Thursday, April 16, 2020

General Weather and Climatological Stats Update for First Half April 2020 Plus a Bit of Other Stuff

Lovely spring day on a grassy expanse at the edge of the Ellipse, Washington, D.C., 2:06 p.m., April 15, 2020

I was on one of my now-regular daytime walks between my apartment at Q and 22nd St NW and office at L'Enfant Plaza SW during this time of COVID-19 and massive (nearly) coast-to-coast lockdown.

Same spot as above but looking the other way toward the DAR headquarters, at the western edge of the Ellipse, Washington, D.C., 2:03 p.m., April 15, 2020

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Yes, I'm still able to go into work as my office is in the building that also houses the L'Enfant Hilton Hotel. If I worked at the agency itself, this would not be an option. What's more, there are only 3 (and occasionally 4) of us in the office, and for the past month, it has just been me there.

View of the U.S. Capitol building and National Mall from near the Washington Monument, Washington, D.C.,
2:21 p.m., April 15, 2020

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I had purchased lunch -- at a place called Penn Grill -- and ate it on this grassy expanse. The post-strong cold frontal spring weather was breezy, cool, and lovely with temps around 53°F, dew point about 24°F, and a gusty northwesterly breeze (10 to 20 mph).


This entry is just a general weather update to include current monthly, seasonal, and yearly precipitation tallies. I actually wrote most of it on Wednesday late night into Thursday wee hours while watching my comfort old television shows on Antenna TV, Cozi TV, and MeTV.

In the end, I simply didn't get around to finishing and instead I'm completing it tonight, Thursday (April 16th). However, the rainfall / precipitation / temp stats are through April 15th.

Instead, I went down a YouTube rabbit hole of compilations of scary close lightning strikes, most of which involved the recorder and/or others screaming HOLY SHIT!

Pro tip: If you have that much time to react, you WEREN'T struck.


Stunning image of a lightning strike on the Statue of Liberty, 8:45 p.m., Sept 22, 2010; photograph by Jay Fine.

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Anyway, returning to the local / regional weather...

We've had a significant amount of (useful) rainfall in the past several days as a result of two weather systems.

The first system was a strong and complex low pressure with double cold front. The second system was in the form of an upper level disturbance associated with a low pressure system riding along the first system's briefly stalled frontal boundary across North Carolina.

NWS/WPC/NDFD U.S. surface weather map forecast looped 12Z 12 April to 12Z 14 April 2020 showing fronts, precipitation type, and likelihood

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The first system was associated with a major tornadic outbreak across the American South that killed at least 34 people to include multiple fatalities in the usual tornado-magnet, Trump-worshipping, fundie-frenzied states of Mississippi, Georgia, and Tennessee, among others.

NWS/WPC/NDFD U.S. surface weather map forecast looped 12Z 13 April to 12Z 15 April 2020 showing fronts, precipitation type, and likelihood

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In fact, one of the Mississippi tornadoes, rated EF-4 with 190 mph winds, had an estimated width of 2.25 miles -- making it the third-largest ever on record in the United States, according to the National Weather Service. Here is the CWG entry on the matter (link embedded):


Map of Southeastern U.S. Tornado Outbreak of
April 12 - 13, 2020

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This tornado ranks "officially" third -- behind only the May 31, 2013 El Reno, Oklahoma tornado at 2.6 miles wide and the May 22, 2004 Hallam, Nebraska tornado at 2.5 miles wide. The entry notes that there was a May 3, 1999 EF-5 tornado (part of the massive outbreak that day) that struck Mulhall, Okla., that radar suggests was perhaps 4.3 miles wide.

NWS U.S. weather advisories with legend,
0059 UTC 13 April 2020 (8:59 p.m. EDT, April 12, 2020)

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Destruction in Sunday's tornado wasn't worse because the tornado traversed a rather rural part of the state. Below is a Doppler radar image from the above-linked CWG entry.

CWG entry caption: A two-mile-wide tornado swallowed Bassfield, Miss., on April 12. Here, the storm's “BWER,” or Bounded Weak Echo Region, is visible as a doughnut hole in the center of the storm. That's where the powerful updraft motion of the tornado prevents rain from falling. (GR2 Analyst)

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Back to the "DMV"...

Let's start with some radar imagery...

Sterling (LWX) NWS radar in standard composite mode looped 3:30 a.m. - 4:12 a.m. EDT, April 13, 2020

This animated radar image captures a windy, rainy squall line -- not one with particularly strong thunderstorms but lots of wind and heavy rain -- passing through the Metro D.C. area. It is in composite mode, which also shows activity within the clouds, so it tends to look more dramatic.

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Sterling (LWX) NWS radar in standard base reflectivity looped 3:36 a.m. - 4:30 a.m. EDT, April 13, 2020

This animated radar image is in standard base reflectivity within roughly the same time as the image above.

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Sterling (LWX) NWS radar in standard composite mode looped 10:07 p.m. - 10:44 p.m. EDT, April 14, 2020

This was rainfall associated with the second system. It was much cooler than 18 hours when the first system passed through -- about 43F rather than about 63°F. And this composite radar image suggests sleet was in the clouds and melting on the way down.

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Rainfall totals for the period April 12 - April 15, inclusive (ending in the wee hours of the 15th) were in the 2 to 3 inch range across the region with most occurring on April 13th (Monday).

Indeed, the totals on April 13th were daily records at the three airport ASOS stations -- and thus the full records for D.C. and Baltimore proper since those records include the pre-airport periods:

KDCA: 2.84"
KDMH: 2.60"
KBWI: 2.35"
KIAD: 2.31"
KNAK: 1.90"

The April 13th totals were:

KDCA: 2.33" -- daily record

KDMH: 2.22"

KBWI: 1.97" -- daily record

KIAD: 1.79" -- daily record

KNAK: 1.70"

KDMH and KNAK do not have full 30-year record periods from which to have records.

