DeZert News Advisory***Sunday, September 20, 2015***Desert Weather
LIVE! From the Big Bad DeZert
UPDATE! Tuesday, 2 AM
CURRENT REPORTING STATIONS 2:00 AM
BIG BAD DESERT USA CITY SKY/WX TMP DP RH WIND PRES IMPERIAL AP CLOUDY 82 69 64 SE5 29.74S EL CENTRO NAS MOCLDY 79 68 69 SE7 29.76S YUMA AZ PTCLDY 81 69 67 SE9 29.78S 2 AM; 9-22-2015: Watch Dropped
MOST SOUTHERN CALIFORNIA REPORTING STATIONS ARE
REFLECTING VERY WARM OVERNIGHT TEMPERATURES AND
SOUTHERN DESERT REPORTING STATIONS ARE REPORTING
WINDS OUT OF THE SOUTHEAST TO TEN KNOTS.
RAPID CLEARING IS EXPECTED TODAY AND WEDNESDAY.
END OF REPORTING STATION POSTS IN THIS NEWS COMP.
12:30 PM 9-21: Watch Continues
FLASH FLOOD WATCH ENDS AT 11PM PACIFIC
THIS WEATHER EVENT SHOULD BREAK FULLY,
ON WEDNESDAY, WITH RAPID DRYING AND
"CONVECTION AHEAD OF THE LOW LEVEL CENTER
HAS BEEN RATHER CONSOLIDATED AND ROBUST EARLY
THIS MORNING NEAR THE BAJA BORDER...
THE LOW PRESSURE AND A WEAK TROPICAL WAVE
IS MOVING THE MOISTURE NORTHWEST...
NORTHWEST MOVING RAINFALL IS DIMINISHING
AS THE DAY PROGRESSES...
TONIGHT, RAINFALL COULD EXPAND ON THE
DROPPING AIR TEMPERATURES.
RAINFALL SOUTH AND WEST OF MEXICALI,
IN BAJA MEXICO HAS BEEN HEAVY, MID-DAY.
IN ARIZONA AND NEW MEXICO, THE TROPICAL
ENVIRONMENT REPRESENTED THERE WILL BRING A DRAMATIC CHANGE TO PRECIPITABLE WATER VALUES
ABOVE SIX INCHES OF RAIN...AND GIVEN THE
TROPICAL AIRMASS...WOULD NOT BE SURPRISED TO SEE
THESE TOTALS IN ARIZONA AND NEW MEXICO.
AMOUNTS OF ONE TO TWO INCHES ARE POSSIBLE IN
THE RACE COURSE AREA (IMPERIAL VALLEY), TODAY.
ALONG SOUTH AND EAST FACING TERRAIN ARE IN
THE GREATEST RAIN EXPOSURE AREAS...
ESPECIALLY IF THE LOW LEVEL CIRCULATION REMAINS INTACT AND SLOWS AS IT INTERACTS WITH THE MOUNTAINS.
THAT WOULD BE IN A WORSE CASE SCENARIO...
BUT IS WORTH CONSIDERING IN PLANNING. REGARDLESS OF EVENTUAL TOTALS...RAIN RATES
EXCEEDING 2 INCHES PER HOUR IN THE DEPRESSION PATH,
DURING THE HEIGHT OF THE EVENT WILL OVERWHELM
THE FLASH FLOOD GUIDANCE VALUES IN THIS REGION...
SUGGESTING POTENTIAL FOR SIGNIFICANT IMPACTS."
1 AM Monday Morning: Watch continues overnight into September 21:
For Southern California: "THE CORE OF THE UPPER LOW WAS ACTIVE WITH POCKETS OF CONVECTION
BENEATH IT THIS MORNING...AND SHOULD
CONTINUE TO PRODUCE CONVECTION AS IT
APPROACHES SOUTHERN CALIFORNIA MONDAY
NIGHT. EASTERLY MID LEVEL WINDS WILL
CARRY AIR WITH PW VALUES APPROACHING
1.25 TO 1.50 INCHES INTO THE L.A. BASIN
AND NEAR SAN DIEGO...
SO LOCALLY HEAVY DOWNPOURS DO APPEAR
POSSIBLE IN MORE DIRECT ASSOCIATION
WITH THE UPPER LOW RATHER THAN THE
|Southern California rain deluge threat moves from the tropical depression, which now is moving farther east, to the steering desert low pressure, making Los Angeles and San Diego heavy downpours possible today, Monday, Sept 21.|
Race Event Location thru Tuesday Evening
"MAXIMUM RAINFALL AMOUNTS SHOULD BE REALIZED
THERE (Imperial County) WITH WIDESPREAD
2 INCH AMOUNTS LIKELY AND ISOLATED AMOUNTS OF 3 TO 4 INCHES POSSIBLE.
A FLASH FLOOD WATCH WAS ISSUED FOR
THE MOUNTAINS AND EASTERN DESERTS
DUE TO MODERATE CONFIDENCE IN WIDESPREAD
FLASH FLOODING POSSIBILITIES FOR MONDAY
AFTERNOON THROUGH TUESDAY."
5 AM Sunday Sept. 20: The Baja Weather Service reports today, the planned Imperial Valley race could be impacted by a tropical depression currently located west of Baja South this morning. Race activities could be impacted by the adverse impacts of heavy rainfall in the region, this week.
Rainfall generated from the system and potential flash flooding from the the depression is expected to move north into Southern California Monday, September 21 and Tuesday, September 22. Current forecast models place the center of circulation of the tropical disturbance, driving through Imperial Valley during the week, full of scheduled desert off-road racing festivities.
The National Weather Service reported today: "Deep atmospheric moisture associated with this disturbance is expected to produce heavy rains across portions of the Baja California peninsula and northwestern Mexico today, and over portions of southern California and Arizona on Monday and Tuesday. These rains could produce life-threatening flash floods and mud slides, especially in mountainous areas".