Saturday, April 1, 2017

A 7-Year 10-Meter Es Propagation Study Using PropNET - Part 1 of 5

Please credit and Art Jackson KA5DWI if it used outside this Blog. Thanks
Releasing this Study after a 6 Year Delay:
This was the final study after 7 consecutive years of observing, recording, and analyzing 10-Meter PropNET data for the Spring/Summer Es season. I had published my 5-Year Study for the Proceedings of the Central States VHF Society Conference in 2010, updated for a 6th year and published it and presented it to the conference in 2011.

In 2011, Solar Cycle 24 had finally began its rise and in early May 2012 a hot-water line broke under the slab of the Shack and resulted a 45 day downtime as repairs were completed.  During 2012, the teaching profession took all of my time, but was able to finish two drafts of a 7-Year analysis. Early 2013 was the beginning of another rough year personally. My wife and I decided that retirement was in our immediate future. I looked to publishing the 7-Year Study again, but after reviewing 2012 and 2013 data, it was obvious that the past 2 seasonal results were contradictory to the past Study. Solar Cycle 24 had a strong negative effect on Es and this study was irrelevant.

In the Spring of 2014, I retired and moved to the high desert of Arizona.  In January 2016, I released on the Blog what Solar Cycle 24 had done to Es propagation. I did not participate in PropNET, but saw indications that Es propagation had returned to some extent using Weak Signal Propagation Reporter (WSPR).

I believe that this study is now relevant. We are quickly approaching the bottom of Solar Cycle 24 and a return to the properties seen in the Study will now return.

Interests and Curiosity:

I believe that I came from the last generation of Citizen Band Radio operators who took the operating skills learned there and used them to operate proficiently in Amateur Radio.  Although I agree that the old “good buddy” days changed the Citizen Band for the worse, it helped a large number of those operators to become good Hams.  The early CB operators, whether they wanted to or not had to learn to operate in and around occasions when the ionosphere lit up and was reflecting signals.  Good ground wave contacts were virtually impossible at times.  Many would operate very late at night for local rag-chews because it was the only time that the 11-Meter band was quiet.  It was not uncommon at these late hours to complete (accidentally although illegal) a contact with someone 500-1000 miles away.  The term “short-skip” was used to describe this condition that what today is called Sporadic Es propagation.    

Since becoming a Ham in early 1979, the 10-Meter Ham band has always been one of my favorite places to operate. I was lucky that during this time, 10-Meters was roaring with DX as Cycle 21 was nearing its peak.  The band was pure DX.  As a Novice, I remember listening for European beacons at the upper end of the Novice portion (CW from 28.100 - 28.200 MHz) and then moving back to the low end and working many of them till about noon local time. In the late afternoon, 10-Meters was full of both Asian and Oceania signals. During the fall and winter months the band was quite predictable. Using George Jacob’s - W3ASK “Shortwave Propagation Handbook”, his monthly article in CQ Magazine, plus the latest WWV solar indices it was not too hard to figure out when and to where 10-Meters was open.

I collected a large number of countries with relatively low-power, a good 10-Meter Yagi (a CB conversion), and a good curiosity and understanding of F2 propagation. Except for some occasional Central and South American signals, once it was 2 to 3 weeks after the Spring Equinox, 10-Meters flatly died out.  That sudden loss of propagation resulted in many to run off to other bands and overlook the development of Es propagation later in the month of April and early May.  

I was a FM/TV Broadcast Band DX’er well before becoming a Ham, and afterwards once I became a Ham. My first year as a Ham, I realized as DX activity on the lower television channels was occurring, 10-Meters was also open to regions not normally open in times of F2 propagation.  I suddenly remembered my past CB experiences of what we called “short-skip”.  Actually too late into the Es season, I enjoyed a few good Es QSOs in the CW portion of 10-Meters before the F2 propagation finally showed up again in September.

My interest in “Mode A” Satellites (2-Meters up/10-Meters down) in the early 1980’s resulted in also becoming active in 2-Meter SSB, known as Weak-Signal.  I clearly remember hearing N. American 10-Meter FM repeaters and operators in between AO-10, RS-5, 6, 7 and 8 and then working several more SSB and CW QSOs on 10-Meters during the Spring and Summer. The end result of my satellite activity was my first 2-Meter SSB Es QSO. I have found nothing more exciting than working 2-Meter Es and my curiosity about this Es grew.

