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Tropical Storm FRED Forecast Discussion Number 10

2015-09-01 10:49:42| National Hurricane Center (Atlantic)

Issued at 500 AM AST TUE SEP 01 2015 000 WTNT41 KNHC 010849 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 AM AST TUE SEP 01 2015 After a brief convective hiatus between about 0000-0200 UTC, deep convection has redeveloped over the center of Fred and also in the northern semicircle. Several passive microwave satellite images indicate that Fred's low-level center is a little south of the previous advisory track, due to southerly vertical wind shear displacing most of the convection to the north of the center. However, that same imagery also indicated that Fred still has a low-level circulation that is quite robust, including a nearly closed 20 n mi diameter eye. The initial intensity of 55 kt is based on a blend of Dvorak satellite intensity estimates of T4.0/65 kt from TAFB and T3.0/45 kt from SAB. The initial motion estimate is 300/10 kt based on microwave fixes. Fred is expected to move between west-northwest and northwest for the next 72 hours as a mid-level ridge to the north of the cyclone gradually builds westward. After that time, a turn toward the north-northwest and north is forecast due to a deep-layer trough currently over eastern Canada that is expected to dig southeastward over the central Atlantic and erode the ridge. The NHC model guidance is in decent agreement on this developing pattern change. However, there are significant differences in the model solutions with the HWRF, GFS, and GFDL models keeping Fred stronger and making the northward turn sooner, whereas the weaker solution models like the UKMET and ECMWF take a weaker and more vertically shallow cyclone farther west before turning it northward. The official forecast track is a little south of the previous advisory track, mainly due to the more southerly initial position, and follows a blend of the weaker UKMET and ECMWF solutions. Fred is expected to gradually weaken throughout the forecast period as the cyclone moves into an environment of increasing southwesterly vertical wind in excess of 20 kt and drier and more stable air, and over SSTs of near 26 deg C. The NHC intensity forecast is a little lower than the previous advisory, as well as the consensus model IVCN. 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 01/0900Z 18.0N 26.1W 55 KT 65 MPH 12H 01/1800Z 18.8N 27.4W 45 KT 50 MPH 24H 02/0600Z 19.7N 29.2W 40 KT 45 MPH 36H 02/1800Z 20.3N 30.7W 35 KT 40 MPH 48H 03/0600Z 21.0N 32.3W 35 KT 40 MPH 72H 04/0600Z 22.3N 35.5W 30 KT 35 MPH 96H 05/0600Z 23.7N 38.6W 25 KT 30 MPH 120H 06/0600Z 26.0N 40.7W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Hurricane JIMENA Forecast Discussion Number 23

2015-09-01 10:49:09| National Hurricane Center (East Pacific)

Issued at 200 AM PDT TUE SEP 01 2015 000 WTPZ43 KNHC 010848 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 200 AM PDT TUE SEP 01 2015 Jimena has changed little since the previous advisory. Microwave data indicate that the hurricane has concentric eyewalls, and the eye temperature has actually warmed a bit during the past few hours. Since the overall satellite presentation has changed little, and Dvorak estimates are T6.0 from TAFB and SAB, the initial intensity is held at 115 kt. Jimena has an expansive outflow shield radiating outward 400 to 600 n mi in all directions from the center, and the UW-CIMSS shear analysis is currently showing less than 5 kt of shear affecting the hurricane. The SHIPS guidance shows the shear staying 5 kt or less for the next 48 hours, and less than 10 kt for the next 72 hours. Sea surface temperatures gradually decrease ahead of Jimena, but they are at least 26C for the entire forecast period. Therefore, there don't seem to be any egregiously hostile conditions during the next few days to induce a quick weakening trend. As has been the case for days, the hurricane models show a gradual weakening trend through the five-day period, while the GFS and ECMWF continue to maintain a much stronger hurricane. As a compromise between these scenarios, the NHC intensity forecast lies near the top end of the intensity guidance, or close to the SHIPS model. This forecast is a little higher than the previous official forecast. The initial motion is 280/11 kt. Jimena is expected to turn west-northwestward toward a break in the subtropical ridge within the next 12 hours, and then northwestward and north-northwestward by days 3 through 5. This forecast reasoning is unchanged from prior advisories, but the track guidance envelope did shift a little west after 48 hours on this cycle. The updated NHC track is therefore nudged westward as well and is close to the TVCN model consensus. FORECAST POSITIONS AND MAX WINDS INIT 01/0900Z 16.4N 139.1W 115 KT 130 MPH 12H 01/1800Z 16.9N 140.5W 110 KT 125 MPH 24H 02/0600Z 17.4N 141.8W 105 KT 120 MPH 36H 02/1800Z 17.9N 142.7W 100 KT 115 MPH 48H 03/0600Z 18.3N 143.4W 95 KT 110 MPH 72H 04/0600Z 19.4N 144.4W 85 KT 100 MPH 96H 05/0600Z 20.7N 145.2W 75 KT 85 MPH 120H 06/0600Z 22.5N 146.3W 65 KT 75 MPH $$ Forecaster Berg

