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Hurricane AMANDA Forecast Discussion Number 16

2014-05-26 16:37:52| National Hurricane Center (East Pacific)

Issued at 800 AM PDT MON MAY 26 2014 000 WTPZ41 KNHC 261437 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 AM PDT MON MAY 26 2014 Amanda has changed little during the past 6 hours, including an intermittent eye embedded within a ragged CDO feature containing cloud tops colder than -70C. A blend of final T-numbers and current intensity estimates from TAFB and SAB, and an ADT value of T6.3/122 kt, yields an average of 114 kt. Thus, the initial intensity of Amanda has been lowered to 115 kt for this advisory. Smoothing through the many fits and starts yields a 12-hour average motion of 345/04 kt, which is used for the advisory motion. Otherwise, there are no significant changes to the previous advisory track or reasoning. Amanda is expected to move slowly north-northwestward to northward between a broad mid-level trough to its west and a weak subtropical ridge situated to its east over Mexico for the next 72 hours or so. After which some slow erratic motion is possible when the cyclone is expected to weaken into a shallow system and become trapped within weak steering currents. The global and regional models are in good agreement on this developing scenario. As a result, the official forecast track is essentially just an update of the previous advisory track, and is close to the consensus model TVCE and the FSSE model. The deep-layer vertical wind shear across Amanda is assessed at around 25 kt by both the GFS-based SHIPS model and UW-CIMSS, and these strong shear conditions are expected to continue for at least the next 36 hours. As a result, steady to rapid weakening is forecast to begin later today, especially if significant cold upwelling develops beneath the slow-moving hurricane. The NHC intensity forecast is similar to the previous advisory, and closely follows the intensity consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 13.2N 111.6W 115 KT 135 MPH 12H 27/0000Z 14.0N 111.9W 100 KT 115 MPH 24H 27/1200Z 14.9N 112.2W 85 KT 100 MPH 36H 28/0000Z 15.7N 112.4W 70 KT 80 MPH 48H 28/1200Z 16.1N 112.4W 55 KT 65 MPH 72H 29/1200Z 16.8N 112.1W 40 KT 45 MPH 96H 30/1200Z 17.1N 111.8W 30 KT 35 MPH 120H 31/1200Z 17.3N 111.8W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Hurricane AMANDA Forecast Discussion Number 14

2014-05-26 04:40:22| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SUN MAY 25 2014 000 WTPZ41 KNHC 260240 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 PM PDT SUN MAY 25 2014 Since Amanda peaked in intensity earlier today, there has been some erosion of deep convection in the southwestern quadrant of the cyclone, likely due to onset of moderate south-southwesterly wind shear. A pronounced dry slot is also noted wrapping around the southern half of the circulation in geostationary and microwave imagery. Satellite intensity estimates have decreased slightly, and the initial intensity is set to 125 kt, based on blend of Final-T and CI numbers. The initial motion is 335/03. The cyclone is located between a mid-level ridge to the east-northeast and a mid-/upper-level trough to the west. A weak deep-layer south-southeasterly to southerly flow between these two features should steer Amanda north- northwestward and then northward during the next few days. A turn toward the north-northeast is forecast in about 72 hours when the aforementioned mid- to upper-level trough approaches the cyclone. After that time, a much weaker Amanda should stall or begin to drift westward or southwestward as a shallow feature in the trade wind flow. The model guidance this cycle has shifted westward again, and the official forecast is adjusted in that direction. It lies on the eastern side of the guidance envelope, nearly midway between the previous forecast and the multi-model consensus TVCE through 72 hours and south of the previous forecast late in the period. Moderate to strong south-southwesterly vertical wind shear, combined with gradually decreasing sea surface temperatures along the forecast track, should cause Amanda to quickly weaken during the next few days. In about 3 days, the model guidance shows the low- and mid-level circulations of Amanda decoupling as the cyclone interacts with the trough to its west. The entrainment of substantially drier and more stable air should then cause whatever remains of Amanda to degenerate into a remnant low by day 5. The official forecast is slightly lower than the previous one in the short term and close to the multi-model consensus ICON. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 12.6N 111.4W 125 KT 145 MPH 12H 26/1200Z 13.0N 111.6W 110 KT 125 MPH 24H 27/0000Z 14.0N 111.9W 95 KT 110 MPH 36H 27/1200Z 15.0N 112.1W 80 KT 90 MPH 48H 28/0000Z 15.9N 112.1W 65 KT 75 MPH 72H 29/0000Z 16.6N 112.0W 50 KT 60 MPH 96H 30/0000Z 17.4N 111.4W 35 KT 40 MPH 120H 31/0000Z 18.0N 111.2W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Kimberlain