Throughout the years on 2-Meter SSB, I have operated with an extremely modest station.  I have always attempted to be ready and waiting on any propagation opportunity rather than creating my own by putting together a “Big Gun” set-up.  I have achieved a great amount of success on 2-Meter SSB with that effort (43 states, 202 Grid Squares) thanks in part to being prepared for many Es openings.  In the 1980’s I learned that listening to 10-Meters, along with watching for signals on analog TV Channels 2-7 was the perfect way to be ready.  On a couple of occasions, I have worked the same station on 10 and 2-Meters within the same Es opening.  In May 1986, I worked my 50th 10-Meter state (Oklahoma) on 10-Meter Sporadic Es just as 2-Meters opened up.  I completed a 1450-mile QSO on 2-Meters in that same opening.  I always noticed that some of the best 2-Meter Es openings I had experienced were preceded, during or followed by excellent 10-Meter Es events.

In 1987, I became active on 6-Meters, and the following year on AMSAT-Oscar 13 Modes B and J.  Sadly my 10-Meter activity suffered in the process. Still it was not uncommon that at least during Field Days that I would operate “1C” (mobile) running on 10-Meters searching for that potential Es opening. Due to work and travel, from the mid 1990’s until after 2000, my Ham activity was again very limited.  I still tried to make an effort to at least make sure the rigs worked, and would show up on 10 and 6-Meters during Field Day and other summer contests to experience Es propagation.  My curiosity never waned. On numerous occasions I would discuss and share experiences with others as to what was behind Es propagation. I spent many an afternoon and evening rag-chewing with other VHF aficionados about the phenomena.  I also seemed to be more thrilled making 10, 6 and 2-Meter Es QSOs than most of the F2 ones on the HF bands.

In 2001, I retired from a 30-year profession and again had an opportunity to operate what was my favorite HF band.  Ham Radio had changed much in a few short years, and I was somewhat surprised by the lack of activity on 10-Meters.  I found the band much too quiet during the spring and summer months. I also personally concentrated on 6-Meters as we were enjoying the peak of Cycle 23.  In 2002 as my Ham activity was on the upswing, I ran across a new Ham Radio activity called Beaconet on a VHF/UHF digital interest Yahoo Group. The Beaconet group was using the BPSK31 mode instead of AX.25 Packet for identification.  I was impressed with BPSK31 because of its ease of use between a rig and the computer sound card without utilizing a TNC.  I had completed a few BPSK31 QSOs on HF and learned that many signals could be copied and worked in a narrow bandwidth and minimal conditions.   

In 2003, I could not locate the Beaconet group.  I inquired on the Yahoo Group that I first noticed Beaconet and got an immediate response from Ev Tupis, W2EV.  Beaconet was alive and well, but it was now called PropNET.  Immediately, I was drawn towards doing something positive with it.  In late spring of 2004 while using software named MultiPSK, I participated more in a “lurker” (listening only) mode on 10-Meters.  I was very satisfied with the results. Using a sequenced formatted transmission, each reception of a PropNET participant’s signal was logged by the software and a daily “Catch Report” was generated.  Many of my past memories of how and when Es formed were being jogged about, and a number of old theories were being recalled.  I could now capture, then use from a statistically sound sampling of real data that I could compile, review, and analyze. I decided that for the 2005 Spring/Summer Es season I would become a full-time participant in PropNET in order to produce a propagation study.

For 2005, W2EV Ev Tupis, N7YG Jeff Stienkamp, and KF6XA Dave Donnelly had made major changes for the betterment of the entire PropNET group. It brought in more participants and raised the sample of users to make a better study.  New software called PropNetPSK easily configured your own transmissions, logged complete and partial receptions of PropNET transmissions, produced an hourly Catch Report, and most important now updated real-time propagation maps via a Telnet connection known as LiveXchange (LiveX). With the ability to see your call on a map, interest picked up in the Ham community. I had a sampling that would easily satisfy the “Central Limit Theorem” used in statistical workings. In late April 2005 I became a full-time participant of PropNET.

Despite quite a few years of working Es, many of my personal opinions and theories immediately proved to need refinement.  I compiled a statistical summary of the 2005 Spring/Summer Es season and my first thought was that I needed to it again for 2006. The data for 2005 was clean, but it needed more support.  In 2006, overall conditions seemed to be much better.  The data gathered was much improved, although at times I had more problems with the software. After gathering these 2 years of data, many of trends that occur with Es were more clearly defined, but still a third year of data was needed to insure that the prior two years were consistent.

