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Hurricane MATTHEW Forecast Discussion Number 18

2016-10-02 16:57:03| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT SUN OCT 02 2016 000 WTNT44 KNHC 021456 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 AM EDT SUN OCT 02 2016 The eye of Matthew has become obscured on visible satellite images, which is often an indication of weakening. Microwave images showed a distinct dry slot over the southwestern and western portions of the circulation. Also there has been a persistent, but inexplicable, cluster of deep convection located a couple of degrees to the east of the hurricane and the effect of this feature on Matthew's intensity evolution is unknown. An Air Force Hurricane Hunter aircraft investigated the northeastern eyewall, the strongest part of the circulation, and found that the winds had decreased somewhat from earlier this morning. The intensity is set to 120 kt for this advisory. The vertical shear is not forecast to become much stronger while Matthew is in the Caribbean, so the hurricane should remain near category 4 status for the next 36-48 hours. Once Matthew moves into the Atlantic, some increase in shear along with a decrease in oceanic heat content should result in a little weakening. However, there is significant uncertainty in the 3-5 day forecast intensities. After a northwestward motion, the center has meandered westward over the past few hours. Matthew is expected to turn northward and move between a mid-level ridge to the east and a weak trough over the Gulf of Mexico for the next few days. Later in the forecast period, the global models show a slight building of a ridge to the northeast of Matthew which would induce a turn toward the left in 3-5 days. The timing and magnitude of this turn is still uncertain however. Looking at the better-performing models, the track guidance suite is bracketed by the GFS model on the left and the HWRF model on the right. The official forecast is slightly west of the multi-model consensus and very similar to the previous NHC track. 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 02/1500Z 14.0N 74.6W 120 KT 140 MPH 12H 03/0000Z 14.9N 74.8W 120 KT 140 MPH 24H 03/1200Z 16.1N 75.0W 115 KT 130 MPH 36H 04/0000Z 17.7N 74.7W 115 KT 130 MPH 48H 04/1200Z 19.5N 74.5W 110 KT 125 MPH 72H 05/1200Z 23.2N 75.0W 100 KT 115 MPH 96H 06/1200Z 26.5N 76.0W 95 KT 110 MPH 120H 07/1200Z 29.5N 76.5W 90 KT 105 MPH $$ Forecaster Pasch

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Hurricane MATTHEW Forecast Discussion Number 17

2016-10-02 10:59:57| National Hurricane Center (Atlantic)

Issued at 500 AM EDT SUN OCT 02 2016 000 WTNT44 KNHC 020859 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT SUN OCT 02 2016 The overall organization of the hurricane has changed little overnight, with the small eye remaining distinct in infrared satellite pictures. A very recent AMSR2 microwave overpass showed no indication of an eyewall replacement, but there was a notable dry slot between the inner core and the outer bands over the southern portion of the circulation. Although Dvorak data T-numbers decreased slightly at 0600 UTC, the objective and subjective CI numbers are about the same as before, so the initial intensity will remain 130 kt for this advisory. Another Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Matthew this morning, which should provide a better assessment of the hurricane's current strength and structure. Although some weakening is predicted during the next couple of days, Matthew is expected to remain a powerful hurricane when it approaches the islands of the Greater Antilles in a couple of days. The upper-level wind environment is expected to remain favorable over the Bahamas, and warm waters in that area should allow Matthew to maintain much of its intensity while it moves over that area later in the forecast period. Matthew has been moving slowly west-northwestward during the past few hours, but the longer-term motion estimate is northwest or 320 degrees at 4 kt. The forecast track reasoning remains unchanged from before. Matthew should move slowly northwestward today, and then turn northward tonight as a mid- to upper-level trough develops over the eastern Gulf of Mexico. This motion will take Matthew towards Jamaica, western Haiti, and eastern Cuba over the next couple of days. After that time, the global models bend Matthew back toward the north-northwest between the aforementioned trough and a developing ridge off the northeast United States coast. The dynamical models are in good agreement on this scenario through 72 hours, with increasing spread thereafter. The GFS, ECMWF, and UKMET are along the western side of the guidance at days 4 and 5, while the HWRF is along the eastern side. The latest NHC track is close to the model consensus through day 3, but is west of the consensus at 96 and 120 h, to be closer to the typically better performing global models. 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 02/0900Z 13.9N 74.1W 130 KT 150 MPH 12H 02/1800Z 14.6N 74.5W 125 KT 145 MPH 24H 03/0600Z 15.6N 74.7W 120 KT 140 MPH 36H 03/1800Z 17.1N 74.7W 115 KT 130 MPH 48H 04/0600Z 18.8N 74.5W 110 KT 125 MPH 72H 05/0600Z 22.6N 74.8W 105 KT 120 MPH 96H 06/0600Z 25.5N 75.5W 100 KT 115 MPH 120H 07/0600Z 28.0N 76.2W 95 KT 110 MPH $$ Forecaster Brown

