WTNT43 KNHC 190255
TCDAT3
 
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082011
1100 PM EDT THU AUG 18 2011
 
SATELLITE IMAGES DURING THE LAST FEW HOURS BEFORE SUNSET INDICATED
THAT THE LOW-LEVEL CIRCULATION OF THE WAVE OVER THE WESTERN
CARIBBEAN SEA WAS BECOMING BETTER DEFINED WITH LOW CLOUDS MOVING
WITHIN NORTHWESTERLY FLOW OFFSHORE OF THE COAST OF NORTHEASTERN
HONDURAS. MICROWAVE DATA FROM THE PAST SEVERAL HOURS CONFIRM THAT
THE SYSTEM HAS A LOW-LEVEL CIRCULATION AND A RECENT 0134Z SSMIS
PASS EVEN HAS A WEAK RING FEATURE IN THE 37 GHZ CHANNEL.
SIGNIFICANT 24H PRESSURE FALLS OF 3 TO 4 MB HAVE ALSO BEEN OBSERVED
AT BUOY 42057...WHICH HAVE LONG BEEN A HALLMARK OF TROPICAL CYCLONE
FORMATION.  DVORAK ESTIMATES OF T2.0 FROM BOTH TAFB AND SAB...IN
ADDITION TO THE ABOVE DATA...SUPPORT ADVISORIES BEING INITIATED ON
A TROPICAL DEPRESSION.  A PEAK 1-MIN WIND OF 27 KT FROM THE BUOY
AND EARLIER ASCAT DATA SUGGEST AN INITIAL INTENSITY OF ABOUT 30 KT. 
 
THE DEPRESSION DOES NOT HAVE MUCH TIME TO STRENGTHEN BEFORE
THE CIRCULATION INTERACTS WITH THE NORTHERN COAST OF HONDURAS.
ONLY MODEST STRENGTHENING IS FORECAST...WHICH IS IN GOOD AGREEMENT
WITH THE MODEL CONSENSUS.  GIVEN HOW CLOSE THE SYSTEM IS TO
LAND...IT IS ALSO QUITE POSSIBLE THE DEPRESSION MAY NOT STRENGTHEN
AT ALL AND WEAKEN OVER THE HIGHER TERRAIN OF HONDURAS.
 
THE INITIAL MOTION ESTIMATE IS 270/10.  A MID-LEVEL RIDGE OVER THE
GULF OF MEXICO SHOULD GENERALLY STEER THE SYSTEM TO THE WEST OVER
THE NEXT SEVERAL DAYS.  THIS SCENARIO IS SUPPORTED BY MOST OF THE
GLOBAL MODELS...WITH THE GFDL FORECAST OF THE DEPRESSION MOVING
INTO THE SOUTHERN BAY OF CAMPECHE BEING CONSIDERED AN UNLIKELY
SOLUTION.  THE NHC FORECAST LIES BETWEEN THE DYNAMICAL MODEL
CONSENSUS AND THE ECMWF MODEL.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/0300Z 15.4N  82.1W   30 KT  35 MPH
 12H  19/1200Z 15.5N  83.4W   30 KT  35 MPH
 24H  20/0000Z 15.7N  84.9W   35 KT  40 MPH...INLAND
 36H  20/1200Z 15.9N  86.6W   35 KT  40 MPH...OVER WATER
 48H  21/0000Z 16.2N  88.5W   35 KT  40 MPH
 72H  22/0000Z 17.0N  93.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  23/0000Z...DISSIPATED
 
$$
FORECASTER BLAKE/BROWN
 

WTNT43 KNHC 190841
TCDAT3
 
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082011
500 AM EDT FRI AUG 19 2011
 
THE CENTER OF THE DEPRESSION HAS NOT BEEN EASY TO LOCATE THIS
MORNING.  BASED ON EXTRAPOLATION FROM EARLIER MICROWAVE DATA...THE
CENTER IS ESTIMATED TO BE ON THE SOUTHERN EDGE OF A SMALL
CLUSTER OF DEEP CONVECTION OFF THE COAST OF NORTHEASTERN HONDURAS. 
THIS YIELDS AN INITIAL MOTION ESTIMATE OF 270/10.  THE DEPRESSION
IS EXPECTED TO MAINTAIN A MORE-OR-LESS WESTWARD MOTION FOR THE
REMAINDER OF ITS EXISTENCE WHILE BEING STEERED BY A MID-LEVEL RIDGE
LOCATED ACROSS THE NORTHERN GULF OF MEXICO.  THE OFFICIAL TRACK
FORECAST IS VERY CLOSE TO THE PREVIOUS ONE AND LIES AT THE SOUTHERN
EDGE OF THE GUIDANCE ENVELOPE...NEAR THE GFS...ECMWF...AND THE
SIMPLER BAM MODELS.  ALTHOUGH A 72 HOUR FORECAST POINT IS
PROVIDED...IT IS LIKELY THAT THE HIGH TERRAIN OF GUATEMALA AND
SOUTHERN MEXICO WILL HAVE ANNIHILATED THE LOW-LEVEL CIRCULATION BY
THAT TIME.

