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Hurricane FRED Forecast Discussion Number 6

2015-08-31 10:36:52| National Hurricane Center (Atlantic)

Issued at 500 AM AST MON AUG 31 2015 000 WTNT41 KNHC 310836 TCDAT1 HURRICANE FRED DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 AM AST MON AUG 31 2015 Fred's overall cloud pattern has only changed slightly since the previous advisory. However, the inner-core convection has increased markedly, including the development of a well-defined, vertically deep, 15 n mi diameter eye as noted in recent AMSR and AMSU passive microwave satellite data. Upper-level outflow is good in all quadrants. The initial intensity has been increased to 70 kt based on a blend of satellite intensity estimates of T4.0/65 kt from TAFB, a UW-CIMSS ADT value of T4.4/75 kt, and a NHC objective Dvorak T-number of T4.5/77 kt. Fred has maintained a steady northwestward motion but has slowed down some, and is now moving 305/10 kt. The track forecast and rationale remain unchanged from the previous advisory. Water vapor-derived winds indicate that the break in the subtropical ridge to the northwest of the Cape Verde Islands is beginning to fill in based on previous southwesterly winds now having been replaced by east-northeasterly mid- to upper-level winds. Fred is expected to continue its northwestward motion for the next 12-24 hours and pass near or over the Cape Verde Islands of Boa Vista this morning, and over or near Sao Nicolau, Sao Vicente, and Santo Antao late this afternoon and into tonight. As the ridge builds steadily westward to the north of Fred, the hurricane should gradually turn toward the west-northwest by 36 hours and beyond. This will bring the cyclone over progressively cooler waters and into increasing vertical wind shear conditions. The official forecast track is just an update of the previous advisory track, and lies close to the consensus of the GFS and ECMWF model tracks. The vertical shear is expected to remain quite low at less than 5 kt for the next 12 hours as Fred is passing through the Cape Verde Islands archipelago. With ocean temperatures remaining above 27 deg C during that time, some additional strengthening is possible. After the hurricane clears the Cape Verde Islands, however, the combination of decreasing SSTs, decreasing mid-level moisture, and increasing west-southwesterly vertical wind shear should induce a gradual weakening trend. The NHC intensity forecast is similar to the previous advisory and closely follows the IVCN consensus model through 36 hours, and is lower than IVCN from 48-120 hours. Please note that the track/cone graphic, an automatically generated product, does not have the capability of displaying warnings for the Cape Verde Islands. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 15.6N 22.9W 70 KT 80 MPH 12H 31/1800Z 16.6N 24.3W 75 KT 85 MPH 24H 01/0600Z 17.9N 26.1W 70 KT 80 MPH 36H 01/1800Z 19.0N 28.0W 65 KT 75 MPH 48H 02/0600Z 19.7N 29.8W 55 KT 65 MPH 72H 03/0600Z 20.8N 33.4W 45 KT 50 MPH 96H 04/0600Z 22.0N 36.9W 35 KT 40 MPH 120H 05/0600Z 23.0N 40.0W 30 KT 35 MPH $$ Forecaster Stewart

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Hurricane JIMENA Forecast Discussion Number 18

