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Philly_Weather1

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Philly_Weather1 last won the day on June 15

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    Philly, PA

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    Long Range, Severe Weather, Tropics
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    Inside the CCB of a snowstorm

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  1. We do it again tomorrow, marginal severe but same area as today
  2. 2009 500mb Mean May14th-June 14th Same time period 2019 Temperature Anomalies 2009 Temp Anomalies 2019 Two main differences in the flow: 1) Split flow to the west significantly more amplified in 2009 2) More zonal in the eastern 1/3 of the country in 2019. Low pressure up in Canada causing heights to be lower in the middle of the country in 2009. Also appears that there were lower heights across the SE US overall. There were some big storms hitting the West Coast, propping up riding in the lower Plains/4 corners, and then causing troughing in the SE US as systems dropped in from Canadian low. An ugly pattern for sure
  3. Mt Holly showing SPC slight risk, mostly for this afternoon. HRRR and NAM showing MCS potential. Likely wind/hail but as stated last night, possible iso tornado as well.
  4. So last month+ we have seen N. Pac wavetrain continue to influence N. American pattern with storminess Below is an image of the 850mb OLR (blue for negative, yellow for positive) 850 streamlines, and wave activity flux (pockets of observed temp/velocity interruptions). And in the North Pacific, arrows of wave activity have been pointing to the U.S and that is part of the reason forstormineas. They are simply lined up one after the other. However, last 5 days or so, there has been a disturbance in the Pacific basin. Wave flux has been and is currently being split into 2, one area retracting to the W. Pacific. The other to the east as a HP area is forced up (area of +OLR anomalies). Rough caveman drawing is rough but you can see the orange shading expanding north, cutting off wave flux pattern. So what is the cause? Equitorial Kelvin wave approaching the dateline forcing up ringing in the Mid-latitudes in front and behind it. However, over the next 10 days, MJO wave will finally move out of the Indian Ocean and into the Pacific. We will be heading into phases 5-6-7 (5 is in progress). So wet weather will return late June to early July, pending NAO influence interactions of east coast. There is a difference in the N. Hemisphere pattern from last 6 weeks, most notably jet stream has less perturbations overall as summer temperatures warms things up and less volatility compared to spring. So a break coming up after this week, some unsettled weather to return late month into early July. But as you can see from the forecast, MJO activity through the first half of July ssubsides significantly. There is also an equitorial Rossby wave that will be making it's way west. Something to keep an eye on.
  5. Looking through some of the 0z guidance and SREF/HREF, I would adjust the timing to mid-late evening and expand west into N. Va and C. MD. Appears to be the best location for hail and tornado.
  6. Haven't paid too close attention to the models through the day but oof, 0z NAM looks ominous for severe storms tomorrow night in EPA, NJ, DE, E MD. Possible hail and tornado. Directional shear isn't tremendous but you do have some there. Strong PVA entering the region tomorrow night.
  7. Unlikely to last long is right, E. Asia jet starting to fire up and the getting active again in the W. Pac. There is an expected WWB (and actually a strong easterly wind burst). But the N. Hemisphere polar jet has retracted some compared to earlier in the month. Still, an active pattern is likely in 2-3 weeks time. Of course, that doesn't leave much room when this week is expected to be active in 2/3 of the country. Really interesting atmospheric signals coming up the last few days. Hopefully I'll have a chance to go over them with all of you soon.
  8. This week will be a whole lot of yuck. Stalled boundary thanks to a -NAO will allow low pressure areas to ride along it and create more chances for precip. Current surface pressure charts show multiple areas of low pressure, one dropping in from Canada, and the other in the Plains. The one in the Plains is associated with a warm front boundary and this will slide into our area as it collides with the Canadian system. For the next several days the upper air pattern will be fighting it out over who is stronger. NAM from this morning Taking a look at 500mb, rough caveman drawings show that in the purple bubble in Ohio we have some shortwave energy, followed by shortwave energy in the Plains associated with the boundary. Then in Canada and further west over the Rockies are other disturbances. Taking a peak at the wide view we see the root cause of the problem... There is a strong -NAO block over Greenland! This causes a blockade and backs up the storm systems in Canada. Multiple low pressure areas that are having a difficult time advance. Towards W. Canada there is an Omega Block, another HP area that is not allowing storm systems through. Undercutting that are troughs in the W. US and Plains (in green), with another trough in Canada. This parade of troughs will move along a stalled upper air pattern, with the line of demarcation in orange. So we see the beginning of a rainy pattern for the next several days taking shape. This is the NAM for early tomorrow morning around 8 AM. Most of these showers begin out towards W. Pa/W. NY later this afternoon and slowly make their way overnight through the region. Continues through the afternoon tomorrow... And then overnight, a particularly vigorous shortwave energy along the stalled frontal boundary will bring with it frontogenesis (quick clash of airmasses) and we could actually see some strong storms overnight in the immediate Philadelphia area Sunday night into early early Monday morning. And that will really be the theme of the week. On and off shower activity, some of it on the stronger side. Until the -NAO Greenland blocking fades later this week. The North American pattern is put on hold, and made all the worse with W. Canada ridging requiring storms to undercut it in the W. US and make their way east into the blocked pattern. The end result is several periods of rain each day. Depending on which side of the boundary Philly ends up on will determine if it stays on the slightly above average side or slightly below average side. Here is the NAM temperature anomaly forecast for tomorrow. Before any warm boundary moves through, we will be slightly below average. And that may have to wait until Monday. And again, overnight Sunday into Monday storms may be on the stronger side.
  9. There were signs from the early model run that we could have a strong line of storms, but certainly did not expect that!
  10. Can see cloud tops building on latest satellite in S.PA, MD, heading east. Could be some strong storms coming through.
  11. SPC released discussion for W. PA for the thunderstorms, some could get strong with gusty winds. Not a whole lot of instability but not nothing either, plus plenty of cold air aloft and have trough swinging through which will add enough in terms of thermal gradient and you get stronger storms
  12. Looking increasingly likely for a 1-2 punch with a line forming after the first batch pushes north.
  13. Some hints that it tries to occluded over NE, which would drop heights to low 550s. I'll have to check 250-300mb to see if more amplification is possible as trough turns negative.
  14. You can see things starting to take shape. This setup is eerily similar to a winter storm forming in the south and riding up the coast. It will bring with Gulf and Atlantic moisture feeds. Meanwhile, cold front advancing helping to aim southern low trajectory depending on interaction. Here is NAM showing longwave trough picking up southern low. 850mb view. Also can see potential tracks, one more inland and one more coast. Rough caveman drawing. Heaviest precip will occur to the northwest of the low where GOM/Atlantic moisture feeds clash with cold air in the mid-levels and above. NAM shifting the axis over to C.MD through C. PA and into SNY. There will also be a heavy band of precip to the northeast of the low associated with a warm front and that appears destined for NJ/LI/SNE. We shall see how it goes. Could see some rumbles of thunder, especially in NJ. Strong warm air advection and fronto showing up on models. We will see short burst of heavy rain which means watch out for flash flooding. Some spots may see up to 2", and general 0.25-0.5" expected through most of the Mid-Atlantic into NE.
  15. Pretty on pace from earlier, perhaps expanding the heavy precip further west in MD/PA, just depends on when the cold front "grabs" the southern low. NAM showing 1-2" of rain, so morning commute Thursday will be sloowwww in Philly. Evening commute slow in SNE. NYC seems to get it by lunch time so they get spared the horrible commute.
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