949 
fxus64 kmob 070539 aaa 
afdmob 


Area forecast discussion 
National Weather Service Mobile Alabama 
1134 PM CST Friday Nov 6 2009 


Aviation... 
06 UTC taf cycle. 
General VFR conditions to prevail throughout the forecast as a 
strong high pressure system remains entrenched over the region. 
Strong radiational cooling will make patchy shallow fog possible 
overnight especially near water sources and low lying areas which 
could temporarily reduce visibilities near the surface to MVFR and 
even IFR conditions. 08/jvw 


*****************************previous discussion********************* 




Short term [tonight and saturday]...large surface high pressure...over 
the eastern U.S. Down into the northern Gulf...moves eastward to off 
the middle Atlantic coast on Saturday. This is a large high with the 
western extent going well back into eastern Texas. Will remain 
rainfree in the near term as the deepest moisture will be confined 
over the southern reaches of the Gulf...in the vicinity of an old 
trough of surface low pressure. Coolest temperatures =>mid 30s tonight 
over the northern zones where wedge of high pressure is strongest and 
winds lighter. Daytime highs on Saturday in the middle 70s on average. /10 


Long term [saturday night through friday]...strong synoptic scale 
ridge of high pressure is forecast to hold into Sunday over the 
western Atlantic into the southern states. Meanwhile...a more 
complicated picture will be evolving over the Gulf. The various global 
spectral models of the GFS...Canadian...UKMET and Euro vary on their 
handling of what will happen with the old surface trough over the Gulf 
and how Ida interacts with it. Upper level trough of low pressure 
advancing eastward across Texas allows height falls to spread over 
the western half of the Gulf Sunday. This will act to pull lower 
surface pressures over the Gulf...northward. Initially...with the 
approach of the middle level height falls...a non-tropical wave of 
surface low pressure looks to form over the western Gulf Sunday and 
begin lifting north northeast toward the central Gulf Coast. This 
feature then looks to merge within the broadening cyclonic circulation of 
what will be Tropical Storm Ida...moving northward through the 
central Gulf on Monday. The latest guidance by the National Hurricane 
Center transitions Ida into an extratropical storm by Wednesday over 
the eastern Gulf. 


Will be moving into a wet period during the first half of next week. 
The main concerns though will be over the marine area and coastal 
zones as we enter the new week. The interaction between the strong 
high over the southeast and the lowering pressure to the south will 
contribute to moderate to strong easterly winds. Considering the 
latest forecast of winds and that we are moving through a Spring 
tidal cycle...where there are large ranges between high and low 
tide...we could be dealing with some coastal flooding issues over 
portions of the coastal zones beginning late in the weekend. 
Forecasters feel that problems could begin along east facing 
shores...including the western coast of Mobile Bay by late Sunday 
night as we approach higher tides. At same time 20 to 25 knots of 
easterly winds impinge along the coast. We are just outside of the 
window for issuing a coastal Flood Watch on this shift...but one will 
likely be forthcoming on later shifts. 


The eventual track of Ida and its complex interaction with the non- 
tropical low in the western Gulf will have to be carefully monitored. 
If Ida moves further west than currently forecast...a stronger 
onshore flow will likely develop...enhancing the coastal flooding 
threat across the region. Stay tuned on this developing weather 
situation 


By middle and late week...what's left of Ida looks to be to our 
southeast...with our area being on the drier side of the 
circulation. Did tweak daytime highs lower Monday and Tuesday due to 
the impact of clouds/rain and easterly winds. No other changes made 
to the remainder of the forecast Wednesday through Friday. /10 


&& 


Aviation [18z taf cycle]...VFR conditions expected through the 
forecast with high pressure over the Carolinas firmly in control of 
our weather. 34/jfb 


&& 


Marine...surface high pressure over the eastern Seaboard will 
persist through this weekend...maintaining an easterly flow across 
the coastal waters. Winds will strengthen through the weekend as 
Tropical Depression Ida approaches the Yucatan Channel...and a non- 
tropical low develops over the western Gulf. Winds well offshore 
have been close to Small Craft Advisory (sca) conditions already today 
and will be close tonight. For now...confidence not high enough to 
issue Small Craft Advisory so will keep exercise caution wording in for tonight. Have 
gone ahead and issued Small Craft Advisory beginning late tomorrow morning for all 
marine zones except Mobile Bay as winds approach 20 knots and seas build 
to near 5 feet close to shore to 7 feet well offshore. Winds and seas 
look to only increase further on Sunday and a Small Craft Advisory will likely be 
needed for Mobile Bay. As Ida moves into the southern Gulf of Mexico 
on Monday...it will likely begin to become absorbed by a non tropical 
low and its associated cold front moving east out of the western 
Gulf. Increased swell and winds approaching near gale force are 
possible over the open waters by Monday and Tuesday. Also...the 
increased southerly swell will create tides one to two feet above 
normal. If Ida and the non tropical low merge further west than 
currently indicated...the flow will become more southeasterly by 
Monday...which would further enhance tide levels and the coastal 
flooding potential. 


For additional information on Tropical Depression Ida...refer to the 
latest forecasts and discussions by the National Hurricane Center in 
Miami. 34/jfb 


&& 


Fire weather...a large area of surface high pressure will continue 
over the southeast United States through the weekend. Easterly winds 
in the mixed layer will steadily increase by Sunday due to the 
influence of the high to the east and a wave of surface low pressure 
that begins to ease northward over the western Gulf. The weekend 
looks rainfree. Lowest daytime humidities are forecast to be above 
critical levels through the weekend. Average environmental dispersion on 
Saturday becomes good by Sunday. Wet weather moves in area wide for 
the start of next week with breezy conditions setting up along the 
coast as low pressure moves eastward. /10 




&& 


Preliminary point temps/pops... 
Mobile 47 78 54 79 / 00 00 05 05 
Pensacola 51 76 56 77 / 00 00 05 05 
Destin 57 74 61 76 / 00 00 00 05 
Evergreen 37 77 43 79 / 00 00 00 05 
Waynesboro 38 79 44 79 / 00 00 00 05 
Camden 38 77 43 79 / 00 00 00 05 


&& 


Mob watches/warnings/advisories... 
Alabama...none. 
Florida...red flag warning until 5 PM Friday for the following zones: 
coastal Escambia...coastal Okaloosa...coastal Santa Rosa... 
inland Escambia...inland Okaloosa...and inland Santa Rosa. 


MS...none. 
GM...Small Craft Advisory from 10 am Saturday to 6 PM Tuesday for the 
following zones: coastal waters from Destin to Pensacola Florida 
out 20 nm...coastal waters from Pensacola Florida to Pascagoula 
MS out 20 nm...waters from Destin to Pensacola Florida from 20 
to 60 nm...and waters from Pensacola Florida to Pascagoula MS 
from 20 to 60 nm. 


&& 


$$ 

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