How to Forecast

by Eric

Check out my Forecast page which has a collection of current charts and outlooks all on one page.


To get started….I believe it’s critical to understand some foundational things before you dive into the fun part of weather. If you skip to some of the advanced stuff too early, you might get by for awhile, but it will eventually catch up to you.  You can memorize what certain topics mean…but you will always struggle with understanding why. This is important in weather, because every day is unique…and you often need to draw from that foundational knowledge to interpret new situations.

Key Message: if it seems boring, too basic, or too difficult… stick with it and make sure you understand it 100%. It will come back to serve you multiple times later. 

Ok, let’s dive in…

Learning Forecasting

1. How weather is created and moves across the US

Basic Topics: The jet stream, high/low pressure, troughs/ridges, shortwaves, fronts.
Advanced Topics: Jet streak Entrance/Exit, types of jet stream patterns (zonal flow, vs. omega blocks, etc.), trough tilts (positive vs. negative), trough placements vertically at different elevations of atmosphere (it’s not usually perfect vertical in the atmosphere) – and the impact of wind associated

2. How to read weather charts

Basic Topics: things like pressure or temperature gradients, wind barbs, surface observations, soundings (mentioned earlier), etc. etc. But knowing how all of those impact and are different at the different parts of the atmosphere. 200/300, 500, 700, 850, 925, 1000/Sfc. They sound trivial, but each one is uniquely important to what is going on.
Resources: https://www.youtube.com/watch?v=CdriWGlYR2k&list=PLnjboQ2ku8GAt1OG-43VexTgFZdRSl2w0

3. The ingredients necessary for Thunderstorms

Basic Topics: see Thunderstorm Ingredients
Advanced Topics: Learn as much as you can about reading a Sounding (Skew-T and Hodograph) ← this is normally a semester of college work. There’s a lot and it’s difficult. You don’t have to know all of it…but you should be able to look at a skew-t and see the red/green lines + parcel trace and know how that impacts the atmosphere. Same with Hodograph. Curvature, Streamwise vs. Crosswise, Storm Relative Motion, etc.
Resources: https://www.youtube.com/watch?v=ztrDMo6f0Ls and https://www.youtube.com/watch?v=SJUqR26nJBE

Forecasting Strategy

When it comes to forecasting, the key is to do it often (it’s always easier to start from a baseline of the previous day, than to start completely from scratch). I know this isn’t always possible, but just sharing. 
I also find it helpful to follow some sort of structure or flow each time. Forecast the same way every day.  As you learn more, you’ll find it easier to discover where your forecasting has gaps and you’ll make those gaps for the next day. I feel like every day I get better but also realize what I missed the day before. 

Example Forecast Strategy (very basic outline)

1. What is going on/moving in upper atmosphere (jetstream area ~200/300mb).
Use Global models (ECMWF or GFS) if you are more than a few days out.
Use Regional models (NAM) if you are < 2 days out. 
Use Mesoscale Analysis page if you are same day

2. What is going on/moving in middle atmosphere (~500mb)
Use Global models (ECMWF or GFS) if you are more than a few days out.
Use Regional models (NAM) if you are < 2 days out. 
Use Mesoscale Analysis page if you are same day

3. What is going on/moving near the surface (Surface Observations)
Surface Analysis     Satellite “Clouds” (Red Layer)      Satellite “Water Vapor”      Soundings (every 12hrs)

4. Do I have my Thunderstorm Ingredients?  If so, which ones are strongest? Where?

5. Do I have significant gaps in my Thunderstorm Ingredients? What is missing?  Where?

6. Compare #1-5 above against different models and ensembles (blended models)

FAQ

Q: What apps should I use?
A: There aren’t really great ‘mobile apps’ for forecasting.  A solid radar app (RadarScope, Radar Omega) only tells you “what is happening” right now – it does not predict the future.  

I would avoid weather apps like Weather Bug, etc. that have radar features like “Futurecast” which try to show radar in the future.  The main reason is because you don’t know which forecast model that came from and you can’t look at all the other parameters that contributed to that. 

“Wx” is one of the more comprehensive apps that links to many of the resources mentioned above. It’s not super UI-friendly, but once you get used to it, there’s a lot there.



Q: What are good apps for looking at current weather?
A:
1. A good radar app is essential. Radar Scope and Radar Omega are the leaders. Both have tiered subscriptions that, in my opinion, are very valuable if you are serious about detail.
2. A good satellite app is also helpful. I like SatSquatch. This is free for just satellite, but the paid option allows you to overlay other parameter data (like CAPE, temp, wind, lapse rates, etc) which can be helpful.

Future Updates Planned
-Specific values/thresholds ("criteria") to look for when forecasting
-Advanced Weather / Forecasting Resources