Tropical Storm Edouard

Post Tropical Storm Edouard Track Satellite 1700 Hours July 6 2020
Post Tropical Storm Edouard Track Satellite 1700 Hours July 6 2020

Tropical Storm Edouard Forming Wind SpeedTropical Storm Edouard – NWS National Hurricane Center Miami FL 500 PM AST Mon Jul 06, 2020 (see Monday video below)

Although Edouard continues to produce some deep convection, recent satellite imagery and scatterometer data indicate that the center of the cyclone has merged with a frontal boundary. Therefore, the system is now classified as extratropical and this is the last advisory. The scatterometer data showed max winds of 35-40 kt, so the initial intensity remains 40 kt. The 35 kt wind radii were also increased in the southeast quadrant based on the scatterometer data.

The post-tropical cyclone is forecast to continue moving quickly northeastward for the next day or so until it is absorbed into a larger frontal zone over the north Atlantic late Tuesday or early Wednesday. The NHC track and intensity forecast is close to the global model consensus, and all of those models are in good agreement for the next 24 h.

This is the last NHC advisory on Edouard. Additional information on this system can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 42.7N  46.0W   40 KT  45 MPH - Post-Tropical (WSW St. John's, Canada)
 12H  07/0600Z 45.1N  40.7W   40 KT  45 MPH - Post-Tropical (WSW St. John's, Canada)
 24H  07/1800Z 48.5N  33.2W   40 KT  45 MPH - Post-Tropical (WSW Baltimore, Ireland)
 36H  08/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL  1100 AM AST Mon Jul 06, 2020

Visible satellite imagery continues to show that the low-level center of Edouard is exposed to the southwest of the area of deep convection. A frontal boundary is approaching the system from the northwest and there are signs that Edouard’s extratropical transition has begun. Subjective and objective intensity estimates from TAFB and UW/CIMSS are between 35-45 kt, and the initial intensity has been raised to 40 kt based on the above, and the rapid forward speed of the cyclone. ASCAT data should provide a better assessment of Edouard’s intensity very shortly.

Edouard is racing northeastward with an initial estimate of 055/32 kt. The cyclone should continue on this general speed and heading over the next day or two as it remains embedded within an area of strong southwesterly flow. The updated NHC track forecast is again near the middle of the guidance envelope and very similar to the previous advisory.

Cooler waters, strong southwesterly vertical wind shear, and the approaching frontal zone should cause Edouard to complete its extratropical transition within the next 6-12 hours. Little change in strength is expected as this occurs. Gradual weakening should begin on Tuesday, and the post-tropical cyclone is forecast to dissipate within a frontal zone over the north Atlantic in a couple of days.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 40.8N  50.0W   40 KT  45 MPH - Tropical Storm (ESE St. John's, Canada)
 12H  07/0000Z 43.2N  44.5W   40 KT  45 MPH - Extra Tropical (ESE St. John's, Canada)
 24H  07/1200Z 46.7N  37.1W   40 KT  45 MPH - Extra Tropical (ESE St. John's, Canada)
 36H  08/0000Z 50.0N  29.0W   35 KT  40 MPH - Extra Tropical (WSW Baltimore, Ireland)
 48H  08/1200Z 53.0N  20.0W   30 KT  35 MPH - Extra Tropical (WSW Galway, Ireland)
 60H  09/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Sun Jul 05, 2020 

Satellite images indicate that the cyclone has become better organized during the past several hours, with a large convective burst causing a better-defined low-level circulation. While the center is now becoming exposed due to southwesterly shear, the maximum winds have almost certainly increased from earlier, so the initial wind speed is set to 35 kt. A recent partial ASCAT pass of at least 30 kt outside the RMW also supports the upgrade to a tropical storm, and the CIMSS satellite consensus (SATCON) is even higher than the analyzed intensity.

Edouard is moving northeastward even faster than before, or 055/30 kt. Model guidance is in fairly good agreement on a quick northeastward or east-northeastward motion for the next couple of days before the system degenerates into a trough. Extratropical transition is anticipated by 24 hours due to forcing from a middle-latitude trough and a frontal boundary. Some minor strengthening of Edouard due to the transition process is possible over the next day or so before the global models show a gradual weakening. The track forecast has been adjusted a bit faster to account for the latest guidance and initial forward speed, and the intensity forecast has also been nudged upward to account for the current wind speed.