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Hurricane MATTHEW Forecast Discussion Number 13

2016-10-01 10:47:52| National Hurricane Center (Atlantic)

Issued at 500 AM EDT SAT OCT 01 2016 000 WTNT44 KNHC 010847 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT SAT OCT 01 2016 Matthew has changed little in organization since the past advisory, with a small eye surrounded by a central dense overcast featuring cloud tops colder than -80C. The eye has become a little less distinct, suggesting at least that the hurricane is no longer intensifying. In addition, the raw intensity estimates from the CIMSS ADT technique are slightly lower than they were six hours ago. Based on these trends, the initial intensity is reduced to 135 kt. An Air Force Reserve Hurricane Hunter aircraft is scheduled to reach Matthew near 1200 UTC. The initial motion is now 270/6. Matthew remains south of a low- to mid-level ridge over the western Atlantic. The dynamical models forecast this ridge to weaken over the next 72 hours as a mid- to upper-level trough develops over the Gulf of Mexico. This evolution should cause Matthew to turn northwestward after 24 hours and northward by 48-72 hours. The guidance generally agrees with this scenario. However, there is a spread between the GFS forecast of landfall in Jamaica and eastern Cuba and the ECMWF forecast landfall in southwestern Haiti. The guidance becomes more divergent after 72 hours. The GFS shows a turn toward the north-northwest, which brings the center closer to the northwestern Bahamas and Florida. This model is near the western edge of the guidance envelope. The ECMWF is near the eastern edge of the guidance envelope and shows the center east of the Bahamas by 120 hours. Adding to the uncertainty is the eastward shift of the Canadian model since its previous run. Given the uncertainty, the 96 and 120 hour forecast points are changed only slightly from the previous forecast. This part of the forecast track lies to the east of the GFS, but to the west of the Canadian, ECMWF, and NAVGEM models. It is also a little to the west of the various consensus models. Matthew should experience significant shear for the next 24 hours or so, as water vapor imagery shows westerly flow blowing into the hurricane underneath the impressive outflow pattern. This should cause some weakening. After that time, the dynamical models suggest the shear should decrease, which should allow Matthew to at least maintain its intensity. The new intensity forecast shows a slightly weaker intensity than the previous advisory through 72 hours based mainly on current trends. Subsequently, the hurricane is likely to interact with the land masses of Jamaica, Cuba, and Hispaniola, leading to some weakening and disruption of the structure. Between this and uncertainty about how much shear Matthew will encounter north of Cuba, the new forecast shows only modest strengthening after Matthew reaches the Atlantic north of Cuba. There is also the possibility of fluctuations in intensity caused by eyewall replacement cycles at any time during the forecast period. 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 01/0900Z 13.3N 72.8W 135 KT 155 MPH 12H 01/1800Z 13.3N 73.6W 130 KT 150 MPH 24H 02/0600Z 13.8N 74.5W 120 KT 140 MPH 36H 02/1800Z 14.9N 75.1W 110 KT 125 MPH 48H 03/0600Z 16.2N 75.7W 110 KT 125 MPH 72H 04/0600Z 19.5N 76.0W 110 KT 125 MPH 96H 05/0600Z 23.0N 76.0W 90 KT 105 MPH 120H 06/0600Z 26.0N 76.5W 95 KT 110 MPH $$ Forecaster Beven

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Hurricane MATTHEW Forecast Discussion Number 12

