Outside the Central Bank's headquarters on Dublin’s quays this week, the Irish summer delivered one of its weather shocks.

Torrential rain burst over neglected gutters and pools formed around street corners. Tourists looked stunned.

Inside, the economists of the Central Bank were describing their own economic shock: a no-deal Brexit.

As the deadline of 31 October looms and the politics of Brexit makes the possibility of a disorderly UK departure seem more real, the Central Bank has used its latest Quarterly Bulletin to sketch out what we might expect if it comes to pass in just three short months.

This exercise has been tried before. But this time, all minds have been concentrated and numbers honed by the looming October deadline.

In broad terms, the economy was predicted to grow next year by 4.1%. Under a no-deal Brexit, it would grow by just 0.7%.

There would be 34,000 fewer jobs next year and over the next ten years there would be 110,000 fewer jobs. The overall size of the economy would be reduced from what it could be over the next decade by 6%.

The Central Bank says its forecasts are worse than scenarios carried out earlier this year by the Department of Finance and the ESRI because they have factored in the knock-on effects a no-deal Brexit may have.

This means that if it happens, individuals and companies may be spooked into spending less and investing less. This would mean less money throughout the economy.

But the broad brush strokes probably hide the worse potential impacts of a disorderly Brexit. 

Parts of the country most dependent on food production and agriculture are most exposed. According to the Central Bank, one-in-five jobs in the Border and Midland region are in this industry compared to one-in-twelve nationally.

And then there's the UK economy. While we have rightly concentrated our attention on what the impact might be in Ireland, the Central Bank points out that the expected hit to the UK economy will in turn hit our exports, particularly if there’s a big fall in the value of sterling. 

Much of this is already happening. This week has seen sterling slide to almost 92p against the Euro.

Exporters are worried. Consumer sentiment has turned cautious. People here are saving more.

Over in the UK, businesses are investing less. There are fewer tourists from the UK visiting Ireland.

The politics of Brexit offers little guidance. In fact, the politics is adding fuel to the uncertainty.

In the midst of all of this uncertainty, the fact that the economy is continuing to expand at full tilt is quite remarkable.

If it wasn’t for the looming dark cloud of Brexit, this summer bulletin from the Central Bank would be a seasonal show stopper full of glorious detail about the thousands of jobs created in the economy and the remarkable absence of the inflation bogeyman.

We would all be talking about unbearable overheating and not scurrying for cover from a feared Brexit downpour.