Real/unreal conditional

1. If X is happening, Y should have happened by now.

To my mind, the "if" in this structure expresses "accepting that", while the "should have" is epistemic, and expresses "less certainty" than the "has" in this version:

2. If X is happening, Y has happened.

If the speaker doesn't expect to witness Y, the structure is unremarkable:

3. If John is sitting in Reception, Bill should have noticed him by now.

(The speaker doesn't know if Bill has noticed John.)

In the original sentence, however, Y (the storm) would have happened "here", and the speaker would have witnessed it. So instead of speculation, the sentence seems to me to express "puzzlement":

4. If the storm is moving as quickly as the meteorologists say, it should have been here by now. [But it isn't here. Now why would that be? Are the meteorologists incompetent? Has the wingbeat of a giant roc interfered with the pressure distribution? Or did I just get my sums wrong?]

In the "type II conditional" version, on the other hand, the "if" expresses "supposing that", and the sentence as a whole seems to express "doubt in what the meterologists say":

5. If the storm were moving as quickly as the meteorologists say, it should/would have been here by now. [But it isn't here. So it can't be moving as quickly as the meteorologists say.]

___

Interpretations of if-statements do vary, though.

MrP

Hi MrP

Now that I look at the original poster's sentences again with more time at my disposal, I realise that it's the past participle been that I don't like. My ear tells me it's the wrong verb:
'If the storm is moving as quickly as the meteorologists say, it should have been here by now.'

I think the sentence would improve considerably if we replaced been with, say, arrived:
'If the storm is moving as quickly as the meteorologists say, it should have arrived here by now.'

I find that perfectly correct English. What does your educated native ear say? Should + the perfect infinitive have been to me denotes a state of affairs, not action, and my ear objects to this perfect infinitive have been coupled with by now.

Whether you agree or disagree with me, I must say English grammar is a very fascinating field of study and I enjoy reading your erudite analyses of sentence structures.

Cheers
CB

MrPedantic wrote:

I think the "have been" in this structure is related to e.g. 1. Have you ever been to Moscow? 2. "Have you seen MrQ?" "Yes, I'm afraid he's been and gone." Though seemingly stative, as you say, "have been" here does imply motion – either "going there and back", as in #1, or "coming here, staying, then going away", as in #2. (I would take the original sentence in the #2 sense.)

I fully agree that this implication of "motion" exists in such constructions.

To me, in many of the perfect forms "have" opens the doors for the past to enter the present, in many disguises

Each time I see a "have" in a perfect or similar construction, I think process and transition. That is, until the context tells me otherwise.