Interesting Weather Information

Monday, October 30, 2017

Cold Weekend, Cold Winter?


The weekend we just enjoyed was a cold one.

On Saturday (OCT 28) the high temperature was 41° tying the record Cold High Temperature set in 1910.

On Sunday (OCT 29) it was even colder. The high was only 39° but the record Cold High Temperature for that date is 34° set in 1925.

The last time we had a high temperature as cold as 39° was March 15, 2017 when the high was 33°.

Of course you have to have chilly air to have a high of 39° but chilly air can warm 20° with bright sunshine.

Thick Weekend Cloud Cover

The key to the weekend chill is thick cloud cover working with the chilly air. The cloud cover above us Saturday was 18,000 to 20,000 feet thick (or a bit more).  Enough sunshine gets through to brighten the night sky but not enough to warm the ground which warms the air.

Thick cloud cover  kept the air cold over the weekend.

The clouds were not as thick on Sunday, but thick enough that the weak, late October sunshine could not mix them out.

"Mixing out" means surface heating by the sun causes thermals of warm air to rise. If air rises it has to sink nearby to replace the rising air. This exchange mixes the moist air in the clouds with drier air and the cloud layer can thin or completely evaporate.

In summer clouds mix out much more easily because of the strong sunshine than in the other seasons.


Now to answer the question from Steve Horstmeyer's What's It Mean Meme #2.

One weekend of cold weather is not evidence that an entire season will be cold.

Now if we see the pattern that caused the chilly weekend persist and cold days are becoming common it could signal a trend.

For now we have to watch the  La Niña that is strengthening in the Equatorial Pacific.

More on that and other winter trends as they develop.

-Steve Horstmeyer

Friday, October 27, 2017

Wooly Bear - or - Wooly Bull?

Does the Wooly Bear predict the severity of the coming winter?

The short answer is no!

Wooly Bear caterpillar at Otto Armleder Memorial Park October 27, 2017


Folklore tells us more black means a longer, colder snowier winter and the position of the black tells you what part of winter will be the biggest headache. The Wooly Bear in the photo is black at its head and tail-end so tradition tells us winter will have a harsh beginning and end but a  long, mild, uneventful middle.

The Wooly Bear's body has 13 segments which tradition tells us correspond to each of the 13 weeks of winter. 


Wooly Bear folklore has a rich, long history and has it origins in Colonial America.  
The year 1938 was a banner year of the Wooly Bear myth. 

In that year Dr. Howard Curran, curator of entomology from the American Museum of Natural History, went to Bear Mountain State Park, up the Hudson River from New York City,  He counted the brown bands on 15 Wooly Bears and made the first winter prediction based on the caterpillars that eventually become Isabella Tiger Moths.  

The story was published by the New York Herald Tribune and picked up by the national press. 


Wooly Bear - Northeast U.S.
Wooly Worm - Southeast U.S.
Hedgehog Catepillar - because it often curls up in a defensive position when touched

What's Really Going On?

The amount of black and orange-brown depends on the age and species of the Wooly Bear. If the eatin' has been good during autumn there is more black and less orange-brown.

The Wolly Bear is telling you something, but it is about the recent past not the future. Good-for-caterpillar conditions mean fat and healthy Wooly Bears and more black not a harsh winter.

Isabella Tiger Moth (Pyrrharctia isabella) - the second part of a Wooly Bear's life. 

Friday, September 15, 2017

9th Anniversary of Hurricane Ike in Cincinnati

Here are graphics and animations I posted on SEP 13/14, 2017 in a variety of spots for the anniversary of Hurricane Ike.

You are free to use these for NON COMMERCIAL PURPOSES as long a proper attribution is given.

Gustav, Hanna and Ike. I was sent to Lake Charles, LA to help our station there with Gustav and when off duty drove into the decaying eyewall of CAT 1 Gustav.

Sunday SEP 14, 2008 Ike approaches Cincinnati

Track of Ike compared to the Great Galveston Hurricane of 1900. Both made landfall on Galveston Island, TX and both caused damage all the way to the Atlantic coast of Canada.

Saturday, August 19, 2017

Here is My Approach to Shooting the Eclipse

What I Want To Photograph

  • Several shots of the eclipse before and after totality.
  • Several near totality shots.
  • The solar corona during totality
  • Using a second camera a time-lapse of the location darkening and brightening into and out of the eclipse

Factors in My Equipment Selection

I will be on location broadcasting live on FOX19 NOW and social media so I cannot manage a large, cumbersome set up. - Light weight equipment, easy t hadle and adjust, no astronomical telescope, a modern DSLR fits the bill.

I will need to broadcast as I shoot. - Maybe handheld shooting - requires fast shutter speed for sharp image and to reduce light to sensor.