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Hurricane AMANDA Forecast Discussion Number 13

2014-05-25 22:42:18| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SUN MAY 25 2014 000 WTPZ41 KNHC 252042 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 200 PM PDT SUN MAY 25 2014 Conventional and microwave satellite imagery indicate that Amanda likely peaked in intensity around 1200 UTC this morning and has started weakening since then. The CDO feature has decreased in size and become more ragged looking during the past few hours, and the small eye is becoming less distinct and cloud-filled in visible imagery. A 1459 UTC SSMI/S microwave image revealed that Amanda possessed a pinhole eye, which usually means that an eyewall replacement cycle is not far behind. The initial intensity has been decreased to 130 kt based on a blend of final T-numbers from TAFB and SAB ranging from T5.5/102 kt to T6.5/127 kt. Although UW-CIMSS ADT estimates remain at T6.9/137 kt, the raw values have dropped to T6.1/117 kt, which further supports lowering the initial intensity. Amanda is now moving northward to north-northwestward or 350/04 kt. The hurricane is forecast to maintain this general motion for the next 3 days or so as the cyclone remains embedded in southerly steering flow between a broad deep-layer trough to its west and a weak mid-level ridge to its east. After that time, Amanda is forecast to weaken fairly significantly and become a shallow cyclone that could briefly stall before turning westward or southwestward when it comes under the influence of a large low-level subtropical ridge to its north. The model guidance suite has shifted westward this cycle, including the consensus model TVCE. However, the latter model is biased by a more westerly track of the UKMET model that initialized a very weak cyclone instead of a more robust category 4 hurricane. Therefore, the official track forecast remains similar to the previous track and lies to right of TVCE, near the eastern portion of the guidance envelope and closer to the ECMWF model. Cold upwelling and occasional intrusions of dry mid-level air should slowly erode the inner-core convection over the next 24 hours or so. An eyewall replacement cycle is also possible, which would act to hasten the weakening process. By day 2 and beyond, the combination of cooler water, drier air, and increasing southerly vertical wind shear should induce more rapid weakening, and Amanda is forecast to degenerate into a non-convective remnant low by day 5. The NHC intensity forecast is similar to the previous advisory and the intensity consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 12.3N 111.3W 130 KT 150 MPH 12H 26/0600Z 12.8N 111.4W 115 KT 135 MPH 24H 26/1800Z 13.6N 111.6W 105 KT 120 MPH 36H 27/0600Z 14.6N 111.7W 90 KT 105 MPH 48H 27/1800Z 15.6N 111.7W 75 KT 85 MPH 72H 28/1800Z 17.1N 111.5W 55 KT 65 MPH 96H 29/1800Z 18.0N 110.9W 35 KT 40 MPH 120H 30/1800Z 18.4N 110.6W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Hurricane AMANDA Forecast Discussion Number 12

