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May 2023 EZNews

Hello and thanks for reading the 25th edition of EZNews!

We really appreciate those that have recently joined, renewed their annual membership or signed up for auto-renewal. We truly appreciate your generosity which helps support our continued innovation and growth moving forward. For members new to EZWxBrief, you won't find EZWxBrief in the App Store or Google Play Store. For the best user experience, EZWxBrief is optimized to run as a progressive web app (PWA) and must be installed on your device which takes less than 10 seconds per device. Follow the link above or see the 140+ page Pilots Guide for more information on how to install EZWxBrief as a PWA on all of your devices.


Keeping the NWS informed


In late April, Dr. Scott Dennstaedt was asked to be the keynote presenter and a panelist to a group of forecasters and other weather professionals from many facets of the aviation community to include the local Weather Forecast Offices (WFOs), Aviation Weather Center (AWC), Center Weather Service Units (CWSUs), National Transportation Safety Board (NTSB) and other stakeholders in aviation safety. This included well over 80 attendees from locations throughout the country. The goal was to provide them with a better understanding how the private sector in aviation, specifically general aviation, utilize the terminal aerodrome forecasts (TAFs) in their daily flight planning. It was good to hear their perspective as well which often does not have a great understanding of the needs of the general aviation pilot and instead will often focus on the needs of "heavy iron." After the presentation, it was decided that there needs to be a similar discussion with general aviation as the primary focus. That will likely be held early next year.

The Daily EZ Weather Brief...route planning edition


Starting on Monday, May 15th at 8 a.m. eastern time, Dr. Scott Dennstaedt will be providing a slight addition to the normal programming on his daily YouTube live broadcast. Every Monday, he will pick a route and show how to use the EZWxBrief progressive web app to plan a flight as it relates to weather. Some of the broadcasts will focus a flight that is proposed for the same day and others may show the process for extended range planning (more than a day in advance).

Even if you are not an EZWxBrief subscriber (you should be!) you will have the opportunity to learn how a CFI and aviation weather expert analyzes the weather along a route. If you want to tune in, please visit the EZWxBrief YouTube channel at https://youtube.com/@ezwxbrief and subscribe and click on that notification button so you won't miss his broadcast. If you can't attend live, you can watch the recorded version shortly after the broadcast ends. Hope to see you there and please let other pilots know about this educational opportunity.


Coming soon...an interview with Captain Doug Morris


If you own the Pilot Weather: From Solo to the Airlines eBook or softcover, you will recognize Doug's name. Scott and Doug collaborated nearly a decade ago to write the new gold standard of aviation weather texts and published it back in October 2018. For those that are unfamiliar with Doug's background, he is the captain of a Boeing 787 for Air Canada where he flies this aircraft to many locations throughout the world.


This interview will be broadcast live on the EZWxBrief YouTube channel where Scott will fire off some difficult questions at Doug to learn more about flying the Boeing 787 in and around adverse weather. Doug has unique qualifications since he is also a meteorologist. So we will ask him questions such as how he manages to navigate through the mesoscale convective systems in the Intertropical Convergence Zone (ITCZ). Hint: He's not relying on datalink weather!


We are working on a date and time for this program and will announce that shortly. Meanwhile, you can monitor the EZWxBrief community page where it will be formally announced. Also keep an eye out for a future blog post about this program.


Legacy AIRMET retirement delayed


As mentioned in the November 2022 EZNews, the legacy AIRMET is being retired. Public comments have been received and a vendor was hired to determine the overall impact of this change. Pulling the plug on this ubiquitous product is not an easy task. It must be coordinated with hundreds of vendors and government agencies so that they can be sure to have switched over to the Graphical AIRMET (G-AIRMET) which has been the operational product since 2010. The legacy AIRMET should be retired sometime in 2024 at the earliest, possibly later.


Clues buried in the forecast


To many pilots, the simulated reflectivity forecast (a.k.a. forecast radar) from the High Resolution Ensemble Forecast (HREF) you see below may look like some light precipitation that is expected over the Great Lakes region. However, there's more information packed into this forecast than what meets the eye.

