High Wind in Alaska, July 21, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKDT TUE JUL 21 2009

.ANALYSIS AND UPPER LEVELS...
FORECAST ATTENTION IS ON AN IMPRESSIVE NEARLY VERTICALLY STACKED 978
MB LOW THAT CONTINUES TO SPIN JUST WEST OF BRISTOL BAY. WIDESPREAD
RAIN SHOWERS AND VERY GUSTY WINDS HAVE BEEN OBSERVED WITH THIS SYSTEM
AND WILL CONTINUE TODAY. TOWARDS THE EASTERN PERIPHERY OF THIS
SURFACE LOW IS A FRONTAL BOUNDARY THAT WILL CONTINUE TO MOVE OVER
SOUTHCENTRAL ALASKA AND CROSS THE ANCHORAGE AREA TONIGHT.

IN THE UPPER LEVELS A RIDGE CONTINUES TO MOVE EAST OUT OF
ALASKA...WHILE THE LARGE UPPER LEVEL LOW ASSOCIATED WITH THE SURFACE
LOW SLOWLY MOVES EAST. THIS UPPER LEVEL FEATURE WILL BEGIN TO STALL
AND SLOWLY WEAKEN AS IT MOVES TOWARDS MAINLAND ALASKA.

.MODEL DISCUSSION...
MODELS AGREE FAIRLY WELL IN THE SHORT TERM. IN THE MIDDLE AND LONG
TERM THE MODELS AGREE THE LOW WILL EVENTUALLY WEAKEN AND
RETROGRADE...HOWEVER THERE IS SOME SIGNIFICANT DIFFERENCES OF THE
POSITION AND STRENGTH OF THE LOW ONCE IT BEGINS TO RETROGRADE. FOR
LONG TERM GUIDANCE WILL STICK WITH THE ECMWF SOLUTION...AS IT HAS
BEEN MORE CONSISTENT FROM RUN TO RUN.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
A RATHER UNCOMMON JULY HIGH WIND EVENT IS UNFOLDING ACROSS
SOUTHCENTRAL ALASKA. AS THE LOW IN THE BERING CONTINUES TO STRENGTHEN
A TIGHTER PRESSURE GRADIENT WILL BEGIN TO SET UP ACROSS THE AREA. AS
A SURFACE FRONT APPROACHES EXPECT HIGHER PRESSURE BEHIND THE FRONT TO
REVERSE THIS FLOW AND INITIATE INTENSE WINDS AROUND TURNAGAIN ARM AND
THE HIGHER TERRAIN SURROUNDING ANCHORAGE.AT THIS TIME AREAS IN
EASTERN ANCHORAGE AND AROUND TURNAGAIN ARM ARE EXPECTED TO RECEIVE
THE STRONGEST WINDS. FOR THIS REASON WE HAVE DECIDED TO POST HIGH
WIND WARNING FOR THIS EVENT. ALTHOUGH WIND WILL NOT QUITE HIT THE
74MPH CRITERIA...DUE THE THE RARITY HIGH WIND IN JULY AND THE LARGE
AMOUNT OF PEOPLE OUTDOORS WE FEEL IT WILL STILL BE A SIGNIFICANT
EVENT.

IN ADDITION TO THE GUSTY WINDS ON LAND...VERY GUSTY WINDS WILL
POSSIBLE OVER COASTAL WATERS OF SOUTHCENTRAL ALASKA. SUSTAINED GALE
FORCE WINDS WILL OCCUR TODAY AND NUMEROUS GALE WARNINGS HAVE BEEN
POSTED...INCLUDING FOR PRINCE WILLIAM SOUND. OCCASIONAL GUSTS TO
STORM FORCE WILL ALSO BE POSSIBLE LATER TODAY...CREATING HAZARDOUS
SEA CONDITIONS.

.HYDROLOGY...
SOME HEAVY PRECIPITATION IS ALSO POSSIBLE WITH THIS SYSTEM. WHILE
STRATIFORM PRECIPITATION WILL OCCUR TODAY...BY TOMORROW A STRONG
SUBTROPICAL JET IS EVIDENT IN THE MODELS. THIS JET WILL SUPPLY THIS
SYSTEM WITH ENHANCED TROPICAL MOISTURE AND CREATE THE POSSIBILITY OF
SOME LOCALLY HEAVY RAIN IN ADDITION TO WHAT HAS ALREADY FALLEN TODAY.
ALONG THE KENAI PENINSULA...INCLUDING SEWARD AND WHITTIER...THERE MAY
BE SOME MINOR URBAN FLOODING. IN ADDITION...THE KENAI AND TRAIL
RIVERS HAVE ALSO BEEN RUNNING HIGH DUE TO RECENT SNOW AND GLACIER
MELT...AND THIS ADDED PRECIP WILL BRING THE RIVER VERY CLOSE TO FLOOD
STAGE. BECAUSE CURRENT FORECASTS DO NOT TAKE EITHER RIVERS TO FLOOD
STAGE OR FORECAST RAINFALL RATES FAST ENOUGH TO INITIATE URBAN
FLOODING...WE ARE POSTING A FLOOD WATCH FOR THE ENTIRE KENAI
PENINSULA. IF MORE RAIN THAN IS CURRENTLY PREDICTED DOES OCCUR THAN
AN UPDATE TO A POTENTIAL ADVISORY OR WARNING MAY BE NEEDED.

.WESTERN...
GUSTY WINDS AND RAIN WILL BE PREDOMINANT ACROSS WESTERN ALASKA. GALE
FORCE WINDS WILL BE POSSIBLE NEAR THE ALASKA PENINSULA AND WILL
DIMINISH AS THE CENTER OF THE LOW APPROACHES. AS THIS LOW IS NOT
EXPECTED TO MOVE AWAY FROM THIS AREA IN THE SHORT TERM...IT APPEARS
RAIN AND GUSTY WINDS WILL OCCUR THROUGH THE WORK WEEK.

.BERING AND ALEUTIANS...
ON THE BACK SIDE OF THE SURFACE LOW VERY GUSTY WINDS HAVE BEEN
OBSERVED ACROSS THE ALEUTIAN ARC. NUMEROUS GALE WARNINGS ARE IN
EFFECT FOR THE AREA...AND OCCASIONAL GUSTS TO STORM FORCE WILL BE
POSSIBLE WITH THIS SYSTEM. HAVE HAD MANY CALLS THIS MORNING REGARDING
THE GUSTY WINDS IN THE ALEUTIANS...AND WINDS WILL REMAIN GUSTY UNTIL
THE CENTER OF THE LOW PASSES OVER THE ISLANDS. IN ADDITION TO THE
STRONG WINDS PERSISTENT RAIN AND LOW CEILINGS WILL ALSO ACCOMPANY
THIS SYSTEM...AND SHOULD PERSIST THROUGH THE WORK WEEK.

.LONG TERM FORECAST...
BY THE END OF THE WEEK THE STRONG BERING LOW WILL EVENTUALLY WEAKEN
AND BEGIN TO RETROGRADE. A MORE AMPLIFIED PATTERN WILL SET UP...AS
HIGH PRESSURE BUILDS ACROSS THE EASTERN PART OF THE STATE BRINGING
CALMER CONDITIONS. RAIN SHOWERS SHOULD PERSIST ACROSS THE WESTERN
PART OF THE STATE...AS LIFT FROM THE DEPARTING LOW WILL STILL BE
PRESENT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101 125...FLOOD WATCH 121 125
MARINE...GALE 120 125 129 132 150 155 170 171 179 351 352
FIRE WEATHER...NONE

TARALDSEN JUL 09