Home › discussion
 

Keywords :   


Tag: discussion

Tropical Depression Fifteen Forecast Discussion Number 4

2019-10-15 16:33:08| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Tue Oct 15 2019 000 WTNT45 KNHC 151433 TCDAT5 Tropical Depression Fifteen Discussion Number 4 NWS National Hurricane Center Miami FL AL152019 1100 AM AST Tue Oct 15 2019 The depression doesn't looking very healthy compared to 24 hours ago when tightly curved convective bands wrapped around the center. Over the past 12 hours, the convection has devolved into an elongated north-to-south band of stratiform deep-layer cloudiness with embedded clusters of moderate to deep convection. The western semicircle of the broad circulation has degraded with at least two small low-level circulations revolving southward around the mean center. A 1045Z partial ASCAT-A pass indicated that the low-level center was located west of 21W longitude, so the initial position was adjusted farther west. Intensity estimates range from T1.5/25 kt from TAFB and the partial ASCAT pass, to 33 kt and 37 kt from UW-CIMSS ADT and SATCON, respectively. For now, the intensity will be held at 30 kt, which is an average of these estimates. The initial motion estimate remains northwestward, or 320/08 kt, but this motion is of low confidence given the broad nature of the cyclone. Surprisingly, the models remain in quite good agreement that the depression will move generally northwestward during the next couple of days and pass over or just east of the northeastern Cabo Verde Islands. A turn to the west-northwest is forecast by 72 hours and beyond due to the weak and shallow system being steered by the low-level easterly trade wind flow. The new NHC track forecast has been nudged a little to the left or west of the previous advisory track, mainly due to the more westward initial position, and lies close to the tightly packed consensus models. The environmental conditions are expected to remain somewhat conducive for slight strengthening during the next 12-18 hours. Although no longer explicitly forecast, it is still possible that the depression could briefly become a tropical storm later tonight if a burst of deep convection can develop and tighten up the inner-core wind field. By late Wednesday, however, the combination of a sharp increase in southwesterly vertical wind shear, drier mid-level air, and SSTs less than 26C should induce steady to rapid weakening, resulting in the cyclone degenerating into a remnant low by 36 hours and dissipating in 72-96 hours. Regardless of whether or not the depression becomes a tropical storm before passing near the Cabo Verde Islands, the primary threat from this system is the potential for locally heavy rainfall and flash flooding in those islands. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 15.6N 21.6W 30 KT 35 MPH 12H 16/0000Z 16.5N 22.4W 30 KT 35 MPH 24H 16/1200Z 17.7N 23.4W 30 KT 35 MPH 36H 17/0000Z 18.5N 24.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 17/1200Z 19.4N 26.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 18/1200Z 21.6N 30.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/1200Z...DISSIPATED $$ Forecaster Stewart

Tags: number discussion tropical depression

 

Tropical Depression Fifteen Forecast Discussion Number 3

2019-10-15 10:46:03| National Hurricane Center (Atlantic)

Issued at 500 AM AST Tue Oct 15 2019 000 WTNT45 KNHC 150845 TCDAT5 Tropical Depression Fifteen Discussion Number 3 NWS National Hurricane Center Miami FL AL152019 500 AM AST Tue Oct 15 2019 The depression remains poorly organized this morning with only loosely fragmented curved bands observed within the broad circulation. The satellite intensity estimates suggest that the cyclone has not strengthened, and the initial wind speed remains 30 kt, which is near the high end of the Dvorak estimates. The center of the cyclone has been challenging to locate, and the satellite center fixes from TAFB and SAB were about 60 n mi apart. The initial motion is estimated to be northwestward, or 325 degrees, at 10 kt, but this is of low confidence given the broad nature of the system. The depression is expected to move generally northwestward during the next couple of days steered by a mid-level ridge over western Africa. A turn to the west-northwest is forecast beyond a couple of days when the weak and shallow system is expected to be steered by the low-level flow. The NHC track forecast takes the center of the depression near the eastern Cabo Verde Islands later today, and this forecast lies near the various consensus models. The environmental conditions are expected to remain generally favorable for about the next 12-24 hours, so there is some chance that the cyclone could become a tropical storm during that time. However, given the large size of the system, significant intensification is not expected. On Wednesday, a pronounced increase in southwesterly wind shear, drier air, and cooler SSTs should end the opportunity for strengthening and cause the cyclone to become a remnant low in about 2 days when the shear is forecast to be very strong. All of the models show the cyclone opening up into a trough within 3 or 4 days. Regardless of whether or not the depression becomes a tropical storm before passing near the Cabo Verde Islands, the primary threat from this system is the potential for locally heavy rainfall and flash flooding in those islands. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 15.6N 20.9W 30 KT 35 MPH 12H 15/1800Z 16.4N 22.0W 35 KT 40 MPH 24H 16/0600Z 17.5N 23.0W 35 KT 40 MPH 36H 16/1800Z 18.4N 24.1W 30 KT 35 MPH 48H 17/0600Z 19.4N 25.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 18/0600Z 21.5N 29.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/0600Z...DISSIPATED $$ Forecaster Cangialosi