I did my absolute best on the third year to remove any of the past difficulties I had within the prior two. The goal was to produce reliable and clean data. The third year was the best and most thorough year of all. With this third year I compiled a comprehensive 3-year study for those years of data.  Unfortunately, working on a Bachelor’s Degree and starting a teaching career delayed its completion late enough that I decided to participate for a 4th year to put the “icing on the cake”.  It was a good decision.  Once again the teaching career, my certification and a well desired vacation during the best time to present a study put me in the position to add a 5th year.  By the 4th year, consistent trend-lines had developed,in and the 5th, 6th and the 7th year’s data made them more precise and trend lines that were closely tied to actual data.

The fifth year (2009) was the minimum of solar cycle 23. Conditions were excellent and results had a positive effect on my analysis. The PropNET group decided during the fall of 2009 to change its 10-Meter operating frequency from 28.131 to 28.1188 MHz.  The move placed PropNET activity 1200 Hz below the recognized 10-Meter PSK31 calling frequency and allowed the software to capture non-PropNET activty.  I did have concerns that it would affect the data gathering efforts, but once the season was over it actually complimented it.  With the arrival of Cycle 24, the “beginning to end” of season trends were harder to define.

In 2011, the ability of PropNET participants to “robot” was added to the software.  In addition, if the 1500 Hz area was covered by a signal, the PropNET package was transmitting below or above 1500Hz.  I was not convinced that this improved capture numbers, nor did I participate as a “Robot” as it was counterproductive to my intents, hearing PSK31 signals.

No one year was perfect, but any inconsistencies never had a serious affect on the overall numbers gathered. All attempts to be consistent in operations were maintained throughout the 7 years as to working habits, rigs and antennas.  The same software PropNetPSK (PNP) was used on three very similar desktop computers; except that one ran Windows ME, one ran Windows XP Home and the third ran XP Pro. 

Operating and Background Information:

Location (QTH): North Richland Hills, Texas (Northeast Tarrant County near Ft. Worth). Grid Square – EM12ju.  Terrain: 640 feet Elevation and hills 50-60 feet higher one-third to one-half mile northeast to east.

Rig Transceiver – Yaesu FT-747GX 
Auto ID transmissions were set normally at 5 to 6 times per hour. The BPSK31 Auto ID lasts for about 30 seconds (2.5-3 minutes an hour). 57 minutes+ per hour are spent listening for other PropNET and Non-PropNET stations. 
It was operated in this mode normally from 07:00 to 23:00 local Central Daylight Time (-5 hours UTC) for the first 3 years and 24 hours for the last 4.

Rig Lurker (monitor only) – Radio Shack HTX-10.
This rig was an outstanding performer for a receive-only operation. It was run during late night and early morning hours for 3 years.  I also ran this mode while on any trip or vacation. Its good sensitivity and AGC was perfect for the reception of BPSK31 signals and outperformed the Yaesu for non-PropNET signals as it is broad-banded (3,000 Hz).

Antennas: Primary antenna was a 3-Element Yagi (30+ year old Hustler converted CB) at 30 feet high and usually pointed east-north-east (70 degrees azimuth). The secondary antennas were a 120-foot Inverted-V Doublet, a Cushcraft ATV-3 vertical, a Lakeview 10-Meter Hamstick, or a 102 inch CB mobile whip used when weather conditions were a concern, or when I was on a trip for a few days.  At least three-quarters of my operating was with the Yaesu FT-747GX into the Yagi.

Computers: Dell Dimension P3 1 GHz WinME, P4 1.8 GHz WinXP Home, and P4 3 GHz WinXP Pro desktop computers.

