Fix cross track point perturbation

[SorooshMani-NOAA]

Fixes #118

[SorooshMani-NOAA]

@WPringle I think the failed tests are due to wrong references. I'll do more testing on all the 3 storms from NHC, but can you check if you see anything wrong with the changes I made?

[WPringle]

@SorooshMani-NOAA Thanks for fix! Although it's strange since alpha already looks like it should be positive always and reason for not needing abs() value.

[SorooshMani-NOAA]

Although it's strange since alpha already looks like it should be positive

@WPringle I actually realized that later, but just wanted to be extra sure, the main fix was related to how 1 dim arrays where being incorrectly meaned or diffed

[WPringle]

Although it's strange since alpha already looks like it should be positive

@WPringle I actually realized that later, but just wanted to be extra sure, the main fix was related to how 1 dim arrays where being incorrectly meaned or diffed

oh right, gotcha. think everything looks good

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 21.29%. Comparing base (eede830) to head (5b7c4e4). Report is 14 commits behind head on main.

Files	Patch %	Lines
ensembleperturbation/perturbation/atcf.py	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #122 +/- ## ======================================= Coverage 21.29% 21.29% ======================================= Files 28 28 Lines 3762 3762 ======================================= Hits 801 801 Misses 2961 2961 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.