Drought remains a significant threat to the humid tropical montane forests of the Eastern Himalaya. Nevertheless, existing monitoring frameworks often fail to capture the complex ecohydrological interactions of these sensitive ecosystems. This study introduces the Multivariate Water Stress-Vegetation Health Index (MWS-VHI), which integrates hydro-meteorological and biophysical variables, including rainfall, soil moisture, evapotranspiration, vegetation indices (NDVI and EVI), and land surface temperature. The index was scaled to a 0-100 range and coupled with Markov chain modelling to quantify its persistence, recurrence, and transition probabilities across defined ecosystem states. Analyses across five representative forest sites in Mizoram revealed strong resilience under high and very high vegetation health states, with gradual transitions between stress levels and no abrupt shifts between extreme drought and optimal conditions. Furthermore, sensitivity and Monte Carlo perturbation tests confirmed the robustness of the index, indicating that rainfall and soil moisture are the most significant parameters influencing forest growth in the region. The findings highlight that forests of Mizoram, while generally resilient, remain vulnerable to prolonged low-water-state conditions that recur less frequently but persist longer once established. The MWS-VHI framework provides a reliable, scalable tool for drought monitoring and forecasting in montane tropical forests. Its integration of vegetation health metrics with hydro-meteorological drivers provides actionable insights to support climate adaptation and mitigation, as well as forest management and biodiversity conservation measures in the region under future climate change scenarios.