Why an SS Richard Montgomery explosion would threaten the Thames

What if SS Richard Montgomery grounded and exploded in August 1944?

The Thames estuary and London would face a major blast and wave, although grounding and water depth would affect the exact result.

The scenario places the detonation in August 1944, while the ship's explosive cargo was still fresh. A major blast and damaging water movement in the Thames estuary are predicted. Grounding and partial submergence would affect how the blast propagated, with some force directed upward. The scale is left qualitative, and the most extreme tidal-wave predictions are explicitly qualified. The location of the cargo and its condition both matter to the imagined consequences for London.