DVORAK NUMBERS ARE T2.0 FROM TAFB AND T2.5 FROM SAB...AND THE
INTENSITY WILL BE HELD AT 30 KT.  AN AIR FORCE HURRICANE HUNTER
AIRCRAFT IS SCHEDULED TO INVESTIGATE THE DEPRESSION LATER THIS
MORNING AND SHOULD PROVIDE MORE CERTAINTY IN THE INTENSITY...NOT TO
MENTION THE CENTER LOCATION...IF IT EXISTS AT ALL.  LITTLE TO NO
STRENGTHENING IS EXPECTED OVER THE NEXT 24 TO 36 HOURS SINCE THE
DEPRESSION IS FORECAST TO SKIRT ALONG THE COAST OF...OR MOVE INLAND
OVER...HONDURAS.  THE OFFICIAL FORECAST CLOSELY FOLLOWS THE
INTENSITY CONSENSUS...BUT IF THE DEPRESSION MOVES OVER WATER FOR A
LONGER PERIOD OF TIME IT COULD STRENGTHEN A LITTLE MORE AS SHOWN BY
THE STATISTICAL SHIPS AND LGEM MODELS.  IT COULD ALSO JUST AS
EASILY MOVE OVER LAND AND NEVER RE-EMERGE OVER WATER...WHICH MAY
PRECLUDE ANY INTENSIFICATION AT ALL.

FORECAST POSITIONS AND MAX WINDS
 
INIT  19/0900Z 15.5N  83.2W   30 KT  35 MPH
 12H  19/1800Z 15.6N  84.4W   30 KT  35 MPH...INLAND
 24H  20/0600Z 15.8N  86.0W   35 KT  40 MPH...INLAND
 36H  20/1800Z 16.1N  87.8W   35 KT  40 MPH...OVER WATER
 48H  21/0600Z 16.4N  89.7W   30 KT  35 MPH...INLAND
 72H  22/0600Z 17.0N  94.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  23/0600Z...DISSIPATED
 
$$
FORECASTER BERG/AVILA
 

WTNT43 KNHC 191450
TCDAT3
 
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082011
1100 AM EDT FRI AUG 19 2011
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FOUND THAT THE
WELL-DEFINED CENTER OF TROPICAL DEPRESSION EIGHT WAS ABOUT 30 N MI
NORTHEAST OF THE POSITION IN EARLIER ADVISORIES.  HOW MUCH OF THIS
SHIFT IS DUE TO A CHANGE IN THE MOTION AND HOW MUCH IS DUE TO
REFORMATION OF THE CENTER IS NOT OBVIOUS IN THE DATA CURRENTLY
AVAILABLE.  THE AIRCRAFT HAS REPORTED CENTRAL PRESSURES OF
1004-1005 MB...850 MB FLIGHT-LEVEL WINDS OF 40 KT...AND RELIABLE
SFMR SURFACE WIND ESTIMATES OF 30-35 KT.  THESE DATA SUGGEST THAT
THE CYCLONE IS JUST BELOW TROPICAL-STORM STRENGTH...AND THE INITIAL
INTENSITY REMAINS 30 KT.

THE INITIAL MOTION IS A RATHER UNCERTAIN 275/9.  A LOW/MID-LEVEL
RIDGE OVER THE GULF OF MEXICO AND THE NORTHERN GULF COAST IS
EXPECTED TO GRADUALLY STRENGTHEN DURING THE NEXT 48-72 HR...AND
THIS SHOULD STEER THE CYCLONE GENERALLY WESTWARD TO WEST-
NORTHWESTWARD THROUGH ITS LIFETIME.  THE NEW FORECAST TRACK IS
PARALLEL TO...BUT SHIFTED NORTH OF...THE PREVIOUS FORECAST AND LIES
NEAR THE CENTER OF THE TRACK GUIDANCE ENVELOPE.  THE FORECAST TRACK
HAS THE CENTER PASSING NEAR THE BAY ISLANDS OF HONDURAS TONIGHT AND
OVER THE COAST OF BELIZE SATURDAY OR SATURDAY NIGHT.

THE NEW FORECAST TRACK ALLOWS THE CYCLONE TO SPEND MORE TIME OVER
WATER THAN PREVIOUSLY EXPECTED...AND THIS REQUIRES REVISING THE
INTENSITY FORECAST UPWARD.  THE NEW INTENSITY FORECAST CALLS FOR
THE SYSTEM TO BECOME A TROPICAL STORM IN 12 HR OR LESS AND TO REACH
A PEAK INTENSITY OF 45 KT NEAR THE TIME OF LANDFALL IN BELIZE. 
THIS FORECAST IS A COMPROMISE BETWEEN THE WEAKER GFDL/HWRF MODELS
AND THE STRONGER SHIPS/LGEM MODELS.

THE NEW FORECAST REQUIRES SIGNIFICANT CHANGES TO THE WATCHES AND
WARNINGS AT THIS TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/1500Z 16.1N  83.7W   30 KT  35 MPH
 12H  20/0000Z 16.3N  85.0W   35 KT  40 MPH
 24H  20/1200Z 16.7N  86.8W   40 KT  45 MPH
 36H  21/0000Z 17.1N  88.6W   45 KT  50 MPH...INLAND
 48H  21/1200Z 17.5N  90.5W   30 KT  35 MPH...INLAND
 72H  22/1200Z 18.0N  94.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  23/1200Z...DISSIPATED
 
$$
FORECASTER BEVEN
 