Of note, the precipitation from last night's system actually included a bit of tail end rain/snow mix at KIAD in the wee hours (as reported at the 4 a.m. hour).

As a result, the April 15th daily snowfall for KIAD is "trace" -- a daily record, but not measurable and so therefore not changing the season's paltry 2.9 inches.

KDCA and KBWI ended the season at 0.6 inches and 1.8 inches, respectively.

Seasonal departures (vs. normal amounts) are:

KDCA: -14.8 inches (15.4 inches)
KBWI: -18.3 inches (20.1 inches)
KIAD: -19.1 inches (22.0 inches)

These normal amounts (averages) should drop when the new 30-year base period comes out next year -- the 1991 - 2010 period. I calculated KDCA's snowfall will drop to 13.8 inches, but I could be wrong.

As for the rainfall...

KDCA's 2.33 inches of rain was actually the most in a single calendar day since July 8, 2019 when 3.44 inches of rain fell. It also well exceeds anything that fell during our non-winter winter or in March.

The four-day rainfall also boosted the station totals into year-to-date surplus.

The sole exception of KIAD's season-to-date total.

So, with all that in mind, let's do a precipitation update for the month-to-date, climatological spring to date (i.e., since March 1st), and year-to-date versus the 1981 - 2010 base period except for KDMH and KNAK.

KDCA
Month: 3.38" +1.81" (1.57")
Season: 5.69" +0.64" (5.05")
Year: 11.69" +1.21" (10.48")

KBWI
Month: 2.54" +0.89" (1.65")
Season: 5.59" +0.04" (5.55")
Year: 11.68" +0.18" (11.50")

KIAD
Month: 2.79" +1.02" (1.77")
Season: 4.78" -0.37" (5.15")
Year: 11.35" +0.78" (10.57")

KDMH
Month: 2.99" +1.29" (1.70")
Season: 6.50" +0.49" (5.56")
Year: 11.98" +0.90" (11.08")

KNAK
Month: 2.16" MM
Season: 4.19" MM
Year: 7.76" MM

KDMH went online April 30, 1998 although Sterling lists the base period as beginning in 1999 (Jan 1, 1999?).

As for KNAK, Sterling lists its base period as beginning in 2003. What's more, it only just started issuing daily climo summaries for it, so unlike KDMH, it doesn't even have partial period averages.

Despite the much cooler weather, April is still running a non-trivial amount above normal temperature-wise to include the following (at the three airports):

KDCA: +2.3°F at 56.6°F
KBWI: +3.3°F at 54.5°F
KIAD: +1.5°F at 53.5°F

In absolute terms, the first half of April isn't much warmer than March, which had the following full-month average temperatures (and departures):

KDCA: +6.4°F at 53.2°F
KBWI: +7.3°F at 50.9°F
KIAD: +6.2°F at 50.4°F

I should note that once the NWS updates its climate average base periods next year -- with 1991 - 2020 replacing 1981 - 2010 -- the monthly average temps are likely to increase markedly.

Sterling (LWX) county warning area (CWA) weather advisories updated 9:56 a.m. EDT April 13, 2020

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This update should lessen the appearance and degree (pun intended) of above-to-well-above normal warmth PRECISELY because the climate has gotten warmer.

Sterling (LWX) county warning area (CWA) weather advisories updated 11:42 a.m. EDT April 13, 2020

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As for tonight, I'm home now -- again, during this COVID-19 pandemic or quasi-pandemic time. To be clear, though, this entry is NOT about any matters related to the COVID-19 situation to include what could be a new Astroturfing teabagger movement demanding a return to normalcy / normality...

Yours truly after leaving the Foggy Bottom Whole Foods, Washington, D.C., 7:06 p.m., April 16, 2020

I guess I'm used to wearing a damn facial covering when in stores. I take it off once outside. I have this one that Andrea gave me and two cloth napkin-like ones that Doug gave me.

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Naturally, though, rather than just stating the obvious, which at least has some self-centered utilitarian merit to it -- namely, that truly believe the cost of extreme social distancing mitigation to their (and their families') livelihoods, well-being, and, yes, "happiness" (in the Constitutional sense) is too high versus the anticipated societal benefit of "flattening the curve" to save X number of lives, especially some combo of old/sick, poor, black, and / or brown people -- they are going on with a bunch of horseshit libertarian gibberish.

The GOP cultists are again dying to get into some serious "supply side" tea-bagging action (even if it's a bit more complicated than in 2010). What's really annoying to me is that even when their side has something vaguely useful to consider, as in this situation, they're such transparent and stupid ass-hats that it's impossible to support them.

Hahahah...

As you can tell, though, it is something I would like to and will address in a coming entry.

OK, I think I had better end this entry.

Before doing so, I'm going to post a few more weather-related images, specifically, county warning area (CWA) maps whose combination of colors I find interesting and/or pleasing.

Philadelphia - Mount Holly NWS (PHI) CWA weather advisories updated 4:32 a.m. EDT April 13, 2020

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By the way, I think the NWS/NOAA proposal to change the weather product of "small craft advisory" to "small craft warning" is a dumb one, but I'm not going into that right now -- except to say the public comment period is just a bunch of pro forma nonsense and the decision has probably been made.

Greenburg - Spartanburg NWS (GSP) CWA weather advisories updated 4:34 a.m. EDT April 13, 2020

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Memphis NWS (MEG) weather advisories updated
3:40 p.m. CDT April 14, 2020

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OK, that's all for now, but, Christ, this entry went on forever. My next planned entry in a day or two.

--Regulus

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