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Hurricane AMANDA Forecast Discussion Number 10

2014-05-25 04:47:40| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SAT MAY 24 2014 000 WTPZ41 KNHC 250247 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 PM PDT SAT MAY 24 2014 Amanda has continued to rapidly intensify over the past few hours, with the cloud pattern now featuring a ring of very cold cloud tops surrounding an eye that has quickly cleared out and warmed in the last several infrared images. The latest Dvorak satellite estimates include a T5.5/102 kt from SAB at 00Z, a T6.0/115 kt from a special 02Z TAFB classification, and 92 kt from the UW-CIMSS ADT at 0200Z. Based on a blend of these, the initial intensity has been set to 100 kt, and this could be conservative given the trends seen in the latest infrared images. Additional intensification appears likely over the next 12 to 24 hours. The NHC forecast in the short term is above all of the guidance, but is closest to the FSU Superensemble. By 36 hours, steady weakening is expected to begin as Amanda encounters increasing shear ahead of an approaching mid-/upper-level trough and SSTs cool along the forecast track. The NHC forecast late in the period is close to the intensity consensus. The initial motion estimate is 295/04. Amanda is expected to turn northwestward by 24 hours and northward by 48 hours as the mid-level ridge centered over Mexico weakens. After that time, a continued slow northward motion is expected as a weakening Amanda moves between a re-building ridge to the east and a mid/upper-level trough approaching from the west. The new NHC track forecast is close to the previous one and remains along the east side of the track guidance envelope. At days 4 and 5 the NHC track is close to the FSU Superensemble. The operational intensity estimate of Amanda at 00Z was less than 100 kt. Therefore, this makes Amanda the second earliest major hurricane on record in the eastern North Pacific basin, behind only Hurricane Bud of 2012. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 11.6N 110.7W 100 KT 115 MPH 12H 25/1200Z 11.8N 111.0W 110 KT 125 MPH 24H 26/0000Z 12.3N 111.2W 110 KT 125 MPH 36H 26/1200Z 12.9N 111.4W 100 KT 115 MPH 48H 27/0000Z 13.8N 111.6W 90 KT 105 MPH 72H 28/0000Z 15.0N 111.7W 65 KT 75 MPH 96H 29/0000Z 16.0N 111.5W 45 KT 50 MPH 120H 30/0000Z 17.0N 110.5W 30 KT 35 MPH $$ Forecaster Brennan

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Hurricane AMANDA Forecast Discussion Number 9

2014-05-24 22:33:13| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SAT MAY 24 2014 000 WTPZ41 KNHC 242033 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 200 PM PDT SAT MAY 24 2014 Amanda's eye is becoming more apparent in visible imagery. The hurricane has a fairly small central dense overcast with one prominent convective band curving around the western and northern side of the circulation. Dvorak estimates from TAFB and SAB are T4.0/65 kt, and the objective ADT has been steady around 70 kt for the past few hours. The initial intensity is raised to 70 kt based on the ADT estimate and the development of an eye in visible imagery. Amanda likely has another 36 hours or so of favorable conditions for intensification before southerly vertical wind shear begins to increase. The rate of intensification may have slowed down just a bit, but there's no real good reason not to expect further strengthening in the short term. One potential limiting factor could be upwelling of colder ocean water due to the slow movement of the hurricane during the next few days. The intensity guidance has backed off a bit on this cycle, with many of the models peaking the maximum winds just below major hurricane strength. Only the Florida State Superensemble explicitly shows Amanda becoming a major hurricane in 24-36 hours. Nonetheless, Amanda is forecast to be right around the major hurricane threshold of 100 kt in a day or so. After 36 hours, higher vertical shear should induce a fairly fast weakening trend, and the NHC forecast now shows Amanda becoming a tropical depression by day 5. Amanda's motion remains 290/4 kt. The hurricane should begin turning northwestward within 24 hours and then northward by 36 hours as the mid-level ridge over Mexico weakens. A slightly faster motion may develop in about 48 hours due to a restrengthening of the mid-level ridge over Mexico and an amplification of a mid-level low near 130W. The NHC forecast has again been shifted a bit to the right toward the tracks of the GFS and ECMWF, both of which lie along the eastern edge of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 11.4N 110.3W 70 KT 80 MPH 12H 25/0600Z 11.5N 110.7W 85 KT 100 MPH 24H 25/1800Z 12.0N 111.1W 95 KT 110 MPH 36H 26/0600Z 12.6N 111.2W 100 KT 115 MPH 48H 26/1800Z 13.5N 111.3W 90 KT 105 MPH 72H 27/1800Z 15.0N 111.5W 70 KT 80 MPH 96H 28/1800Z 16.0N 111.5W 45 KT 50 MPH 120H 29/1800Z 16.5N 111.0W 30 KT 35 MPH $$ Forecaster Berg

