Hello and welcome to the 10th edition of EZNews!
At EZWxBrief, we really appreciate all of those subscribers that have recently joined, renewed their membership or signed up for auto-renewal. For those new to EZWxBrief, you won't find EZWxBrief in the App Store or Google Play store. For the best user experience, EZWxBrief is designed to run as a progressive web app (PWA) and must be specifically installed on your device which takes just a few seconds. Please see the Pilots Guide for more information on how to install EZWxBrief as a PWA on your devices. EZWxBrief Version 1.0.8 will be released shortly.
Want a FREE 30 minute 1-on-1 online training session? Here's how...
For a limited time, if you purchase the soft cover or eBook* version of Pilot Weather: From Solo to the Airlines you will receive a free 30 minute 1-on-1 online training session via Zoom with Dr. Scott Dennstaedt. You can use this 30 minutes of time to discuss any weather topic (e.g., icing, turbulence, Skew-T) or perhaps receive training to review the weather for a flight you are proposing.
Don’t wait, this offer is only valid for the first 15 customers who place an order.
Here’s how to purchase your copy of the new gold standard in aviation weather texts and save an additional $5. The total value of this offer is $64! To purchase, please visit https://www.avwxtraining.com/pilotweatherbook and add the soft cover, color eBook* or combo deal to your cart. To get the discount and free 30 minute session, please enter the promotion code FIVEOFFPW when viewing your shopping cart (see image below). You must apply this promotion code to receive this offer. A shipping charge of $10 will apply for domestic orders of the soft cover book. Please allow 7-10 days for USPS delivery.
The online training promo code will be emailed within 24 hours of your purchase. This email will also include instructions on how to redeem this offer. This offer is good through February 10, 2022 for the first 15 customers who order. The free 30 minute promotion code must be used before it expires on April 15, 2022. Online training times are subject to availability. You can conveniently pay via PayPal or you can use other major credit cards (you do NOT need a PayPal account). This offer cannot be applied to any product or service. If you have any questions about this offer, please feel free to contact us and we’ll be happy to help.
*Please note that the eBook requires the FREE Javelin e-reader to download and open the eBook. The eBook is not available for your Kindle or other e-readers. If you purchase the eBook, please allow 24 hours to receive instructions on how to download the Javelin e-reader and Pilot Weather eBook.
Aviation News Talk
Had a great opportunity to talk about cloud types and what to expect on Max Trescott's Aviation News Talk podcast. Check out Episode 218 here or search for Aviation News Talk on the Apple Podcast app.
We'd like to hear your thoughts
Would you be interested in watching a daily weather brief with your morning cup of coffee or tea? The format will be simple. It will consist of a short video that highlights the major aviation weather trouble spots throughout the conterminous U.S and southern Canada. It will not be a comprehensive overview of the weather but will attempt to focus on the current day's adverse weather and if there's time it also might consist of an outlook for the next day or two. The video will be recorded and posted online before 8 a.m. eastern time Monday through Friday. Check out Episode 31 of EZWxChat to see an example.
As a general aviation pilot, would this be useful? Please take this short two question survey to tell us what you think.
Airframe icing forecasts in EZWxBrief
On January 18, 2011, the Forecast Icing Potential available from aviationweather.gov and also available within the EZImagery collections received a much-needed facelift. At that time, the Forecast Icing "Potential" was transitioned to the Forecast Icing "Product" or FIP. This next generation FIP followed in the footsteps of its analysis counterpart, the Current Icing Product (CIP). A little over two years prior, the Current Icing "Potential" also got a facelift and was transitioned to a suite of three products, namely, CIP Probability, CIP Severity and CIP SLD - SLD stands for Supercooled Large Drop icing. It's critical to understand that the new calibrated version of FIP carries more than just a simple name change. Let's take a look at that change and what it means when interpreting it in EZWxBrief today. In addition to the icing forecasts in the EZRoute Profile and EZAirport Meteogram, you can find all of the static imagery analyses and forecast for icing and freezing level in the EZImagery as shown above.
