# How to break a long equation and align it with respect to itself as well as another equation

I have the following two equations which are aligned at the equal sign:

\begin{align}
\bm T_t & = \bm J(\bm\varTheta)\ddot{\bm\varTheta} + \bm D(\bm\varTheta)\dot{\bm\varTheta}^2 + \bm C\dot{\bm\varTheta} + \bm K\bm\varTheta - \bm T(\bm p_{cy}(\hat{\bm\varTheta}), \bm\varTheta, \dot{\bm\varTheta}) \\
%
T_w & = k_{15}\left[ \theta_{16}(t) - \theta_{15}(t) \right]
\end{align}


I would like to split equation 40 so that the + sign of the \bm C\dot{\bm\varTheta} term is aligned underneath the + sign from the \bm D(\bm\varTheta)\dot{\bm\varTheta}^2, whilst still maintaining the alignment at the equal sign for both equations.

I cannot find a way to do this because with the split environment its not possible to align equations, furthermore, if I use align at two places then I get two equation numbers. This means that I have to manually override the one number which results to the equation number being either on the first or on the second line of the first equation, rather than being in-between the lines.

In short, I would like to know how I can achieve something identical to the image below, which I have constructed by means of some pdf preview editing:

Thanks for the help in advance.

\documentclass{article}

\usepackage{bm,mathtools}

\begin{document}

\begin{align}
\begin{split}
\bm T_t & = \begin{aligned}[t]\bm J(\bm\varTheta)\ddot{\bm\varTheta} &+ \bm D(\bm\varTheta)\dot{\bm\varTheta}^2\\
& + \bm C\dot{\bm\varTheta} + \bm K\bm\varTheta - \bm T(\bm p_{cy}(\hat{\bm\varTheta}), \bm\varTheta, \dot{\bm\varTheta})
\end{aligned}
\end{split}\\
T_w & = k_{15}\left[ \theta_{16}(t) - \theta_{15}(t) \right]
\end{align}

\end{document}