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Messages - EricPeterson

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Weather / Re: Western US Dry Season
« on: November 13, 2020, 2117 UTC »
I had 1.1 out in the valley.  More than enough to soak in.  The natural variation in every type of weather exceeds what is changed by global warming. That includes high temperature, rainfall, and hurricane strength and frequency.  What global warming does is nudge weather in the warmer and wetter direction in many places, or warmer and drier in some locations which is what I show above.

I think there's a fair case to be made that global warming exacerbates bad fuel management in the case of the wildfires out west.  There might be two extra weeks of dry before the rainy season in those locations shown.  One week of that might be global warming and one week a natural pattern.  In contrast, in some places the rainy season comes sooner.  It's possible some of that is from global warming (more moisture in general).  It's certainly not a one-sided story.

Weather / Western US Dry Season
« on: November 13, 2020, 0004 UTC »
I wrote a litle code to read the rainfall and high temperature for some stations in California and Oregon with the goal of seeing if the dry season has lengthened.  In many cases it has: https://virtualcoinclub.com/wx/dryseason/  Most notably in Santa Barbara, although the code needs a little work.  I think the missing years are because there was not enough rain adding up to trigger the start of the dry season (no rain in the fall is ok, just means dry season extends to day 365).  Often global warming will be blamed for a longer dry season.  I think that's possible and in future work I'll look at the intensity of the dryness based on high temperature.  But some of the cause of the earlier dry season in Sacramento could be the draining of the delta.  There were once huge wetlands in interior California.

In some cases in Oregon the dry season lasts longer, e.g. Ashland.

I added winter.  Same URL: https://virtualcoinclub.com/wx/temp/  The only real surprise was how much coastal California winter  extreme temperatures have risen.   Some people might miss those temperatures in the teens just north of San Fransisco and a little inland.  But lots of plants can now survive winters that they couldn't in the past.  The downside is interior Calif (still on the todo list) where lack of bitter cold winter temps means more bark beetles survive.

In both MT and MO the coldest temperatures in Jan and Feb have moderated.  December hasn't changed as much.  In the east (ME and SC) Jan hasn't changed as much as Dec and Feb.  Not sure why the heart of winter (Jan) seems to have stayed cooler in the east but it may be an anomaly from some January Arctic blasts in the 70's and 80's.  What is not surprising is that Florida has not become less cold in winter.  In fact January has colder extremes.  A lot of that trend is from just a few incredible Arctic blasts in the early 80's and 1985 that basically finished off the orange trees in Orange county.

The bottom line though, is that global warming is stronger in winter.

Not a lot of good station choices around Gettysburg.  I like to get 98+% coverage although I could rewrite the code a bit to accept sparse data.  But the main problem is the longest record is the 1894-2014 pumping station record.  I can try it, it might be better than nothing.

STATION NAME & ID               STARTą      ENDą   COVERAGE˛   
GETTYSBURG, PA US                1892-11-01   1982-03-31   92%
WESTMINSTER 2 SSE, MD             1893-01-01   1979-01-31   74%
TANEYTOWN, MD US GHCND:USC00188780   1893-01-01   1912-08-31   66%
FENBY, MD US GHCND:USC00183097      1893-02-01   1894-09-30   95%   
BACHMAN S VALLEY, MD US         1893-10-01   1920-07-31   68%
YORK 3 SSW PUMP STATION, PA US      1894-01-01   2014-07-31   89%
HARNEY, MD US GHCND:USC00184090   1899-03-01   1907-12-31   92%
HANOVER, PA US GHCND:USC00363662   1904-04-01   1993-09-30   97%
SPRING GROVE, PA US             1932-01-01   2020-07-31   96%
YORK INDIAN ROCK DAM, PA US         1944-01-01   1946-12-31   100%

Yes, possibly reduced urban heat, and/or a natural cooling trend.  You have to watch for the Tobs issue if you plot averages (which doubles the problem), or highs or lows.  Or you can figure out a trick to remove that problem.  If you see a sawtooth, e.g. rise until 1970-ish, then a big drop, then a slow rise since, then you probably have a Tobs biased plot.

