National Hurricane Center Operational Overview and Challenges in 2019

Image courtesy of AP Dr. Michael J. Brennan Branch Chief, Hurricane Specialist Unit, National Hurricane Center Miami, FL 25 February 2020 2/25/2020 74th Interdepartmental Hurricane Conference 1 2019 Atlantic Hurricane Season

• 18 named storms, 6 hurricanes, including 3 major hurricanes • Dorian impacted the northern Bahamas as a category 5 hurricane producing catastrophic wind and surge damage • Hurricanes Humberto and Lorenzo affected and the , respectively • 6 storms affected the U.S. including Dorian and Barry as hurricanes

2/25/2020 74th Interdepartmental Hurricane Conference 2 Atlantic Sample Size - Fewer Forecasts in 2019 Compared to 2016-18

• 314 Atlantic basin forecasts issued in 2019 • Not as busy as 2016-18 • Close to the long-term average of 320

2/25/2020 74th Interdepartmental Hurricane Conference 3 2019 NHC Track Forecasting Got Off to a Good Start

All but Erin & Gabrielle’s mean Mean 2-day track error 55 n mi 2-day track errors were above Below the previous 5-year mean the 5-year average

*Only includes storms with verifying 48-h forecasts

2/25/2020 74th Interdepartmental Hurricane Conference 4 But 2019 Didn’t Finish as Well

Pablo & Sebastien were late-season, high-latitude 2019 mean 2-day track error 75 n mi storms that NHC and the Much higher previous 5-year mean models struggled with

*Only2/25/2020 includes storms with verifying74th Interdepartmental 48-h forecasts Hurricane Conference Hurricane Pablo 5 NHC Atlantic Official Track Forecast Errors

• Average NHC track forecast errors went up at short range in 2019, but there is still a long term downward trend with significant improvements at all lead times

2/25/2020 74th Interdepartmental Hurricane Conference 6 NHC Atlantic Track Guidance Official forecasts were very skillful and near the best performing models (consensus aids FSSE, HCCA, TVCA) EMXI best individual model, but not as good as NHC or consensus models EGRI was the next best model, followed by AEMI and GFSI NVGI, HMNI, and HWFI trailed in 2019

2/25/2020 74th Interdepartmental Hurricane Conference 7 NHC vs. Global Models in 2019 NHC neck and neck with ECMWF through 48 h, but NHC more skillful at days 3, 4, and 5

NHC NHC

2019

*Skill vs. Climatology and Persistence (OCD5) NHC Atlantic Official Intensity Forecast Errors

• Errors decreased slightly for short lead times, but large spike upward occurred at 96 and 120 h • Second largest annual error at 120 h

2/25/2020 74th Interdepartmental Hurricane Conference 9 NHC Atlantic Intensity Guidance Official forecasts very skillful near the consensus aids HCCA best model from 12 to 48 h, FSSE best from 72 to 120 h HWFI was a strong performer, best individual model at most times HMNI competitive with HWFI early, but trailed late DSHP and LGEM were fair performers, but not as good as HWFI and consensus models GFSI and EMXI had some skill, but not competitive with the remainder of the guidance

2/25/2020 74th Interdepartmental Hurricane Conference 10 Atlantic 2-Day Genesis Verification

• 48-h genesis forecasts were very well calibrated Low bias • Slight low bias at the high probabilities High bias

2/25/2020 74th Interdepartmental Hurricane Conference 11 Atlantic 5-Day Genesis Verification

• 5-day genesis forecasts were noisy, with a notable low bias at 20 Low bias and 30%

High bias

2/25/2020 74th Interdepartmental Hurricane Conference 12 2019 Challenges – Dorian Genesis ECMWF had no clue while the GFS was spot on 5 days out

ECMWF GFS 2019 Challenges – Dorian Genesis

ECMWF still had no clue while the GFS weaker/too far east 2 days out

ECMWF GFS 2019 Forecast Challenges Dorian’s Track and Intensity

Dorian 48 h track guidance 8/27 1200 UTC

Short-term track forecast difficulty occurred when Dorian’s center reformed farther northward on 27 August Resulted in short warning lead time for the 2/25/2020 74th Interdepartmental Hurricane Conference Virgin Islands 15 2019 Forecast Challenges Dorian’s Track and Intensity Hurricane Warning for the Virgin Islands

