Texas Weather with Robin Hamilton

I had the opportunity to speak with Robin Hamilton about Texas XC-weather. Robin holds the current world record in straight distance with a Swift Light, flying 715.2 km from Zapata, TX.

Drylines

Is a dryline a prerequisite for a record day?

I don’t think so. You can fly a record on a normal XC day with nice cloud streets
Sometimes you’ll have convergences help.
Sebastien’s record flight was on a route east of a dryline. Sebastien’s reports sound like he believes the convergence helped
Robin, Johnny Durand, and Dustin Martin’s record flights weren’t assisted by a dryline convergence
Record day: keeping in the air for 10-12 hrs with 30 km/h tailwind

Cloud Streets

Are cloud streets a prerequisite for a record day?

Probably yes, on all days when people flew far there were streets.
Might not always see the clouds, but lifted is organized in lines
As soon as wind >8 mph, start to see streeting
Try to stay with cloud streets, as the areas between too sinky to survive
Streets often start at the coast and grow inwards, visible on satellite (see below)
- Sometimes clouds streets present >24h
- Shallow bays on coast serve as thermal triggers for streets
- By the coast streets already present when you wake up in the morning

*Cloud streets visible on satellite image*

Forecasting Tools

Where do you look?

Primarily XCskies, and National Weather Service. Skysight good for convergences
National Weather Service for satellite images & synoptic charts
- Also offers synoptic charts 3-7 days out: https://www.wpc.ncep.noaa.gov/medr/medr.shtml
XCskies
- Top of usable lift is a worthwhile parameter to check
- Buoyancy-to-shear ratio is useful too, however
  - B2S is sometimes overly pessimistic
    - especially early & late in the day
    - Have experienced B2S between 0 -1, which is lousy; but I was happily bouncing along under a cloud street
    - Does not appear to accurately predict the favorable conditions of a cloud street
  - B2S is a number, but wind can have different directions & strengths along a gradient
    - 45° of direction shift in wind over different altitudes usually a reason for skepticism

When to start

How do you know when to start?

Depends where. Near coast streets dare already there when you wake up
Never launched before 9
All launches south of San Antonio: People are in the air by 9:30 and on their way. 10-10:30-11 is too late for a big flight.
Robin was usually aero-towing, which allowed towing to 1000 m AGL
- Launching too early meant waiting 40 mins until back on a tow line
- With paragliders whinching from trucks, if wind not too strong, could potentially land back and relaunch without delay (as done in Caico). This would favor risking early launch.
Launch time usually given by visual cues
- Height of cloud base: 500m AGL is very little if you fall out of a street
- Usually wait for 2000 ft AGL cloud base
- Visual cloud quality

Flight

3 Phases

Coastal Plain: Flat, 300ft above sea level
Transition phase: Hill country
- Critical phase
- Decide which valley / line to follow up onto plateau
  - Limited LZ’s for landing a HG
  - Limited road access for retrieve
- 3 valleys lead in
Edward’s Plateau
- Could base 1000-2000 ft higher
- Can go fast again

Where to start

Advice: Try to get in some coastal plain flying before hill country starts. This gives you a few hours of good easy flying, arrive at hill country a few hours later and higher.

Launch sites

Long time only had Zapata airfield
- Very good for early morning
- Issues
  - SE blows you into Mexico
  - Laredo airspace, but with hang gliders could avoid that 80% of the time without problems
Hebronville
- 50 miles east, similar to Zapata
- Succesful launchpoint also for PG
- Dave Prentice knows well
Bracketville
- Sebastien’s site
- Rafa & Ben checked it out, appears to work
Cotula (SW of San Antonio)
- 6000 ft runway.
- good starting point
- Flight can follow highway