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Hurricane MATTHEW Forecast Discussion Number 10

2016-09-30 16:49:44| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT FRI SEP 30 2016 000 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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Hurricane MATTHEW Forecast Discussion Number 9

2016-09-30 10:49:12| National Hurricane Center (Atlantic)

Issued at 500 AM AST FRI SEP 30 2016 000 WTNT44 KNHC 300849 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM AST FRI SEP 30 2016 There are no data currently available from the inner core of Matthew, so it is unclear whether the earlier rapid intensification is continuing. A well-defined elliptical eye is seen in data from the Curacao radar. However, the latest satellite imagery shows that the central convection is somewhat asymmetric and that an eye is yet to form. Satellite intensity estimates are 90 kt from TAFB and 77 kt from SAB. Based on continuity from the previous advisory and no improvement in the satellite signature, the initial intensity is held at a possibly conservative 85 kt. It is notable that the rapid intensification has occurred despite an ongoing 20 kt of southwesterly vertical wind shear. The initial motion is 265/12. There is little change to the track forecast philosophy from the previous advisory. A low- to mid-level ridge to the north of Matthew should keep it moving westward or south of westward for the next 36 hours with some decrease in forward speed. From 48-120 hours, the ridge is forecast to weaken and shift eastward as a mid- to upper-level trough moves into the central and eastern Gulf of Mexico. This evolution should cause Matthew to turn northwestward and then northward. There is a significant spread in where the turn will occur and how fast Matthew will move afterwards. The ECMWF and UKMET are on the eastern side of the guidance envelope and slower than the other models, while the GFS and Canadian models are to the left of the center of the guidance envelope and much faster. The various consensus models split these differences in both track and speed, and the new forecast track lies close to them. Overall, the new track is a little south of the previous track through 48 hours and a little west of the previous track from 72-120 hours. The intensity forecast is very problematic. The ongoing shear has so far done little to keep Matthew from intensifying. Despite this, the intensity guidance is in unanimous agreement that the cyclone should weaken from 12-48 hours, most likely due to shear. From 48-96 hours, the shear is expected to diminish, and during that time Matthew is expected to intensify until it interacts with land. The intensity forecast will smooth through what could be some ups and downs in intensity. First, it assumes that the current strengthening will continue for another 12-24 hours, with Matthew reaching major hurricane strength. Then, it keeps the intensity at 100 kt from 24-48 hours, followed by some intensification as the shear lets up. Weakening due to land interaction is forecast after 72 hours. The intensity forecast lies near the upper edge of the intensity guidance, but it is less intense than the HWRF model from 72-120 hours. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 14.0N 69.9W 85 KT 100 MPH 12H 30/1800Z 13.8N 71.2W 95 KT 110 MPH 24H 01/0600Z 13.7N 72.5W 100 KT 115 MPH 36H 01/1800Z 13.9N 73.7W 100 KT 115 MPH 48H 02/0600Z 14.5N 74.8W 100 KT 115 MPH 72H 03/0600Z 17.0N 76.0W 105 KT 120 MPH 96H 04/0600Z 20.5N 76.0W 90 KT 105 MPH...INLAND 120H 05/0600Z 24.5N 76.0W 85 KT 100 MPH...OVER WATER $$ Forecaster Beven

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Hurricane MATTHEW Forecast Discussion Number 8

2016-09-30 08:01:20| National Hurricane Center (Atlantic)

Issued at 200 AM AST FRI SEP 30 2016 000 WTNT44 KNHC 300601 TCDAT4 HURRICANE MATTHEW SPECIAL DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 200 AM AST FRI SEP 30 2016 This special advisory is being issued in lieu of the scheduled intermediate advisory due to the rapid strengthening of Matthew during the past few hours. An Air Force Reserve Hurricane Hunter aircraft reported flight-level winds of 99 kt in the northern eyewall at 700 mb, along with surface wind estimates of 80-85 kt from the SFMR instrument. In addition, the central pressure has fallen to 979 mb. Based on these data, the initial intensity is increased to 85 kt. This also requires significant changes to the intensity forecast, which now calls for Matthew to reach major hurricane status in 24 hours and maintain it through 96 hours. It is unclear how long the rapid strengthening will continue, and the revised forecast could be conservative. There are no changes to the forecast track from the previous regular advisory. It should be noted that despite the rapid intensification, the aircraft data, along with recent scatterometer data, show that the tropical-storm-force winds still extend only a short distance over the southern semicircle. Based on this, no warnings are required for Aruba, Curacao, or Colombia at this time. A warning might be necessary if the southern radii expand or if the center moves to the south of the forecast track. FORECAST POSITIONS AND MAX WINDS INIT 30/0600Z 14.1N 69.3W 85 KT 100 MPH 12H 30/1200Z 14.0N 70.4W 95 KT 110 MPH 24H 01/0000Z 13.9N 72.0W 100 KT 115 MPH 36H 01/1200Z 13.8N 73.0W 105 KT 120 MPH 48H 02/0000Z 14.1N 74.0W 105 KT 120 MPH 72H 03/0000Z 16.4N 75.3W 105 KT 120 MPH 96H 04/0000Z 19.7N 75.6W 90 KT 105 MPH 120H 05/0000Z 23.5N 75.5W 85 KT 100 MPH $$ Forecaster Beven