Wind gust to 111 mph in St. Thomas, U.S. Virgin Islands 2/25/2020 74th Interdepartmental Hurricane Conference 16 2019 Forecast Challenges Dorian’s Track and Intensity Dorian intensity guidance 8/27/18z • Difficulty in Dorian’s intensity forecast: • 100-kt error in 5 day intensity forecast • No model even a had major hurricane

2/25/2020 74th Interdepartmental Hurricane Conference 17 2019 Forecast Challenges Dorian’s Track and Intensity Why such large intensity errors?

Most of the track guidance initially predicted significant land interaction

2/25/2020 74th Interdepartmental Hurricane Conference 18 2019 Challenges Second Deadliest 2019 Atlantic Basin Storm Lorenzo – 19 Direct Fatalities – All Water Related

Hurricane Lorenzo • 11 offshore deaths due to sinking of the tug boat Bourbon Rhode • 3 crewmen rescued

• 8 rip current deaths in the 8 rip current United States from fatalities in the to Rhode Island United States

Sinking of Bourbon Rhode 11 fatalities 2019 Forecast Challenges Sebastien 48-hour Track Forecast Errors

NHC 48-h track errors for Sebastien Consensus model 48-h track errors for Sebastien

Both NHC forecasts and model guidance struggled with Sebastien’s track forecasts 2019 Forecast Challenges Sebastien 48-hour Track Forecast Errors 675 Mile 48-h Forecast Error Largest Since 2003!

Verifying Position

Equivalent to NHC Forecast distance from Miami to Cape Hatteras 2019 East Pacific Hurricane Season

• 17 named storms, 7 hurricanes, including 4 major hurricanes • Lots of short-lived TCs – 4 tropical storms lasted 2 days or less • Lorena, Narda, and Priscilla made landfall in or affected Mexico • Four TCs moved into the central North Pacific basin • ACE was 83% of long-term median

2/25/2020 74th Interdepartmental Hurricane Conference 22 East Pacific Sample Size – A Quiet Year

Quietest EP season since 2011 with 261 forecasts

2/25/2020 74th Interdepartmental Hurricane Conference 23 NHC East Pacific Official Track Forecast Errors

• Track errors increased in 2019 at all lead times, making the recent trends appear a little flat • Still impressive long-term improvements though

2/25/2020 74th Interdepartmental Hurricane Conference 24 NHC East Pacific Track Guidance

Official forecasts very good, but a little less skill than the consensus models in the short term EMXI best individual model, but less skill than the official forecasts and consensus models AEMI close to, but not quite as good as, EMXI EGRI was a strong performer through 96 h, second place model at times. GFSI, HWFI, HMNI are in the middle of the pack NVGI trailed

2/25/2020 74th Interdepartmental Hurricane Conference 25 NHC East Pacific Official Intensity Forecast Errors

• Errors went down in 2019 at the short lead times • Slow downward long-term trend at most periods

2/25/2020 74th Interdepartmental Hurricane Conference 26 NHC East Pacific Intensity Guidance Official forecasts better than the guidance early, but not quite as good as the consensus aids after that. No skill at 96 and 120 h! IVCN, FSSE, and HCCA best models early, but trailed late HWFI was a strong performer through 48 h, but skill dropped off sharply after that DSHP and LGEM only skillful models throughout and were best at 96 and 120 h GFSI and EMXI not very skillful early, but among the better guidance at the long leads

2/25/2020 74th Interdepartmental Hurricane Conference 27 East Pacific 2-Day Genesis Verification

• 48-h forecasts were reliable and well calibrated across the Low bias board

High bias

2/25/2020 74th Interdepartmental Hurricane Conference 28 East Pacific 5-Day Genesis Verification

• 5-day genesis forecasts were well calibrated, Low bias except at 50%

High bias

2/25/2020 74th Interdepartmental Hurricane Conference 29 Thank You

Questions?

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2/25/2020 74th Interdepartmental Hurricane Conference 30