HPC REQUESTS
HIGH IMPACT WEATHER EVENTS WITH LARGE FORECAST UNCERTAINTY
REQUIRING ADDITIONAL OBSERVATIONS

Date: 990110
       Sun, 10 Jan 1999 14:00:22 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

Zoltan...
Strong fast zonal pac flow in models today. There are numerous
shortwaves in this flow with the usual timing and intensity differences
between the models. However all generally agree on strong onshore very
wet flow into the Pac Northwest coast. Downstream effects over interior
noam are minimal. I don't see any need for dropsondes in the EPAC today.

Frank Rosenstein HPC medium range forecaster.
 
 

   Date:  990111
       Mon, 11 Jan 1999 14:36:05 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 
 
 
 

ZOLTAN...
AS YOU SAW EARLIER TODAY THERE IS AN IMPORTANT SJHORTWAVE
IMPACTING THE
PAC NW COAST ON THE 14TH WITH A BROAD TROF ROUGHLY ALONG 135W TO
140W AT
12Z 14TH.

NEXT MORE IMPORTANT ONE IS DUE TO BE NEAR THE PAC NW COAST 12Z
16TH .
THIS SHORTWAVE APPEARS TO BE NR 40N 135W TO 140W AT 12Z 15TH AND
NR 40N
AND 160W AT 00Z 15TH. UNFORTUNATLY THESE ARE EMBEDDED IN VERY FAST
PAC
JET FLOW AND MAY BE OUT OF RANGE OF THE FLIGHT. BY THE TIME THIS
IS IN
RANGE IT WILL ONLY BE 24 HRS UNTIL IT HITS THE COAST.

MRF HAS ANOTHER STRONG SHORTWAVE FOLLOWING THIS ONE WHICH IS
EXPECTED TO
BE NR 40N 155W AT 12Z THE 16TH AND FORECAST TO IMPACT THE PAC NW
BY 00Z
18TH.

FRANK ROSENSTEIN HPC
 
 

   Date:  990112
       Tue, 12 Jan 1999 09:04:32 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

ZOLTAN...

NO CHANGE FROM YESTERDAYS AFTERNOONS DISCUSSION. SERIES OF STRONG
SHORTWAVES INDICATED BY MODELS COMING THRU EPAC IN VERY FAST FLOW.

1. FIRST APPROACHING PAC NW COAST 12Z 16TH.

2. ANOTHER VERY STRONG SYSTEM IN MRF COMING TO COAST 12Z 17TH.

3. ANOTHER EVEN STRONGER ONE BY 00Z 19TH. ALL COMING THRU THE SAME
AREA.
UPSTREAM TARGET AREA AROUND 40N 155W-165W.

4. SUGGEST WE FLY THE LAST TWO STRONGER LOOKING SHORTWAVES COMING
IN
ALSO.

5. IF MRF IS RESONABLE BY 168 HRS...A VERY DEEP SYSTEM COMING
SOUTH OF
ALEUTIANS NR 42N 175W ON 00Z 19TH A FEW DAYS FROM NOW.

FRANK ROSENSTEIN, HPC
 
 

   Date: 990112pm
       Tue, 12 Jan 1999 15:16:21 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

ZOLTAN...
NO DIFFERENT THAN THIS MORNINGS MESSAGE. WILL REEVALUATE TOMMORROW
MORNING BUT AS WE DISCUSSED LOOKS LIKE MORE LIKELY STRONGER
SYSTEMS OVER
THE WEEKEND AND INTI EARLY NEXT WEEK. ESPECIALLY THE SYSTEM
FORECXAST TO
BE NR THE COAST 12Z 17TH ANSD BEYOND.

FRANK ROSENSTEIN HPC
 
 
 

Date: 990113
       Wed, 13 Jan 1999 15:47:53 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@noaa.ncep.gov
 
 

ZOLTAN...

TWO IMPORTANT SHORTWAVES....

1. AFFECTING WEST COAST 12Z 16TH.

2. AFFECTING PAC NW AND OR CA COAST 12Z 17TH. ECMWF/CANADIAN MODEL AND
ENSEMBLES WORK THIS SHORTWAVE INLAND GENERATING A CENTRAL ROCKIES AND
PLAINS STORM BY 12Z 18TH.

3. UPSTREAM THIRD SHORTWAVE NR 45N 160W AT 12Z 17TH IS IMPORTANT FARTHER
CONTROLLING DOWNSTREAM ONE NEAR THE WEST COAST. RECEIVED CALL FROM
JUNEAU CONCERNING NORPEX DROP INTO THIS ONE.

