Unofficial Forecast Global and Basin Tropical Cyclone (TC) ACE from Operational Models

Unofficial Forecast Global and Basin Tropical Cyclone (TC) ACE from Operational Models
Robert Hart, Florida State University, rhart@fsu.edu

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Latest Individual Models Global Perspective: CMC GFS HMONs HWRFs JMA NAVGEM UKM
Deterministic Comparisons by Basin: Global NHEMIS SHEMIS NATL NEPAC NWPAC NIND SIND AUST SWPAC SEPAC SATL
Ensemble Comparisons by Basin: Global NHEMIS SHEMIS NATL NEPAC NWPAC NIND SIND AUST SWPAC SEPAC SATL
Model Global Animations: CMC GFS HWRF JMA NAVGEM UKM Deterministic Ensemble
Important information about these graphics:

They are unofficial, including all tracks and implied intensities. Please use operational outlets for official forecasts, such as local WFOs, NHC, JTWC, and JMA.

All tracks shown here do not explicitly use any of the official location/forecast track (ATCF) data. In other words, all cyclones shown are detected and tracked via raw model output independently of what is officially declared as a tropical cyclone (TC). Of course, the hope is that all official TCs are included by this detection as well as those TCs forecast to develop in the models but not yet officially declared a TC. However, there is no guarantee of this.

If any of this information thus far is confusing to you, forget all of it, or pretend it never happened.

The goal of these graphics is to estimate the aggregate global and basin-level Accumulated Cyclone Energy (ACE) for model-forecast TCs.

In order to only count ACE generated by estimated model TCs of 35kt or greater (per the definition for ACE) the following rules are used for including the cyclone:

The cyclone must have water nearby (within 2° lat/lon) that is 22°C or warmer (thus allows for also counting TCs that have made landfall recently).
The lower-tropospheric thermal wind (VTL) from cyclone phase diagnostics must exceed a value of 5. Once a cyclone has exceeded this, should the value of VTL go below -5, then extratropical transition (ET) is assumed to have occurred and the ACE is no longer included (see HWRF exception below).
The wind used in the ACE calculation is the strongest wind at 850mb within 5° lat/lon, reduced by 20%. This is not optimal, but is the most apples to apples comparison possible here given the 10m wind in the models all have significant biases.
The cyclone's contribution to ACE must last 24 hours.
The above criteria attempt to exclude warm-core cyclones that have formed over land and also warm-seclusion extratropical cyclones over water. Note that the above criteria are imperfect and they will likely require subtle future revision.

For the HWRF runs, only the "core" domain for each run is used. As a result, TC genesis outside the core domain will not be counted here. Also note that the CPS values are not calculated for the HWRF core runs at this time.

The 06, 18Z JMA runs are through 132hr. The 00Z, 12Z JMA runs are through 264hr (through 180hr used here).

The models used here all have very different output gridspacing and thus the ACE values shown here can be different for that reason alone (among many others).

In most cases, clicking on an image or animation will bring up a larger-sized version of it.

The demarcations for the basin-level graphics follow the WMO definitions of the individual basins, as shown below. The two exceptions are the South Atlantic "SATL" and the Southeast Pacific "SEPAC" which have been added here to detect and quantify very rare but important activity in this area. A "Mediterranean" basin may be added in the near future.

Thanks to Chris Landsea (NOAA/NHC) for clarification of the basin definitions (for the official basins) shown above.

As with most products produced on this web site, I am eternally grateful for the efforts of the GrADS and OpenGrADS development teams that make such products possible.

If you have any questions on these graphics or the process please contact Bob Hart at rhart@fsu.edu.