Event Summary      National Weather Service, Raleigh NC

Tropical Storm Ernesto, August/September 2006 Updated 2009/02/17 (Click on the image to enlarge.) Event Headlines ...The remnants of Tropical Storm Ernesto moved across the eastern Coastal Plain of Central North Carolina... ...Most of the significant precipitation from Ernesto fell across the Coastal Plain and Coastal Region of North Carolina... ...Three tornadoes were reported near the coast in Onslow and Carteret Counties... Overview Ernesto initially developed when Tropical Depression five organized just west of the southern Windward Islands at 500 PM on Thursday, August 24, 2006. The system was officially named a Tropical Storm at 500 PM on Friday, August 25. Ernesto continued on a west-northwest course for a few days and briefly reached category 1 hurricane status on Sunday, August 27. Ernesto weakened as the system interacted with land mass over Haiti and Cuba beginning late on Sunday, August 27 and continuing through early on Tuesday, August 29. Ernesto maintained its weak Tropical Storm intensity on August 29 and the tropical storm moved onshore in South Florida very late on Tuesday, August 29. Ernesto weakened as it moved northward across Florida. The system reemerged into the Atlantic near Cape Canaveral as a Tropical Depression very late on Wednesday, August 30. Ernesto strengthened throughout the day on Thursday, August 31 with maximum sustained winds reaching 70 MPH at 200 PM. The Tropical Storm made landfall in Brunswick County, North Carolina near Long Beach at 1130 PM on Thursday, August 31. Ernesto moved north across the Coastal Plain on North Carolina on Friday, September 1, reaching southeastern Virginia as a Tropical Depression during the late afternoon on Friday. The system became extratropical late Friday evening as it moved across eastern Virginia. Additional Details Additional details may become available at the NWS offices directly affected by the storm... The National Weather Service Wilmington NC The National Weather Service Wakefield VA

Ernesto's Track Tropical Storm Ernesto Track (Click on the image to enlarge.)

Maps of Precipitation Totals, Maximum Wind Gusts, and Severe Weather Reports from Tropical Storm Ernesto Precipitation Totals from Tropical Storm Ernesto The map below contains a precipitation analysis for the period in which Ernesto generated precipitation across North Carolina. Maximum Wind Gusts from Tropical Storm Ernesto The map below contains the maximum wind gusts in miles per hour (MPH) from Tropical Storm Ernesto as it moved across North Carolina on Thursday, August 31 and Friday, September 1, 2006. Severe Weather reports from Tropical Storm Ernesto The map below contains severe weather reports received by the National Weather Service during the period in which Ernesto impacted North Carolina on Thursday, August 31 and Friday, September 1, 2006.

Surface Analysis Analyzed surface map from 03Z (1100 PM) on Thursday, August 31, 2006 The surface analysis from 03Z (1100 PM) on Thursday, August 31, 2006 shows Ernesto moving onshore in far southern North Carolina. A stationary front is shown stretching from northeastern North Carolina southwestward into southwestern portion of the state. A Java Loop of surface analysis imagery from 00Z (800 PM EDT) Tuesday, August 30 through 12Z (800 AM EDT) Saturday, September 2, 2006 shows Ernesto moving across the Florida Peninsula and then moving north into far southern North Carolina near Long Beach at 1130 PM on Thursday, August 31, 2006.

Mesoscale Features Ernesto tracked north across the coastal plain of North Carolina. Because of this track much of central North Carolina was excluded from the extremely heavy rain and significant wind gusts that impacted the southeastern and eastern portions of the state. The following images provide a glimpse of some of the mesoscale details including instability, deep moisture, and convergence that remained across the eastern portion of the state. Analyzed mean sea level pressure (black) and surface wind barbs from SPC at 08Z on Friday, September 1, 2006 (300 AM EDT). The surface circulation center of Ernesto is easily seen across southeastern NC. Analyzed surface temperatures (red), dew points (green/yellow), and wind barbs from SPC at 08Z on Friday, September 1, 2006 (300 AM EDT). Note the area of temperatures in the lower and mid 70s across central and western NC with dew points in the upper 60s to lower 70s. A much more tropical air mass is in place along the coast with temperatures near 80 and dew points in the lower 70s. 0-3 Km Storm Relative Helicity (blue) and storm motion vector (brown) from SPC at 08Z on Friday, September 1, 2006 (300 AM EDT). Note the area of greatest Storm Relative Helicity is located just ahead and to the right of the center of circulation. There is a large area of values in excess of 250 units with maximum values greater than 800. 100 MB Mean CAPE values from SPC at 08Z on Friday, September 1, 2006 (300 AM EDT). Note the axis of higher CAPE values across the coastal region of NC. Analyzed precipitable water (green) and wind barbs from SPC at 08Z on Friday, September 1, 2006 (300 AM EDT). Note the area of maximum precipitable water with values in excess of 2.4 inches across the eastern NC. Regional radar imagery from SPC at 08Z on Friday, September 1, 2006 (300 AM EDT). The center of circulation is located just north of Wilmington, NC with nearly all of the significant precipitation located to the north of the storm center.

