Hurricane Joaquin: Searching for consensus

Meteorologists love consensus.

Weather forecast confidence grows when the most trusted forecast models cluster around one outcome. In the forecasting game we call numerical weather prediction, ensemble mean forecasts from a suite of (many) models usually produce a better output than one single reliable forecast model.

But not always.

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European Centre for Medium Range Weather Forecasting

So what happens when you have a potentially major hurricane revving up and heading toward the densely populated and hurricane vulnerable U.S. east coast and most models favor a U.S. landfall, but one of the world's most trusted weather forecast models keeps the storm out to sea?

Increased forecast uncertainty.

The European (ECMWF) model is the most advanced weather forecast model in the world today. It's super charged computing power and high spatial resolution often produces the best forecasts on the planet.

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European Centre for Medium Range Weather Forecasting

You may recall the Euro nailed the forecast for Hurricane Sandy days in advance of other U.S. models, including NOAA's since upgraded GFS.

Still, even the trusty Euro has it's share of misses.

The Euro's recent eastern shift on the track of Hurricane Joaquin has forecasters at NOAA's National Hurricane center paying attention, even as they lean toward the growing cluster of models that predicts a westerly solution and U.S. landfall this weekend. The Euro is now the most notable outlier in a growing pool of westerly spaghetti model tracks for Joaquin.

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Still, echoes of the Euro's success with Sandy reverberate in NHC's forecast discussions for Joaquin.

There is an increased disagreement between the GFS, UKMET, Canadian, and NAVGEM models versus the ECMWF since the last advisory. The ECMWF has continued its forecast of showing a northeastward motion after 72 hours, taking Joaquin just west of Bermuda and out to sea. The other models have all shifted their forecasts to the left and now call for landfall in the Carolinas and the mid-Atlantic states, followed by merger with the baroclinic trough. Given the shift in the non-ECMWF models, a major westward adjustment has been made to the forecast track at 96 and 120 hours, bringing the center of Joaquin near or over portions of the mid-Atlantic states. Due to the use of the ECMWF in the consensus models, the new track lies near the various consensus models. However, it lies well to the east of the GFS and the other similar models.

Here's the official 5 p.m. EDT Wednesday NHC forecast track for Joaquin, a growing chance for a US landfall favoring North Carolina with a storm continuing up the Chesapeake Bay.

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Model intensity forecasts for Joaquin still favor strengthening to Category 3 status.

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NOAA's official forecast predicts a storm with 115 mph winds approaching the Outer Banks Saturday.

FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 24.3N 73.1W 75 KT 85 MPH

12H 01/0600Z 24.0N 73.8W 85 KT 100 MPH

24H 01/1800Z 23.9N 74.5W 90 KT 105 MPH

36H 02/0600Z 24.5N 75.0W 95 KT 110 MPH

48H 02/1800Z 25.8N 75.0W 100 KT 115 MPH

72H 03/1800Z 30.5N 74.5W 100 KT 115 MPH

96H 04/1800Z 36.0N 75.5W 85 KT 100 MPH

120H 05/1800Z 38.5N 76.5W 55 KT 65 MPH

The bottom line?

  • There is growing forecast consensus around a possible weekend landfall in the mid-Atlantic with Joaquin.

  • There is also still a (much) higher than average degree of forecast uncertainty given the Euro's continued easterly (out to sea) forecast track solution.

  • Forecasters will look for increased consensus in Thursday's model runs.

  • Will the Euro come into closer agreement with the suite of models that predict a western solution?

  • All persons along the U.S. east coast should remain on high alert, and in the early stages of preparation and planning for a potential hurricane strike.

Big picture: Flood threat may be the highest danger

While all the talk of eventual storm track and intensity with Joaquin is important, the biggest threat to the greatest number of people is likely to be widespread and potentially deadly flooding. Saturated ground and flooding from the last storm is already an issue in many eastern states. The multi inch to over 1 foot rainfall projections with Joaquin are likely to lead to widespread heavy flood zones this weekend into early next week.

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Stay tuned Thursday as the track projections for Joaquin hopefully show a goring degree of forecast confidence.

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