2016-10-01 04:59:22| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT FRI SEP 30 2016 000 WTNT44 KNHC 010259 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 PM EDT FRI SEP 30 2016 An Air Force reconnaissance plane recently measured a peak SFMR wind of 143 kt and then 138 kt during this mission's eye penetrations. Furthermore, the satellite presentation has improved considerably with a distinct eye surrounded by a ring of very deep convection. The raw objective T-numbers from UW-CIMSS have been above 7.0 since 2100 UTC. On this basis, the initial intensity has been increased to 140 kt, making Matthew a Category 5 on the Saffir-Simpson Hurricane Wind Scale. This is the first Category 5 hurricane in the Atlantic basin since Hurricane Felix in 2007. Matthew probably is near its peak intensity and will likely maintain a similar strength during the next 12 hours or so. Data from the reconnaissance plane show an incipient outer band of maximum winds, indicating that an eyewall replacement cycle could occur soon. This should result in fluctuations in intensity, and given that southwesterly shear is still affecting the cyclone, some weakening is anticipated. However, Matthew is forecast to be a category 4 hurricane by the time it moves near Jamaica and eastern Cuba. Some additional weakening is expected over the high terrain of Cuba. It is noted that none the guidance ever indicated the rapid strengthening of Matthew. Matthew is still moving south of due west or 265 degrees at 6 kt steered by a strong high pressure system over the western Atlantic. In about 12 hours, the hurricane should be on the western edge of the high and ahead of a deepening trough over the Gulf of Mexico. This steering pattern should force Matthew to turn northwestward and then northward at about 5 to 10 kt. The track guidance has been very consistent with this scenario, and there are no reasons to deviate much from the previous NHC forecast. At the end of the forecast period, when Matthew is expected to be in the Bahamas, the track models are in less agreement with both track and speed, increasing the uncertainty in the forecast. The NHC forecast follows closely the multi-model consensus TVCN and TVCX. 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 01/0300Z 13.3N 72.3W 140 KT 160 MPH 12H 01/1200Z 13.3N 73.3W 135 KT 155 MPH 24H 02/0000Z 13.7N 74.2W 125 KT 145 MPH 36H 02/1200Z 14.6N 75.0W 115 KT 130 MPH 48H 03/0000Z 16.0N 76.0W 115 KT 130 MPH 72H 04/0000Z 19.0N 76.3W 115 KT 130 MPH 96H 05/0000Z 23.1N 76.3W 90 KT 105 MPH 120H 06/0000Z 26.0N 76.5W 95 KT 110 MPH $$ Forecaster Avila

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Hurricane MATTHEW Forecast Discussion Number 11

2016-09-30 22:52:34| National Hurricane Center (Atlantic)

Issued at 500 PM EDT FRI SEP 30 2016 000 WTNT44 KNHC 302051 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 PM EDT FRI SEP 30 2016 Matthew has continued to rapidly strengthen at a remarkable rate today. A NOAA Hurricane Hunter aircraft recently reported a peak SFMR wind of 116 kt and flight-level winds of 121 kt. A recent dropsonde from the aircraft indicated that surface winds are around 120 kt. Based on all of these data, the initial intensity is set to 120 kt, an increase of 55 kt in the last 24 hours. The latest pressure estimate from the aircraft is 949 mb, a drop of 44 mb since this time yesterday. Some additional strengthening is possible in the next 12 hours or so, and the NHC forecast reflects that possibility, showing 125 kt at that time. Given the lack of skill of the intensity guidance thus far, this remains a low confidence forecast, and its possible this could be conservative. Since Matthew has now become a major hurricane, eyewall replacement cycles could occur that would lead to some fluctuations in intensity not shown here. After 12 hours, a gradual weakening is shown, following the trend of, but above nearly all of the intensity guidance. Land interaction with Cuba should lead to additional weakening by day 4, but Matthew is expected to remain a strong hurricane through the forecast period. The initial motion is still toward the west-southwest, but the forward speed has slowed a bit, to around 8 kt. The track forecast reasoning has not changed, with Matthew expected to turn westward by 12 hours and then gradually turn toward the north in the next 3 to 4 days as the cyclone moves into a weakness in the subtropical ridge. The track model guidance is in slightly better agreement this cycle through 3 days, although the ECMWF remains right of and slower than the rest of the guidance at days 4 and 5. The GFS, HWRF, and COAMPS-TC are faster and to the left late in the period, although the GFS has trended slower this cycle. The new NHC track has again been adjusted a little to the left through 72 hours given the initial position and motion, and after that time is along the previous official forecast but slower, following the slower trend in the guidance this cycle. The NHC forecast is near the middle of the guidance envelope and is a little to the east of the multi-model consensus at days 4 and 5. 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 30/2100Z 13.5N 71.6W 120 KT 140 MPH 12H 01/0600Z 13.3N 72.8W 125 KT 145 MPH 24H 01/1800Z 13.5N 73.9W 120 KT 140 MPH 36H 02/0600Z 14.1N 74.8W 115 KT 130 MPH 48H 02/1800Z 15.2N 75.6W 110 KT 125 MPH 72H 03/1800Z 18.2N 76.2W 105 KT 120 MPH 96H 04/1800Z 22.0N 76.0W 90 KT 105 MPH 120H 05/1800Z 25.0N 76.0W 90 KT 105 MPH $$ Forecaster Brennan

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