Interfering bids. Overcalls, in NT, over a suit
"I've got a Strong No Trump hand, with a good stop in opponents' suit"
That's really all you need to know. What's interesting is that you are not promising a 5-card suit. (A 5-card suit is a fundamental requirement of a suit overcall).
So, you need to have 15+ HCP, a balanced hand, and a good stopper in the suit bid by your opponents. The stopper is fairly obvious: it's less likely than usual that you can rely on your partner to stop the opponents' suit (because you already know that a good chunk of the cards are to your right), and you know that RHO is reasonably strong, with at least 12HCP.
In the 4th seat and with a balanced hand, you can bid with 3 fewer points, see Protective double.
Oh yes, by the way. A problem with this bid is that you alert the enemy to your strength very early in the bidding, and you might fail to get a large penalty later. If that's the way you think, consider keeping Mum at first. For example, what if they are vulnerable, and you aren't ?
Replying to the overcall
If you use Stayman and Transfers after a normal NT opening, then it's best to use them after a one NT overcall.
Of course, you'll have to modify the point count requirements in Stayman and Transfers down by 3 (from 11 to 8) to account for the extra HCP strength of the Strong NT overcall, compared with the Weak NT opening point count.
Having said that, looking at Deal no. 3291216035, overcaller's partner (advancer) at West has only 6 HCP and a 4-card Heart suit. Incidentally, the bidding shown assumes that the players were not using Stayman and Transfers. If they had been, advancer would have passed. So perhaps with 19 HCP, the overcaller should have bid something else ? Let's have a look.
What about a super strong hand ?
Yes, with 19HCP, the risk of overcalling 1NT is exactly as shown in Deal 3291216035. With 6 HCP, adherence by advancer to NT point count "rules" will lead to a missed game. But 2NT might suggest 20HCP! And if you use the Unusual No Trump convention, which many good players do, it means something totally different (typically, 8+HCP and two 5-cards suits, at least one in an unbid minor).
So here's what you should do.
Basically double for take out, and rebid NT later:
19-20: Double and then bid No Trump
21-23: Double and then jump in No Trump
24-26: Double and rebid 3NT (or double and cue-bid)
Replying to the 1NT overcall, if the enemy meanwhile have continued to bid
Unusual, given that there's only 40 HCPs in the pack?
The opener to your left typically had 12+, so your partner had 15-18HCP to overcall in NT. The enemy's partner to your right has promised ~9+ to bid at the 2 level, leaving you with ~4 at the most! But if you do have 3-4, the points are split pretty equally between the teams. Time to compete!
Can you still use Stayman and Transfers? Not at all easily, no.
But the Lebensohl bid allows you to explain your hand quite well here. In summary:
- a new suit at the 2 level is non-forcing
- a new suit at the 3 level is forcing to game - so your suit must be long, with only 20HCP between you
- double is for take-out
- 2NT starts a weaker auction, e.g. allowing you to bid a suit lower ranking suit than RHO's without forcing to game
See also:
Takeout double
Protective double - fewer HCP required in the 4th seat
Michael's cue bid
Unusual 2 No Trump
Now try the quiz
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