Software: Versions 2.X.X.X, 3.X.X.X and 4.X.X.X PropNetPSK (now PNP) developed and maintained by N7YG Jeff Steinkamp

PropNET and PropNETPSK Program Operations:

  1. The software is configured for the band operated, listening bandwidth, IMD channels, AFC parameters, and other miscellaneous program settings.
  2. A “PHG Code” (used in APRS) for power output, antenna gain, auto-ids per hour, antenna height above terrain, height above sea level, and antenna direction is configured.
  3. An example of the PropNET Auto-ID
    “For Information, please visit
    Call, Band (“hy” for 10-Meters), Grid Square, PHG code as configured, and 4 characters that validates the configured string.
  4. The PropNetPSK software, via the sound card captures and logs the data string. If complete and correct, it is logged by call, grid square and designated as a “Capture”.  If identified as a data string, but it is incomplete or not read correctly, it is designated as a “Partial/Fragment”.
  5. From the receiving station’s Internet connection, both Captures and Partial/Fragments were sent via LiveX to a Website (first years FindU, now direct to PropNET) to update propagation details and real-time maps. Data can now be extracted into a CSV file for report building.
  6. For five years a “Catch Report” was generated at 23:59:59.  The daily report was often sent to a Yahoo Group for archival. For 2 years all data sent via LiveX has been archived and extracted into a CSV data file for data collection.

    A 07/16/2009 10-Meter 24 hour map generated at from LiveX data.
Former Catch Report Excerpt Generated by PropNetPSK:

KA5DWI PropNET^31 - HY 06/29/2007 23:59:58 Z
                                   | Catches per UTC hour |
Call     Grid    Azm   Dist First 000000000011111111112222 Last  Config
          SQ           (KM) Heard 012345678901234567890123 Heard PHGVRA
WB8ILI  EN82PQ     49  1675 01:36  36          423       2 23:53  HY-PHG529765
WD4RBX  EM84NN     81  1338 13:14              341         15:05  HY-PHG500066
K4RKM   EM85VF     79  1405 14:52               21       3 23:50  HY-PHG703066
NZ9Z    EN64BD     32  1492 12:33             45461171   1 23:50  HY-PHG339556
K8VGL   EM69UT     51  1245 12:52             185 1      1 23:33  HY-PHG301066
KI0GU   EN35HF     13  1413 23:26                        2 23:26  HY-PHG7296A6
KC0EFC  EM28OX     17   714 23:29                        1 23:29  HY-PHG700066
KA5DWI  EM12JU      0     0 00:05 656         366666666666 23:54  HY-PHG315365
KD5LWU  DM57RI    295  1144 16:45                 13 1   3 23:17  HY-PHGA16069
N7YG    DM42NF    266  1282 16:15                 2A983772 23:15  HY-PHG513067

Partial Catch List:
23:53:39 HY - ÷e2uk8vgVnhy:[em69ut]PHG301066/^CF16 1753Hz
23:50:14 HY - k4rkm>hy:mqFvf]PHG7030io tr hTete1A8A* 1537Hz
23:46:51 HY - wbõe i>hADooe  2xu]Per10661/^962B 1551Hz
23:43:38 HY - k8vge  5 •[ m69ut]PH13a  66/^CF16 1750Hz
23:39:58 HY - k4rkm>hy:[eoÁheO5vf]PHG70306ítwh  e/^|A* 1533Hz
23:39:06 HY - i 'efc>hy:[em28ox]PHG700066/^BAE7 1541Hz
23:36:50 HY - wb4jfiehH-Eem92xu]PH3.sao aa t/^ie±iB 1554Hz
23:34:01 HY - lTpnanteel r t  rNyeÌt  rner    e   I t re 1402Hz
23:33:36 HY - k8vgl>hy:[em69ut]PHG301d66/t* 1755Hz
23:29:51 HY - n te.t wwwIPropNET  e .tos eai e  naekm>hy:[e5]PHG703066/^1A8A 1538Hz
23:23:36 HY - lem69ut]PHG301u66/^CF16 1754Hz
23:19:45 HY - k4rkm>hy:[em8"vfeHvd0p ee©oï1AÑ* 1534Hz
23:17:37 HY - kd5lwu>hy:[dm57ri]PHGA160O9/^83B8* 1431Hz
Created with PropNetPSK © Version

Daily Report Extracted from LiveX data provided by the PropNet Website (replaced Catch Report):

Developed by Dave Donnelly, KF6XA

PropNET Participants:

The one statistically sound part that the PropNET Project provided was an excellent sample of participants.  At any one time, no fewer than 7 North American PropNET participants were active.  During the daytime and evening hours at least 20 were active.  Unfortunately, North America is not shaped like a circle. Although my QTH was located close to the middle of the United States, PropNET participants were not evenly distributed and using the same antennas, rigs and operating habits.  The end result was that the volume of these captures was skewed towards specific areas of the country. Due to consistently excellent propagation and a cluster of PropNET participants, one-half of the total captures occurred towards the east (67.5° to 112.5° azimuth) from my North Texas QTH.