When the sun is un-obscured the amount of light is way too bright for a digital DSLR. - Special Filters are needed to reduce the radiation load on the sensor.

As the sun becomes obscured the amount of light decreases dramatically so I will need to adjust the camera sensitivity. I will use the camera in manual mode, change f-stop, or shutter speed or adjust a variable ND filter.

I do not know how large the solar corona will be at totality, so ... I need to use a Zoom Lens

Guiding Principles

  •  I need to reduce the amount of solar radiation reaching the camera sensor. 
  • About half of the sun's light reaching the surface is visible or shorter wavelengths (diagrams below).

  • I will use a 720nm IR filter - it allows only IR radiation through the lens to the sensor. The R72 filter should reduce the amount of solar radiation reaching the camera sensor by approximately 50%.
  • Transmission curve for Hoya R72 glass. Courtesy:
  • Hoya R72 glass eliminates almost all of the solar radiation with wavelengths shorter than 700nm. There is a transition from 0% to 97% transmission between 700nm and 750nm. Some very long wavelength visible red will leak into the photographs creating a red hue. For my final photos I will adjust color saturation, brightness and contrast in Photoshop. But this drastically reduces the light levels on the camera sensor.
  • All DLSR cameras have a built-in infrared blocking filter which will reduce the amount of  radiation further. Even though the R72 filter has cut the total solar radiation reaching the sensor in half the amount of IR still reaching the sensor could damage the sensor.
  • The combined transmission corves of the IR cut filter and the R72 filter show that what the camera will record is in the grey zone where both allow some solar radiation through.
Typical Canon IR cut filter transmission, Courtesy

Combined transmission curves of the Canon IR Cut filter and the R72 what gets to the sensor is in the grey zone.

  • To further reduce the amount of radiation reaching the sensor I will use a variable ND filter - this also makes it easy to adjust the settings as the eclipse progresses.

Test Results Saturday 8.19.2017

Canon Mirrorless M3 (Crop Factor 1.66)
Canon Lens EFS 55-250mm Full Zoom (Equivalent Lens Focal Length 415mm)
Canon Mount Adapter EF - EOS M
Manual Focus
Image Stabilization On
1/4000 sec.
F 32
ISO 100
Hoya R-72  720nm IR Filter
Tiffin Variable ND, Set at approximately 4 stops light reduction

Contrast increased (100) and brightness decreased (60), color adjusted in Photoshop

200% enlargement of above

Test Results Sunday 8.20.2017

Canon Mirrorless M3 (Crop Factor 1.66)
Canon Lens EFS 55-250mm Full Zoom (Equivalent Lens Focal Length 415mm)
Canon Mount Adapter EF - EOS M
Manual Focus
Image Stabilization On
1/4000 sec.
F 32
ISO 100
Hoya R-72  720nm IR Filter
Tiffin Variable ND, Set at approximately 6 stops light reduction
Contrast decreased (60) and brightness decreased (50), no color adjustment, in Photoshop

De-saturated the color, did some noise removal and tweaked brightness and contrast, enlarged.

Final Test

Compare to NASA High Resolution Image in Visible Light

Not bad for prosumer equipment vs. a multi-million dollar imaging system.

Test Results II Sunday 8.20.2017

Canon Mirrorless M Modified to Full Spectrum (IR cut filter removed) (Crop Factor 1.66)
Canon Lens EFS 55-250mm Full Zoom (Equivalent Lens Focal Length 415mm)
Canon Mount Adapter EF - EOS M
Manual Focus
Image Stabilization On
1/4000 sec.
F 22
ISO 100
Hoya U-340 UV Band Pass Filter
Tiffin Variable ND, Set at approximately 4 stops light reduction

Hoya U-340 Transmission Curve

  • Hoya U-340 glass transmits virtually no visible light (400nm - 700nm).  
  • This chart is for glass 2.5mm thick. The filter I am using is 2mm thick so I can expect to see some visible light in photos.
  • Spec sheets say that <0.1%, not zero, is transmitted in the visible range by 2.5mm glass.
  • Visible light output from the sun is immense so with a thinner than spec'ed filter and an intense source my camera should record UV, some Visible (skewed to red) and some IR. and yield a creamsicle orange sun before color correction.
  • This set up should decrease visible and IR by 99% and allow through plenty of UV. 


Either set up should work well but using the full spectrum camera with the U-340 filter will mean lower contrast, but less red in the images.

In IR, the first set-up, I will have to be meticulous when focusing manually.

I can reduce the amount of light further by increasing the effect of the variable ND filter up to when the criss-cross pattern appears and reduce reliance on Photoshop.