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Hurricane AMANDA Forecast Discussion Number 8

2014-05-24 16:37:38| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SAT MAY 24 2014 000 WTPZ41 KNHC 241437 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 AM PDT SAT MAY 24 2014 An eye has been observed sporadically in infrared satellite imagery during the past few hours, and recent microwave data has also revealed a small pinhole eye in the 85-GHz channel and a 12-15 n mi eye in TRMM radar data. Satellite classifications are still rising, and Amanda is being initialized as a 65-kt hurricane based on Dvorak estimates of T4.0 from SAB and the UW-CIMSS ADT. Amanda is intensifying rapidly, strengthening by 35 kt over the past 24 hours. Amanda is located over very warm water and in an environment of light vertical wind shear, and all indications are that this period of rapid intensification is likely to continue. The operational SHIPS Rapid Intensification Index (RII) is indicating a 60 percent chance of a 40-kt increase in intensity during the next 24 hours, which is almost 15 times higher than normal. An experimental Joint Hurricane Testbed version of the RII product, which includes additional environmental variables, is showing even higher chances of rapid intensification. Based on this guidance, Amanda is forecast to continue strengthening rapidly, potentially reaching the threshold for major hurricane in about 24-36 hours. After 48 hours, southerly vertical shear is expected to increase, which is likely to cause Amanda's low- and mid-level circulations to decouple. Therefore, fast weakening is indicated toward the end of the forecast period. The updated NHC forecast is higher than the previous one during the first 48 hours to account for the high likelihood of continued rapid intensification, but it is largely unchanged thereafter. Amanda continues on its slow west-northwestward trek, and the initial motion is estimated to be 290/4 kt. A mid-level ridge centered over Mexico should begin weakening soon, which will cause the hurricane's forward motion to slow even further during the next 24 hours. In about 2 days, the mid-level ridge is forecast to restrengthen over the western Gulf of Mexico while a mid-level trough amplifies near 130W. This pattern change should push Amanda northward between days 3 and 5, but the speed is still likely to be fairly slow. The GFS and ECMWF models are located on the right side of the guidance envelope on this forecast cycle, and the NHC forecast has therefore been shifted a bit to the right as well, especially beyond 36 hours. This track is also to the right of the model consensus TVCE. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 11.4N 109.9W 65 KT 75 MPH 12H 25/0000Z 11.6N 110.5W 80 KT 90 MPH 24H 25/1200Z 11.9N 110.9W 95 KT 110 MPH 36H 26/0000Z 12.4N 111.2W 100 KT 115 MPH 48H 26/1200Z 13.1N 111.3W 100 KT 115 MPH 72H 27/1200Z 15.0N 111.5W 80 KT 90 MPH 96H 28/1200Z 16.5N 111.5W 60 KT 70 MPH 120H 29/1200Z 17.5N 111.5W 40 KT 45 MPH $$ Forecaster Berg

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Tropical Storm AMANDA Forecast Discussion Number 7