2015-08-31 04:49:59| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SUN AUG 30 2015 000 WTPZ43 KNHC 310249 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 PM PDT SUN AUG 30 2015 Jimena's cloud pattern has been in a remarkably steady state since the last advisory. The hurricane continues to maintain a large circular eye that has warmed slightly, surrounded by a nearly uniform ring of deep convection. There is a faint asymmetry in the convective distribution, suggestive of northerly or north- northwesterly shear as diagnosed by the SHIPS model output. Satellite classifications were T6.5/127 kt from TAFB and SAB, and UW-CIMSS ADT values have held steady at 6.7/132 kt. A blend of these data is used to set the initial intensity at 130 kt. Even though large-scale atmospheric conditions are forecast to remain relatively favorable around Jimena during the couple of days, the intensity guidance indicates that Jimena should begin to weaken soon. The weakening appears to largely be a function of slowly decreasing SSTs along the cyclone's path. Some westerly shear and a larger drop-off in oceanic heat content later in the forecast period suggest continued gradual weakening should occur, but neither the atmosphere nor ocean should produce conditions hostile enough to result in the cyclone's rapid decline. The one caveat to the intensity forecast is that Jimena, already exhibiting some characteristics of an annular hurricane, could weaken more slowly than forecast. The latest NHC intensity forecast is somewhat above the multi-model consensus and is in best agreement with the HWRF model that shows slower overall weakening. Jimena's heading has been a bit more westerly since the previous advisory, but a longer-term average motion estimate is 290/14. A longwave trough, extending southwestward from the U.S. west coast, has eroded the subtropical ridge ridge between 140-150W. As Jimena nears this weakness during the next few days, its forward speed should gradually decrease on a slightly more poleward heading. In the absence of much steering from days 3 to 5, Jimena should drift northwestward. The latest NHC track forecast has hardly changed from the previous one. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 15.0N 132.5W 130 KT 150 MPH 12H 31/1200Z 15.4N 134.4W 125 KT 145 MPH 24H 01/0000Z 16.2N 136.8W 120 KT 140 MPH 36H 01/1200Z 16.8N 138.6W 115 KT 130 MPH 48H 02/0000Z 17.3N 140.0W 105 KT 120 MPH 72H 03/0000Z 18.3N 141.9W 90 KT 105 MPH 96H 04/0000Z 19.1N 143.0W 80 KT 90 MPH 120H 05/0000Z 20.2N 143.9W 70 KT 80 MPH $$ Forecaster Kimberlain

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Tropical Storm FRED Forecast Discussion Number 5

2015-08-31 04:40:44| National Hurricane Center (Atlantic)

Issued at 1100 PM AST SUN AUG 30 2015 000 WTNT41 KNHC 310240 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 1100 PM AST SUN AUG 30 2015 Fred has been maintaining strong convection in its CDO, and microwave data show a well-defined inner core. Subjective and objective Dvorak intensity estimates have not increased over the past several hours, however. The current intensity estimate is 60 kt, which is slightly above the most recent ADT values from UW-CIMSS. Upper-level outflow is well-defined over the tropical cyclone. The system should remain over marginally warm sea surface temperatures with moderate vertical shear for the next day or so, and sounding data from Sal in the Cape Verde Islands indicate that the Saharan Air Layer is not very prominent ahead of Fred. Given these conducive factors in the short term, the storm is likely to strengthen into a hurricane overnight. By 36 hours, vertical shear is forecast to increase significantly and a weakening trend should be underway by that time. Late in the forecast period, model guidance shows very dry low- to mid-level air affecting Fred with the shear remaining strong. This should result in the cyclone degenerating to a depression by the end of the period. The official intensity forecast is similar to the SHIPS and LGEM guidance and is the same as the previous one. Geostationary and microwave satellite imagery show that Fred continues on its northwestward trek. The track forecast reasoning is unchanged from the previous package. For the next few days, a weakening mid-level subtropical ridge over the eastern Atlantic should result in the tropical cyclone continuing northwestward with decreasing forward speed. Late in the forecast period, the ridge builds westward a bit and this, along with the weakening cyclone responding more to the lower-level flow, is likely to result in a turn to the left with time. The official track forecast is close to a consensus of the ECMWF and GFS solutions and lies on the southern side of the guidance suite. This is basically an update of the previous NHC track prediction. Please note that the track/cone graphic, an automatically generated product, does not have the capability of displaying warnings for the Cape Verde Islands. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 15.3N 22.4W 60 KT 70 MPH 12H 31/1200Z 16.2N 23.7W 70 KT 80 MPH 24H 01/0000Z 17.5N 25.5W 70 KT 80 MPH 36H 01/1200Z 18.8N 27.3W 65 KT 75 MPH 48H 02/0000Z 19.6N 29.0W 60 KT 70 MPH 72H 03/0000Z 20.8N 32.8W 50 KT 60 MPH 96H 04/0000Z 22.0N 36.5W 40 KT 45 MPH 120H 05/0000Z 23.0N 39.5W 30 KT 35 MPH $$ Forecaster Pasch

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Hurricane JIMENA Forecast Discussion Number 17

