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Tropical Storm CRISTOBAL Forecast Discussion Number 5
2014-08-24 22:51:01| National Hurricane Center (Atlantic)
Issued at 500 PM EDT SUN AUG 24 2014 000 WTNT44 KNHC 242050 TCDAT4 TROPICAL STORM CRISTOBAL DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014 500 PM EDT SUN AUG 24 2014 Cristobal's convective cloud pattern has not changed much during the past 6 hours, other than cloud tops having warmed some. Aircraft and satellite data indicate that the inner-core wind field is still broad, with multiple small swirls rotating around a mean center. Air Force Reserve and NOAA reconnaissance aircraft data indicate the central pressure has remained steady at 1001 mb, so the initial intensity will be kept at 40 kt for this advisory. The initial motion is northward or 360/7 kt. The NHC model guidance has come into much better agreement on this cycle with the GFS track having shifted westward and the ECMWF model having shifted eastward. The rest of the models are reasonably close to the GFS and ECMWF solutions. There is one main difference, however, which is the track speed, with the GFS model lagging behind the ECMWF model and some of the other models by more than 500 n mi at 120 hours. Cristobal is expected to continue moving northward through a weakness in the subtropical ridge and slow down over the next 72 hours as a strong upper-level trough east of North Carolina lifts out to the northeast. A second trough currently over the upper Midwest is forecast to dig southeastward along the U.S. east coast by Days 4 and 5 and accelerate the cyclone northeastward over the north Atlantic. The official forecast track has been shifted eastward through 72 hours, and then shows a faster forward speed similar to the ICON consensus model at 96 and 120 hours. Light to moderate northwesterly to northerly shear is forecast to affect Cristobal through 72 hours, which should allow for only slow strengthening to occur. When Cristobal makes a northeastward turn and accelerates after that time, the shear is expected to decrease while the cyclone is over near-29C SST, which should allow Cristobal to strengthen into a hurricane. The NHC intensity forecast is similar to the previous advisory, and closely follows the consensus intensity model ICON. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 24.5N 73.0W 40 KT 45 MPH 12H 25/0600Z 24.9N 73.1W 45 KT 50 MPH 24H 25/1800Z 25.7N 73.0W 50 KT 60 MPH 36H 26/0600Z 26.6N 72.8W 55 KT 65 MPH 48H 26/1800Z 28.4N 72.5W 60 KT 70 MPH 72H 27/1800Z 31.9N 71.8W 65 KT 75 MPH 96H 28/1800Z 35.0N 66.5W 70 KT 80 MPH 120H 29/1800Z 39.5N 58.0W 70 KT 80 MPH $$ Forecaster Stewart
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