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Tropical Storm ULIKA Forecast Discussion Number 13

2016-09-29 16:56:36| National Hurricane Center (East Pacific)

Issued at 800 AM PDT THU SEP 29 2016 000 WTPZ44 KNHC 291456 TCDEP4 TROPICAL STORM ULIKA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192016 800 AM PDT THU SEP 29 2016 Ulika's cloud pattern continues to have a sheared appearance this morning, with only a small area of bursting deep convection to the east of the estimated low-level center location. The initial intensity is set at 40 kt, which is a blend of Dvorak estimates from SAB and TAFB. A very hostile dynamic environment lies ahead of Ulika, with westerly shear forecast to increase to 40-50 kt in 36 hours. Given such unfavorable conditions, the system should degenerate into a remnant low by the weekend, or sooner. The cyclone has turned toward the northwest, and the initial motion is estimated to be around 320/6 kt. The flow on the southern side of a weak low- to mid-level ridge should cause Ulika to turn toward the west-northwest and then west over the next couple of days. The official track forecast is between the latest GFS and ECMWF tracks and only a little bit north of the previous NHC forecast. The next advisory on Ulika will be issued by the Central Pacific Hurricane Center. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 16.7N 139.7W 40 KT 45 MPH 12H 30/0000Z 17.3N 140.4W 35 KT 40 MPH 24H 30/1200Z 17.8N 141.8W 30 KT 35 MPH 36H 01/0000Z 18.0N 143.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 01/1200Z 18.0N 145.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 02/1200Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm MATTHEW Forecast Discussion Number 5

2016-09-29 16:55:42| National Hurricane Center (Atlantic)

Issued at 1100 AM AST THU SEP 29 2016 000 WTNT44 KNHC 291455 TCDAT4 TROPICAL STORM MATTHEW DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 AM AST THU SEP 29 2016 The center of Matthew is exposed to the southwest of the deep convection due to moderate southwesterly shear. Despite the shear, data from an Air Force Reserve reconnaissance aircraft show that Matthew is a little stronger this morning. The aircraft has measured peak 850 mb flight-level winds of 80 kt, and believable SFMR winds of around 60 kt, which is the basis for the initial intensity. The minimum central pressure reported by the aircraft is down to 996 mb. Given the current shear and structure of Matthew, only slight strengthening is predicted during the next 24 hours. The shear is forecast to slowly decrease over the next few days, although there are some differences in the upper-level wind forecasts between the ECMWF and GFS models. The ECMWF keeps a band of southwesterly upper-level winds near Matthew, while the GFS generally shows lower shear. The NHC forecast assumes that there will be a reduction in shear and calls for intensification similar to the previous advisory. The official wind speed forecast is between the lower statistical guidance and the more aggressive HWRF and GFDL models. Matthew is moving at 275/14 kt. The tropical storm is expected to move westward to the south of a mid- to upper-level ridge over the western Atlantic during the next couple of days. In about 48 hours, Matthew should turn northwestward when it approaches the western periphery of the ridge. After that time, the tropical cyclone is forecast to turn northward while a mid- to upper-level trough develops over the Gulf of Mexico. The GFS is still much faster than the ECMWF at taking Matthew northward. Although the east/west spread among the higher quality track models is somewhat smaller this morning, there is still significant spread among the ECMWF ensembles beyond 3 days, and the overall confidence in the track forecast is still low. The new NHC track forecast is essentially an update of the previous forecast and is very close to the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 14.2N 66.3W 60 KT 70 MPH 12H 30/0000Z 14.3N 68.0W 60 KT 70 MPH 24H 30/1200Z 14.1N 70.2W 65 KT 75 MPH 36H 01/0000Z 13.9N 71.8W 70 KT 80 MPH 48H 01/1200Z 13.9N 72.8W 75 KT 85 MPH 72H 02/1200Z 15.3N 74.4W 80 KT 90 MPH 96H 03/1200Z 18.0N 75.2W 85 KT 100 MPH 120H 04/1200Z 21.5N 75.5W 80 KT 90 MPH $$ Forecaster Brown

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