headline - dtn · 2017. 7. 6. · prepared by wdt weatherops forecaster: lawson | 405.801.3919 |...
TRANSCRIPT
Effective: July 06, 2017 – 0400 CT / 0900 UTC
Invest 94L developed into Tropical Depression Four; slight strengthening possible but not expected the next 24 hours.
General Discussion
A trough over the Central Atlantic is generating moderate to strong wind shear just to the northeast of the Lesser Antilles. Despite warm sea-surface temperatures and pockets of lesser shear, notable dry Saharan air is noted via latest satellite imagery. As such, the environment across the North Atlantic Basin is only marginally conducive for tropical development. Further east, Invest 94L, previously an area of low pressure with associated shower and thunderstorm activity, has developed a low-level circulation as well as enhanced convection, and is now Tropical Depression Four. This system is not expected to experience significant organization over the next few days due to the previously mentioned dry air, but some strengthening cannot be ruled out over the next 24 hours. Elsewhere, tropical cyclone development chances will remain low.
Active Tropical Threats
Feature # Name Current Location
5-Day Development Potential
Sustained Wind
Current Movement
04L Tropical Depression Four 13.2N 40.0W 50% 25 knots WNW at 15 knots
Atlantic Tropical Daily Planner
HEADLINE
Prepared by WDT WeatherOps Forecaster: LAWSON | 405.801.3919 | WDTinc.com
Strong Wind Shear
Strong Wind ShearTD Four
Dry Air
Dry Air
Atlantic Tropical Daily Planner
Prepared by WDT WeatherOps Forecaster: LAWSON | 405.801.3919 | WDTinc.com
Environmental Favorability for Tropical Cyclones
Current SST’s Tropical Cyclone Heat Potential
Current Wind Shear Current Mid-Level Dry Air
ECMWF Surface Winds Valid at 0900 UTC July 06 2017
Tropical Depression Four
Position and Intensity Threat Briefing
Feature Center: 13.2N 40.0W Dry Saharan air to the west of Tropical Depression Four is expected to limit significant further development and Four is forecast to remain just below tropical storm strength. Regardless, strong to gale force winds and moderate to rough seas, along with showers and thunderstorms may accompany Four’s passage. Four is expected to track to the west-northwest with an extra-tropical transition and gradual weakening. Minimal impacts are forecast across the Lesser Antilles by day three and four.
Current Movement: WNW at 15 knots
Current Sustained Winds: 25 knots
Current Wind Gusts: 35 knots
Infrared Satellite Image of TD Four5 Day Development Potential
TD 100%
TS 50%
CAT 1 10%
CAT 2 0%
CAT 3 0%
CAT 4 0%
CAT 5 0%
Prepared by WDT WeatherOps Forecaster: LAWSON | 405.801.3919 | WDTinc.com
Atlantic Tropical Daily Planner
Saffir-Simpson Scale Reference
Intensity Wind Speed (KTS)
TD 25 - 33
TS 34 - 63
CAT 1 64 - 82
CAT 2 83 - 95
CAT 3 96 - 112
CAT 4 113 - 136
CAT 5 137 +
Tropical Depression Four Advisory #2 Effective: July 6, 2017 0900 UTC (06/0400 CT)
Storm Center 13.2N 40.0W (about 1246 nm E of the Lesser Antilles)
Current Movement WNW at 15 knots
Sustained Winds/Gusts 25 knots / 35 knots
34 kt Wind Radii 0 NE 0 SE 0 SW 0 NW
50 kt Wind Radii 0 NE 0 SE 0 SW 0 NW
64 kt Wind Radii 0 NE 0 SE 0 SW 0 NW
Forecast Trend Tropical Depression Four has not changed much over the last several hours and has continued to track west-northwestward.
Prepared by WDT WeatherOps Forecaster: FUCHECK | 405.801.3919 | WDTinc.com
WDT FORECAST TRACK
Active Storm Advisory
WIND RADII 34kt+ 50kt+ 64kt+
WDT Forecast Positions and Max WindsTrack Forecast Confidence: Average Intensity Forecast Confidence: Average
Date Forecast Time/Hour Position Sustained Winds Saffir-Simpson ScaleThu July 6 0900 UTC Initial 13.2N 40.0W 25 KT 30 MPH TDThu July 6 1800 UTC 12 Hour 14.1N 43.0W 30 KT 35 MPH TD Fri July 7 0600 UTC 24 Hour 15.0N 46.2W 30 KT 35 MPH TD Fri July 7 1800 UTC 36 Hour 16.3N 50.0W 30 KT 35 MPH TD Sat July 8 0600 UTC 48 Hour 17.5N 53.5W 25 KT 30 MPH TD (DISSIPATING)Sun July 9 0600 UTC 72 Hour 20.5N 59.5W 25 KT 30 MPH REMNANT LOWMon July 10 0600 UTC 96 Hour 23.0N 65.0W 25 KT 25 MPH REMNANT LOW
- - - - - - - -
Initial
24 HR
48 HR
72 HR
96 HR
WDT Forecast Discussion
Observational Perspective: Not much has changed since the previous update. Deep convection continues to form around TD Fours low level circulation with favorable upper level outflow currently overspreading much of the system. Given the storms current structure and most recent satellite derived winds, Tropical Depression Four’s intensity remains at 25 knots.
Intensity Forecast: Not much has changed since the previous update. Currently the system is in a somewhat favorable environment for further development with low wind shear and warm sea surface temperatures, but Saharan dry air is currently beginning to enter the northern periphery of the systems circulation. Given this, some slight additional strengthening is forecast over the next day or so. Afterward, dry air entrainment and increasing wind shear are forecast to weaken the system into a remnant low by day 3 or 4.
Track Forecast: No changes since the previous forecast. With a ridge to the north of TD Four, the system will continue to track west-northwestwards along the southern periphery of this ridge over the next few days. Then as the system gets to the western periphery of this ridge in the western Atlantic, TD Four is then forecast to begin to reduce its current forward motion and begin tracking to the northwest as a remnant low.
WDT’s next advisory will be issued at 1500 UTC / 1000 CT
Tropical Depression Four Advisory #2 Effective: July 6, 2017 0900 UTC (06/0400 CT)
Changes from Previous Advisory
No significant changes since the previous advisory.
Marine Weather Impacts
Strong to near gale force winds with gale force gusts currently extend out about 60 nm from the center of TD Four on the northern and western periphery of its circulation. These winds are currently not forecast to change much over the next few days. Moderate to near rough seas currently extend out 120 nm from the center of TD Four with rough seas forecast to form within the next 12 hours or so.
Onshore Impacts
At this time no onshore impacts are anticipated over the next five days.
Infrared Satellite Image
Active Storm Advisory
Prepared by WDT WeatherOps Forecaster: FUCHECK | 405.801.3919 | WDTinc.com