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Hurricane AMANDA Forecast Discussion Number 18
2014-05-27 04:35:56| National Hurricane Center (East Pacific)
Issued at 800 PM PDT MON MAY 26 2014 000 WTPZ41 KNHC 270235 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 PM PDT MON MAY 26 2014 Amanda's cloud pattern had been reasonably well organized during the day, with the cyclone maintaining a small Central Dense Overcast and an intermittent but faint eye. The eye has since disappeared and the convective structure has become increasingly less symmetric, presumably as a consequence of an increase in southerly vertical wind shear. The cloud pattern has also recently become elongated poleward, with little to no outflow noted to the south. Using a blend of Dvorak T- and CI numbers and recent satellite trends...the advisory wind speed is reduced to 90 kt. Center fixes indicate that Amanda has moved somewhat erratically during the day...but smoothing through these yields an initial motion of 340/04. The cyclone is embedded in a region of weak steering flow between a mid-level ridge over the Gulf of Mexico and a mid- to upper-level trough to the west. This pattern should steer the cyclone slowly northward during the next couple of days. After that time, the forecast becomes more challenging as the model spread increases significantly. The GFS forecasts Amanda to remain a deeper cyclone longer and therefore moves it much farther northeast, while the ECMWF shows the cyclone decoupling sooner and interacting with a disturbance to the its east. As a result, Amanda or its remnants in the ECMWF solution move generally eastward without gaining much latitude. Given the uncertainty, the official forecast is close to the multi-model consensus TVCE and a little to the east of the previous forecast beyond 36 hours. Global models show the shear at its worst during the next 24 hours and then slowly decreasing as the mid- to upper-level trough affecting the cyclone lifts out. Even though upper-level winds are forecast to become anticyclonic late in the period...what remains of the Amanda should be moving over cooler waters and within a region of substantially drier and more stable air in the wake of the aforementioned trough. Thus, it would seem that the shear debilitates Amanda and the other negative factors cause the cyclone to degenerate into a remnant low. The official forecast is lower than the previous one and is a blend of the multi-model intensity consensus ICON and LGEM. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 13.7N 111.9W 90 KT 105 MPH 12H 27/1200Z 14.2N 112.1W 80 KT 90 MPH 24H 28/0000Z 14.9N 112.2W 65 KT 75 MPH 36H 28/1200Z 15.4N 112.2W 50 KT 60 MPH 48H 29/0000Z 15.9N 112.0W 35 KT 40 MPH 72H 30/0000Z 16.5N 111.5W 30 KT 35 MPH 96H 31/0000Z 17.0N 111.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/0000Z 16.9N 111.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Kimberlain
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