Tags: number discussion tropical depression

 
 

Tropical Depression Fifteen Forecast Discussion Number 2

2019-10-15 04:40:38| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Mon Oct 14 2019 000 WTNT45 KNHC 150240 TCDAT5 Tropical Depression Fifteen Discussion Number 2 NWS National Hurricane Center Miami FL AL152019 1100 PM AST Mon Oct 14 2019 The depression has become somewhat less organized this evening. A band of deep convection has developed over the far northern portion of the circulation, but there is little convection over the remainder of the large circulation. A recent partial ASCAT-C overpass suggests that the low-level center is located well southwest of the mid-level turning noted in infrared satellite pictures, and although the scatterometer did not sample the entire circulation, it appears that the 30-kt initial intensity may be generous. The depression is moving northwestward (320 degrees) at about 9 kt. While there is a chance that the center will re-form farther north near the mid-level center and area of deep convection, the overall motion of the system is expected to be northwestward during the next day or two around the southwestward periphery of a deep-layer ridge over western Africa. The models are in generally good agreement on this overall scenario, but since the system is still in the formative stage there is a fair amount of cross-track spread. After 48 hours, the cyclone should turn toward the left as it weakens and is steered by the low-level flow. The new NHC track forecast has been adjusted north of the previous track, but is not quite as far north as the ECMWF and the multi-model consensus. Deep convection is likely to return overnight during the typical nocturnal convective maximum, and low shear and warm SSTs along the path of the cyclone favor strengthening during the next day or so. The large and sprawling structure of the system, however, suggest any intensification should be slow to occur, and the new NHC intensity forecast has been reduced slightly from the previous advisory. By 36 hours, increasing southwesterly shear and cooler SSTs are expected to cause the cyclone to weaken and the system is forecast to degenerate into a remnant low in 2 to 3 days. The NHC intensity forecast most closely follows the statistical SHIPS/LGEM guidance. Regardless of whether the depression becomes a tropical storm or not before passing near the Cabo Verde Islands, the primary threat from this system is the potential for locally heavy rainfall and flash flooding in those islands. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 14.5N 20.8W 30 KT 35 MPH 12H 15/1200Z 15.5N 21.7W 30 KT 35 MPH 24H 16/0000Z 16.8N 22.9W 35 KT 40 MPH 36H 16/1200Z 18.1N 23.9W 35 KT 40 MPH 48H 17/0000Z 19.3N 24.8W 30 KT 35 MPH 72H 18/0000Z 21.6N 27.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/0000Z...DISSIPATED $$ Forecaster Brown

Tags: number discussion tropical depression

 

Tropical Depression Fifteen Forecast Discussion Number 1

2019-10-14 22:40:30| National Hurricane Center (Atlantic)

