marine weather discussion

NWS TPC/National Hurricane Center Miami FL

125 am EDT Sat July 5 2008

Marine weather discussion for Gulf of Mexico...Caribbean Sea and

southwest north Atlc S of 31n W of 55w.

Gulf of Mexico...

latest sfc analysis shows Atlc subtropical ridge extending from

N central FL through the nrn Gulf...with an axis fluctuating

between 27-29n. Close to the ridge axis...winds are typically

light...generally blowing E to se 10 kt or less from 25-27.5n

and SW to W 10 kt or less along the nrn Gulf Coast. Buoy and

C-man reports indicate a large area of seas 2 ft or less over

the NE corner of the Gulf...while 3 to 5 ft seas the rule over

the NW. S of the ridge axis...a tighter pressure gradient

between the Atlc subtropical ridge and low pres over Mexico is

generating a steady E to se stream of winds blowing from The

Straits of Florida through the SW Gulf. Within this area...buoy

42055 near 22n94w continues to report E to se 20 kt winds winds

with some persistence and seas averaging around 6 ft. Other

buoy and ship reports suggest 2 to 4 ft seas over the se Gulf

while the highest seas of 4 to 7 ft are reserved for the SW.

From tonight through mid-week next week...global models indicate

little change to the above pattern. Perhaps the only mention of

change will occur sun into Mon...as low pres strengthens over

the central and nrn plains thanks to a transient shortwave

trough passing through the region. As a result...guidance shows

E to se winds subtly increasing mostly W of 90w during this

time. 00z GFS and its ensembles show steady 20 kt E to se flow

over the SW Gulf from Sun afternoon through late Mon...with some

hint of occasional winds to 25 kt. Expect seas to build to 6 to

9 ft over the SW and likely to 5 to 8 ft offshore the immediate

S TX coast. Tue and Wed guidance shows the low-level flow over

the W relaxing to more typical values.

Otherwise...favorable marine conditions should prevail through

the period except for scattered convection erupting over NE

Mexico...S TX...and adjacent areas of the Gulf thanks to a mid-

to upper-level disturbance across the region. Likewise...

several models show a similar disturbance aloft over the ern

Gulf Mon into Tue...which could also enhance shower and tstm

development E of 88w.

Caribbean...

current sfc analysis shows near to slightly above average sfc

pres extending from the central Atlc into the Caribbean basin.

Under this pattern...moderate to fresh trades cover the area

from 12n-17n between 68w and nearly 80w. Outside of these

areas...evening Quikscat passes from yesterday revealed light to

moderate trades...with 10 kt or less Ely flow noted S of 16n E

of 65w and S of 14n W of 81w. The one exception continues to be

the Gulf of Honduras...where microwave data indicate 20 kt to

nearly 25 kt winds continuing. Seas range from 4 to 6 ft over

the E and SW to 3 to 5 ft over the NW and 6 to 9 ft over the

central Caribbean. Seas in the Gulf of Honduras are estimated

between 5 and 8 ft.

Little change to the above pattern is anticipated through Sun

afternoon. Thereafter...the passage of a tropical wave over the

central Caribbean now along 57w/58w and a resurgence of the

enhanced subtropical ridge observed late in June should cause

trades to become fresh over a large area of the eastern and

central Caribbean. In response...NOAA wavewatch iii guidance

shows a large area of 8 to 12 ft seas building from 12n-17n

between 70w-80w with the Ely swell propagating downstream into

the western Caribbean Tue and Wed.

Meanwhile...the low-level flow begins to back NE over the

eastern Caribbean Mon and Tue as Tropical Storm Bertha tracks to

a pstn a few hundred miles NE of the Lesser Antilles. Regardless

of the exact track of the storm...long period NE swell

propagating away from the storm should begin arriving over the

Atlc passages late Mon or Tue. Exactly how significant the

swell will be will depend very heavily on the track and

intensity of the Bertha. Please refer to latest track and

intensity forecasts being issued by the National Hurricane

Center.

SW Atlc...

a stagnant low-level pattern of subtropical ridging arcing WSW

from 30n67w to 28n80w remains in place over the SW Atlc early

this morning. Close to the ridge axis...winds are relatively

light...blowing mostly se to S 10 to 15 kt N of 26n except for S

to SW near the immediate NE Florida coast. Seas average 3 to 4

ft over most of this area except near the Florida E coast...

where seas of 2 ft or less are most common. S of the ridge

axis...a steady stream of Ely 15 to occasionally 20 kt winds

persist...with the strongest generally S of 22-23n. Seas

average 5 to 7 ft E of the Bahamas and 3 to 5 ft W of the

Bahamas...away from the FL coast. Little change to this pattern

is expected through Mon next week.

Early next week...NHC forecast has T.S. Bertha passing a few

hundred miles N of the Lesser Antilles...heading on a WNW to NW

track. Given the current fcst...winds should begin backing NE E

of 65w late Mon into Tue and increasing. Long period E swell

tracking away from the storm should also begin arriving Tue and

Wed...with NOAA wavewatch guidance now showing 6 to 10 ft seas S

of 28n E of 71w by Wed afternoon. Of course...what ultimately

happens is highly dependent on the track of Bertha. And day 4

and day 5 forecasts typically feature several hundred miles of

error. Please continue to consult all current TPC products for

latest information and fcst on Bertha.

Trcpl N Atlc...

latest NHC fcst tracks Bertha through the nrn waters Tue and Wed

next week. Even before then though...the effects of the storm

will begin to be felt. For example...winds should back NE

across the area sun into Mon and begin to increase. In addition

...Long period NE swell should arrive across the area...causing

seas to build significantly. Given the inherent uncertainties

in tropical cyclone track and intensity fcst...it is likely that

the current fcst will have to be refined several times before

now and the weekend. Please continue to refer to all TPC

products for latest and future information on Bertha.

Atlantic...

.None. Ts conds expected N of 20n E of 65w amz087 Tue into Wed.

Caribbean...

.None.

Gulf of Mexico...

.None.

.forecaster kimberlain. Tropical Prediction Center.