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WTNT44 KNHC 301449
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016
1100 AM EDT FRI SEP 30 2016

Matthew has continued to intensify this morning. An Air Force Reserve Hurricane Hunter aircraft recently measured a peak SFMR wind of 99 kt and a 700-mb wind of 103 kt. Based on these data, the initial intensity is set to 100 kt for this advisory. The aircraft reported that the central pressure had fallen to 968 mb, and also observed a 16 n mi wide eye that is open to the southwest. Water vapor imagery shows a well-established poleward outflow channel, with outflow also expanding in the southwest quadrant.

This intensification has occurred despite analyzed southwesterly shear of around 20 kt. The SHIPS model output shows this shear continuing for the next 36 hours or so, and as a result, the SHIPS and LGEM models show Matthew weakening during this time. This weakening trend is also shown by the HWRF and COAMPS-TC hurricane models. However, I am reluctant to show a decrease in intensity given that the environment around the cyclone does not appear to change much. Some short-term fluctuations in intensity are certainly possible, but the official forecast remains above much of the guidance in the short range and keeps the intensity at 100 kt through 72 hours. Some weakening is shown by days 4 and 5 due to potential land interaction. Late in the period the NHC forecast is closest to the HWRF model.

Matthew has been moving west-southwestward during the past few hours, with an initial motion estimate of 255/10. The cyclone should continue moving south of due west for the next 12 hours to the south of a mid-level ridge nosing into the northern Caribbean Sea. After that, Matthew should gradually turn poleward as the ridge retreats eastward and a trough moves into the eastern Gulf of Mexico. There remains a large amount of spread in the guidance, both along and across track. The ECMWF, ECMWF ensemble mean, and the UKMET are slower and on the right side of the guidance envelope at 48 hours and beyond. The GFS, GEFS ensemble mean, HWRF, and COAMPS-TC are faster and farther to the left. The new NHC track forecast has been adjusted a little to the south in the first 36 hours due to the initial motion, and lies a little south of the consensus and close to the GFS at this time range. Beyond that time, the official forecast is an update of the previous one and lies a little to the east of the latest multi-model consensus and a bit to the west of the GFS/ECMWF blend.

It is important to remind users that average NHC track forecast errors are around 175 miles at day 4 and 230 miles at day 5. Therefore, it is too soon to rule out possible hurricane impacts from Matthew in Florida.

FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 13.7N 70.8W 100 KT 115 MPH 12H 01/0000Z 13.5N 71.9W 100 KT 115 MPH 24H 01/1200Z 13.5N 73.3W 100 KT 115 MPH 36H 02/0000Z 13.8N 74.3W 100 KT 115 MPH 48H 02/1200Z 14.7N 75.0W 100 KT 115 MPH 72H 03/1200Z 17.5N 76.0W 100 KT 115 MPH 96H 04/1200Z 21.5N 76.0W 90 KT 105 MPH 120H 05/1200Z 25.5N 75.7W 85 KT 100 MPH

$$ Forecaster Brennan

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