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Hurricane PAINE Forecast Discussion Number 6

2016-09-19 10:36:53| Tropical Depression LIDIA

Issued at 300 AM MDT MON SEP 19 2016

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Post-Tropical Cyclone JULIA Forecast Discussion Number 21

2016-09-19 04:40:30| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT SUN SEP 18 2016 000 WTNT41 KNHC 190240 TCDAT1 POST-TROPICAL CYCLONE JULIA DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 1100 PM EDT SUN SEP 18 2016 Strong shear and dry mid-level air have continued to take a toll on Julia today. The cyclone has become an exposed swirl of low clouds devoid of significant deep convection for more than 12 hours. Based on this, Julia is being designated a post-tropical remnant low, and this will be the final NHC advisory on this system. The initial wind speed is set to 25 kt, which is based on the earlier ASCAT data, but this could be generous. The cyclone may produce some disorganized thunderstorms during the overnight convective maximum period, but increasing southwesterly shear on Monday should limit any organization or persistence of the activity. The low should gradually spin down and dissipate in a couple of days. Julia is moving northwestward at about 6 kt. A turn toward the north is expected overnight ahead of a shortwave trough moving into the southeastern United States. After that time, the remnant low is forecast to meander over eastern North Carolina until dissipation occurs. Moisture from the remnants of Julia are expected to interact with a frontal boundary moving into the Mid-Atlantic and Northeast United States. This is likely to produce local heavy rainfall from eastern North Carolina northward to the northeastern U.S. during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 32.2N 78.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 12H 19/1200Z 33.2N 78.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 20/0000Z 34.4N 77.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 20/1200Z 34.9N 77.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 21/0000Z 35.1N 77.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 22/0000Z...DISSIPATED $$ Forecaster Brown

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Tropical Storm PAINE Forecast Discussion Number 5

2016-09-19 04:38:28| Tropical Depression LIDIA

Issued at 900 PM MDT SUN SEP 18 2016

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Tropical Storm KARL Forecast Discussion Number 19

2016-09-19 04:38:28| National Hurricane Center (Atlantic)

Issued at 1100 PM AST SUN SEP 18 2016 000 WTNT42 KNHC 190238 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 1100 PM AST SUN SEP 18 2016 Karl is a poorly organized tropical storm. Satellite data indicate that the low-level center is exposed to the southwest of a few patches of deep convection. The initial intensity is again held at 35 kt, in agreement with the earlier scatterometer data and a Dvorak classification from TAFB. The cyclone continues to struggle in an environment of southwesterly shear and dry air. In fact, total precipitable water imagery shows dry air wrapping around the west and south sides of the circulation. The models indicate that the shear should lower on Monday, and remain relatively light during the next several days. Since Karl is expected to track over progressively warmer waters, between 28-30 deg C, and move into a more conducive atmospheric environment, strengthening seems likely. The NHC intensity forecast is largely an update of the previous one, but it is a touch lower at the 12-h point given the current poor initial structure of Karl. This forecast is in best agreement with the SHIPS model. The system is moving westward at 13 kt, and that general motion should continue for the next 12-24 hours as Karl remains on the south side of a subtropical ridge over the central Atlantic. A west-northwestward motion is expected to begin by Monday night, followed by a turn to the northwest by mid-week when the cyclone moves toward a weakness in the ridge. Although the models agree on the overall scenario, there is a fair amount of spread by the end of the forecast period. The NHC track forecast is slightly faster than the model consensus, giving a little more weight to the GFS and ECMWF models. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 18.3N 46.3W 35 KT 40 MPH 12H 19/1200Z 18.5N 48.3W 35 KT 40 MPH 24H 20/0000Z 19.1N 50.9W 40 KT 45 MPH 36H 20/1200Z 19.8N 53.4W 45 KT 50 MPH 48H 21/0000Z 20.7N 55.9W 50 KT 60 MPH 72H 22/0000Z 23.1N 60.9W 60 KT 70 MPH 96H 23/0000Z 26.5N 65.0W 70 KT 80 MPH 120H 24/0000Z 28.8N 66.9W 80 KT 90 MPH $$ Forecaster Cangialosi

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Tropical Storm KARL Forecast Discussion Number 18

2016-09-18 22:59:25| National Hurricane Center (Atlantic)

Issued at 500 PM AST SUN SEP 18 2016 000 WTNT42 KNHC 182059 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 500 PM AST SUN SEP 18 2016 Deep convection has gradually been increasing and becoming a little better organized since the previous advisory now that light upper-level southeasterly flow has replaced the previous hostile vertical wind shear conditions. Visible satellite imagery and ASCAT surface wind data from 1200Z-1300Z indicate that Karl's circulation remains well-defined, especially the inner-core wind field. The ASCAT data also revealed a large patch of 35-kt winds 60-100 nmi north and northeast of the center, and that is the intensity used for this advisory. The ASCAT data supports trimming back the 34-kt wind radius in the northeastern quadrant. Karl continues to move westward or 275/13 kt. Karl is expected to move westward along the southern periphery of the Bermuda-Azores ridge for the next couple of days, followed by a west-northwestward motion on days 3-5 as the cyclone approaches a weakness in the ridge located between Bermuda and the Bahamas. The global and regional models are in general agreement on this track scenario through 72 hours, After that time, the models diverge significantly with the GFS, Navy COAMPS, and GFDL models taking Karl farther west as a weaker and more shallow cyclone, whereas the ECMWF, UKMET, and HWRF models move Karl more northwestward as a stronger and deeper system. For now, the official forecast track remains a compromise between these extremes, close to the consensus model solutions, due to the lack of a stable, consistent run-to-run forecast by the models. The GFS and ECMWF models continue to forecast the vertical wind shear to decrease to less than 10 kt from now through the end of the forecast period, with near-zero shear values occuring at times between 72-120 hours. Such low shear values continue to favor a strengthening trend, especially since Karl will be moving over 30C SSTs by days 4 and 5. However, a somewhat dry mid-level environment is expected to temper the intensification process a little due to occasional intrusions of dry air into the inner-core region of Karl's circulation. Once the cyclone develops an eye feature, then strengthening will become more robust due to the low wind shear conditions and high sea-surface temperatures. Since these parameters can not be forecast very far in advance, the official intensity forecast continues to show slow strengthening throughout the period and remains close to the intensity consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 18.3N 45.0W 35 KT 40 MPH 12H 19/0600Z 18.5N 47.0W 40 KT 45 MPH 24H 19/1800Z 19.0N 49.7W 40 KT 45 MPH 36H 20/0600Z 19.7N 52.2W 45 KT 50 MPH 48H 20/1800Z 20.5N 54.7W 50 KT 60 MPH 72H 21/1800Z 22.9N 59.7W 60 KT 70 MPH 96H 22/1800Z 25.4N 64.2W 70 KT 80 MPH 120H 23/1800Z 28.0N 67.0W 80 KT 90 MPH $$ Forecaster Stewart

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