Precipitation Distribution Relative to Ernesto's Track Forecasters at the NWS Raleigh were primarily concerned with heavy rain and flooding with Ernesto's modest intensity. Forecasters were interested in looking at Ernesto's direction of motion as it approached the coastline; they were also interested in bulk shear parameters, the location of the surface trough and several other factors. A few days before landfall, it became clear that Ernesto's storm track was expected to be from the south-southwest (SSW) to north-northeast (NNE). Recent climatology studies would suggest that the distribution of the heaviest rainfall would be favored across locations slightly west of the storm track. On Wednesday, and especially Thursday, it became clear that the most significant precipitation would fall slightly east of the storm track. The model depiction of the bulk shear was strongly indicating that the majority of the heavy rain would fall east of the storm center. The image below shows the 6 hour NAM80 forecast, valid at 0600Z 2006/09/01 for the 850 - 300 MB bulk shear vector, shown shaded in color for magnitudes greater than 30 knots. The models consistently showed a strong (>40 kts), predominant cross-track shear. This favored a right of track distribution of the heaviest rainfall. (Click on the image to enlarge.) The location of the surface trough was also expected to be a significant factor in the precipitation distribution. The heaviest rainfall distribution typically favors locations near the area of strongest convergence along a quasi stationary front. One of the more difficult forecast determinations ahead of Ernesto was the location of the surface boundary. The boundary was somewhat diffuse and the model projections tended to place the boundary further west (near the U.S 1 corridor) along the strongest gradient of theta-e. The image below is an MSAS depiction of surface weather at 0600Z 2006/09/01 which was about 3 hours after Ernesto made landfall in Brunswick County, NC. The MSAS analysis depicts surface wind streamlines with a double image for surface theta-e and surface based computed Lifted Index. The HPC analysis of the stationary front is overlaid. It appears the track of Ernesto moved headlong into the front near Goldsboro. (Click on the image to enlarge.) Post storm analysis shows that the heaviest rain fell in a corridor stretching from near Wilmington, NC northeast to near Greenville, NC , and then northeast to just east of Ahoskie, NC. The axis of heaviest rainfall was skewed to the right of the track with a sharp decrease in rainfall to the left of the track. The image below is an analysis of the rainfall based on rain gauge data and radar estimates. As shown in the HPC analysis below, the heaviest rain fell just east of the storm track across North Carolina.

Radar Imagery A loop of 0.5 degree reflectivity imagery and warnings from 0000Z (800 PM EDT) Thursday, August 31, to 1801Z (201 PM EDT) Friday, September 1, 2006 highlights the development and progression of the convection associated with Ernesto. Base reflectivity imagery from the Wilmington, kltx WSR-88D radar at 0150Z (950 PM) on Thursday, August 31, 2006. Base reflectivity imagery from the Raleigh, krax WSR-88D radar at 0602Z (202 AM) on Friday, September 1, 2006.

Forecast Decision Process Items that worked during the event include... Utilizing research by Meredith Croke & NC State along with findings by Joel Cline and refined by Rod Gonski provided forecasters with greater than normal forecast confidence for a critical weather event. The AWIPS procedure that depicted the 4 panel display of moisture transport, frontogenesis, potential vorticity and upper divergence really helped a lot. The enhanced confidence level before the event can be attributed to at least some degree to the great collaborative research we enjoy at the NWS Raleigh with NC State University along with the training provided to implement those findings into the operational arena.

Case Study Team Phil Badgett Rod Gonski Gail Hartfield Jeff Orrock Scott Sharp Jonathan Blaes For questions regarding the web site, please contact Jonathan Blaes. NWS Disclaimer.