Ramblings of a Graduate Student

Late last evening, the National Hurricane Center (NHC) declared that a cluster of showers and thunderstorms over the far southwestern Gulf of Mexico had become organized enough to have the title “Tropical Depression”. Then, overnight, it became Tropical Storm Hermine. The graphic above depicts the forecast track of Hermine.

Associated with the tropical storm will be copious amounts of tropical moisture. As this moisture streams northward, along with Hermine, it will interact with a weak frontal zone. This interaction will allow for enhanced rainfall across portions of Oklahoma. Take a look at the forecast 5-day rain fall amounts from the Hydrometeorological Prediction Center (HPC).

Many people are focused on Major Hurricane Earl tonight, wondering what the eventual path will be. The official forecast from the National Hurricane Center (NHC) continues to keep Earl just off the east coast of the United States. However, because of the large size of Earl’s wind field, a hurricane watch has been issued for portions of North Carolina. Even if the eye does not make landfall, it should be close enough that portions of North Carolina will experience some wind and rain.

The eventual path of Earth will be dictated by events that are currently well removed from the hurricane. A strong short-wave trough at 500 mb is forecast to race across the northern plains over the next few days. The southeast shear downstream of the trough axis is forecast to help “steer” Earl to the north and northeast. The speed at which the short-wave trough moves across the northern United States will be impacted by the strength of the ridge over the eastern United States (center denoted by a “N” below).

Rotating around the periphery of the east coast ridge are several mid- or upper-level lows (denoted by small letter “x”). Currently, these upper-level lows are resulting in strong shear (by hurricane standards) across the top of Earl. As these upper-level lows continue to move westward, away from Earl, the shear should decrease allowing for possible strengthening. Might these upper-level lows aid the destruction process of the ridge?

I still don’t think it is wise to rule out a potential North Carolina landfall. Even if Earl does not make direct landfall, it will be close enough to cause significant societal impacts. A second area where landfall is possible is in New England, as hurricane Earl races ahead of the vigorous 500mb short-wave trough.

Hurricane Earl has intensified to a category 4 hurricane today, passing within 100 miles of San Juan, Puerto Rico. As you can see from the radar images, Earl is extremely well organized.

I know the official National Hurricane Center (NHC) forecast (as of this writing) calls for Earl to miss the east coast of the United States, I have seen enough stuff today to leave me with serious concerns with this forecast. All interested on the east coast, from South Carolina to Maine, should monitor Earl’s progress extremely closely. It is far from certain that Earl will not make landfall along the east coast…

When viewing National Hurricane Center (NHC) forecast graphics, people tend to focus on the specific location of the icons, or the path between the icons. Taking the forecast at face value, the east coast of the United States has nothing to worry about with Hurricane Earl.

Unfortunately, hurricanes are not simply points in the Atlantic Ocean. They are large, spiraling storms that can span several hundred miles. Even if the eye of the hurricane does not pass directly overhead, dangerous weather might be still affect your area. Also, there is considerably uncertainty with hurricane track and intensity forecasts as the forecast time increases. Thus, forecast track errors can exceed 200 miles 4 and 5 days out. Keeping this uncertainty in mind, several major cities along the east coast need to monitor closely for possible impacts from Hurricane Earl. Both New York City and Boston are within the “Cone of Uncertainty“.

After a relatively slow start to the Atlantic hurricane season, the Atlantic Ocean is showing signs of becoming more active. The National Hurricane Center (NHC) is currently issuing advisories on two tropical cyclones, and monitoring a third area of showers and thunderstorms for (low probability) potential for tropical cyclone development.

Hurricane Danielle (contained in yellow circle below) is currently located in the central Atlantic (southeast of Bermuda). Danielle is currently undergoing intensification, but poses no threat to the United States and only an indirect threat to Bermuda at this point. This is the result of a large trough located over the eastern United States. (Thick white dashed lines below indicate the mean long-wave trough axis.) In addition to this large trough, several smaller troughs are rotating through the larger scale flow (indicated by thin white dashed lines). This trough will tend to act like a protective barrier for the east coast. This is because of the southwesterly wind and increased wind shear that can be found on the east side of the trough. The southwesterly wind will help steer Danielle back to the north and ultimately northeast over the next few days, as was discussed on Day 234.

To the south and east of Hurricane Danielle, Tropical Storm Earl (forecast track contained in red circle) is also strengthening. This tropical cyclone is far enough removed from the previously mentioned trough, that it will have an opportunity to avoid being steered out to sea. All model guidance develop Earl into a hurricane over the next few days, and I see no reason to doubt this. Interests in the Gulf and East Coasts need to be aware of Earl as the potential will exist for a US landfall late next week. (It’s still too early to know any specifics, this is just one of many possibilities.)

In the southwestern Gulf of Mexico, the NHC is monitoring showers and thunderstorms along a remanent frontal boundary. It appears that the showers and thunderstorms will make landfall in either far south Texas or Mexico before having a change to develop into a tropical cyclone. However, to play it safe, the NHC has given a 10% chance of tropical cyclone development in this general area.

(Note: Since I didn’t describe it above, the orange contours above are 500mb height contours from the latest RUC model analysis.)

The National Hurricane Center (NHC) has been tracking an area of showers and thunderstorms in the eastern north Atlantic Ocean the past few days for possible signs of tropical cyclone development. Yesterday, the NHC classified this area of convection as Tropical Depression #6. Today, the NHC updated Tropical Depression #6 to Tropical Storm Danielle.

Above is the forecast track of Danielle. It is expected to remain at sea, well away from land. This is due in large part to a large trough forecast to develop across the central north Atlantic Ocean. This trough will increase the southwesterly winds ahead of Danielle and help “curve” Danielle away from any land. Should this trough fail to materialize as expected, Bermuda would currently have the greatest chance at experiencing direct impacts of Danielle. (However, a lot can change over the next 5 days.)

Well, two days ago I posted that the National Hurricane Center (NHC) was monitoring the remnants of Tropical Depression #5 for possible development of a tropical cyclone. Well, that possibility ended as the remnants of tropical depression #5 moved ashore without developing into a tropical cyclone. Showers and thunderstorms across the northwestern Gulf of Mexico states will be possible over the next day or so as the remnants move through. In the wake of these showers and thunderstorms, the heat will build back in by the weekend.