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Hurricane JIMENA Forecast Discussion Number 22

2015-09-01 04:45:32| National Hurricane Center (East Pacific)

Issued at 800 PM PDT MON AUG 31 2015 000 WTPZ43 KNHC 010245 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 PM PDT MON AUG 31 2015 Jimena is experiencing another eyewall replacement. Satellite data show a double eyewall structure within the hurricane's inner core, with the eye having become cloud-filled and less defined throughout the day. There has also been a dramatic warming of cloud top temperatures during the past 12 hours or so. Dvorak intensity estimates have decreased substantially since the last advisory, and a blend of latest Final T- and CI-numbers from TAFB and SAB is used to lower the intensity to 115 kt. Although the vertical wind shear should be extremely low and Jimena should still be moving over SSTs greater than 28 deg C during the next 48 hours, the intensity guidance shows slow weakening. Neutral thermodynamic conditions and a notable drop-off in oceanic heat content along the cyclone's track likely contributes to a decrease in intensity, at least in the statistical guidance. Regardless, internal dynamics in the hurricane's inner core are likely to be key to the short-term intensity forecast, and given Jimena's current structure of multiple wind maxima at large radii, it is reasonable to expect a slow decay during the next few days. Only at days 4 and 5 does westerly shear increase and the waters become marginally warm. That being said, the large-scale factors do not support anything more than a slow filling. The one caveat is that the cyclone's slow movement could induce oceanic upwelling and result in faster weakening. The new intensity forecast is lowered some from the previous one and is a bit lower than the multi-model consensus after 24 hours, in best agreement with the FSU Superensemble output. The initial motion estimate is 285/14. The tail of a mid-latitude trough, extending south-southwestward from the Pacific Northwest, is forecast to temporarily weaken the subtropical ridge between 140- 155W during the next day or two. As a result, Jimena's forward speed should decrease very soon, and the cyclone should continue to gradually decelerate over the next couple of days. A northwestward to north-northwestward drift in response to the weakness in the ridge is shown by the global models from days 3 to 5. The new track forecast is close to the multi-model consensus, albeit not as far east as the consensus in the latter part of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 16.3N 138.1W 115 KT 130 MPH 12H 01/1200Z 16.6N 139.5W 105 KT 120 MPH 24H 02/0000Z 17.2N 140.9W 100 KT 115 MPH 36H 02/1200Z 17.8N 142.0W 90 KT 105 MPH 48H 03/0000Z 18.3N 142.8W 85 KT 100 MPH 72H 04/0000Z 19.2N 143.7W 75 KT 85 MPH 96H 05/0000Z 20.5N 144.3W 65 KT 75 MPH 120H 06/0000Z 22.0N 144.9W 55 KT 65 MPH $$ Forecaster Kimberlain

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Tropical Storm FRED Forecast Discussion Number 9

2015-09-01 04:41:06| National Hurricane Center (Atlantic)