2015-08-30 22:38:03| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SUN AUG 30 2015 000 WTPZ43 KNHC 302037 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 200 PM PDT SUN AUG 30 2015 After Jimena's cloud pattern appeared somewhat ragged this morning, it has recently become more symmetric and better organized. The latest infrared images indicate that a ring of cloud tops colder than -70 deg C surround the center, and the eye has increased in diameter and become more distinct. The larger eye suggests that eyewall replacement could now be complete, and this is likely the reason why the hurricane has begun to re-intensify. Dvorak classifications at 1800 UTC were 6.0/115 kt from SAB and 6.5/127 kt from TAFB, with the latest UW-CIMSS ADT value between these two estimates. Based on the latest appearance of Jimena, the initial wind speed is set near the high end of the estimates at 125 kt. As mentioned in previous discussions, Jimena is expected to remain in a low wind shear environment for the next several days. However, the cyclone is expected to track over progressively cooler water, which should cause the hurricane to slowly weaken. The official intensity forecast shows some short-term strengthening, following the current trend, and then predicts a slow decay. This forecast is higher than all of the guidance during the next day or so, but falls in line with the SHIPS model from 36-120 h. Jimena is moving a little faster toward the west-northwest, 295/13 kt. This motion is expected to continue for about 24 hours while a subtropical ridge remains to the north and northeast of the cyclone. After that time, Jimena is forecast to decelerate as steering currents weaken in response to an amplifying trough extending southwestward from the western United States. There was little change in the latest model guidance, and the NHC forecast is largely an update of the previous one. This forecast lies close to the GFS and ECMWF models. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 14.7N 130.9W 125 KT 145 MPH 12H 31/0600Z 15.2N 133.0W 135 KT 155 MPH 24H 31/1800Z 16.0N 135.5W 125 KT 145 MPH 36H 01/0600Z 16.6N 137.4W 115 KT 130 MPH 48H 01/1800Z 17.1N 138.9W 105 KT 120 MPH 72H 02/1800Z 18.0N 141.1W 95 KT 110 MPH 96H 03/1800Z 18.8N 142.5W 85 KT 100 MPH 120H 04/1800Z 19.8N 143.5W 75 KT 85 MPH $$ Forecaster Cangialosi

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Tropical Storm FRED Forecast Discussion Number 4

2015-08-30 22:35:26| National Hurricane Center (Atlantic)

Issued at 500 PM AST SUN AUG 30 2015 000 WTNT41 KNHC 302035 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 PM AST SUN AUG 30 2015 Fred has continued to strengthen this afternoon. A new burst of deep convection has developed over the center, with the CDO becoming more symmetric. Late afternoon visible satellite pictures also reveal increased banding in all quadrants. AMSR-2 and GCOM microwave data from late this morning indicated that Fred continues to exhibit a well-defined inner core with a closed low-level ring in the 37 GHz imagery. The initial intensity has been raised to 55 kt, which is in agreement with a subjective data T-number of 3.5 from TAFB and T3.4 from UW/CIMSS ADT. Fred is forecast to remain in a favorable environment characterized by very low vertical wind shear, warm water, and sufficient mid-level moisture during the next day or so. Therefore, additional strengthening is expected and the NHC forecast calls for Fred to become a hurricane tonight or early Monday. This is supported by the statistical guidance and the HWRF model which bring Fred to hurricane status. In about 36 hours, the tropical cyclone will be moving into a more hostile environment of increasing southwesterly shear, cooler sea surface temperatures, and a more stable air mass. This should result in weakening throughout the remainder of the forecast period, and the new NHC forecast weakens Fred to a tropical depression by 120 h. Fred has been moving faster than predicted today, and the initial motion estimate is 310/14 kt. The forecast track philosophy remains unchanged from before. The cyclone should move northwestward toward a break in the subtropical ridge during the next day or so. In a couple of days, Fred should turn west-northwestward as the ridge rebuilds to the north of the cyclone over the eastern and central Atlantic. The updated NHC track forecast is a little north of the previous advisory after 48 hours to be in better agreement with the GFEX (GFS and ECMWF) consensus model. Please note that the track/cone graphic, an automatically generated product, does not have the capability of displaying warnings for the Cape Verde Islands. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 14.4N 21.3W 55 KT 65 MPH 12H 31/0600Z 15.6N 22.8W 65 KT 75 MPH 24H 31/1800Z 16.9N 24.6W 70 KT 80 MPH 36H 01/0600Z 18.2N 26.3W 65 KT 75 MPH 48H 01/1800Z 19.2N 28.2W 60 KT 70 MPH 72H 02/1800Z 20.6N 31.7W 50 KT 60 MPH 96H 03/1800Z 21.8N 35.5W 40 KT 45 MPH 120H 04/1800Z 22.8N 39.0W 30 KT 35 MPH $$ Forecaster Brown

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