ROSENSTEIN HPC
 
 
 

Date: 990114
       14 Jan 1999 14:40:28 -0500
   From:
       John Leathers <John.Leathers@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>
 
 
 

     Issued Thu Jan 14

     In addition to the previously discussed area along the Wa and Or
     coasts we have an area of uncertainty on day 3 (Sun) centered over
     about 40n 100w which is in Nebraska. There is disagreement among the
     models as to the strength and speed of a shortwave fcst to be near
     that area at that time.
 

     Leathers...HPC Medium Range
 
 
 

Date:  990115
       15 Jan 1999 08:43:33 -0500
   From:
       Stephen Flood <Stephen.Flood@noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 
 

     Zoltan,

     I am sending this to you 2 ways to make sure you get it. Today's area
     of uncertainty is the same location as yesterday... 42N/124W...for
     days 4-5 (Tue-Wed) and concerns precipitation.

     Steve Flood
 
 

Date: 990115 pm
       15 Jan 1999 13:26:40 -0500
   From:
       John Leathers <John.Leathers@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>
 
 
 

     January 15...

     We see nothing in the new 12z run of the avn to change your plans from
     what was previously discussed today.

     Leathers...HPC Medium Range
 
 

Date: 990116
No written message was received from HPC. Steve Flood identified the following systems of interest:
99012012    40N    125W
99012100    65N    150W
99012112    40N    97.5W
 
 

Date:
         Sun, 17 Jan 1999 10:47:17 -0500
     From:
         Robert Oravec <roravec@ncep.noaa.gov>
       To:
         Zoltan Toth <ztoth@ncep.noaa.gov>
 References:
         1 , 2
 
 
 

DATE: 990117

Zoltan,

Our target verification area would be to the east of the Appalachians
across the mid Atlantic region near 40N 75W.  The disagreements among
the medium range models involve the amount of low level cold air which
will be in place ahead of an eastward moving closed low.  Subsequently
the implied precipitation type to the east of the Appalachians is our
concern today.

The verification time would be 1200 UTC 1/22/99 centered at 40N 75W

Bob Oravec
HPC/Forecast Operations Branch
 
 
 

   Date: 990118
       Mon, 18 Jan 1999 15:05:42 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@noaa.ncep.gov
 
 

1. Large amount of uncertainty with a strong shortwave in the plains
12z/ 22 Jan along 95W. This appears to be a hvy pcpn producer.
2. Another pac shortwave approaching the west coast 00z 23 Jan. A good
deal of timing and intensity differences.
Rosenstein HPC
 
 
 

   Date: 990119
       Tue, 19 Jan 1999 15:00:44 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

1. Deep trof and closed low in the plains at 12z 22 Jan with expected
hvy rainfall in the Ms valley and Great Lakes with possible hvy snow
across portions of the upper Ms Valley and wrn Great Lakes. A fair
amount of unceratinty handling this feature.

2. Next strong pac trof approaching the west coast 12z 23 Jan has a lot
of uncertainty with intensity/timing and configuration. Important model
differences on day 5 pcpn over the west coast and inland into the
Rockies.

Rosenstein HPC
 
 
 
 

Date: 990120
       Wed, 20 Jan 1999 08:39:08 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

This mornings models are in very good agreement on the closed low moving
from the srn plains to the great lakes region with mdt/hvy rain and snow
on the back side.

Very large model differences continue with the next trof approaching the
Pac Northwest at 00z 23 Jan and continuing thru 00z 24 Jan. Request
recon here as per ytdas discussion.

Rosenstein HPC
 
 

Date:  990120pm
       Wed, 20 Jan 1999 15:10:15 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

Four areas of concern...

1. Deep closed low and trof in the lower Ms valley ejecting newd toward
the Great Lakes region from 00z 23 to 00z 24 Jan.

2. Large amount of uncertainty with a trof approaching the Pac Northwest
coast 00z 23 Jan to 00z 25 Jan. This is likely to be both a heavy rain
and heavy snow producer with a snow threat for SEA.

3. Heavy pcpn threat mostly or all snow for the srn coast of Ak with a
deep Pac storm west of the state again during the period 00z 23 Jan.

4. Mrf  has another significant looking shortwave dropping sewd thru the
Glfak toward the Pac Northwest 12z 26 Jan with uncertainty shown by
ensembles and other models.

