Half Fail

Dew point wasn’t even 70. Relax bro. Weather wasn’t ideal but you can’t use that as an excuse. 80% humidity? Ha. That actually sounds like a dry morning in any place not called a desert.

I'd suggest some longer tempo runs of 15km or so X3 per week at race pace for strength and not dropping your mileage so far out from a race. You should really be keeping your mileage up high even up to a week or so out from your race. You're body doesn't need such an extended taper. Also definitely get in one long easier paced run per week of 1.5-2hrs, preferably with some hills. That should make a huge difference.

It's tough to run to potential in a half on less than 30 miles/week. I would try to get to consistent 40 mile week, with a peak closer to 50. The long runs need to be there no matter what the goal is. It isn't surprising that the wheels fell off at 10 miles when you hadn't run over 7 miles in training. Would recommend most get to at least 12-13 miles, if not 14-15.

As far as the plan goes, it doesn't look horrible minus the lack of a long run. 5 days/week is fine. 3 easy runs of 40:00-60:00, 1 workout (warm up, 8k-10k worth of threshold- straight or broken, cool down), 1 long run (at least 10 miles, build to 14-15, alternate goal pace or even goal marathon pace every other weekend- 3-6 miles straight or broken).

Something like that would help with the endurance side of things.

Appreciate it, all makes sense. I should clarify, I was doing longer runs, up to 2 hours for 12.5ish miles, but the last of which was 7 weeks out from the race. Felt strong on goal pace and tempo runs leading up, but had a feeling the mileage had dropped to low too far out.

I'm going to focus on the positive for a second. You ran a substantial PR that's the good news.

Your second 5K might have been your undoing,

Upper 23 1st 5 k, a minute faster for the second 5K, 25 and low change for the 3rd 5 k, approximately 29 minutes for the last 5 k. Those were approximately your 5K splits.

You just didn't have enough long runs to support your half marathon goals. You need to run 8 to 12 miles every week as a long run when training for a half marathon.

And you need to have a second run of six to eight miles every week. That second run of that six to eight miles each week could be a five mile or 10 km race,

Easy runs the rest of the week unless you want to throw in some sort of speed workout (ie 3/4 to 1-1/4 repeats)