Although skewed towards the east, propagation to that direction was generally the best indication for a slow or highly active day.  As the good conditions to the East started, for the rest of the day the other directions would follow. The population of active PropNET users results in good numbers from Southeast to North to West.  Due to my location and PropNET population, numbers were much lower to my South and Southwest.

As noted, most of the participating stations in the seven years were clearly located in the eastern half of the United States. The vast majority of those stations participating in the PropNET Project have been captured at one time or another by my operation.

The Data:
After 7 years of collecting PropNET captures and partials, the final results were as follows:

PropNET participants only:
Dates: April 25 to August 15, 2005-2011 Documented (Measurements taken from April 20 to August 31)
Captures and Identified Partials: 87,001 (Average 12,428 per season, 110 per day, near 5 per hour and 10 per active hour)
Active Hours with Propagation: 8,611 out of 18,984 possible hours (45.36% = 10.9 hours/day)
Calls: 198
Grid Squares: 123
States - 41, includes Hawaii and 2 Canadian Provinces
DX: Puerto Rico and Venezuela

The Arduous Task of Compiling the Data:

I came from a financial background (Financial Institution operations) and have been working with statistical and financial data for over 30 years. I have worked with many word processing, spreadsheet, database, and file extract/data import software packages since the creation of the modern personal computer.  Compiling this data was “second nature” to me. I could compile a season’s worth of statistical data within a few days.    

The data used in this analysis was primarily derived from the PropNetPSK “Catch Reports” and files extracted from LiveX created by KA5DWI.  On several occasions, due to the failure of the software or problems between LiveX and me, reporting was manually calculated. This procedure was highly accurate.

The capture data analysis only includes stations captured at the QTH of KA5DWI in grid-square EM12ju. It does not include stations that captured KA5DWI, nor any other PropNET participant station’s data.  I used nearby participants in the same time zone on rare occurrences (primarily power failures) for probability statistical data only due to any software or hardware failures at my QTH. 

Each daily “Catch Report” or data export was opened and then parsed into an Excel spreadsheet for each annual Es season.  Proper accounting procedures were used to insure that totals were correct and verified throughout the entire process. Prior to 2009, partial/fragment data was loaded into separate Excel worksheets and with the use of the “Data-Filter” routine, were identified and assigned as catches by call, date, and time.  These identified partials were added to the totals derived from the Catch Report detail.

The only inaccuracies that occurred in the compiling of data are due to multiple captures from another station’s single transmission.  Whenever signals were strong, it was not uncommon for the two or three channels (IMD) in the software to each capture the transmission. The software was not capable of eliminating duplicate entries. Strong BPSK31 signals that were over-modulated tended to do likewise. I was only able to remove duplicate partials. I am certain that in the best conditions, some totals were inflated. These were not large enough to have skewed the overall results, but we will consider them weighted since excellent propagation conditions were the cause.  Duplicate captures will have no bearing on probability statistics.  No major changes to software settings were made during the season that would affect or change the controlled conditions.  Therefore, inflated accumulated numbers occur evenly throughout each season.

Statistically the numbers compiled are sound.  There was at any time during the sevens years gathered enough active stations to produce a statistically reliable sample of data (Central Limit Theorem).  Of the 198 different stations captured, 18 were captured near or well above 1,000 times in 7 years.  The analyzed captures and identified partials averaged almost 12,500 per year.  34 PNP stations account for 90% of the total data.

The Spring/Summer “Es” Season:

When the first individual season study was first begun in 2005, my opinion based on experience was that for 10-Meters, the Spring/Summer Es season occurred from about May 1 till August 11.  Once I compiled the data for 2005, I determined that I was slightly incorrect.  The season begins a few days earlier and ends many more days later.  I extended the data gathering efforts from April 20 till August 15 for the study.  I should have extended the end date of each seasonal study much later (2 weeks at least), but other obligations, such as pursuing a college degree kept me from doing so efficiently for the first four years. I still was active many of those days and did retain my data. To make up for the lack of activity, I used data primarily from John Ainsworth, N5XYO in DM90 to complete 2 more weeks of probability analysis to help better define the end of the Es season.   

