portions of our area. Wind gusts still an unknown so not playing that up. Tomorrow morning, if everything is on track will highlight MODERATE to possibly ISOLATED Major impact. We will have seen worse in the past decade. PRE: I think is likely though it may stray slightly from the 1000KM 24 hr separation requirements. I still need to recheck those requirements in a PPT that I haven't yet found, on line. AND we need a 4+" requirement, which am unsure will be met-am not following local data there along the OHIO River. Still, i see guidance that successfully pointed to what I think is a PRE near the OHIO River (slightly further s of where i thought this morning, but do see there attached). It should reform in southern PA tomorrow and drift into NJ by 4AM Wednesday, drifting ene from there. Whether it colocates with the subsequent TC torrential rainfall???

EXPERIMENTAL from WPC for Wednesday... Extreme precip monitor... recurrence interval. Let's see what happens for this D3 issuance at about 09z/30. Unsure whether this is issued twice daily? Generates from WPC QPF, therefore, if we miss the qpf, we miss the ARI. Please read the background for this.

No basic changes from my perspective using multiple guidance from the 00z/30 model cycle. Appears to me to be moderate to spotty major impact event due to antecedent ground saturation. Title will probably upgrade to MODERATE-iso MAJOR tomorrow morning but for now I like the 2-8" swath. You can see the HPC 4-6" yellow swath attached. FFA for NJ and points southwest. My guess i s OKX issues later today. I can see them waiting, to deal with whatever the results of the afternoon convection that will produce spotty 1" amounts in our area today. I think we'll see a PRE in the upper Ohio Valley today near the Ohio River... (may already be forming), then that redevelops across southern PA Tuesday, into NJ Wednesday morning, then the TC rains in earnest Wed night-Thursday morning. For now staying with 2-8". It is my expectation that there will be some large rivers that reach moderate FS, but that is solely dependent on 3"+ averaged over the ENTIRE river basin, so too early to be sure where, though I focus on NJ, PA. Wind: keeping tropical gusts for now...could see iso 50 kt but think it best to focus on rain. IF 50 kt were to occur, that would enhance the potential for widespread power outages--a fickle forecast, dependent mainly on wind gusts exceeding 40 kt. Think it best to keep this part lower visibility for now. The second graphic added is the 00z/30 6 HR SPC HREF MAX qpf for Tue afternoon, showing a focus near I76...where I think a PRE will reform. I did not examine the multitude of 00z/30 GEN/WAA products. A PRE is not guaranteed, nor a PRE rainfall swath of 3+" not guaranteed to be colocated with the primary 4+ swath later on. 534A/30.

48 hr HRRR example for PA PRE? May be starting there???

My next more thorough eval at 6A Monday. Noting the 18z GFS op qpf seems to have a PRE trying to form I76 Tuesday. I'll be keeping an eye on this. Doesn't take much to triple the yield in this subtle situation that models tend not to forecast very well.

I’m out of touch w anything on NWS terminology changes 2018 onward. Other than EF2 or bigger I’m of the opinion that big wind is big wind. Many of these wind events are highly concentrated meso or miso scale. Bottom line if you’re in the general warning. No surprises. Just be smart safe. In advance I know most disagree. IMO Just too darn hard to get much useful and reliable lead time on the Majority of small hurricane related tors m. Knowing the best 2 hour window of opportunity can be useful.

I doubt very very much if NWS locally is Ignoring National centers NHC and WPC. Both have our area nailed fir a sizable event!

Thanks. I think of major in terms of Public impact. WPC Noon update has widespread 2+. This is not Irene Lee combo. Someone correct me if I’m wrong. The places that exceed 6. will have big problems starting w basin and small stream. We can’t be wrong about Major. I think that is coming for a few spots but can’t determine for another day. That would be my take if I were briefing.

I don't have a screen shot for that hour, but you can use this site to go back and put in the zulu hours (09z for 5am, 10z for 6AM and the correct date for the OKX radar and you should see what you're looking for. Thanks, Walt Walt

Here is what I'm expecting for our area, excludes anything happening in our subforum prior to 2PM Tuesday August 31. 06z/29 3K NAM and to some extent the 00z/29 EC are suggesting a PRE develops in the central PA mountains Tuesday afternoon-evening, on the north edge of the 2"PW axis, in 850-700MB weak FGEN, WAA; and then spreads east into our sub forum by 4AM Wednesday. These PRE's are composted 24 hr separate events from the TC rainfall, can last 6 hours and dump 3+" rainfall in a narrow stripe (I do not think NYC last Sat night was a PRE since it occurred with 15 hours Henri landfall). Have added a little composite information...just shift it west a bit. Then presuming the EC OP is correct about the heaviest rain occurring Wednesday night -midday Thursday, we should have a a general 2-8" rainfall by Thursday night, max axis unknown since modeling is tending to shift slightly north directly across our area. IFFF a PRE does occur in our area, I can see iso 10" rainfall. I expect more flooding (possibly MAJOR for a couple of forecast river stages) than the ensembles are posing for some of the forecast rivers. Just a little too early to highlight but as in Henri, the ensembles did not capture the stage rises that occurred in NJ. FF potential I think is pretty high, based on 6 hr FFG, and attached departure from normal precipitation. Wind: I can see gusts 50 kt, but that will be in part dependent on IDA intensity and combined high pressure gradient on the north side of the storm, with the presumption IDA crosses NJ. No further comment from myself til tonight. Have a good day. Finally added the graphics at 739A/29--sorry for the overnight. Remember, this is not gospel but what I'd be briefing EM's as a stand alone briefer with NHC/WPC guidance and ensemble/operational model support.

You're probably correct. I do think its going to take a some 40-50 kt gusts to make this a big player. That is possible in northeast flow Thursday the 2nd. IFFFF IDA goes north of us, then southerly gusts. Potential exists...just need to be careful about overping so far in advance. I'm more worried about a PRE--some model signs in PA late Tuesday moving east overnight Tue night.

Am not ignoring NORA potential for enhancing rainfall potential ~ the 5th-6th. More on NORA Monday morning.

Have to walk the dogs, and so an update of words ~7-730A. A general moderate impact, possibly spot major (areas of considerable flooding, mayybe pockets of wind/soft ground related power outages??) .