I'm trying to figure out if I'm in good enough shape to PR on my 5K coming up on Thanksgiving (currently 18 days away). Here are the stats:
5K PR 30:16 (2011)
Today I had a great training run. 1 mile warmup (11mm), 1 mile fast (9:36 w/ 2 very short hills), 1+ mile recovery (walk/jog), 1 mile fast (9:32, flat), cooldown. 4.5 miles total.
Lately I've been running about 10 miles a week, 2-5 miles per run with a pace usually in the 10-11:30 mm range. Under 10 for speed work.
Because my stride is so short, I don't think the McMillan running calculator is accurate for me.
For example, if I put in a 9:32 mile it gives me a 33:14 5K time. I can beat that easily.
But if I put in a 30:16 5K, it gives me a mile time of 8:40. I've never been able to run that fast in my life. I'm running very hard, 200 steps per minute, to achieve 9:32. My fastest mile ever is 9:20.
So, what you do think my 5K time will be? Points to whoever is closest.
Guadalupe River Run 10K April 2013 (1:01:36) PR!!
Turkey Trot 5K Nov 2012
RSS Fun Run 10K May 2012 (1:03:17)
Mermaid Run 10K May 2012 (1:09:37)
Turkey Trot 10K Nov 2011 (1:05:20)
Firefly 5K Oct 2011 (49:14) - with DH and DS at son's pace
The difficulty of the course is sometimes the greatest influence, as I am sure you know. The other thing that matters the most is your actually training route along with other routines, overall miles and so on. If you have the opportunity to do some additional speed work along with extended out a few longer runs, then it will benefit your efforts and confidence (even in a few short weeks), so getting beyond the 10 miles per week schedule will really help.
I agree with you about some of the difficulties with running calculators. They offer ballpark estimates, but there are just too many other variables to be considered on an individual basis and per specific race challenges.
It sounds like you are doing wonderfully with intervals, so my only recommendation would be to add another training day and push out a few long runs beyond five miles. (Implement a couple of 10k tempo runs, for example).
Anyway, back to your original question, you can certainly PR on the Thanksgiving 5k. A few extra things and the 9.1 or 9.2 per mile is consistent with a predicted finish time between 28:21 to 28:52...you can do it and continue to improve.
You should read through all the documentation that accompanies McMillan's Pace Calculator. 8:40 is the prediction for a 1-mile race, not a mile in the middle of a training run. You're right that the Calculator is unlikely to be accurate for you, but your short stride really has nothing to do with it. The Calculator assumes "...you are properly trained for that distance." 10 or so miles per week is not nearly enough to be considered "properly trained" by McMillan standards.
All that aside, your current PR pace is about 9:44 per mile. You are already running faster than that in training, admittedly not 3 miles straight. Try taking less recovery between your fast miles, say 1/2 mile instead of a full mile. I wouldn't be surprised if you take a minute of your PR, and the potential is there for hitting 28 minutes within a few months, with continued training, particularly if you can increase your weekly mileage.