Rosenstein HPC
 
 
 

   Date: 990121
       Thu, 21 Jan 1999 15:06:37 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov
 
 
 

Two areas of uncertainty and concern

1. Heavy pcpn expected along the ak coast from sw to se with two event.
First occuring 00z 23 Jan thru 00z 24 Jan and a second shortwave 12z 25
Jan.

2. West coast of the U.S. a great deal of uncertainty with a heavy pcpn
event mainly for Ca with hvy rain and higher elev hvy snowfall. Period
from 00z 23 Jan thru 00z 26 Jan.

Rosenstein HPC
 
 
 

   Date: 990122
       22 Jan 1999 09:49:28 -0500
   From:
       Stephen Flood <Stephen.Flood@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>

     Zoltan,

     The two areas of high uncertainty that are reachable from NORPEX
     flights are :

     1) 35N/125W from 23 Jan/1200 to 25 Jan/1200. This concerns possible
     heavy precipitation...rain at low evevations and snow at higher
     elevations...for much of the state of CA.

     2) 55N/150W from 23 Jan/1200 to 25 Jan/1200.

     This event is similar to the first one...concerning possible heavy
     precipitation for the southern coastal mountains of AK.

     Steve Flood
 
 

Date: 990123

No written request from HPC. Steve Flood was concerned about Alaska precipitation event around 990126-27.
 
 
 

Date: 990124

No written request from HPC. Steve Flood was concerned about
1)    Alaska precip at 99012700
2)    Washington-Oregon precip event, 990128-29
3)    Large uncertainty regarding short wave over New Maxico, 990128-29
4)    Precip event in the east, 990129-30
 
 
 
 

Date: 990125

Steve Flood is concerned about:
Day3     precip event,     45N 125W
                precip/wind        38N    98W
Day4    precip/wind        49N    125W
                precip/wind        38N    98W
Day5       precip                35N    84W
                precip                48N    125W
 
 
 
 
 

   Date:  990125 pm
       25 Jan 1999 15:47:42 -0500
   From:
       Stephen Flood <Stephen.Flood@noaa.gov>
    To:
       Zoltan.Toth@noaa.gov

     Zoltan,

     Taking a look at the latest AVN...NOGAPS...and CANADIAN, it still
     looks like the area between 46N and 52N and 125W along the Pacific NW
     coast is a critical area for possible heavy PCPN days 4-5 (FRI-SAT).

     The area farther E is as follows:

     Day 3---35N/105W...PCPN
     Day 4...40N/80W....PCPN
     Day 5...35N/75W....PCPN

     Steve Flood
 
 
 
 

   Date: 990126

       26 Jan 1999 16:46:51 -0500
   From:
       Paul Mausser <Paul.Mausser@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>

     Zoltan:

     The feature that we are most concerned with is the major shortwave and
     upper trof that will be impacting the Pacific Northwest coast with
     heavy rain and potential flooding problems from snowmelt due to the
     amount of mild Pacific air being brought onshore.

     The area of interest will be between lat. 30N and 45N; between lon.
     120W and 130W beginning on day 4 (Sat. Jan. 30), or the coasts of WA,
     OR and northern CA.

     Paul Mausser
 
 
 
 

   Date: 990127
       27 Jan 1999 15:16:15 -0500
   From:
       Paul Mausser <Paul.Mausser@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>
 

     Zoltan:

     Once again I think that the greatest area of concern is the Pacific
     Northwest where there is the potential for at least 4-6 inches of pcpn
     along the immediate WA/OR coastline with only slightly lower amounts
     in the Cascades and Coast Range.  Slightly lower amounts, although
     still significant (1-3 inches) are possible as far south as
     northwestern CA.  This is in association with a major trof forecast to
     dig toward the west coast in the medium range period.

     The area of interest is similar to yesterday:  lat. 30N-50N, long.
     120W-140W beginning on day 3 (Sat. Jan. 30).

     This trof is also of particular interest due to the potential effect
     it may have on the downstream cutoff low forecast to develop over the
     southwestern U.S..  Most of the models seem to be converging toward
     the solution that the ECMWF was suggesting for the last few days.
     This will have significant impact on the 5-day pcpn forecast for the
     southeastern U.S., where there is the potential for widespread 2-3
     inch amounts from the Gulf coast into the Tennessee valley.

