A weather data processing apparatus comprising: a storage configured to store three-dimensional data of a cumulonimbus, the three-dimensional data including data of a density of raindrops, observed by a weather radar; and a processor configured to execute a display process for effecting three-dimensional image display of the cumulonimbus, wherein the processor is configured to: acquire the three-dimensional data from the storage; detect a core of the cumulonimbus, the core being a mass of raindrops with the highest density, by using a principal component analysis process to calculate a principal component based on a correlation between x, y, z variables at three-dimensional vertices of the three-dimensional data; calculate core detection data for effecting three-dimensional image display of the core; and execute a display process for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, wherein the processor is configured to: generate, as the display process, display information for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, in response to a request from a computer via a network; and transmit the display information to the computer via the network. a storage configured to store three-dimensional data of a cumulonimbus, the three-dimensional data including data of a density of raindrops, observed by a weather radar; and a processor configured to execute a display process for effecting three-dimensional image display of the cumulonimbus, wherein the processor is configured to: acquire the three-dimensional data from the storage; detect a core of the cumulonimbus, the core being a mass of raindrops with the highest density, by using a principal component analysis process to calculate a principal component based on a correlation between x, y, z variables at three-dimensional vertices of the three-dimensional data; calculate core detection data for effecting three-dimensional image display of the core; and execute a display process for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, wherein the processor is configured to: generate, as the display process, display information for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, in response to a request from a computer via a network; and transmit the display information to the computer via the network. acquire the three-dimensional data from the storage; detect a core of the cumulonimbus, the core being a mass of raindrops with the highest density, by using a principal component analysis process to calculate a principal component based on a correlation between x, y, z variables at three-dimensional vertices of the three-dimensional data; calculate core detection data for effecting three-dimensional image display of the core; and execute a display process for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, wherein the processor is configured to: generate, as the display process, display information for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, in response to a request from a computer via a network; and transmit the display information to the computer via the network. generate, as the display process, display information for effecting the three-dimensional display of the cumulonimbus and the three-dimensional image display of the core, based on the three-dimensional data of the cumulonimbus and the core detection data, in response to a request from a computer via a network; and transmit the display information to the computer via the network.