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Hurricane Fernanda Forecast Discussion Number 26
2017-07-18 10:36:40| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Tue Jul 18 2017 000 WTPZ41 KNHC 180836 TCDEP1 Hurricane Fernanda Discussion Number 26 NWS National Hurricane Center Miami FL EP062017 200 AM PDT Tue Jul 18 2017 Fernanda is gradually weakening. The eye of the hurricane is no longer apparent in satellite images, and dry slots are evident in microwave images over the eastern portion of the circulation. The cloud pattern now consists of a fairly circular central dense overcast with curved bands surrounding the convective mass. The Dvorak CI-numbers are 5.0/90 kt from TAFB and SAB, and the ADT values from UW-CIMSS are similar. Based on these estimates, the initial intensity is lowered a little to 90 kt. Fernanda is still over relatively warm sea-surface temperatures, but it is headed for cooler waters, and by 24 hours it should be crossing the 26 deg C isotherm. These cooler waters combined with drier air and a significant increase in southwesterly wind shear that begins in a few days should cause the cyclone to steadily weaken. Fernanda is predicted to be a remnant low by the end of the forecast period when the SHIPS model shows the shear increasing to near 30 kt and the environmental mid-level relative humidity values below 40 percent. The NHC intensity forecast is similar to the previous one and generally follows the intensity model consensus. The track forecast philosophy for Fernanda remains unchanged. The hurricane continues to move northwestward at 8 kt toward a weakness in the ridge caused by a mid- to upper-level trough to the northeast of the Hawaiian Islands. This general motion is expected to continue for the next 24 hours or so. After that time, the trough is forecast to lift out, allowing the ridge to rebuild to the north of the weakening system. This pattern change should cause Fernanda to turn westward to west-northwestward. Only small changes were made to the previous NHC track forecast, and the new one lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 15.4N 132.8W 90 KT 105 MPH 12H 18/1800Z 16.1N 133.7W 80 KT 90 MPH 24H 19/0600Z 16.9N 134.8W 70 KT 80 MPH 36H 19/1800Z 17.4N 136.1W 60 KT 70 MPH 48H 20/0600Z 17.8N 137.6W 55 KT 65 MPH 72H 21/0600Z 18.6N 140.6W 45 KT 50 MPH 96H 22/0600Z 19.3N 143.7W 35 KT 40 MPH 120H 23/0600Z 19.9N 147.6W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi
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Tropical Depression SEVEN-E Forecast Discussion Number 3
2017-07-18 04:53:12| Tropical Depression LIDIA
Issued at 900 PM MDT Mon Jul 17 2017
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Hurricane FERNANDA Forecast Discussion Number 25
2017-07-18 04:40:38| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Mon Jul 17 2017 000 WTPZ41 KNHC 180240 TCDEP1 Hurricane Fernanda Discussion Number 25 NWS National Hurricane Center Miami FL EP062017 800 PM PDT Mon Jul 17 2017 Conventional satellite and two earlier GMI and GCOM-W1 microwave images indicate partial erosion in the southeast quadrant of the eyewall. Inner core cloud top temperatures have warmed, particularly over the aforementioned quadrant and in the western portion. A blend of the subjective and objective Dvorak estimates yields a lowered initial intensity of 95 kt for this advisory. Continued gradual weakening is forecast through the forecast period due to the cyclone traversing cooler oceanic SSTs and moving into a more stable and drier air mass with increasing vertical shear. The official forecast has been adjusted down a bit from the previous forecast based on the lowered initial intensity and follows the IVCN multi-model consensus. The initial motion is estimated to be northwestward, or 310/8 kt. Global models show a large amplitude mid- to upper-level tropospheric trough situated to the northeast of the Hawaiian Islands lifting northeastward around the 48-hour period, allowing the subtropical ridge to the north of Fernanda to rebuild westward. This change in the synoptic steering pattern should cause the cyclone to turn back toward the west-northwest and continue in this motion through day 5. The NHC forecast track is adjusted to the right of the previous advisory beyond day 3 and is in between the GFS/ECMWF blend and the TVCN consensus. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 14.7N 132.2W 95 KT 110 MPH 12H 18/1200Z 15.4N 133.1W 85 KT 100 MPH 24H 19/0000Z 16.2N 134.2W 75 KT 85 MPH 36H 19/1200Z 16.9N 135.4W 70 KT 80 MPH 48H 20/0000Z 17.3N 136.7W 65 KT 75 MPH 72H 21/0000Z 18.0N 139.8W 50 KT 60 MPH 96H 22/0000Z 18.6N 142.7W 35 KT 40 MPH 120H 23/0000Z 19.3N 146.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts
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Tropical Storm Don Forecast Discussion Number 2
2017-07-18 04:36:39| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Mon Jul 17 2017 000 WTNT45 KNHC 180236 TCDAT5 Tropical Storm Don Discussion Number 2 NWS National Hurricane Center Miami FL AL052017 1100 PM AST Mon Jul 17 2017 Before completing its mission in Don, the Air Force Reserve reconnaissance aircraft twice measured reliable surface winds around 40 kt via the SFMR instrument, and that is set as the initial intensity for this advisory. A burst of deep convection which began just after 2000 UTC has persisted for the past several hours, and small clusters of lightning have periodically occurred near the estimated center. Don is embedded within a narrow east-west zone of low shear, and that shear is expected to remain low for another 24 hours or so. Since the cyclone has a compact circulation, significant changes in intensity--both up and down--become more likely. Therefore, given that the environment looks favorable for the next 24 hours, the new NHC intensity forecast shows strengthening up to 50 kt as Don approaches the Windward Islands. After 24 hours, increasing westerly shear should induce weakening while Don moves through the southeastern Caribbean Sea, and the cyclone is expected to degenerate into an open wave by 72 hours, if not sooner. Since model guidance varies widely between only showing an open wave (most of the global models) to Don reaching hurricane strength (HWRF and some of the statistical models), it cannot be stressed enough that confidence in the intensity forecast is very low at this time. Don's initial motion is 280/16 kt. There is also a bit of uncertainty in the track forecast, especially in Don's future forward speed, since most of the global models don't show a strong enough vortex to provide a tracker. However, the general trend is for Don to move just north of due west and speed up by 24 hours. The updated NHC track forecast is a little faster than the previous forecast after 24 hours, mainly based on the latest GFS and ECMWF global model fields. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 11.3N 54.6W 40 KT 45 MPH 12H 18/1200Z 11.6N 57.0W 45 KT 50 MPH 24H 19/0000Z 12.0N 61.2W 50 KT 60 MPH 36H 19/1200Z 12.3N 65.4W 45 KT 50 MPH 48H 20/0000Z 12.5N 69.6W 40 KT 45 MPH 72H 21/0000Z...DISSIPATED $$ Forecaster Berg
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Tropical Storm Don Forecast Discussion Number 1
2017-07-17 23:02:07| National Hurricane Center (Atlantic)
Issued at 500 PM AST Mon Jul 17 2017 000 WTNT45 KNHC 172101 TCDAT5 Tropical Storm Don Discussion Number 1 NWS National Hurricane Center Miami FL AL052017 500 PM AST Mon Jul 17 2017 An Air Force Reserve reconnaissance aircraft investigating the area of low pressure located east-southeast of the Windward Islands has found a small, but well-defined surface circulation and a small area of tropical-storm-force winds over the eastern semicircle of the circulation. The associated convection is not particularly well organized, but there is a curved band located to the north of the center and a couple of bursts have formed closer to the small circulation center this afternoon. Based on these data, advisories are being initiated on a tropical storm, the fourth of the 2017 Atlantic hurricane season. Don is currently within a low shear environment and over warm water, so some strengthening is possible tonight and Tuesday. Once the system enters the eastern Caribbean Sea, strong upper-level westerly winds and strong low-level easterly flow are likely to cause the small circulation to open up into a trough. As a result, dissipation is forecast within 72 hours. Don is moving westward or 275/15 kt. The tropical storm is forecast to move quickly westward within the strong trade-wide flow for the next few days. The NHC track is along the southern edge of the guidance envelope, closest to the HFIP corrected consensus prediction. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 11.2N 52.6W 35 KT 40 MPH 12H 18/0600Z 11.5N 55.5W 40 KT 45 MPH 24H 18/1800Z 11.8N 58.9W 40 KT 45 MPH 36H 19/0600Z 12.0N 62.8W 40 KT 45 MPH 48H 19/1800Z 12.2N 67.0W 40 KT 45 MPH 72H 20/1800Z...DISSIPATED $$ Forecaster Brown
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