Tropical Update 10pm July 10

The National Hurricane Center now predicts the future Barry will become a tropical storm by Thursday and a hurricane by Friday.

The system is becoming better organized, and it is almost a

tropical depression. Satellite images show a persistent area of

deep convection near the estimated center with loosely organized

bands surrounding that feature. Earlier, the NOAA Hurricane Hunters

found that the pressure has dropped a little to 1009 mb, although

the center is not yet well defined. The estimated initial intensity

is still 25 kt based on surface observations and the NOAA dropsonde

data.

The broad low is moving west-southwestward at about 8 kt. The track

models are in general agreement that a mid-level ridge centered over

the Rockies should cause the system to move slowly westward on

Thursday and west-northwestward on Friday. After that time,

however, the models diverge considerably with some solutions showing

an abrupt northward turn toward a weakness in the ridge and others

showing a more gradual one. The latest GFS run has shifted to the

west of its previous track, closer to the previous NHC forecast,

while the HWRF model has shifted to the right. Based on the overall

guidance spread, this track forecast is nudged to the east of the

previous forecast to be closer to the various consensus models,

which typically are the most reliable. However, this forecast is

still near the western edge of the model envelope. It should be

noted that track errors are typically larger for potential tropical

cyclones than more mature systems. In addition, the run-to-run

consistency in the track models has been poor, so confidence in the

details of the forecast is not high at the moment.

Since the system is still in the formative stage, only slow

strengthening is likely during the next 12 hours or so. However,

after that time more significant strengthening is likely due to

very warm SSTs across the northern Gulf of Mexico, a fairly moist

atmosphere, and a favorable upper-level pattern over the system.

The NHC intensity forecast is largely an update of the previous one

and shows the system becoming a tropical storm on Thursday and a

hurricane by late Friday. Additional strengthening is likely

beyond the 48-hour point and the time it makes landfall, which is

predicted to occur in a little less than 3 days. This forecast is

fairly close to the IVCN and HCCA models.

Key Messages:

1. A tropical depression is expected to form on Thursday over the

northern Gulf of Mexico. Conditions appear favorable for this system

to strengthen to a hurricane that will bring storm surge, rainfall,

and wind hazards to the central Gulf Coast.

2. A dangerous storm surge is possible in portions of southern and

southeastern Louisiana where a Storm Surge Watch is in effect.

Additional storm surge watches may be needed on Thursday. Residents

in these areas should monitor the progress of this system and listen

to any advice given by local officials.

3. A Hurricane Watch is in effect for much of the Louisiana coast

and additional tropical storm or hurricane watches and warnings

could be needed on Thursday. Residents in the watch area should

ensure they have their hurricane plan in place.

4. The slow movement of this system will result in a long duration

heavy rainfall threat along the central Gulf Coast and inland

through the lower Mississippi Valley through the weekend and

potentially into early next week. Flash flooding and river flooding

will become increasingly likely, some of which may be significant,

especially along and east of the track of the system.

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