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Tropical Depression TWELVE-E Forecast Discussion Number 2

2014-08-18 10:46:20| Tropical Depression LIDIA

Issued at 200 AM PDT MON AUG 18 2014

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Tropical Storm KARINA Forecast Discussion Number 21

2014-08-18 04:37:16| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SUN AUG 17 2014 000 WTPZ41 KNHC 180237 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 800 PM PDT SUN AUG 17 2014 Karina's cloud pattern has changed little in organization over the past several hours. The system remains a sheared tropical cyclone, with all of the deep convection displaced to the west-southwest of the low-level center. The intensity is kept at 40 kt for this advisory, which is only slightly above the most recent Dvorak estimates and is consistent with earlier scatterometer data. The easterly shear over Karina is due to a combination of an upper-level anticyclone to the north-northeast and the outflow from a developing system to the east. The global models indicate that the anticyclone will shift eastward and weaken, which could result in some decrease in shear. However since Karina will be traversing marginal sea surface temperatures during the next several days, only slight strengthening is predicted. This is the same as the previous official wind speed forecast and very close to the latest intensity model consensus. The storm continues to move west-southwestward with gradually decreasing forward speed, and the initial motion estimate is 255/10 kt. A weak mid-level ridge to the north of the storm should maintain a west-southwestward to westward heading for the next couple of days. However, the interaction with the developing cyclone to the east and another, weaker, disturbance to the west of Karina should result in a slowing of the forward motion. Around the end of the forecast period, a broad fetch of west-southwesterly flow feeding into the larger cyclone to the northeast should cause Karina to reverse its heading and move northeastward. The new official track forecast is somewhat farther west of the previous one at days 2-5, but not as far west as the latest track model consensus. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 17.5N 130.4W 40 KT 45 MPH 12H 18/1200Z 17.0N 131.7W 40 KT 45 MPH 24H 19/0000Z 16.5N 133.0W 45 KT 50 MPH 36H 19/1200Z 16.4N 134.0W 45 KT 50 MPH 48H 20/0000Z 16.4N 134.8W 50 KT 60 MPH 72H 21/0000Z 16.5N 136.0W 45 KT 50 MPH 96H 22/0000Z 16.5N 136.5W 45 KT 50 MPH 120H 23/0000Z 17.5N 135.0W 45 KT 50 MPH $$ Forecaster Pasch

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Tropical Storm KARINA Forecast Discussion Number 20

2014-08-17 22:44:45| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SUN AUG 17 2014 000 WTPZ41 KNHC 172044 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 200 PM PDT SUN AUG 17 2014 Karina's convective pattern has continued to wax and wane over the past 6 hours. Another burst of deep convection with cloud tops to -80C has developed near and to the west through southwest of the partially exposed, well-defined low-level circulation center. Recent objective intensity analyses from CIMSS AMSU and ADT yield estimates of 42-44 kt, and a recent ASCAT-B overpass at 1847 UTC indicated several 36-37 kt surface wind vectors northwest and west of the center. Based on a blend of these values, the initial intensity is held at 40 kt. Karina appears to have made the much expected turn toward the west-southwest, and the initial motion is now 255/11 kt. Karina is expected to continue moving toward the west-southwest and slow down considerably over the next 72 hours as a broad high pressure system builds to the north and west of the cyclone. Karina could even stall on Day 3 as steering currents collapse. After that, a large developing disturbance located about 700 n mi east of the cyclone is forecast by all of the global models to evolve into an unusually large low pressure system that will gradually pull Karina back to the east-northeast and northeast on Days 4 and 5. The official forecast track has been shifted farther west, but not as far west as the consensus model TVCE due to the uncertainly involved in exactly how much influence and timing that the large disturbance east of Karina will have on the tropical cyclone. Moderate easterly mid- to upper-level shear is expected to affect Karina for the next 18 hours or so, which should inhibit any significant intensification. After that, however, the shear is forecast by the SHIPS model to decrease to less than 10 kt, during which time some intensification could occur while the cyclone remains over marginal SSTS of at least 26C. By 48 hours and beyond, the easterly shear is expected to increase again due to strong upper-level outflow associated with the aforementioned large disturbance to the east of Karina. The increasing shear, coupled with decreasing SSTs, should cap any intensification that might have occurred. The GFDL and HWRF models bring Karina back to hurricane strength at around 120 hours, but this seems unlikely due to the cyclone being over sub-26C SSTs at that time. The NHC intensity forecast is similar to the previous advisory and TO the ICON intensity consensus model. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 17.7N 129.5W 40 KT 45 MPH 12H 18/0600Z 17.3N 130.8W 40 KT 45 MPH 24H 18/1800Z 16.7N 132.3W 45 KT 50 MPH 36H 19/0600Z 16.3N 133.4W 45 KT 50 MPH 48H 19/1800Z 16.3N 134.3W 50 KT 60 MPH 72H 20/1800Z 16.4N 135.0W 45 KT 50 MPH 96H 21/1800Z 16.7N 135.2W 45 KT 50 MPH 120H 22/1800Z 17.1N 134.4W 45 KT 50 MPH $$ Forecaster Stewart