2014-05-25 16:59:05| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SUN MAY 25 2014 000 WTPZ41 KNHC 251458 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 AM PDT SUN MAY 25 2014 Amanda has continued to rapidly strengthen this morning, although the hurricane is likely near its peak intensity. The 15 n mi diameter eye remains quite distinct in infrared and first-light visible satellite imagery, and a solid ring of cloud tops as cold as -75C surround the eye. Subjective classifications at 1200 UTC from TAFB and SAB were T7.0/140 kt and T6.5/127 kt, respectively. The ADT estimate from UW-CIMSS was T6.6/130 kt, and those values have continued to steadily increase to T6.8/135 kt as of 1330 UTC. A blend of these intensity estimates easily support increasing the intensity to 135 kt, which is just below category 5 strength on the Saffir-Simpson Hurricane Wind Scale. Amanda appears to have stalled during the past few hours and is now drifting slowly northward or north-northwestward at around 2 kt, a motion that has been well forecast in previous advisories over the past 2 days. Amanda is expected to maintain a general northward motion over the next 72 hours as the hurricane moves into a combined southerly steering between a mid-/upper-level trough to its west and a mid-level ridge to its east. By days 4 and 5, Amanda is expected to be a significantly weakened and more shallow cyclone that is forecast to slow down and turn westward under the influence of a large low-level subtropical ridge located from Baja California westward into the central Pacific Ocean. The NHC track forecast is similar to the previous advisory and lies near a blend of the FSSE and TVCE models. Amanda has likely reached its peak intensity, or is very close to it. Although the SHIPS intensity model indicates SSTs warmer than 29C exists beneath and ahead of the hurricane, various SST analysis products at 1200 UTC this morning indicate that cold upwelling has already begun beneath the cyclone, and this cold upwelling should be exacerbated even further now the cyclone is moving at a forward speed of only 2 kt. As a result, steady weakening is expected within the next 12 hours or so. By 36 hours and beyond, southerly to southwesterly winds shear is forecast to increase to more than 20 kt, which should further enhance the weakening process. By day 5, the global models are in good agreement on the low- and upper-level circulations decoupling, which could result in Amanda becoming a remnant low at that time. The official intensity forecast is similar to the previous advisory, and closely follows the intensity model consensus IVCN, which is well below the SHIPS and LGEM models through 36 hours. Amanda is now the strongest May hurricane on record in the eastern Pacific basin during the satellite era. If Amanda were to reach an intensity of 140 kt, it would become the earliest category 5 hurricane on record, beating out Hurricane Ava of 1973. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 11.8N 111.1W 135 KT 155 MPH 12H 26/0000Z 12.2N 111.3W 130 KT 150 MPH 24H 26/1200Z 13.0N 111.4W 120 KT 140 MPH 36H 27/0000Z 14.0N 111.6W 105 KT 120 MPH 48H 27/1200Z 15.0N 111.7W 90 KT 105 MPH 72H 28/1200Z 16.5N 111.5W 65 KT 75 MPH 96H 29/1200Z 17.6N 110.7W 45 KT 50 MPH 120H 30/1200Z 18.6N 110.0W 30 KT 35 MPH $$ Forecaster Stewart

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Hurricane AMANDA Forecast Discussion Number 11

2014-05-25 10:39:45| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SUN MAY 25 2014 000 WTPZ41 KNHC 250839 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 200 AM PDT SUN MAY 25 2014 Amanda is still rapidly intensifying. The eye has become more distinct and a large ring of cloud tops colder than -70C surround the center. The Dvorak classifications from TAFB and SAB are 6.5/127 kt and 6.0/115 kt, respectively. A blend of these estimates and the latest ADT values from UW-CIMSS support increasing the initial wind speed to 120 kt, making Amanda a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. The major hurricane could gain some more strength today while the atmospheric and oceanic environments remain conducive for intensification. After that time, however, southerly shear is expected to increase and that should start the weakening process. The GFS and ECMWF models show Amanda beginning to tilt vertically in response to the shear in about 24 hours, with the low- and mid-level centers eventually decoupling. Gradually decreasing sea surface temperatures and drier mid-level air should also aid in the weakening trend. The NHC intensity forecast is a little above the previous one in the short term to account for the higher initial wind speed, but is otherwise unchanged and follows the intensity model consensus IVCN. The cyclone is moving slowly west-northwestward, with the initial motion estimate the same as before, 295/4. A turn to the northwest is expected today followed by a northward motion tonight as Amanda gets embedded in the flow between a mid- to upper-level trough to its west and a mid-level ridge to its east. A northeastward turn is predicted in about 4 days when the trough to the west of Amanda gets closer to the system. The NHC track forecast is very close to the previous one and near the latest FSSE and TVCE guidance. Based on the current intensity of the system, Amanda is the second strongest May hurricane in the eastern Pacific basin on record, behind Hurricane Adolph in 2001. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 11.7N 110.9W 120 KT 140 MPH 12H 25/1800Z 11.9N 111.2W 125 KT 145 MPH 24H 26/0600Z 12.5N 111.3W 120 KT 140 MPH 36H 26/1800Z 13.4N 111.4W 105 KT 120 MPH 48H 27/0600Z 14.3N 111.5W 90 KT 105 MPH 72H 28/0600Z 15.6N 111.6W 65 KT 75 MPH 96H 29/0600Z 16.4N 111.0W 45 KT 50 MPH 120H 30/0600Z 17.5N 110.0W 30 KT 35 MPH $$ Forecaster Cangialosi

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