Edouard is the earliest known 5th named storm on record for the Atlantic basin in the satellite era (1966-present), breaking the record formerly held by Emily on July 12, 2005.

FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 37.2N  56.9W   35 KT  40 MPH - Tropical Storm (ENE St. George's, Bermuda)
 12H  06/1200Z 39.6N  51.7W   40 KT  45 MPH - Tropical Storm (ESE New York, NY)
 24H  07/0000Z 42.9N  44.6W   40 KT  45 MPH - Depression (ESE St. John's, Canada)
 36H  07/1200Z 46.5N  37.3W   35 KT  40 MPH - Depression (ESE St. John's, Canada)
 48H  08/0000Z 50.0N  29.0W   30 KT  35 MPH - Depression (WSW Baltimore, Ireland)
 60H  08/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Sun Jul 05, 2020

The depression is accelerating northeastward, away from Bermuda. It continues to produce deep convection primarily to the south of its center with little change in the organization since yesterday. The most recent TAFB Dvorak classification supports maintaining the intensity at 30 kt. Scatterometer data that will likely arrive after the issuance of this advisory may provide more information about the current surface wind structure of the cyclone.

No substantial changes were made to the NHC forecast. The cyclone will continue to accelerate northeastward or east-northeastward during the next day or two. It is possible that the depression could open into a trough at some point today as its forward speed increases, but most of the dynamical guidance indicates it will persist long enough to undergo extratropical transition on Monday. Minimal strengthening is possible today as the forward speed of the depression increases and it begins to get some positive baroclinic support. In fact, nearly all of the global models indicate that the system will produce tropical-storm-force winds around the time it becomes fully extratropical, and this is reflected in the official forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 34.5N  63.0W   30 KT  35 MPH - Depression (WSW St. George's, Bermuda)
 12H  06/0000Z 36.6N  59.3W   35 KT  40 MPH - Tropical Storm (WNW St. George's, Bermuda)
 24H  06/1200Z 39.5N  53.0W   35 KT  40 MPH - Tropical Storm (ESE New York, NY)
 36H  07/0000Z 42.5N  46.2W   35 KT  40 MPH - Low (ESE St. John's, Canada) 
 48H  07/1200Z 45.8N  39.6W   35 KT  40 MPH - Low (ESE St. John's, Canada)
 60H  08/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Sat Jul 04, 2020

The depression remains poorly organized, with a shrinking area of deep convection to the south of the partially exposed center. The intensity remains 30 kt pending receipt of scatterometer data this evening, perhaps generously. The cyclone should accelerate to the east-northeast over the next couple of days as it encounters stronger mid-level flow. The track guidance is tightly clustered, and no significant changes were made to the previous forecast.

After tonight’s diurnal convective maximum period, the chances of the depression to strengthen are fairly low due to increasing shear and cooler waters. Thus only a slight increase in wind speed is forecast, similar to the model consensus. Extratropical transition is shown in a couple of days due to the system becoming embedded in a front and a mid-level trough. It is possible, however, that the depression will open up into a trough on Sunday, as suggested by the latest GFS model, but for now this forecast maintains continuity with the previous one.

Locally heavy rain and gusty winds from the depression should start on Bermuda during the next few hours.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 32.5N  66.3W   30 KT  35 MPH - Depression (WSW St. George's, Bermuda)
 12H  05/1200Z 34.0N  63.8W   35 KT  40 MPH - Tropical Storm (WNW St. George's, Bermuda)
 24H  06/0000Z 37.0N  59.1W   35 KT  40 MPH - Tropical Storm (WNW St. George's, Bermuda)
 36H  06/1200Z 39.7N  53.5W   35 KT  40 MPH - Tropical Storm (ESE Shelburne, Canada)
 48H  07/0000Z 42.5N  47.5W   35 KT  40 MPH - Low (ESE Biscay Bay, Canada)
 60H  07/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Sat Jul 04, 2020 

Overall, the depression’s organization hasn’t changed much since the last advisory. Cloud tops have warmed a little, but the overall pattern is the same, with deep convection limited to the south of the center. Late-arriving ASCAT-C data from earlier this morning showed max winds of 25-30 kt southeast of the depression’s center and is the primary basis for maintaining the 30 kt intensity.