Even if you have not looked at any other forecasts (e.g., prog charts, constant pressure charts, etc.) the first thing to note is the pattern that is presented in this instantaneous precipitation forecast. This clearly has an oval or circular shape that might even look like a spiral if you consider the area in the Northeast and Quebec, Canada. That's the first clue that this is associated with a large-scale upper-level (and likely occluded) weather system.


Why does this matter? This is important because such a system is a signal for cold air aloft over this region. Couple that with warm air at the surface and you might get what are referred to as instability rain or snow showers. Remember that showery precipitation is a convective process. This is clear from the forecast by noticing the cellular instantaneous precipitation pattern. Warm air near the ground and cold air aloft creates a large, and therefore, unstable lapse rate. Instability is, of course, just one ingredient in the convective recipe. Moisture and some form of outside energy contribution are the other two key ingredients.


No, this isn't deep, moist convection that you may see during the passage of a springtime cold front, but instability showers that often have rather low cloud tops. In fact, the tops of these showers are all likely below FL200 and much will likely be below 15,000 feet.

In the 500 mb forecast shown above, you can see a very large high-amplitude pattern across the U.S. and southern Canada. Specifically, notice the large upper-level trough over the Great Lakes and southern Ontario, Canada that matches the pattern of the simulated reflectivity forecast above. This kind of closed upper-level low is typically associated with a late-stage occluded weather system as can be seen in the surface analysis below over the same general region.

The typical progression of this precipitation is that it will "flare up" in the late morning to mid-afternoon as the heating of the day kicks in. However, this largely depends on how warm the ground is in the early morning and how cold it may be aloft. Of course, a weather system over the Great Lakes and draw moisture from these bodies of water as well as from the Atlantic Ocean.

While severe or extreme turbulence is not a huge worry in this showery precipitation, airframe icing is the biggest threat. There was no shortage of pilot weather reports (PIREPs) for icing on this day as can be seen on the EZMap showing a wide range of reports from light to severe over a six hour period. This includes several urgent pilot reports including the one below of heavy rime icing from 6,500 to 4,700 feet during a descent from an ERJ-145 near Cleveland.

These urgent PIREPs triggered the Aviation Weather Center to issue the SIGMET below for severe icing in the region downwind of Lake Erie from 4,000 to 8,000 feet MSL.

If you drill down using a Skew-T diagram over the Cleveland, it matches closely to what is occurring in this area. The sounding analysis below shows a saturated layer from 3,000 to 5,000 feet MSL. Temperatures in this layer are slightly below freezing. Although this is a relatively thin layer, the lapse rate in this layer is slightly greater than the moist adiabatic lapse rate...this is referred to as moist absolute instability. In other words, it is most unstable the atmosphere can be when it is saturated. This tends to wring out a lot of supercooled liquid water. Moreover, the entire profile here is capped by a very deep temperature inversion that will ultimately cap the vertical development of any clouds. But this still doesn't tell the complete story...the potential icing layer is deeper.

You must lift a parcel of air from the surface to better describe the magnitude of this icing threat. Below is the same sounding analysis, but also shows a surface-based parcel in magenta. This clearly shows the instability near the surface which extends up to the equilibrium level at roughly 9,000 feet MSL. In fact, you can see a fairly healthy area of convective available potential energy (CAPE). Therefore, the icing threat extends from the freezing level at 3,000 feet up to 9,000 feet. This matches the PIREP above pretty well.

Last but not least, all of these charts and diagrams are available in the EZWxBrief progressive web app. Do you want to learn more about the Skew-T log (p) diagram? Then consider purchasing the Skew-T log (p) and Me: A Primer for Pilots written by Dr. Scott Dennstaedt. It is available in both softcover and eBook format.


Most pilots are weatherwise, but some are otherwise™


Dr. Scott Dennstaedt

Weather Systems Engineer

Founder, EZWxBrief™

CFI & former NWS meteorologist






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