2014-05-24 10:34:06| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SAT MAY 24 2014 000 WTPZ41 KNHC 240834 TCDEP1 TROPICAL STORM AMANDA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 200 AM PDT SAT MAY 24 2014 Amanda has continued to become better organized during the past 6 hours, with the system now showing a well-defined central dense overcast and increasing outer convective banding. Satellite intensity estimates are 55 kt and 45 kt from SAB and TAFB. In addition, Advanced Dvorak Technique estimates from CIMSS are near 60 kt, and a recent AMSU intensity estimate from CIRA was 76 kt. Based on this, the initial intensity is increased to 55 kt, and this could be conservative. The initial motion estimate is 295/04. There is little change to the track forecast or the track forecast reasoning. Amanda is moving slowly around the southwestern side of a weak mid-level ridge centered over Mexico. This current slow motion is expected to continue for the next 24 hours or so. A turn toward the northwest is shown around 36-48 hours, with a slight northward acceleration expected late in the period as the ridge restrengthens to the east and a mid/upper-level trough approaches from the west. The new forecast track is similar to, but slightly faster than, the previous track. The Rapid Intensification Index of the SHIPS model shows a 50-70 percent chance of rapid strengthening during the next 24 hours, with Amanda expected to remain over warm water in a light vertical wind shear environment. The SHIPS, GFDL, HWRF, and Florida State Superensemble models also call for rapid strengthening. Based on this, the intensity forecast calls for rapid intensification for 24-36 hours, and it is possible that Amanda could strengthen more than currently forecast. After 48 hours, a combination of increasing shear caused by the approaching trough and decreasing sea surface temperatures along the forecast track should cause steady to rapid weakening. The new intensity forecast is a little stronger than the previous forecast through 48 hours, and after that it shows a faster weakening than the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 11.4N 109.6W 55 KT 65 MPH 12H 24/1800Z 11.7N 110.3W 65 KT 75 MPH 24H 25/0600Z 11.9N 110.9W 80 KT 90 MPH 36H 25/1800Z 12.2N 111.3W 85 KT 100 MPH 48H 26/0600Z 12.7N 111.6W 90 KT 105 MPH 72H 27/0600Z 14.0N 112.0W 75 KT 85 MPH 96H 28/0600Z 15.5N 112.0W 60 KT 70 MPH 120H 29/0600Z 17.5N 112.0W 45 KT 50 MPH $$ Forecaster Beven

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Tropical Storm AMANDA Forecast Discussion Number 6

2014-05-24 04:32:07| National Hurricane Center (East Pacific)

Issued at 800 PM PDT FRI MAY 23 2014 000 WTPZ41 KNHC 240232 TCDEP1 TROPICAL STORM AMANDA DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 PM PDT FRI MAY 23 2014 Amanda has organized quickly over the past few hours. Deep convection now wraps more than halfway around the estimated center position, and an AMSR-2 microwave pass a few hours ago showed the development of a mid-level eye feature. Based on the latest ADT estimate from UW-CIMSS the initial intensity has been increased to 50 kt. Now that Amanda is developing inner-core structure, it seems likely that the cyclone will be able to take advantage of the favorable environment and intensify, possibly rapidly, during the next day or so. The SHIPS model shows the shear remaining 10 kt or less for the next 36 hours, and the SHIPS RI index shows a 58 percent probability of a 30-kt intensity increase in the next 24 hours. The official intensity forecast has been adjusted sharply upward and shows Amanda becoming a hurricane by 24 hours. A peak in intensity is shown at 48 hours, however, it is possible that Amanda could strengthen more than indicated here. After 48 hours, the shear will begin to increase ahead of an approaching trough and the cyclone will be moving over somewhat cooler waters, which should result in gradual weakening. The NHC forecast is a little above most of the guidance through 24 hours and is close to the IVCN intensity consensus after that time. The initial motion estimate is 290/04, as the cyclone continues to move slowly around the southwestern side of a weakening mid-level ridge centered over Mexico. This slow west-northwestward motion is expected to continue for the next 24 to 36 hours. A turn toward the northwest is shown around 48 hours, with a gradual northward acceleration expected late in the period as the ridge restrengthens to the east and a mid/upper-level trough approaches from the west. The track model guidance has trended somewhat faster this cycle, especially by day 5, and the official forecast has been adjusted in that direction. Otherwise, the new NHC track is largely an update of the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 11.2N 109.1W 50 KT 60 MPH 12H 24/1200Z 11.4N 109.7W 60 KT 70 MPH 24H 25/0000Z 11.7N 110.6W 75 KT 85 MPH 36H 25/1200Z 11.9N 111.1W 80 KT 90 MPH 48H 26/0000Z 12.2N 111.4W 85 KT 100 MPH 72H 27/0000Z 13.2N 111.7W 75 KT 85 MPH 96H 28/0000Z 15.0N 112.0W 65 KT 75 MPH 120H 29/0000Z 17.0N 112.0W 55 KT 65 MPH $$ Forecaster Brennan

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