Issued at 500 PM AST Mon Oct 14 2019 000 WTNT45 KNHC 142040 TCDAT5 Tropical Depression Fifteen Discussion Number 1 NWS National Hurricane Center Miami FL AL152019 500 PM AST Mon Oct 14 2019 The large low pressure system that moved off the coast of Africa yesterday has gradually become better defined based on earlier ASCAT scatterometer wind data and recent visible satellite imagery. Several fragmented curved bands have been developing during the past several hours, especially in the northern semicircle, and the aforementioned ASCAT passes indicated that winds of 30-32 kt were present northwest of the center. The initial intensity is set at 30 kt based on a blend of the scatterometer wind data and a satellite intensity estimate of T1.5/25 kt from SAB, and the rather broad nature of the depression. A surge of mid-level dry air has recently penetrated into the inner-core region, causing some erosion of the central deep convection. However, this is expected to be a temporary condition with convection returning later tonight and early Tuesday during the normal nocturnal convective maximum period. However, the large size of the cyclone -- more than 1000 nmi wide -- should prevent any rapid or significant intensification. With very low vertical shear conditions forecast by the GFS and ECMWF models to continue for the next 24 to 36 hours, at least some modest strengthening seems likely given the unusually warm SSTs of near 28.5 deg C that the cyclone will be traversing during that time. By 48 hours, the shear is forecast to increase from the southwest in excess of 25 kt, resulting in weakening into a remnant low shortly thereafter. By 72 hours and beyond, the shear is expected to increase to more than 40 kt, which will cause rapid weakening and dissipation by the 120-h period, if not sooner. The official intensity forecast is similar to a blend of the NOAA-HCCA and IVCN consensus models, and the GFS- and ECMWF-based Decay-SHIPS statistical intensity models. The initial motion estimate is northwestward or 310/07 kt. The latest NHC model guidance is in very good agreement on the tropical cyclone moving generally northwestward around the southwestern periphery of a deep-layer ridge for the next 48 hours. Thereafter, the models diverge significantly based on how soon the cyclone weakens and turns westward within the low-level easterly trade wind flow. The ECMWF holds on to a vertically deeper system a little longer than the GFS, UKMET, HWRF, and HMON models, resulting in a longer northwestward track. However, since the cyclone will likely have become a vertically shallow remnant low by 72 hours, the NHC official forecast track is a little to the left of ECMWF solution, closer to the TVCN and HCCA consensus model tracks at 72 and 96 h. FORECAST POSITIONS AND MAX WINDS INIT 14/2100Z 13.2N 20.2W 30 KT 35 MPH 12H 15/0600Z 14.3N 21.1W 35 KT 40 MPH 24H 15/1800Z 15.5N 22.4W 40 KT 45 MPH 36H 16/0600Z 16.7N 23.4W 40 KT 45 MPH 48H 16/1800Z 18.1N 24.6W 35 KT 40 MPH 72H 17/1800Z 20.4N 26.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 18/1800Z 21.4N 29.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 19/1800Z...DISSIPATED $$ Forecaster Stewart

Tags: number discussion tropical depression

 

Post-Tropical Cyclone Melissa Forecast Discussion Number 13

2019-10-14 16:38:55| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Mon Oct 14 2019 000 WTNT44 KNHC 141438 TCDAT4 Post-Tropical Cyclone Melissa Discussion Number 13 NWS National Hurricane Center Miami FL AL142019 1100 AM AST Mon Oct 14 2019 Melissa has transitioned to an extratropical cyclone. Shallow convection has become displaced greater than 100 n mi from the center, and Melissa's circulation has become embedded within a frontal zone. The inner-core now consists of a swirl of low clouds with a large amount of cool post-frontal stratocumulus wrapping into the northern and western portions of the circulation. A recent ship report just southwest of the center indicated gale-force winds are still occuring in association with Melissa, and 35 kt will be this advisory's initial intensity. The extratropical cyclone is expected to gradually weaken over the next day or so, and dissipate before it reaches the Azores. Melissa is now moving at 080/20 kt and is embedded within mid-latitude westerlies. This general motion is expected to continue until the cyclone dissipates. This is the last advisory on Melissa from the National Hurricane Center. Additional information on this system can be found in High Seas Forecasts issued by the National Weather Service...under AWIPS header NFDHSFAT1 and WMO header FZNT01 KWBC. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 41.0N 51.4W 35 KT 40 MPH...POST-TROP/EXTRATROP 12H 15/0000Z 41.4N 46.6W 35 KT 40 MPH...POST-TROP/EXTRATROP 24H 15/1200Z 41.4N 39.3W 30 KT 35 MPH...POST-TROP/EXTRATROP 36H 16/0000Z...DISSIPATED $$ Forecaster Latto

Tags: number discussion forecast melissa

 

Sites : [316] [317] [318] [319] [320] [321] [322] [323] [324] [325] [326] [327] [328] [329] [330] [331] [332] [333] [334] [335] next »