I read in the WA Residential Landlord Tenant Act that a lease over 12 months must be notorized. Is this enforceable?

Because an oral rental agreement can be valid, the failure of the long term written agreement to fully comply with statutory requirements does not necessarily void the written agreement entirely.

The judge hearing the case may decide that the lease is definite for one year and converts to a month to month rental after the one year. Alternatively, the judge may decide that the agreement follows that statutory Residential Landlord-Tenant Act which has the default rental period as month to month.

In general, the tenant can be liable for the rent for the entire rental period. However, the landlord has a duty to mitigate the landlord's damages in case the tenant abandons the rental.

How much you would end up paying for breaking your rental agreement depends on your specific facts. You should review those facts with local attorneys who likely are more aware of local practices of the court and the rental market.