Tuesday, August 15, 2017

Maysville, KY Area Flash Flooding July 22 - 23, 2017 - Synoptic Analysis


During the evening of Saturday July 22, 2017 and the early morning hours of Sunday July 23, 2017 thunderstorms trained roughly along the Ohio River over southern Ohio and northern Kentucky resulting in nearly 8" of rain in approximately a 12 hour period.

Flash flooding claimed one life and there was extensive property and infrastructure damage in the area mostly from Maysville, KY to the northwest into Bracken Co.

The Synoptic Setting

During the afternoon of Saturday July 22, 2017 GOES-16  showed a very active convective environment across southern Indiana, southern Ohio and northern Kentucky.  

The GOES 16 Mesoscale Domain Sector (MCD) 1-minute satellite loop below showed multiple outflow boundaries and multiple lines of small convective cells acting to help initiate convection in the region. 

GOES 16 Mesoscale Domain Sector Saturday afternoon July 22, 2017 Courtesy: CIRA, Colorado State University.

 Surface analysis charts (below) showed a regional-scale convergence zone (solid black line) likely caused by three factors. 
  1. After two days of thunderstorms along and south of the front there were multiple outflow boundary remnants in the region.
  2. Pre-frontal convergence was occurring south of the quasi-stationary front.
  3. The synoptic air flow and terrain were interacting to increase the convergence.

The front, drawn as a cold front on the 00z surface, chart quickly became quasi-stationary as several weak, small lows rippled northeastward along the boundary.

Surface analysis 00z 23Jul2017. Note I used convergence (-divergence) to place boundaries and fronts - not traditional pressure, wind and dew point data. A well defined convergence zone is shown as a black solid line.  See below for the animated gif version, every two hours from 00z to 12z . Plotted with Digital Atmosphere 2015.

An animated gif radar loop from KILN starting at 00z 23 July 2017 and continuing through 12z July 2017 (8 PM EDT 22nd - 7 AM EDT 23rd) shows thunderstorms training to the southeast and increasing in intensity and coverage as interaction with the surface convergence zone took place.

From the 925 hPa and 700 hPa 00z streamlines it is obvious that the waves of rain were being steered by the winds at or around 700 hPa. 

In fact northwesterly flow dominated from above 900 hPa upwards past 450 hPa on the 00z KILN sounding steering the convective storms to the southeast.

Plotted and analyzed with Digital Atmosphere 2015

Plotted with RAOB

500 hPa

500 hPa analysis charts (height in geopotential meters, vorticity 10^-5 sec^-1) show a fast-moving shortwave trof moving out of Alberta, heading southeast and weakening across the northern Great Lakes.  In response 500 hPa heights fell across southern Ohio and northern Kentucky. At KILN the heights fell from 5880 m at 00z to 5830 m at 12z 23 JUL 2017. At KBNA the corresponding heights were 5920m and 5890m. The 500 hPa temperature at KILN fell during the same period from -4°C to -8°C. Further investigation will likely reveal the cooling aloft aided in maintaining the heavy rain clusters. The 5880m geopotential height contour highlighted in red to emphasize the height falls. Charts: Courtesy U.S. Taxpayers available at:

Rainfall Totals

The highest radar estimated rainfall total (7.96" new algorithm, 6.0" old algorithm) was southwest of Ripley, OH and 5.4 miles northwest of Maysville, KY (as mapped by RadarScope) over rural northwest Mason Co. KY.

Radar totals compared favorably with amounts reported to NWS ILN by observers. 

Even though surface observations were non-existent near where radar indicated the highest rainfall total, at the red "X", approximately 5.4 miles northwest of Maysville, a water rescue and flash flooding reported near Minerva (red circle) increases my confidence that the radar estimates were reliable. In addition a localized radar rainfall maximum of  6.80", is indicated 6.0 miles south-southwest of Maysville (yellow circle)  near where NWS ILN observers  reported 7.42" of rain. Courtesy NWS ILN.

Flooding was extensive and damage to property and infrastructure was extensive in this hilly area with deep, steep-sided creek valleys flowing into the Ohio River. One person was killed when his mobile home was washed into a tree and broke apart.

Convergence at the Surface

Convergence is what happens on an interstate highway as you approach an accident that is blocking part of the roadway. Divergence is what happens when you pass the accident. The same thing happens with flowing air for a variety of reasons.

When air converges at the surface, the air that piles up has only one way to go and that is up.

Convergence/Divergence from Change of Wind Speed
Convergence and divergence in the atmosphere or on the interstate. By: Steve Horstmeyer

On approaching the wreck,  the number of vehicles in a given distance increases - they converge. Once the accident is in your rear-view mirror the vehicles spread out again - they diverge. In the atmosphere is wind speeds decrease down stream convergence will take place unless there is some compensating motion.