Just like CIP, FIP consists of a suite of products, namely, FIP Probability, FIP Severity and FIP SLD. FIP severity includes the 25-percent and 50-percent masked FIP severity forecasts. With the addition of these three products, FIP Probability is now a calibrated probability forecast. While the FIP Severity field and FIP SLD field will look similar, the FIP probability field looks a bit different at lead times beyond six hours.
The old potential field wasn't calibrated, meaning that it was not a statistical probability. The colors representing the potential field were contoured at 95, 85, 75, 65, …, etc. However, for CIP and FIP's transition from an icing potential to an icing probability, the developers found that when calibrating it, they could not statistically justify probabilities in excess of 85 percent. As a result, the highest probability shown in red (below) indicates a 85-percent or greater probability of icing using the forecasts (75 percent on aviationweather.gov).
What's the difference between a calibrated and uncalibrated forecast?
First, CIP is an analysis. An analysis is not an icing forecast, but a glimpse of the icing environment in the recent past. CIP builds the icing environment based on observational data such as METARs, PIREPs (positive and negative), NEXRAD, satellite and lightning in addition to the various numerical weather prediction parameters supplied by the Rapid Refresh (RAP) model’s three hour forecast. Of course, we’re rarely 100-percent certain that icing exists, so the product is shown as a statistical probability. FIP, on the other hand, is strictly model-based and must take all of its icing diagnostics from the RAP model alone making for more uncertainty. Consequently, it will never be as good as CIP, but does provide valuable guidance for many pilots even out to 18 hours.
Here’s the crux of the difference between the potential (uncalibrated) and probability field (calibrated); as the forecast lead time increases, the probability of icing will generally decrease due to forecast uncertainty. If you look at a FIP probability forecast starting at two hours you will notice that the icing probabilities will generally decrease as lead time increases to 18 hours. It may appear to the unwary eye as if the icing is dissipating or lessening over time. While that may indeed be what is forecast to happen, the most likely reason for the decreasing probability is the uncertainty in the forecast, not a natural dissipation of icing. In other words, with a model-based solution, can you really be sure of an icing event that’s nearly 18 hours in the making with a high certainty? The old potential field didn't take this uncertainty into account. The result of the new calibrated field is a forecast with a 12 hour lead time doesn’t generally exceed a probability of 50 percent. At a forecast lead time of 18 hours, it's rare to see anything over 35 percent.
This will also affect the FIP masked icing severity. With a 12-hour forecast, the 50 percent masked severity field (shown below) will rarely show anything more than gray, which reflects the increase in uncertainty with forecast lead time. Even at 6 and 9 hours, the lack of any forecast probabilities above 60 percent will be evident.
Below is a comparison of the 12-hour maximum icing potential field (left) with the 12-hour maximum icing calibrated field (right). It is very evident that there's a marked decrease in values after the product was switched to a calibrated icing probability field. With the potential field there are lots of locations with values of 75 and greater. However, the calibrated probability field doesn’t exceed 45-percent which demonstrates the uncertainty with an increase in forecast lead time.
Over the last decade there have many “under the hood” improvements in the icing analyses and forecasts to include a better scheme for icing in convection, more accurate cloud top estimation, and enhanced supercooled large drop (SLD) forecasts. Keep in mind that the SLD forecast is still an uncalibrated potential field as discussed in this post. These more recent improvements did not change the look-and-feel of the product, but provides an added margin of safety for the flying public.
EZWxBrief also provides a calibrated forecast for icing in the EZRoute Profile and EZAirport Meteogram views. Shown above on the left is an early departure at 20Z from Denver showing the icing probability profile. Notice the probability is as high as 68 percent over Clayton Municipal Airpark (KCAO) at 8,000 feet MSL. On the right is about 12 hours later for a 10Z departure and while the icing areal coverage lessens quite a bit in this area for this departure time, the probabilities are much lower with a maximum shown at 30 percent due to the longer lead time.
Most pilots are weatherwise, but some are otherwise™
Dr. Scott Dennstaedt
Weather Systems Engineer
Founder, EZWxBrief
CFI & former NWS meteorologist
