Saturday, September 26, 2015

Saturday Night Weather Update; The Blocking High, Coastal Trough, and Upper Level Low Battle for Meteorological Supremacy

**This entry was posted Sept. 26, 2015.**

A rainy fall day on the grounds of Colgate University, Hamilton, N.Y., Sept. 2013. Image source here.

This image isn't directly related to this entry -- I just like it. Of note, the source site itself looks kind of interesting: Dick Carr's Big Bands, Ballads, & Blues. I'll have to explore it a bit.

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Weather Update ...

We really are in a somewhat peculiar weather pattern with a persistent blocking high over Maine ridging down the coast into the mid-Atlantic; a weak low pressure / inverted trough over the North Carolina Outer Banks, and some upper level energy over the Ohio River valley. There is sort of a battle between the high and the surface and upper low -- to be clear, the high will always win out and instead it just has to move away.

A lot of showery precipitation has broken out across Virginia.

Sterling (LWX) NWS radar in enhanced composite mode, 7:18PM EDT September 26, 2015.

Ordinarily, this would be indicative of heavy rainfall imminent, but not in the current pattern.

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Sterling (LWX) NWS radar in enhanced base mode reflectivity, 7:24PM EDT September 26, 2015.

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Of note, one of the commenters in this CWG entry -- he is a regular one -- linked to a site called "Tropical Tidbits," specifically, to the Numerical Model Prediction section that is buried inside the site here.

It includes as much model information as you could want and with excellent color graphics (much superior to that given on the actual NCEP Model Guidance page).

I've already bookmarked this page for future use.

You have to click on "Global" for the GFS and (low-res) ECMWF (the high-res is, of course, not available to the public) or "Mesoscale" for the various NAM (4km, 12km, and 32km resolution). You can also pick another region -- by focusing on the Northeast and total precipitation, you get the following two images:

GFS 18Z Sept. 26, 2015 showing total precipitation for the northeastern quadrant of the U.S. valid at hour 132 / 6Z Oct. 2, 2015.

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NAM-12km 18Z Sept. 26, 2015 showing total precipitation for the northeastern quadrant of the U.S. valid at hour 84 / 6Z Sept. 30, 2015.

Obviously, there are big discrepancies even with the different time scales.

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The Sterling discussion at 311PM seems to downplay everything yet there is a chance of precipitation in the forecast for each of the next five days. There is also a coastal flood warning in effect along the Chesapeake and here in D.C. for the tidal Potomac owing to elevated tides and a northeasterly flow.

High-resolution surface weather map for the northeastern U.S. and adjacent regions, 21Z (5PM EDT) Sept. 26, 2015.

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Of note, the actual surface weather map (above) shows not much of anything -- it's one of those things where you just have to know how to read it and, of course, have all the other upper level, model, and radar data.

Sterling (LWX) county warning area (CWA) advisories as of 8:28PM EDT September 26, 2015.

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The variably cloudy sky this afternoon and evening has featured an interesting and sometimes dramatic-looking, shifting array of clouds rolling in from the east. By sunset, as I was walking back from the gym, there was a dark looking cloud bank off to the south (not surprising, in retrospect, given the radar image).

I had assumed we weren't getting anything. However, at this point, it might rain a lot, a little, or virtually not at all. It's a very low confidence forecast.

I'm home now after a good gym workout. I'm also cooking dinner. I'm going to post a jukebox Saturday night entry shortly. I plan to go out later. I might stop at Floriana and go back to No. 9.

I've posted this scanned old photo before but I'd like to post it again: It was taken on a rainy autumn day in northern New Jersey (perhaps Montclair) in or around 1972.

I think my mom and dad were together that day and one of them took the photo. Not sure why they were driving up there since we were in Monmouth County in and around Long Branch.

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For tomorrow, I need to spend a few hours editing a proposal for work, so I might not update the blog until Monday. Also, I have to attend as a note-taker a two-day DOE workshop in Alexandria -- getting there at 830AM, which will be a pain in the butt. This will certainly affect (preclude) any late night blogging on Monday and Tuesday.

Oh, yes, it rained briefly while I was writing this entry.

--Regulus

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