Issued at 1100 PM AST MON AUG 31 2015 000 WTNT41 KNHC 010240 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 1100 PM AST MON AUG 31 2015 Fred's inner-core deep convection has collapsed, and what thunderstorm activity remains is very ragged in appearance. Although the convection may make somewhat of a comeback on the diurnal maximum tomorrow morning, the current degradation of the cloud pattern necessitates downgrading the system to a tropical storm. The current intensity estimate is a rather uncertain 60 kt. As Fred moves away from the Cape Verde Islands, the environment ahead becomes increasingly unfavorable with increasing shear, progressively drier mid-level air and increased stability. The official intensity forecast is a blend of the latest SHIPS and LGEM guidance. Given the storm's current appearance and the hostile future environment, however, Fred may weaken faster than indicated here. The center has become difficult to track, and my best guess of the initial motion is 310/10 kt. A mid-level ridge to the north of Fred is forecast to build gradually westward. This should cause the cyclone to turn toward the west-northwest. A more westward track with time is also consistent with Fred becoming a shallower cyclone steered more by the low-level flow. The official forecast remains on the southern side of the guidance envelope and is mostly a blend of the latest GFS and ECMWF predictions. This is also very similar to the previous NHC track forecast. 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 01/0300Z 17.9N 25.2W 60 KT 70 MPH 12H 01/1200Z 18.6N 26.6W 55 KT 65 MPH 24H 02/0000Z 19.6N 28.2W 50 KT 60 MPH 36H 02/1200Z 20.5N 29.9W 45 KT 50 MPH 48H 03/0000Z 21.1N 31.6W 40 KT 45 MPH 72H 04/0000Z 22.2N 34.8W 35 KT 40 MPH 96H 05/0000Z 23.5N 38.0W 30 KT 35 MPH 120H 06/0000Z 25.0N 41.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Pasch

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Hurricane FRED Forecast Discussion Number 8

2015-08-31 22:42:05| National Hurricane Center (Atlantic)

Issued at 500 PM AST MON AUG 31 2015 000 WTNT41 KNHC 312041 TCDAT1 HURRICANE FRED DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 PM AST MON AUG 31 2015 Fred likely peaked in intensity this morning. Microwave data received since the previous advisory shows that the eye has become open over the southern semicircle, however, the center remains embedded in an area of cloud top temperatures below -70C. Although Dvorak T-numbers have changed little since the previous advisory, the initial wind speed has been lowered to 70 kt, based on the degraded inner-core structure. The environment ahead of Fred is expected to become increasingly hostile with marginal sea surface temperatures, increasing southwesterly shear, and less favorable thermodynamic conditions. As a result, steady weakening is predicted. Since Fred is a small tropical cyclone, it is likely to succumb to the shear faster than indicated by the statistical guidance, and the NHC forecast is slightly lower than the SHIPS/LGEM models. Despite warmer SSTs along the forecast track at days 4 and 5, the shear and dry mid-level air are likely to cause Fred to become a remnant low by the end of the forecast period. The initial motion estimate is 310/10 kt. The center of Fred will pass near or over the northwestern Cape Verde Islands through early tonight. A turn toward the west-northwestward is expected on Tuesday as the subtropical ridge to the north of Fred builds westward. A west-northwestward heading should then continue during the remainder of the forecast period. The GFS and ECMWF models remain on the southern side of the guidance envelope and the NHC forecast is near a consensus of these typically reliable models. The NHC forecast at the long-range leans a bit closer to the ECMWF, which shows a weaker Fred moving more westward. 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 31/2100Z 17.2N 24.6W 70 KT 80 MPH 12H 01/0600Z 18.2N 25.9W 65 KT 75 MPH 24H 01/1800Z 19.2N 27.7W 60 KT 70 MPH 36H 02/0600Z 20.1N 29.3W 55 KT 65 MPH 48H 02/1800Z 20.8N 31.0W 45 KT 50 MPH 72H 03/1800Z 22.0N 34.0W 35 KT 40 MPH 96H 04/1800Z 23.2N 37.5W 30 KT 35 MPH 120H 05/1800Z 25.0N 41.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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