Failing to emphase some region using transparency on a spherical surface

EmphaseSelectedRegion.m

%% Main function
function [] = EmphaseSelectedRegion()
%[
    % Create data
    [X, Y, Z, Data] = createTestData();
    
    % Select max - xxdB region
    maxData = max(max(Data));
    W = ones(size(Data));
    W(Data < (maxData/1.2)) = 0;
      
    % Plots
    figure(1)
    
    subplot(2, 2, 1)
    surf(X, Y, Z, Data); shading interp; title('The data');  colorbar;
    
    subplot(2, 2, 2)
    surf(X, Y, Z, W); shading interp; title('The selected area'); colorbar;

    subplot(2, 2, 3)
    WAlpha = 0.5 + 0.5*W; % non selected => alpha = 0.5, selected ==> alpha = 1.0
    surf(X, Y, Z, WAlpha); shading interp; title('Alpha value'); colorbar;

    subplot(2, 2, 4); %%%%% Here non selected area is not appearing with an alpha = 0.5 %%%%%
    surf(X, Y, Z, Data, 'AlphaData', WAlpha, 'FaceAlpha', 'interp'); shading interp; title('Emphased data (not working)'); colorbar;    
%]

%% Function for creating test data
function [X, Y, Z, Data] = createTestData()
%[
    DEG2RAD = pi / 180;
    
    % Define spherical measurement grid
    azimuths = linspace(0, 360, 361) * DEG2RAD;
    elevations = linspace(0, 180, 181) * DEG2RAD;

    % Define spots location and spreading
    spotAzim = [45 180 -45] * DEG2RAD;
    spotElev = [45 90 135] * DEG2RAD;
    spotSigma = [45.0 35.0 55.0] * DEG2RAD;
    
    % Transform grid to cartesion
    [A, E] = ndgrid(azimuths, elevations);
    X = cos(A) .* sin(E);
    Y = sin(A) .* sin(E);
    Z = cos(E);
    
    % Define the data
    Data = zeros(size(A));
    count = length(spotAzim);
    for ki = 1 :count,
    
        % Transform spot to cartesion
        xspot = cos(spotAzim(ki)) .* sin(spotElev(ki));
        yspot = sin(spotAzim(ki)) .* sin(spotElev(ki));
        zspot = cos(spotElev(ki));
    
        % Compute angle between spot and each point in measurement grid
        DP = X * xspot + Y * yspot + Z * zspot;
        CPX = Y * zspot - Z * yspot;
        CPY = Z * xspot - X * zspot;
        CPZ = X * yspot - Y * xspot;
        CP = CPX .* CPX + CPY .* CPY + CPZ .* CPZ;
        Delta = atan2(CP, DP);
        
        % Create spot values
        ll = exp(- Delta.^2 / (2*spotSigma(ki)^2));
        ll = ll / max(max(ll));

        Data = Data + ll;
        
    end
%]