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Tropical Storm KARINA Forecast Discussion Number 16

2014-08-16 22:38:42| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SAT AUG 16 2014 000 WTPZ41 KNHC 162038 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 200 PM PDT SAT AUG 16 2014 The cloud pattern has continued to deteriorate today, with the low-level center now removed from the deep convection due to moderate easterly shear. T-numbers have decreased to T2.0 and T2.5 on the Dvorak scale, and a recent partial ASCAT pass shows maximum winds of 35 knots. On this basis, the intensity has been set at 35 knots. Although Karina has weakened, it most likely will begin to re-strengthen in about 24 hours when the circulation moves over warmer waters and into weaker shear. In fact, the HWRF insists on bringing Karina back to hurricane status in 3 days. The NHC forecast is not that aggressive and brings the winds only to 50 knots in agreement with the intensity consensus. Microwave and conventional fixes indicate that the center has been moving just south of due west or 260 degrees at 10 knots. The ridge to the north of Karina is expected to amplify a little more forcing the cyclone to move on a west-southwest track for the next 2 to 3 days. After that time, the steering currents are expected to collapse due to the development of several disturbances nearby, and that pattern will keep the cyclone meandering for the remainder of the forecast period. Most of the dynamical track guidance forecast a sharp but slow turn to the right before Karina arrives at 132 degrees longitude. Given the weak steering flow, the NHC forecast shows little movement between 3 and 5 days. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 17.9N 125.0W 35 KT 40 MPH 12H 17/0600Z 17.7N 126.4W 35 KT 40 MPH 24H 17/1800Z 17.5N 128.4W 40 KT 45 MPH 36H 18/0600Z 17.0N 129.8W 40 KT 45 MPH 48H 18/1800Z 16.5N 131.0W 45 KT 50 MPH 72H 19/1800Z 16.0N 132.0W 50 KT 60 MPH 96H 20/1800Z 15.5N 132.0W 50 KT 60 MPH 120H 21/1800Z 15.5N 132.0W 50 KT 60 MPH $$ Forecaster Avila

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Tropical Storm KARINA Forecast Discussion Number 14

2014-08-16 10:38:58| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SAT AUG 16 2014 000 WTPZ41 KNHC 160838 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 200 AM PDT SAT AUG 16 2014 Karina continues to be affected by about 15 kt of easterly vertical wind shear, with the low-level center located just to the northeast of a burst of convection with cloud tops colder than -80C. Satellite intensity estimates are 45 kt from TAFB and 35 kt from SAB. In addition, a recent ASCAT overpass showed 35-40 kt winds about 40 n mi north of the center. Based on these data, the initial intensity remains 40 kt. The initial motion is now 285/9, with Karina continuing to be steered by a subtropical ridge to the north. This ridge will build westward during the next couple of days, followed by an amplification of a ridge well north of the Hawaiian Islands. These developments should result in Karina turning westward later today and then turning a little south of due west during the middle of the forecast period. The steering current are expected to collapse after 72 hours as a mid/upper-level trough likely develops off the west coast of North America and other areas of disturbed weather develop east and west of the cyclone. During this time, the GFS and Canadian models forecast a loop back to the east, the ECMWF and UKMET models forecast a slow westward motion, and the NAVGEM and GFS ensemble mean forecast a slow northward motion. The official forecast track compromises between these forecasts by showing a westward drift. Overall, the new track is again similar to the old track and near the multi-model consensus. The large-scale models forecast the shear to decrease during the next 48 hours or so. However, Karina will be moving over gradually decreasing sea surface temperatures, and the forecast track keeps the center near the 26C isotherm after 48 hours. In the short term, Karina is expected to weaken a little more. While the official forecast keeps the system as a tropical storm, an alternate scenario is shown by the SHIPS and LGEM models, which forecast it to weaken to a depression. After 48 hours, the guidance suggests Karina could re-intensify if it is not absorbed by one of the nearby disturbances. The latter part of the official forecast reflects this by showing modest strengthening. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 18.1N 122.9W 40 KT 45 MPH 12H 16/1800Z 18.2N 124.4W 35 KT 40 MPH 24H 17/0600Z 18.2N 126.4W 35 KT 40 MPH 36H 17/1800Z 18.0N 128.4W 35 KT 40 MPH 48H 18/0600Z 17.6N 130.1W 35 KT 40 MPH 72H 19/0600Z 16.5N 132.5W 40 KT 45 MPH 96H 20/0600Z 16.5N 133.5W 40 KT 45 MPH 120H 21/0600Z 16.5N 134.0W 45 KT 50 MPH $$ Forecaster Beven

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