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Tropical Storm Bertha

TROPICAL STORM BERTHA UPDATE

Published on August 3, 2014 10:26 PM | Comments

Below is the NHC discussion, and some links to news - sorry to have been a little AWOL on this storm, we took a break this weekend and also had server issues!

Bertha Hits The Dominican Republic

Tropical Storm Bertha Takes Aim at Bahamas, Turks and Caicos

TROPICAL STORM BERTHA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 500 PM EDT SUN AUG 03 2014

After Bertha's cloud pattern became a little better organized earlier today, there has been little change in its overall appearance over the past several hours. There are limited banding features over the eastern semicircle of the circulation, and the deep convection is a little ragged-looking. The upper-level outflow is becoming a little better defined, but there is still some northwesterly shear over the system. The current intensity is kept at 40 kt based on earlier observations from the Hurricane Hunter aircraft. The numerical guidance has become a little less bullish on future strengthening, but the Decay-SHIPS model still calls for the cyclone to become a hurricane in 60-72 hours, as does the official forecast. It should be noted, however, that the intensity model consensus no longer predicts Bertha to become a hurricane.

Based on an earlier center fix from the aircraft, the working best track has been adjusted a little to the east of the previous estimates. The center location is not obvious on the latest visible imagery, and the initial motion estimate is a somewhat uncertain 325/16 kt. The track forecast for the next 48 hours or so is slightly complicated by a low- to mid-level disturbance that is currently near Florida. The U.K. Met. Office global model forecast shows Bertha interacting with this disturbance and moving a little closer to the United States east coast than earlier runs. Other global models such as the GFS do not show as much interaction and keep Bertha farther offshore. The new official track forecast has been nudged a little to the left of the previous one and is very close to a consensus of the latest GFS and ECMWF solutions.

Some video from Saturday:



Tropical Storm Bertha

Published on August 1, 2014 1:14 PM | Comments

Tropical Storm Bertha has formed. We're traveling today, but more updates soon.

TROPICAL STORM BERTHA DISCUSSION NUMBER
3 NWS NATIONAL HURRICANE CENTER MIAMI FL
AL032014
1100 AM AST FRI AUG 01 2014

Bertha is disorganized this morning. While satellite imagery shows a well-defined low-cloud swirl exposed just west of the main convective mass, reports from an Air Force Reserve Hurricane Hunter Aircraft show that the wind field more resembles that of an open wave. The aircraft did report 56 kt winds at 1500 feet to the east-northeast of the center, along with an area of SFMR surface winds in excess of 40 kt. Based on this, the initial intensity is increased to 45 kt.

The initial motion is now 295/18, and over the past few hours Bertha may be moving even faster. The cyclone is currently being steered by the flow around the Atlantic subtropical ridge and this should continue for the next 48 hours or so. After that time, the cyclone is expected to turn northward into a break in the ridge caused by a deep-layer trough over the eastern United States. This should be followed by recurvature into the westerlies over the Atlantic north of Bermuda. The track guidance remains in good agreement with this scenario, and it has changed little since the previous advisory. The new forecast track is therefore an update of the previous forecast.

Bertha is currently experiencing about 15-20 kt of southwesterly vertical wind shear. and water vapor imagery shows dry mid-/upper-level air near the storm. The forecast track calls for Bertha to interact with one or two upper-level troughs during the next 48-72 hours, which should cause some shear and dry air entrainment to continue. This, combined with the current lack of organization, suggests little change in strength should occur during the next 48 hours or so. After that time, Bertha is expected to move into an environment of less shear and greater moisture. The intensity forecast calls for modest strengthening during that time, but it is weaker than all of the guidance except the Florida State Superensemble. An alternative scenario is that a combination of shear, dry air entrainment, and land interaction causes Bertha to degenerate to a tropical wave during the next 48 hours, followed by possible regeneration in the 72-120 hours when the system reaches the more favorable environment.