The Purpose of the Study and What it shows:

I do not pretend to have any solid answers to what causes Es. Many others, most notably Emil Peacock –W3EP, Jim Kennedy – K6MIO/KH6, Patrick Dyer – WA5IYX, J.A. Pierce – W1JFO, and Melvin Wilson – W1DEI/W2BOC have investigated and documented the phenomena.  Others continue to analyze it today. But after my own operating experience and documentation, I began to believe that most were concentrating on the answers to its creation and that maybe there was some bias towards the normality and predictability of what Es will display.  I never believed that “Sporadic” was a good term to call it.   

The purpose of the study was to show that Es was a very natural and predictable propagation phenomenon, and that there was nothing too magical about it. I researched this on a mathematical, not a scientific basis.  Finally, it was incorrect for it to be called “Sporadic”.  I believe that this study clearly accomplishes it.  Es propagation of this nature should have a totally different description for its occurrence.  Along the way I made some interesting observations that should create forums for future discussions. I believe that the intensity of Es can influenced from outside elements.  But, in no way should these outside elements have any influence on the central point of the study in that seasonal Es are predictable.

The study is broken down into the following parts:
  1. Numerical activity, such as statistics yearly, daily, weekly, and hourly during the season.
  2. Distance analysis hourly by segments.
  3. Directional analysis hourly throughout the season.
  4. Probability analysis by weekly segments, by week, by hourly segments, and hourly.
  5. Spring/Summer Es Seasonal Calendar.  

I want to thank everyone involved with the PropNET organization.  Without the founders, programmers, forward-thinkers, and its participants, a study of this magnitude could not have been accomplished.

Solar Conditions during this 7-Year Study:

I have experienced on many occasions solar conditions having both an adverse and positive effect on Es conditions. Most notably, I have observed enhanced Es thanks to the beginning of a minor magnetic storm from a coronal mass ejection (CME). Some of my best late season 2-Meter Es events were due to these events. On the other hand, many excellent Es events on 10 and 6 Meters were abruptly ended by solar flares.

The 7 years could not have been more perfect as we have experienced one of the most prolonged bottoms of a solar cycle. For the first 6 years, solar flux was never high enough to support F2 propagation. MUF never was higher than 21 MHz. The final year, 2011 was there any real indication of an F2 influence. The low levels of solar activity kept disturbances to a minimum, therefore having only a minor impact.  Only twice in 7 years could I determine a prolonged affect. The first was very early in the season of 2008 and the second in mid-July 2010.  In 2011, the sun had become much more active. Whether it had a negative affect on Es propagation is difficult to determine.  Although it was the 2nd lowest productive year, the least productive season was during the minimum of the cycle (2008).

The following charts show average solar flux and the Ap indices for the 7 year period and the spring/summer season:   
From 2005 to 2008, solar flux steadily declined.  In 2009 it increased slightly and by 2011 it had finally exceeded 2006 levels. The Ap indices declined in succession for five years.  Solar flux averaged 80 or below for 5 years, slightly above 90 and at 100 for one year each.

Disclaimer for the 7-Year Study

This 7-Year Study occurred at the end of Solar Cycle 23, the lull between, the beginning of Cycle 24. It ended as Cycle 24 began to take off. It was learned during Cycle 24, that the predictions of the beginning of the season, the peak of and the ending of the Spring/Summer Es season was much harder to define. Also, as Cycle 24 developed it had deterred Es activity. It was an exponential (mathematical) decline through the peak. See:
Now that we are entering the end of this solar cycle, this study should be relevant again.

Spring/Summer Es Intensity Year to Year:

Due to the ending of Cycle 23, I thought that we would see a consistent improvement each year until we reached the bottom of the cycle.  After 7 years I have noticed that although there are indeed year to year consistencies, Es have their own schedule.  If any pattern was recognized in the study, it was that there could be a 3 year cycle (2 good years, 1 not so good).

The individual year hourly percentage breakdown shows a clear dual-peaked diurnal pattern for the last 5 of the 7 years measured.  If the first 2 years are averaged, there is a dual peak.  Only 2 consecutive years were extremely close in their hourly patterns (2009 & 2010).

The preceding charts are running 3 consecutive years of actual hourly captures throughout the total 7 years measured.  As noted earlier in every three consecutive years, one year’s activity is typically less than the other two. 

Next: How he Season Begins and Ends

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