Predict my half marathon time (Page 3)

1:42:30

My 10k PR came 2 weeks after my HM PR, 45:18 vs 1:40:19.  Had optimal running weather for both (~45-50F) like what you will have.  I did tempo/speed work as part of my HM training which was very helpful in helping gauge what pace I should be able to hold.  Go out and do a 5-7 mile tempo run to see what it feels like for you.

Do all you can to cut corners to avoid adding distance to your run. 

It's not true in every case, but it is the case with the OP. 

What I mean is this - if I'm running 30mpw and pull a 41 min 10k, and then I say I'm going to do a HM - on the same 30mpw, the prediction/fitness/running economy isn't going to change. If I do 30mpw and do a 1:35 HM and then decide to do a 5K on 30mpw, the volume doesn't change the prediction. The focus might change a bit, some longer runs, or faster runs but I'm still a 30mpw guy doing a 5K. 

If I all of a sudden double my volume, then my previous race isn't much use for prediction, since the added volume is going to make me faster overall.

This whole business about if you want to do a longer distance, the volume has to get longer doesn't make sense, other than the obvious minimums (which is where the marathon mcmillan calc is aggressive). Even worse is the thought that if you move back from HM to 10k you should somehow be running less.

I would set the priorities a little differently than this. Before adding in the 1-mile repeats I would recommend to add a couple of medium-length runs (e.g., 7-9 miles) during the week, as support for the long run. Those should help to make the long run feel a lot less of a stretch. Also, it seems that the OP may be limited by endurance more than by pace, based on his 5k time.

N=1, but I did 1:36 off of very similar volume and zero training miles faster than the HM pace I ran (and I don't have a massive historical base and am definitely in the middle of the bell curve when it comes to natural talent).  I still say OP can get under 1:40 pretty readily.

I have only run one marathon and a half dozen HMs, but for me, every race was determined by the last 5K (10K for the marathon). In a good performance, I could up the perceived effort which often means holding a pace rather than speeding up.

In my last race (20K), I ran 9:30 pace for the first third, 9:00 for second third (with "hills"), and 8:40 for the last third. For comparison, my training pace is 10+.

This thread became so much more than I hoped for (in a very good way).  Again I thank everyone for their input.

In the interest of continuing the thread and providing a tiny bit more information, I did a run yesterday at a harder/faster pace.  The km splits are in the log but the summary is that it was a 9k run, avg pace was 4:44/km or 7:38/mile.  I didn't look at my watch to try to go at a particular pace, I just ran at a pace that felt "comfortably hard" and one that I felt I could continue for a fairly long while.  When I stopped, I felt like I could have kept going at that effort level for quite a while longer.

One run isn't really a lot of information to go off and it's probably a bit short to use as a HM reference but it is what it is.

and the winner is........   well, before I announce a winner we need to decide if it's "price is right" rules or just the closest to the actual time.

acumenjay was closest without going over at 1:46:47 but Scout was closest to the actual time with the 1:50 prediction.  My final time was 1:49:22 - race report found here

Basically, I think Scout's (and others) prediction based on of a lack of hard runs and volume that was my main undoing but I also got a nasty sinus cold about 5 days before the race that still hasn't fully gone away.  Just to finish me off, we had a nice 20-25 MPH wind hitting us at about a 45 degree angle for the last 7k.  I was on pace for 1:45 or a little under up to that point.  The wind probably cost me about 2 mins but ultimately, I chalk it up to the training that I did (or didn't do).  Not having run at that pace for that long left me in rough shape towards the end of the run and the wind and hills just killed me even though everything felt really easy up to that point.

It was a great learning experience.