 I'll try to download and plot later.

One caveat although it was not a cherry pick  The first station I did was Kentfield CA because I wanted a long record station near the coast near one of the wine country fires.  There are undoubtedly interior CA stations that have warmed more in the summer and I will find one in the interior doing another search for CA stations.

Summers are warming in the west when measured by extreme temperatures (highest temperature for the month).  Don't want average temperatures since temperatures at night are not an issue.  Can't use average temperatures anyway due to the time-of-day observation bias issue that makes it look like temperatures are dropping  when they are actually rising.  In a nutshell, the observers used to go out and set the min/max thermometer manually every day in the early evening.  But that meant that the max for the next day may in fact be the max for the current day if the next day is cooler.  Then switching to morning resets the min would be duplicated if the next day's min was warmer.  Finally switching to electronic min/max there would be no bias but unfortunately the new data would be incompatable with the old data.  So instead I simply find the max temperature for each month.   Thus the time-of-day issue is moot.

Hotter days out west are a problem, creating for example higher rates of evapotranspiration and soil moisture decrease.  That's the main reason that the average drought (which starts and ends naturally) is more severe than the average drought years ago.  Up to 4F rise per century (with a lot of natural variation) in Utah:

In the east it's a different story.  Summer extremes are dropping.  You would not know that from reading the news, but their sources are usually ASOS sensors at airports.  Those run hot especially in hot weather.  And as we know they are next to the runway.  Here's a rural Maine station with a 5F drop per century in July:

Here are all the stations I did with a link to the data and code https://virtualcoinclub.com/wx/temp/. The data came from here: https://www.ncdc.noaa.gov/cdo-web/search  I did not cherry pick any data.  I simply sorted by oldest starting date and looked for stations that continue to the present day with 98% or more data (although I prefer 99% or 100%).  The first station I found with that criteria with the list sorted by oldest starting date was the one I downloaded and plotted.

Weather / Atlantic hurricanes are slowing down at landfall
« on: October 12, 2020, 0206 UTC »
There are a couple papers on slowing hurricanes.  One is about Atlantic hurricanes https://www.nature.com/articles/s41612-019-0074-8 and seems reasonable by my analysis.  They compute the mean rate of motion and show a drop in the slowest 5% of storms

(fig 1b) and corresponding changes in direction (fig 1d).  However I do not believe the first part of the title "Hurricane stalling along the North American coast ..." is quite accurate.  I believe that stalling, where steering currents break down, and the hurricane drifts, then stops or almost stops, then drifts in another direction, is a rare weather event.  I believe those weather events are determined by natural cycles.  The slowing is real though, in the 4-6 mph hurricanes, and the reasons in the paper are plausible.

The analysis I did uses the same HURDAT2 data they used.  However I did not use HURDAT2 landfall markings because I do not believe those are consistently applied.  In particular landfalls at non-6-hour intervals are captured in newer but not older data.  Instead i used the NOAA GLOBE data which contains elevation data in which any elevation greater than -500 meters is non-ocean.  The gist of my algorithm is finding all  landfalls for each storm and then finding the slowest.  In the case of Claudette the second landfall was slowest.  For Wilma the first of three landfalls was the slowest. Dorian had only one point of landfall (7 meters).  Thus I will miss some landfalls on very small islands.  But those misses will be consistent through the record and not affect the trend other than possibly lowering its statistical validity a small amount.

The code is linked on the webpage: https://virtualcoinclub.com/wx/slow/   Here are the 70 year trends

  The 0-3 mph landfalls ("stalled") do not have a statistically significant trend.  There is too much natural variation in those types of weather patterns.  But the 4-6 mph landfalls have increased  significantly.   The 0-6 landfalls as a whole have risen from 40% to 50% of total landfalls.  That means hurricanes and tropical storms in the Atlantic basin are generally slowing down at landfall.

