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Area forecast discussion 
National Weather Service Miami Florida 
820 am EDT Sat Jul 5 2008 


Update...updated current forecast to let the dense smoke advisory 
expire. Surface observation across the area showed visibilities have increased 
to 3 sm or better across the eastern metropolitan areas. Rest of the forecast 
package remains the same. 


Rgh 


Aviation...areas of smoke from fireworks continue to linger over 
the East Coast metropolitan this morning with visibilities down to around 
1 mile in spots. The smoke can be expected to continue across the 
East Coast metropolitan until around 13z before mixing thins it out. 


By 14z, thunderstorms and rain will begin to develop and become numerous across S Florida 
with most activity expected over the eastern half although pushing 
slowly inland. With such weak steering flow, apf will also have 
thunder in the vicinity. Thunderstorms in the vicinity at all sites as exact timing of any 
storm is too difficult and will amend as necessary. 


30/kob 




&& 


Previous discussion... /issued 411 am EDT Sat Jul 5 2008/ 


Discussion...msas analysis shows an inverted trough lying off the Southeast 
Florida coast. Meanwhile...water vapor imagery shows an upper low 
spinning over the Lake Okeechobee region early this morning. GPS 
met data shows precipitable waters  at about 1.8 inches at mia. Mimic moving precipitable water 
imagery shows deeper moisture poised to move into the area from 
the southeast. GFS initialized best with these features...so am leaning 
towards its wetter solution for the East Coast today. Reasoning is 
that there will be very good convergence from the surface to 700 mb 
along the East Coast today...as the inverted trough moves into the 
area. Also...GFS shows a weak middle level shortwave moving into the 
area this afternoon. Good upper level divergence will be present 
today as well...as the upper low will remain near the lake this 
afternoon. Therefore...have increased probability of precipitation across the eastern half 
of the area...where the best low level convergence/upper level 
divergence will co-exist. The Gulf Coast will be drier...due to 
less convergence and slight subsidence on the back side of the 
upper low...but will keep chance probability of precipitation there as the Gulf sea breeze 
will ignite some activity during the afternoon. 


Forecast soundings East Coast show cape near 4000 j/kg...lifted indice's near -8 
and k indices in the middle 30s. 500 mb temperatures will be at around -8.5c. So 
it will be unstable...and with the large scale lift expected due 
to the aforementioned factors...numerous thunderstorms are 
expected along with locally heavy rainfall due to weak steering 
flow and training of cells expected. Therefore...added heavy 
rainfall wording to the forecast. There likely will be a few strong 
storms as well. 


Should mention that dense smoke advection remains in effect until 8 am 
EDT East Coast. Visible is down to 1 3/4 miles at several locations 
early this morning...and could fall lower right around 
sunrise...so will keep the advisory up. 


For Sunday...upper low weakens while pulling away from the area. 
However...GFS remains consistent in showing a low/middle level trough 
moving northwest across the area on Sunday...keeping deep tropical 
moisture in place along with good large scale convergence. 
Therefore...kept with the inherited likely probability of precipitation all areas. 


Monday and beyond...ridge will be aligned across central and North 
Florida. This will lead to a prevailing easterly flow regime 
locally. GFS/European model (ecmwf) show moisture remaining high on Monday...so 
still could be wet...but some drying takes place throughout the 
week. So have gone with a downward trend in probability of precipitation through the 
extended forecast. Convection each day will focus across the 
interior/Gulf Coast each afternoon. 


Marine...winds will remain 15 knots or less with seas of 4 feet or 
less through the period as the pressure gradient will remain 
rather weak. East flow will prevail with surface ridge axis north 
of the area. 


Fire weather...no concerns due to high moisture levels. 


&& 


Preliminary point temps/pops... 
West Palm Beach 88 75 87 77 / 70 30 70 40 
Fort Lauderdale 87 76 86 77 / 70 40 70 50 
Miami 88 76 87 78 / 70 40 70 50 
Naples 90 73 89 73 / 40 30 60 40 


&& 


Mfl watches/warnings/advisories... 
Florida...none. 


Am...none. 
GM...none. 
&& 


$$