AOPA Pilot Magazine - October 2020 - 96

FINALLY!
A CARD
FOR PILOTS.

P&E

WX WATCH

Valid: Wed 2020-07-29 21Z." Translated,
this means you're looking at a forecast nine
hours in the future, on Wednesday, July
29, 2020, at 21Z. Ideally, you want the latest initialization time available, bearing in
mind that there can be a delay between the
actual update and the time you receive it.
You can select valid times by clicking on buttons corresponding to the forecast intervals
that interest you.
FOUR MODELS

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There are plenty of websites that let you
access forecast models, but lately I've been
using pivotalweather.com and weathernerds.org. Once you log on, you'll see 10
or so model acronyms posted on the homepage, so click on one and off you go. What are
the strengths of each model?
The GFS (Global Forecast System)
is often called the "American" model,
as opposed to what is usually called the
"European" model put out by the ECMWF
(European Center for Medium-Range
Weather Forecasts). The GFS comes out
four times a day, with each initialization
making predictions for up to 384 hours
(16 days) in three-hour increments. This
makes it great for scoping out the weather
for trips up to two weeks in the future.
Just remember a cardinal rule: Forecast
accuracy of any model decreases with
time. The ECMWF model initializes every
12 hours, and predicts 240 hours into the
future. Maybe that's the reason why the
European model has a reputation for
greater accuracy. But the European model
is stingy with its data. It puts out far fewer
products-just pressure, winds, temperature, and precipitation-compared to
the GFS's dozens of datasets. But both let
you check out the weather in the United
States as well as the tropics, Europe, and
the Middle East.
The NAM (North American Mesoscale)
model comes out every six hours and predicts
for intervals out to 84 hours, or three days. Its
focus is on the continental United States, and
its resolution is denser than the GFS.
The HRRR (High Resolution Rapid
Refresh) model is worth a look in the
warmer months. That's because it puts out
"future radar" imagery. Click on the "composite reflectivity" or "1 km AGL [base]

96 | AOPA PILOT October 2020

reflectivity" links and up pops predictive
radar echoes. This imagery isn't meant for
making tactical weather-related decisions,
but it's great for advance situational awareness. The HRRR is a speed demon in that
it initializes every hour and can predict out
to 18 hours.
There are at least 20 additional models
but those will be more than enough to get
you started. Especially when you consider
that-geek alert!-if you click on a point in
the models' maps a Skew-T Log P chart fills
your screen. Studying numerical weather
prediction models may not count toward a
legal weather briefing, but with future radar,
future Skew-Ts, and forecasts days ahead of
any TAFs, what's not to like?
AOPA
EMAIL tom.horne@aopa.org

Partner-created content
SATELLITE WEATHER
PROVIDES WINTER FLYING
PILOTS WITH...
Icing NOWcast and freezing
levels. Icing NOWcast depicts the
current icing potential, severity,
and supercooled large droplets
in 3,000-foot layers from the surface up to 24,000 feet across the
continental United States. Freezing levels indicate the heights at
which the air temperature is at
or below freezing in contoured
increments of 100s of feet.
Two kinds of radar. High-resolution
composite radar is available coast
to coast and updates every 2.5
minutes-that's twice as fast as
ADS-B. Base reflectivity radar, updated every 5 minutes, shows what
is coming out of the bottom of the
storm and is beneficial to pilots flying below 10,000 feet.
Storm tracks and echo tops allow
you to monitor the speed and
direction of the most significant
weather.
aopa.org/siriusxm

http://www.weathernerds.org http://www.pivotalweather.com http://www.weathernerds.org http://www.AOPA.org/creditcard http://www.AOPA.org/creditcard http://www.aopa.org/siriusxm

AOPA Pilot Magazine - October 2020

Table of Contents for the Digital Edition of AOPA Pilot Magazine - October 2020