Weather / Re: Looking dry again for the Mid Atlantic
« on: October 05, 2020, 1823 UTC »
Jason thinks Delta remnants could hit us Sat night.  Also tweeted that rapid intensification is "definitely possible".

Weather / Re: Looking dry again for the Mid Atlantic
« on: October 05, 2020, 1200 UTC »
picked up  0.11 with the overnight showers here in the valley.  Better than nothing...

Weather / Re: Atlantic hurricanes corrected for improved detection
« on: September 30, 2020, 1431 UTC »
Yes, binning is a problem.  Even without binning, TS and hurricanes are relatively rare events that don't provide sufficient numbers to do statsitics on annual numbers.   Perhaps grouping years would help with that.  But as you can see on the lower charts where I plot the detection trends, there are lots of dots at zero, 50% and 100%.  That means that in many years, with just one or two or three storms, it's likely that  zero percent or 100% of storms went near land or stayed away from land out of happenstance.  Lots of happenstance can affect the trend.  I removed all the year-bins with zero storms in that bin.  Also those are not in the trend calculation.  Python makes some of those things very easy to do.

But yes, bins are discrete, their thresholds  are arbitrary, "near land" is a binary choice, etc.  Bins could be gaussian with overlap.  Near land could be graded.  There are ways to help deal with the small numbers problems that come with binning.

Weather / Re: Atlantic hurricanes corrected for improved detection
« on: September 30, 2020, 1213 UTC »
The >=125 knot storms exceeded the weaker hurricanes in years like 2004.  There were more tropical storms which is a different chart:
Really should not be surprising in those years where natural cycles and manmade warming allow strengthening of many storms, even the majority, but only if they can get past the tropical storm or weak hurricane (blue above) threshold.  What happens then is two things.  They strengthen and weaken, and the planes fly out and catch the strongest winds at peak strength.

I believe the increase in the most intense  storms is a real effect of both ocean warming and better measurement.  It's hard to separate those.

Weather / Atlantic hurricanes corrected for improved detection
« on: September 30, 2020, 0052 UTC »
I read the HURDAT database with some python and looked for hurricanes that came close to land.  To get figure out land, I used NOAA GLOBE which is linked on the page.  The NOAA GLOBE data is a set of simple raster files, binary files with nothing but 16 bit integers representing meters of elevation for every square km of the globe  (roughly square km for lower latitudes, varies at higher latitudes).  If the meters of elevation is -500, then that's ocean.  The code to read in the raster files and determine elevation  for any lat/lon is very simple using the rasterio library.  I think installing that sucked in GDAL which is a pretty large library, but I seem to have both on my mac now.

Anyway once I figured out how to determine if hurricanes came close to land, or not, then I assume that  percentage should be constant.  There's no reason for that percentage to change.  I used it to correct the tropical storm and hurricane numbers in the HURDAT database.  Web page with explanation, source code and instructions is here: https://virtualcoinclub.com/wx/count/count.html    There's a very striking increase in very strong hurricanes (high end cat 4 and cat 5):

Also tropical storms are increasing.  Other hurricanes are flat.  Some of the TS increase may be policy changes.  I can't correct for those, only presumed observation changes based on the heuristic above.  If you want to recreate the graphics you'll need to install matplotlib.  It's a very nice package for simple bar graphs, line graphs and scatterplots.

Weather / Re: Very cold mornings with frost here in MD
« on: September 22, 2020, 0137 UTC »
Here in the valley it was 34 on Sunday AM and 37 with fog this morning.  But tonight is colder than last night at the same time so I think we'll be 34 again.  Hopefully escape the frost again.  I still have a lot of tomatoes.

Weather / Hurricane Teddy
« on: September 17, 2020, 0234 UTC »
Any Mainers?  Remember when the euro was the only model predicting Sandy's left turn?  Now the euro is an outlier again predicting  Teddy will go left into eastern Maine:

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