# RELEASE NOTES: nhc_guidance_v5.1.0

* **Model Version:** nhc_guidance_v5.1.0
* **Released to NCO on:** 03/11/2026
* **Release Tag:** [v5.1.0 Repository](https://vlab.noaa.gov/gitlab-community/NWS/Operations/NCEP/NHC/TSB/nhc-guidance-suite.git)

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## 🌀 Purpose and Scope
The National Hurricane Center (NHC) utilizes a suite of simplified tropical cyclone track and intensity forecast models and consensus forecast models.

* **Model Methodology:** All intensity models are statistically based. Track models include simplified dynamical models, statistical models, and processing that reformats output from global models.
* **Major Upgrade:** This version includes the retraining of SHIPS/LGEM, SHIPS-RII, and DTOPS to incorporate data from the 2025 hurricane season.
* **Operational Context:** The suite runs on demand for any number of storms requested by NHC/CPHC during each six-hour forecast cycle when storms are present in the Atlantic, East Pacific, and Central Pacific basins.
* **Platform:** Operational execution occurs on the National Weather Service (NWS) Weather and Climate Operational Supercomputing System (WCOSS).

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## 🛠 System Environment

### Primary Developers
Rachel Zelinsky (NHC/TSB), Matt Onderlinde (NHC/TSB), Mark DeMaria (CIRA/CSU), Kate Musgrave (CIRA/CSU), John Kaplan (OAR/AOML), Jon Martinez (CIRA/CSU), and other contributors.

### Software and Compilers
* **Compiler:** `ftn`
* **Build Modules:** `PrgEnv-intel/8.3.3`, `intel/19.1.3.304`, `craype/2.7.17`
* **Runtime Modules (JNHC_GUIDANCE):** `grib_util/1.2.4`, `wgrib2/2.0.8`, `ve/nhcg/v5.1`
* **Python Dependencies:** `numpy`, `xarray`, `scipy`, `pyresample`, `toml`

### WCOSS Model Dependencies
* `gfs/v16.3`
* `hwrf/v13.2`
* `hmon/v3.2`
* `hafs/v1.0`
* `ens_tracker/v1.3`

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## 📂 Package Modifications

### Documentation (`doc/`)
* **Removed:** All previous documentation.
* **New:** `nhcg_v5.1.0_release-notes.docx`, `nhcg_v5.1.0_implementation-instructions.docx`, `nhcg_v5.1.0_test-plan.docx`, and `nhcg_v5.1.0_production-overview.pdf`.

### Model Parameters (`parm/`)
Significant updates to 2026 coefficient and regression files:
* **DTOPS:** Updated AL and EP coefficients and EMX regression data for 2026.
* **SHIPS:** Updated `ship126_coef_atlc.dat`, `shipl26_coef_epac.dat`, `ships26_coef_atic.dat`, and `ships26_coef_epac.dat`.
* **RII2O:** Updated AL and EP coefficient and probability files.
* **Attributes:** Updated `eoch_attribute_v1.txt`, `sohc_attributes.txt`, and `satnc_to_bin.toml`.

### Code and Scripts
* **Jobs:** Added `SATDIR` for GOES 18/19 Channel 13 files.
* **Bugzilla Fixes:**
    * **1427:** Removed `date` command in `JNHC_GUIDANCE`.
    * **239:** Removed unused code containing "go to" statements.
    * **1643:** Fixed end-of-file error in `dtops_run_combined.sh`.
* **Added Source:** `satnc_to_bin.py`, `test_satnc_to_bin.py`, and `irrp_check.f90`.
* **Removed Scripts:** `hcca_nhc_to_ATCF.py`.

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## 📉 Data Flow

### Key Inputs
* **WCOSS Models:** Grib2 GFS and ECMWF files for SHIPS and LGEM.
* **Trackers:** NCEP Global, HAFS, HWRF, and HMON model trackers.
* **Satellite/Obs:** GOES 18/19 imagery, SST Analysis, and OHC Analysis for SHIPS.
* **NHC/CPHC:** Storm compute files (`.com`), IP source files (`.ip`), and b-deck files.

### Primary Outputs
* **Critical Output:** ATCF a-deck and GFS SHIPS output text files.
* **Other Output:** ECMWF SHIPS output files and HCCA output logs identifying included models.
* **Research Data:** IR radial profiles and principal component files returned to NHC.

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## ⚡ Performance and Resources

| Metric | Specification |
| :--- | :--- |
| **Runtime (Per Storm)** | ~3–4 minutes of CPU time |
| **HCCA Training Script** | < 10 minutes |
| **Disk Space (Guidance)** | < 10 MB per storm run |
| **Disk Space (HCCA)** | < 1 GB for inputs and outputs |
| **Concurrency** | Max 5 storms simultaneously; others are queued |

### Resource Specifications
* **jnhc_storm_datachk.ecf:** 2 ncpus, 500MB memory.
* **jnhc_guidance.ecf:** 2 ncpus, 5GB memory.
* **jnhc_guidance_hcca_train.ecf:** 1 ncpu, 10GB memory.

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## 📡 Dissemination
Model output is distributed via a dbnet alert to NCO Dataflow, which inserts the data into an LDM queue for transmission to NHC, CPHC, and WPC ATCF systems. No dissemination modifications were required for this delivery.