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The catenary degree is an invariant that measures the distance between factorisations of elements within an atomic monoid. In this paper, we classify which finite subsets of 
$\mathbb{Z}_{\geq 0}$ occur as the set of catenary degrees of a numerical monoid (that is, a co-finite, additive submonoid of 
$\mathbb{Z}_{\geq 0}$). In particular, we show that, with one exception, every finite subset of 
$\mathbb{Z}_{\geq 0}$ that can possibly occur as the set of catenary degrees of some atomic monoid is actually achieved by a numerical monoid.
Let 
$\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}M$ be a commutative cancellative monoid. For 
$m$ a nonunit in 
$M$, the catenary degree of 
$m$, denoted 
$c(m)$, and the tame degree of 
$m$, denoted 
$t(m)$, are combinatorial constants that describe the relationships between differing irreducible factorizations of 
$m$. These constants have been studied carefully in the literature for various kinds of monoids, including Krull monoids and numerical monoids. In this paper, we show for a given numerical monoid 
$S$ that the sequences 
$\{c(s)\}_{s\in S}$ and 
$\{t(s)\}_{s\in S}$ are both eventually periodic. We show similar behavior for several functions related to the catenary degree which have recently appeared in the literature. These results nicely complement the known result that the sequence 
$\{\Delta (s)\}_{s\in S}$ of delta sets of 
$S$ also satisfies a similar periodicity condition.