No changes of significance were made to the NHC track or intensity forecast. The official forecast is still based on the track and intensity consensus, with extra weight given to the dynamical models for the intensity. The depression is forecast to accelerate east-northeastward in the flow between a trough to its north and a ridge to its south. A combination of shear and dry air will likely prevent it from getting better organized, and no substantial strengthening is expected. By Monday morning, baroclinic forcing could allow the system to strengthen slightly before it undergoes extratropical transition or merges with a non-tropical weather system. Alternatively, the system could open into a trough on Sunday as its forward speed increases, as depicted by most of the global models. Since most of those models also show the low reforming a day later before it becomes extratropical, the NHC forecast carries the system as a continuous cyclone for the sake of simplicity. It should be stressed that the rain and gusty winds associated with the system as it passes near Bermuda overnight will be the same regardless of the state of its circulation.

FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 31.8N  67.3W   30 KT  35 MPH - Depression (WSW St. George's, Bermuda)
 12H  05/0600Z 33.1N  65.2W   35 KT  40 MPH - Tropical Storm (WNW St. George's, Bermuda)
 24H  05/1800Z 35.3N  61.6W   35 KT  40 MPH - Tropical Storm (WNW St. George's, Bermuda)
 36H  06/0600Z 38.3N  56.3W   35 KT  40 MPH - Tropical Storm (ENE Ocean City, MD)
 48H  06/1800Z 41.0N  50.0W   35 KT  40 MPH - Tropical Storm (ESE Shelburne, Canada)
 60H  07/0600Z 44.0N  43.0W   40 KT  45 MPH - Tropical Storm (ESE St. John's, Canada)
 72H  07/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Sat Jul 04, 2020

Late yesterday, a small low-pressure system developed near the end of a boundary over the western Atlantic. The low persisted overnight while producing convection that has shown increasing signs of organization. Although the low’s center has recently become obscured, earlier one-minute visible imagery confirmed that it is well-defined. The system therefore meets the necessary criteria to be designated as a tropical cyclone. A TAFB Dvorak classification of 2.0 is the basis for the 30 kt initial intensity.

The depression is moving quickly toward the east-northeast, caught in the flow between a mid-level ridge to its south and a a trough to its north. This steering pattern is expected to be fairly stable for the next day or so, and the guidance is in good agreement that the cyclone will continue on its current general heading with an increase in forward speed during the next couple of days. The NHC track forecast closely follows the TVCN and HCCA consensus aids.

The depression has a sheared appearance, with no convection northwest of its low-level center. A combination of strong upper-level westerly winds and dry mid-level air to the northwest are likely the cause of this, and it is unlikely that the cyclone will get much better organized during the next day or two. That said, some minimal strengthening is possible, even if only due to the expected increase of the cyclone’s forward speed. The NHC intensity forecast is based on a consensus of the HWRF, HMON, and GFS models. It is worth noting that the statistical guidance indicates more strengthening is possible, but this is not currently supported by any dynamical models. There is less agreement on the system’s future beyond the weekend. It could open into a trough and dissipate or persist long enough to undergo extratropical transition. Since this is the first advisory, the official forecast is somewhat conservative and maintains the system as a closed low for 60 h, but it could certainly dissipate sooner than that.

FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 31.1N  68.7W   30 KT  35 MPH - Depression (WNW St. George's, Bermuda)
 12H  05/0000Z 32.1N  66.5W   35 KT  40 MPH - Tropical Storm (WSW St. George's, Bermuda)
 24H  05/1200Z 34.0N  63.5W   35 KT  40 MPH - Tropical Storm (ENE St. George's, Bermuda)
 36H  06/0000Z 36.4N  59.4W   35 KT  40 MPH - Tropical Storm (ENE St. George's, Bermuda)
 48H  06/1200Z 39.2N  52.7W   35 KT  40 MPH - Tropical Storm (ESE New York. NY)
 60H  07/0000Z 41.7N  46.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  07/1200Z...DISSIPATED

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Video: Tropical Storm Edouard forms, earliest fifth named storm on record