The Tax Cuts and Jobs Act of 2018 limited Personal Casualty Losses so that you can now only deduct casualty losses in the case of a federally declared disaster. If that occurs you have the option to deduct your losses in the year the loss occurs or the year before the loss occurs. This means you could amend your 2018 tax return to immediately deduct a loss from a 2019 disaster. However, keep in mind that you can only deduct the portion of the loss not covered by insurance so you may need to wait to see what will be covered by your insurance company first. Also be aware that you can only deduct these losses if you itemize and there are deductions and AGI limitations relating to deducting these losses.
For more information from the IRS see IRS News Release 2019-17.