     Paul Mausser
 
 

Date: 990128
       28 Jan 1999 13:15:56 -0500
   From:
       Paul Mausser <Paul.Mausser@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>
 

     Zoltan:

     The area of concern today is still along the Pacific Northwest coast
     where the digging trof will bring locally heavy pcpn to parts of WA,
     OR and northern CA beginning in the short range period.  The MRF has
     backed off a bit on total amounts, but this should still be a heavy
     pcpn event.

     A shortwave rotating through the base of this trof appears to be the
     one which will have an effect on the ultimate track of the strong
     closed upper low that will be lifting out of the southwestern U.S. and
     moving out toward the mid-Atlantic coast.  The expected track of this
     system could lead to a wide area of heavy rainfall with max amounts
     exceeding 5 inches this period over portions of the Mississippi, Ohio
     and Tennessee valleys.

     Thus the area to watch is with the shortwave fcst to be in the base of
     the trof beginning on day 2 (Sat. Jan. 30).  The area is lat. 30N-40N
     and lon. 125W-145W.

     Paul Mausser
 
 

Date: 990129
       Fri, 29 Jan 1999 15:02:19 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov

Zoltan

Timing of an approaching epac shortwave to the Pac Nw coast between 12z
02 Feb and 12z 03 Feb seems to be our next problem. Downstream model
differences are not as dramatic fro now. Rosenstein HPC.
 
 

Date: 990130
No request from HPC.
 
 
 

Date: 990131
No written request from HPC. Steve Flood was concerned about:
1)    99020412    40N    82.5W, precip, winds - possible snow storm in the east.
2)    99020412    42.5N    125W, precip, winds
3)    99020300    52.5N    120W    precip, winds
 
 

Date: 990201
       01 Feb 1999 15:09:47 -0500
   From:
       John Leathers <John.Leathers@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>

     Feb 1....

     The new AVN run is somewhat slower and a little stronger with the
     shortwave off the w coast on day 3 (thu) or 72 hrs. This looks like a
     continuing area of uncertainty and your ideas of this morning still
     look good.

     Leathers...HPC Medium Range
 
 
 

Date: 990202
       02 Feb 1999 15:00:28 -0500
   From:
       John Leathers <John.Leathers@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>

     Feb 2...

     There continues to be an area of uncertainty off the w coast north of
     40N and out to 150W. Shortwaves are still being fcst to move thru that
     region on all three days of our fcst from Fri to Sun. The most intense
     storm is likely to be approaching the coast on day 4 (Sat). The new
     AVN run does not show any significant change.
 

     Leathers...HPC Medium Range
 
 

Date: 990203
No written request from HPC. Franklin Rosenstein was concerned about the heavy precipitation event on the west coast between 990206-990208.
 
 
 
 

Date: 990204
       04 Feb 1999 15:07:13 -0500
   From:
       John Leathers <John.Leathers@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>
 
 
 

     Feb 4...

     Todays AVN run offers no surprises once again from the solutions of
     last nights models. We continue with the same area of uncertainty off
     the w coast as the upper trof shifts ewd to move onshore on day 5
     (Tue).
 

     Leathers...HPC Medium range
 
 
 
 

   Date: 990205
       Fri, 05 Feb 1999 12:42:32 -0500
   From:
       Franklin Rosenstein <frosenstein@ncep.noaa.gov>
    To:
       ztoth@ncep.noaa.gov

Uncetainty with the next strong Pac trof approaching the west coast
between 12z 8 Feb and 12z 09 Feb. This continues the very wet spell for
the Ca coast. There is a good deal of uncertainty on how far south the
trof will extend and how much energy is in the base. Ukmet and ecmwf
bring hvier rainfall into srn ca while nogaps and mrf would keep hvier
pcpn farther nwd. Rosenstein HPC
 
 
 

Date:    990207
No written request from HPC. Steve Flood was concerned about :
low pressure wave in the east:
day4    37N    92
day5    38N    85W

next precipitation event on west coast:
day4    50N    125W
day5    50N    123W
day6    40N    130W
 
 
 
 

Date:     990208
       08 Feb 1999 15:44:03 -0500
   From:
       Stephen Flood <Stephen.Flood@noaa.gov>
    To:
       Zoltan Toth <Zoltan.Toth@noaa.gov>
 

     Zoltan,
 
     I took a quick look at the new avnens and the 12Z/08 NAVY NOGAPS and
     heres how it looks:
 
     Day 3 52N/125W  pcpn
 
     Day 4 49N/124W  pcpn
 
     Day 5 40N/120W  pcpn
 
 
     Steve Flood