Divergence and the flip side of the coin convergence is defined as the percent change in area per unit time. In three dimensions it is the percent change in volume per unit time.

Convergence along a Front/Boundary and Into a  Cyclone
Drawn by: Steve Horstmeyer based on originals by Leung Wai-hung at

Divergence Along a Ridge or Out of an Anticyclone
Drawn by: Steve Horstmeyer based on originals by Leung Wai-hung at

Divergence/Convergence Couplets in 3D Air Motion

Drawn by: Steve Horstmeyer based on originals by Leung Wai-hung at

By convention divergence is positive and convergence is negative. When there is convergence at the surface the only way the air can go is up.

Definition: Divergence/Convergence
Arrows represent surface winds at the corners of an area, originally a square.  As the square moves downwind the winds diverge and the square becomes a rectangle, larger in area than the original. Divergence has taken place. Later the rectangle is transported downwind and the winds now converge. The area of the rectangle decreases. Convergence has taken place. Note more can happen to the square, it can be rotated, lifted and contorted into new shapes. In addition we should really look at convergence and divergence in 3D and compute it for volumes of air. By: Steve Horstmeyer

Trajectories vs. Streamlines and Surface Convergence

Streamlines show a snapshot of the winds, they are an instantaneous view of air flow at a single point in time. Connect the dots to form streamlines and the big picture of air flow at one point in time is visible. The wind at any point is the tangent to the streamline at that point, 

Streamlines do not predict where an air parcel is going unless the weather systems are in a steady-state. That means the systems are stationary, the systems are not decaying or strengthening (i.e. the pressure gradient is not changing) and the systems are not filling or deepening (i.e the central pressure is not changing). This may seem confusing but if a cyclone, for example, grows larger and the central pressure does not change, the pressure gradient decreases.

 If you traverse the map below from Illinois, Missouri and Arkansas to the northeast and east you can see how the horizontal distance between individual streamlines is decreasing.  From Cincinnati eastward along the Ohio River heading eastern Kentucky and West Virginia the streamlines are noticeably closer.

I have added divergence values on the second map and on the third have shaded in the "channel" in which the air is flowing into and through the area that received flash flooding.

The "channel" is confined to the north by the front and to the south by a high pressure system.

Plotted and analyzed with Digital Atmosphere 2015

Plotted and analyzed with Digital Atmosphere 2015

Plotted and analyzed with Digital Atmosphere 2015


A trajectory is the path a parcel of air follows through time. The motion of a parcel of air is the combination of the winds of the weather system, the movement of the system and the change in strength of the system. If a system is in steady state trajectories are the same as streamlines. Trajectories are most often calculated in three dimensions.

The image below shows the trajectories of air originating in northeast Arkansas at 18z 22 July 2017, the afternoon before the flash flooding event in the vicinity of Maysville, KY. 

Note how the trajectories in the NOAA ARL HYSPLIT model are concentrated along the Ohio River. The paths are concentrated there because the air is in effect "channeled" between the front to the north and the anticyclone to the south. Several of the trajectories are spurious in post-event analysis. 

The video below the image uses the same data and goes into additional details.

Surface Maps

On the maps below notice that where you find high pressure the contour value is positive indicating divergence at the surface. Where there is low pressure like the front or the convergence line the value is negative indicating convergence. In addition, areas of surface convergence are areas of rising air.  The greater the convergence the faster the upward motion and the greater the chance thunderstorms will be enhanced.

Because of the three reasons mentioned in the video the surface convergence line (solid black) persisted through the evening of JUL 22 into Sunday morning JUL 23 and was a major player in the flash flooding event.

Plotted and analyzed with Digital Atmosphere 2015

Model Runs: NAM 4K  00z 23 JUL 2017 Run 

Below are cross section diagrams roughly from Jackson, KY (southeast) to Wilmington, OH northwest. The background shading is wind speed and the contours are vertical velocity in microbars/sec.  In pressure coordinates upward motion is negative because pressure decreases upwards.

Translucent shading shows selected areas of upward motion along and near the surface convergence zone highlighted only to draw attention to them.  Typical of high resolution models trying to resolve features near the size of the grid the NAM 4K has trouble pinning down the location of the upward motion.

In addition by 06z it appears convective feedback is beginning to dominate the output because of unrealistic increases in both upward and downward vertical motion.

Even though the high resolution models resolved the vertical motion associated with the surface convergence zone it is unlikely that a forecaster, using that alone, would have predicted  8" of rain in 12 hours.

However using all the available information presented here and watching the system as it developed, flash flooding, given the steep terrain and expected training was a forecast that most experienced meteorologists would have made.

Cross Sections Plotted with RAOB using  NAM 4K Bufkit data archived by Iowa State University.